1. health and fitness
2. disease

2013/2014
Raquel Cristina Naldinho Souto
Novel Biomarkers of Acute Kidney Injury
março, 2014
Raquel Cristina Naldinho Souto
Novel Biomarkers of Acute Kidney Injury
Mestrado Integrado em Medicina
Área: Nefrologia
Trabalho efetuado sob a Orientação de:
Professor Doutor Manuel Jesus Falcão Pestana de Vasconcelos
Trabalho organizado de acordo com as normas da revista:
Kidney International
março, 2014
Souto: Novel Biomarkers of AKI
Title
Novel Biomarkers of Acute Kidney Injury
Author
Raquel C. N. Souto
Integrated Master in Medicine
Serviço de Nefrologia, Faculdade de Medicina da Universidade do Porto, Porto, Portugal
Correspondence
Raquel C. N. Souto
Faculdade de Medicina da Universidade do Porto
Alameda Professor Hernâni Monteiro
4200-319 Porto
Portugal
E-mail: [email protected]
Running headline: Novel Biomarkers of AKI
Word count: 4487
Abstract word count: 220
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Souto: Novel Biomarkers of AKI
Abstract
Acute kidney injury (AKI) is associated worldwide with increased mortality, prolonged
hospital stay and greater medical costs, being a risk factor for poor prognosis. These dire clinical
consequences are in connection with its delayed recognition, which is traditionally verified by
detection of oliguria and the elevation of serum creatinine. Hence, novel biomarkers of AKI, with
the ability for prompt and accurate diagnosis have been defined as a prime research goal. Innovative
technologies, from proteomics to functional genomics have identified several candidate molecules.
The purpose of this work was to concisely review current available data on the most promising
candidate biomarkers of AKI, discussing their clinical applicability and future prospects. Published
data from studies of both urinary and serum biomarkers suggests that these molecules may have
great potential to advance the fields of anesthesiology, critical care and nephrology. Despite the fact
that the basic and clinical published data on this subject is substantial and supportive, the evidence
was found to be yet insufficient in order to recommended their clinical usage according to the
current clinical practice guidelines. In conclusion, these novel biomarkers need validation in larger
studies, that include a wider range of patient populations, in order to fully demonstrate to both the
scientific and clinical communities, that there is increased diagnostic benefit over traditional
markers, allowing for improved medical care.
Keywords: Acute Kidney Injury; Acute Kidney Injury: diagnosis; Biological Markers; Biological
Markers: metabolism; Biological Markers: blood; Biological Markers: urine.
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Souto: Novel Biomarkers of AKI
Introduction
In acute kidney injury (AKI) there is an abrupt decrease in kidney function which is a
prevalent illness1 associated with significantly increased mortality, medical costs and length of
hospital stay.2 Moreover, patients that initiate renal replacement therapy (RRT) show a mortality
rate that surpasses 50%, adding further relevance to the evidence that AKI presents a specific and
independent risk factor for poor prognosis.3 The delayed detection of AKI may be related to these
unfavorable outcomes. The diagnosis of AKI is verified based upon the detection of oliguria and the
elevation of serum creatinine (SCr) 4 although steep detectable rises in SCr could remain
unrecognized for up to 48–72 hours.4,5
In the last decade a major change in nomenclature occurred, with AKI overturning the
classic designation "acute renal failure", in acknowledgment that injury could have important
clinical outcomes even without clear-cut decline of kidney function. Nowadays AKI's classification
is still dependent on surrogate measurement of glomerular filtration rate (GFR) despite the above
mentioned conceptual change.
Considering that the Risk Injury Failure Loss of kidney function End-stage kidney disease
(RIFLE)6 and also the more recent Acute Kidney Injury Network (AKIN) criteria 7 still adopt urine
output and SCr for the definition of AKI, SCr has now been the gold standard to assess renal injury
in the last hundred years.8
In 2012, the Kidney Disease Improving Global Outcomes (KDIGO) work group fused
RIFLE and AKIN classifications into a single classification of AKI for research and clinical usage.
AKI has been staged in severity according to the AKIN criteria, being defined as a rise in SCr ≥ 0.3
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Souto: Novel Biomarkers of AKI
mg/dL in 48 hours or an rise in SCr to ≥ 1.5 times baseline (measured or presumed to have occurred
in the previous 7 days), or an urine volume < 0.5 mL/kg/h for 6 hours. 9 According to a recent
systematic review that abide by KDIGO criteria, as many as 1 in 5 adults and 1 in 3 children
worldwide experience AKI during a hospital episode of care. 1 AKI is no longer regarded as
byproduct of major illness, having achieved recognition as a serious contributor of both long and
short term morbility/mortality in its own right.
Given the dire clinical consequences of AKI, biomarkers to detect it earlier and with
accuracy are eagerly anticipated. The intent of this work is to concisely review current available
data on the most promising candidate biomarkers of AKI, discussing their strengths, shortfalls and
future development strategies.
Biomarkers of Acute Kidney Injury
In 2005 the American Society of Nephrology defined as a prime research target the
development of biomarkers for AKI, promoting early identification, clinical decision making and
allowing for better outcomes.10 Since AKI's pathophysiology can be an intricate process, markers of
risk, injury amplification and recovery are also desirable. The optimal characteristics in the quest
for the perfect AKI biomarker are listed in Table 1.
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Souto: Novel Biomarkers of AKI
Table 1 - Acute Kidney Injury: optimal biomarker properties.
Optimal biomarker properties
Perfectly sensitive and specific for AKI
Adequate for early identification of injury
Straightforward detection in noninvasive samples (e.g. serum/urine)
Reflects etiology and duration of injury
Provides broad diagnostics window
Allows for risk stratification and predicts reversibility
Unaffected by other clinical and biological factors
Levels suitable to monitor illness course and therapeutic response
Cost-effective
Prompt and trustworthy results
Abbreviations: AKI, acute kidney injury.
Emerging technology, over the past decade, that allows for high-throughput detection and
characterization of proteins and metabolites has raised hopes and likelihood of identifying the above
mentioned traits in a single molecule. Basic and clinical research in this area are advancing towards
this ideal marker of disease with numerous candidates in development, which are being thoroughly
analyzed in diverse medical fields.
In terms of clinical application, it is paramount that it proves accuracy alongside earlier
detectability, exceeding the current gold standard that is SCr. Nonetheless, the interpretation of
these research studies needs to be attentive, because it is crucial to distinguish between reported
ability to predict injury in patients with early developing AKI from their ability to validate AKI
diagnosis in patients with previously confirmed AKI. Clinically, the impact on these two entities is
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Souto: Novel Biomarkers of AKI
quite distinct.
Still, there is doubt as to whether these biomarkers have suitable prognostic accuracy for
both early detection of AKI and established AKI. Comparing the performance of these biomarkers
directly is complicated by the heterogeneity in the reporting criteria and diverse range of data
emerging from studies in patient subgroups prone to AKI (e.g., post-cardiac surgery, sepsis, postkidney transplant).
In order to establish clinical relevance of newly developed markers, an essential aspect is to
ascertain to what degree they provide additional prognostic information relative to established risk
markers.11 Traditional approaches include determining discrimination, which is the most routinely
applied tool in researching AKI biomarkers. It employs conventional features of test performance
such as specificity, sensitivity and also predictive values that enable the generation of summary
characteristics, most noticeably the area under the receiver-operating curve (AUC). 12,13 The AUC
estimates the probability of a biomarker to distribute accurately any two randomly selected patients,
recognizing which one suffers from AKI. Plus, AUC is also used in the prediction of future clinical
episodes.
Whilst analyzing the fast evolving literature, it is decisive to keep in mind what the marker
is supposed to be reflecting, i.e. it may depict functional renal status or it may be a byproduct of
injury therefore pointing to active kidney damage. Hence, biomarkers to be addressed in this review
where assigned to four principal categories (Table 2).
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Souto: Novel Biomarkers of AKI
Table 2 - Different types of AKI biomarkers.
Biomarker Types
1 Functional Markers
Biomarkers
a Serum Creatinine
b Serum Cystatin C
2 Low-Molecular Weight Proteins a Urine Cystatin C
3 Up-Regulated Proteins
a Kidney Injury Molecule-1
b Interleukin-18
c Neutrophil Gelatinase-Associated Lipocalin
d Liver Fatty Acid Binding Protein
4 Tubular Enzymes
a Alpha-Glutathione s-Transferase and Pi-Glutathione sTransferase
b Gammaglutanyl Transpeptidase and Alkaline Phosphatase
c N-Acetyl-beta-D-Glucosaminidase
1. Functional markers
1. a. Serum creatinine
Serum creatinine (SCr) results from muscle cell degradation, hence an indirect measure of
glomerular filtration efficiency, translating into significant limitations as an AKI marker, as stated in
Table 3. It has long been known to be greatly influenced by age, gender, race, body weight, muscle
metabolism, total body volume, protein intake and drugs, thus having poor predictive accuracy for
renal injury.14 Minute or nil change in SCr may coexist with significant renal disease on account of
both increased tubular secretion of creatinine and renal reserve. 15,16 At times, medically induced
adjustments to the volume status of critically ill patients creates ample variations in SCr
concentrations. A SCr increase may remain undetectable up to 2-3 days after a kidney injury, thus a
faulty marker of disease.17 Lastly, in animal models, sepsis decreased creatinine production,
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Souto: Novel Biomarkers of AKI
possibly limiting the early detection of AKI,18 once more stressing the limitations of current renal
injury diagnosis methods.
Table 3 - Disadvantages of using Serum Creatinine measurements for AKI diagnosis.
Disadvantages of Serum Creatinine Measurements
Depends upon steady state GFR
Neglects minor changes in GFR
Lags behind GFR changes
Nonspecific for AKI
Modified by clinical factors (e.g. age, gender and drugs)
Abbreviations: AKI, acute kidney injury; GFR, glomerular filtration rate.
1.b. Serum Cystatin C
Cystatin C is a low molecular weight molecule (13kDa), member of the cysteine proteinase
inhibitors and made at stable rate by all nucleated cells. 19,20 In the glomerulus it is freely filtered,
reabsorbed and catabolized, with no evidence of tubular secretion, 20 therefore serum CyC (sCyC)
measurements have been widely assayed to gauge GFR in chronic kidney disease (CKD) patients. 21–
23
Equations to estimate GFR using sCyC appear to be clearer and more exact than creatininebased equations.24 Additionally equations that integrate sCyC and SCr appear to improve upon those
using each of the two markers alone.25-27 A 2002 meta-analysis found support for the claim that
sCyC to be more reliable than SCr–based methods to detect minor reductions in GFR.23 sCyC has
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Souto: Novel Biomarkers of AKI
been noted to be elevated faster than creatinine after a decrease in GFR, 28,29 and it may also be
preferable to SCr in estimation of mortality and cardiovascular outcomes.30
However, circulating cystatin C concentrations may be enhanced by corticosteroid
administration,31 thyroid dysfunction32,33 and malignancies,34 skewing the interpretation of sCyC
levels. Contrary to other latest AKI markers, measuring sCyC is usually accessible in hospital
settings using automatic analysis with rapid turnover. Yet, it must be noted that relevant
discrepancies in CyC measurements between laboratories has been found.35 To remedy these issues
a reference CyC material has been produced and characterized. 36
Herget-Rosenthal and coworkers assessed intensive care unit (ICU) patients (n=85),
showing that sCyC performed well diagnosing AKI [AUC=0.82 (95% confidence interval (CI)
0.71–0.92)], and had predictive abilities in detecting the urgency for RRT. 28 In a 2011 multi-centre
study by Royakkers and colleagues that enrolled 151 subjects with comparable clinical background
found an inferior performance (AUC=0.72).37 Amongst 318 patients without AKI on ICU entry,
initial sCyC was predictive of sustained AKI [AUC=0.80 (CI 0.71–0.88)], but displayed discreet
prediction capacity by day 7 in hospital [AUC=0.65 (CI 0.58–0.71)]. 29 Still, the benefit of
measuring sCyC as opposed to SCr has delivered mixed results regarding its utility in a number of
studies.38,39 In a recent systematic review a wide variation in the reported sCyC levels was
underscored, moreover no consensus was achieved for threshold levels of CyC that may mark AKI
diagnosis or AKI risk.40 In the diagnosis of AKI, sCyC acts as a marker of GFR, thus it lacks
accuracy in differentiating CKD from AKI. Therefore, for the time being, sCyC measurements are
more prone to remain in the assessment of CKD.
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Souto: Novel Biomarkers of AKI
2. Low-Molecular Weight Proteins
2.a. Urine Cystatin C
In healthy kidneys, the urinary CyC (uCyC) is actively reabsorbed in the proximal tubules,
being practically undetectable in urine analysis. 41–43 Detection of uCyC reflects tubular dysfunction 44
which may prove to be a more timely marker of renal injury given that it indicates injury to
proximal tubules cells. Howbeit, recent data show that uCyC is increased by albuminuria. 45
Measuring uCyC is possible through a automated nephelometric commercially available assay that
highly accurate, rapid and precise.41
Levels of uCyC determined 6 h after cardiac surgery were predictive of AKI (AUC=0.72),
improving upon both Neutrophil Gelatinase-Associated Lipocalin and sCyC measured at the
identical time point.46 In another study by Koyner et al., this time evaluating uCyC performance
upon ICU admission, also found favorable results [AUC=0.72 (CI 0.61–0.83)]. 47 However, in other
clinical studies reported results suggest fairly poor diagnostic test characteristics.48,49
Theoretically, uCyC is a very auspicious AKI marker, nonetheless recent meta-analysis
calculated a pooled AUC of 0.64, presenting only slight diagnostic value.40
3. Up-Regulated Proteins
3.a. Kidney Injury Molecule-1
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Souto: Novel Biomarkers of AKI
Kidney injury molecule 1 (KIM-1) is a transmembrane glycoprotein present in damaged
tubular epithelial cells in both acute and chronic illness, that sheds a cleavable ectodomain. 50,51
KIM-1 was initially found to be extensively upregulated in an animal model of kidney ischemia. 52
Besides having a role in tubular regeneration processes through phagocytosis of apoptotic cells 50 it
is found lacking in normal kidneys. 53 These data together with the knowledge that the 90kDa
ectodomain was cleaved and excreted in urine51 triggered more research into urinary KIM-1.
In preclinical studies for renal injury induced by pharmacological agents KIM-1 was found
to be an appropriate biomarker, which has been recognized by the Food and Drug Administration
and the European Medicines Agency. 54,55 A semi-quantitative assay obtained in 15 minutes was
described for KIM-1, enabling quick diagnosis of AKI much sooner than conventional markers such
as SCr.54
In the first published study in humans, a 1U increase in normalized KIM-1 was associated
with a greater than 12-fold risk for the presence of ischemic acute tubular necrosis (ATN), 56 and in a
subsequent work, AUC of 0.90 was the reported value of KIM-1's accuracy in the diagnosis of
AKI.57 These clinical studies credit KIM-1 to be highly competent at differentiating ATN from
controls and also other types of kidney disease such as CKD. 56,57 On the other hand, its performance
in early prediction of clinical AKI lags behind the accuracy that it demonstrates in identifying
established AKI.57 Moreover, an ICU study reported that from a total of 82 patients that developed
AKI within the first 48h upon admission, its predictive performance was insufficient [AUC= 0.55
(CI 0.47–0.62)].58
Numerous reports have examined its diagnostic properties in adult cardiopulmonary bypass
(CPB) patients. Liang et al. reports a modest AUC figure for progressive AKI detection [AUC=0.69
(CI 0.61–0.78)].59 Conversely, in a study comparing the performance of six candidate urinary
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Souto: Novel Biomarkers of AKI
biomarkers measured 2 hours following CPB for the early detection of AKI, in a prospective cohort
of patients undergoing cardiac surgery (n=103) AKI developed in 13% and KIM-1 achieved the
highest AUC [AUC=0.78 (CI 0.64-0.91)].60 Moreover, high levels of KIM-1 levels were
independently associated with adverse clinical outcomes, such as the need for dialysis, in a group of
patients (n=201) with established AKI,61 hence KIM-1 may have a relevant prognostic function
coupled to diagnostic benefit.
Even though Huang et al. systematic review highlighted a few inconsistencies between
available studies,62 the availability of a rapid assay and its specificity for ischemic renal injury are
compelling advantages for this AKI biomarker.
3.b. Interleukin-18
Neutralization of interleukin-18 (IL-18) in animal models, conferred protection from
ischemic AKI,63,64 establishing a possible role for this cytokine as marker of AKI, and promoter of
the pathogenesis in ischemic renal injury.65 IL-18 was easily detectable in animals subjected to
ischemic AKI but absent in controls, hence suggesting an early marker ability.63
In an early cross-sectional human study examining patients (n=72) with a wide array of
renal disorders, IL-18 was markedly increased in patients with established AKI from ischemia,
although not in patients with AKI from urinary tract infection, CKD, nephrotic syndrome, or those
with pre-renal failure, with AUC diagnosis of ATN of 0.95. 66 In a cohort of 138 critically ill patients
presenting acute respiratory distress syndrome (ARDS), IL-18 predicted progression within 24h to
AKI (AUC=0.73) prior to creatinine based criteria were met, and the urine IL-18 value on day 0
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Souto: Novel Biomarkers of AKI
was found to be an independent predictor of mortality. 67 A posterior report described the time course
of IL-18 detection after CPB, with urine IL-18 rising at 4–6h post surgery, peaking at over 25-fold
at 12h, and maintaining and elevated plateau for up to 48 hours. 68 AUC for the diagnosis of AKI at
4, 12, and 24h after CPB were 61, 75, and 73% respectively, while levels of SCr detected AKI only
48–72h after CPB.68
In a study of patients admitted to ICU (n=451), 86 of whom developed AKI, IL-18 levels
were correlated with sepsis and 28-day mortality but showed low predictive value of AKI
development within 24 hours (AUC=0.62).69 There is a concerning possibility that generalized
inflammatory states could be a confounding factor since IL-18 is a cytokine know to be produced
by inflammatory cells such as lymphocytes and macrophages. 70 A more recent report on 82 adult
patients that within 48h of admission into ICU developed AKI established a mediocre AKI
prediction performance of IL-18 [AUC=0.55 (CI 0.47–0.62)].58
Further studies have analyzed the plausible benefits of IL-18 as an early marker for AKI in
diverse clinical settings such as CPB49, contrast-induced nephropathy (CIN)71 and renal transplant
recipents.72 Although preliminary clinical data promoted IL-18 as a powerful marker for AKI
diagnosis66 its adequacy may appear less obvious in heterogeneous populations. 58,69 Besides,
consensus thresholds still need to be addressed for risk stratification 67 and more research is essential
to quantify the influence of generalized inflammation on IL-18 readings.
3.c. Neutrophil Gelatinase-Associated Lipocalin
Neutrophil gelatinase-associated lipocalin (NGAL) is a small protein with an estimated
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Souto: Novel Biomarkers of AKI
molecular weight of 25-kDa, initially detected in a subset of leukocyte granules, 73,74 currently
known to be an ubiquitous epithelial cell protein with bacteriostatic effects.75,76 It plays relevant
roles in cellular recovery with epithelial growth inducer capacity and a protective effect from
ischemia.77-79 As a small protein, at the glomerulus it is freely filtered undergoing complete
reabsorption in the proximal tubule.
In animal model studies, NGAL gene expression was found to be upregulated in renal
ischemia–reperfusion injury, alongside increased early excretion of urinary NGAL (uNGAL). 76,80
This could be interpreted as either due to augmented production and excretion by distal tubules or
indicate faulty reabsorption by damaged proximal tubules.
Leading on from their animal work to clinical studies, Mishra et al. first validated the
biomarker value of NGAL after examining 71 pediatric patients undergoing CPB, obtaining an
impressive AUC value of 0.99 measuring uNGAL at a 2-hour timepoint. 81 Further studies have
described increments in plasma and urinary NGAL subsequent to cardiac surgery in adults yet its
performance at predicting AKI has been less conclusive. 46,49,82,83 In a 2008 study, a unique
measurement of uNGAL strongly predicted AKI (AUC=0.95), and levels fitted with the need for
nephrologist consultation and/or dialysis.84
In 2011, Parikh and coworkers reported NGAL's course in post-cardiac surgery patients
using large cohorts of both pediatric and adult patients, with AUC values for plasma NGAL
(pNGAL) and uNGAL ranging from 0.56 to 0.71, suggesting differences could possibly be
associated with age and comorbidities. 85,86 After cardiac surgery, the relationship between urinary
NGAL and AKI varied with baseline renal function, with optimal discriminatory performance in
patients with normal preoperative function87 perhaps explaining the increased predictive values in
pediatric populations. Still, in another adult ICU clinical study, NGAL's ability to predict
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Souto: Novel Biomarkers of AKI
development of AKI within 48 h of admission was found to be poor [AUC= 0.55 (CI 0.48–0.63)].58
A meta-analysis including 19 studies resulted in AUC of NGAL for AKI prediction to be
0.83, with the highest AUC values for the prediction of CIN (AUC=0.89) and the lowest in
critically ill patients (AUC=0.73).88 Data showing that sepsis may alter NGAL evolution patterns 89
warrants the need for more studies on how this biomarker can be used with confidence in critically
ill patients. To further attest the clinical relevance of NGAL as a biomarker of AKI, less
homogenous populations need to be enrolled in future studies.
3.d. Liver Fatty Acid Binding Protein
Liver fatty acid binding protein (L-FABP) is a small (14- kDa) cytosolic protein present in
the liver, the gastrointestinal tract, and the kidney's proximal tubule cells, that is hepatically
synthesized. Urinary L-FABP is not present in healthy controls but if subjected to ischemia, there is
a significant reduction of its megalin-mediated endocytosis in proximal tubules.90-92 Preclinical
studies demonstrated that L-FABP protected cells from toxicity and oxidative stress, with urinary
excretion acting as an early marker of kidney injury.93-95
Urinary L-FABP has demonstrated to achieve AKI diagnostic levels before the elevation of
SCr, in clinical research where AKI was generated by ATN, sepsis, nephrotoxins, cardiac surgery,
and radiocontrast agents.92,96–99 In 2010, Fergurson and colleagues published a cross-sectional study
that included 92 hospitalized patients with AKI, that yielded a AUC of urinary L-FABP for
identification of AKI in comparison to controls of 0.93. 90 Additionally L-FABP was found to be a
significant independent predictor of dialysis-free survival.100
For the most part, clinical data has corroborated the benefit of L-FABP as a biomarker of
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Souto: Novel Biomarkers of AKI
AKI, even though large prospective studies and solid data on the influence of liver injury in LFABP urinary levels have not been published. Nonetheless, in 2011 the ELISA kit for urinary LFAPB detection was approved for health insurance reimbursement by the Japanese Ministry of
Health.9
4. Tubular Enzymes
4.a. Alpha-Glutathione s-Transferase and Pi-Glutathione s-Transferase
Alpha-glutathione s-transferase (α-GST) and pi-glutathione s-transferase (π-GST) belong to
a group of ubiquitous detoxification enzymes that are expressed by kidney cells but not typically
found in urine. Following injury, nephron distribution of gluthatione s-transferase isoenzymes was
studied, with α-GST found to be present in proximal cells, while π-GST was detected in distal
tubules.101
Westhuyzen and colleagues examined the benefit of single or combined measurements of
urinary tubular enzymes in predicting AKI, in a prospective pilot study, where 4 of the 26
consecutive critically ill adult patients admitted to the ICU were studied. 102 Indexed to urinary
creatinine concentration, α-GST and π-GST not only were significantly higher in the AKI group on
admission and remained elevated at 24 h but also had excellent discriminating power for AKI (AUC
of 0.893 and 0.929 respectively).102 By contrast, in a report by Walshe and coworkers that analyzed
urine samples collected over the 48 hours after ICU admission from 40 consecutive patients who
were admitted with a diagnosis of sepsis, concluded that both α-GST and π-GST enzymes were
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Souto: Novel Biomarkers of AKI
poor AKI predictors.103
Lastly, the diagnostic utility of α-GST and π-GST was evaluated during a prospective study
of 123 adults undergoing cardiac surgery by Koyner et al. 47 The prediction ability for identifying
stage 1 AKI (as defined by AKIN classification) of these enzymes was modest, with AUC of 0.59
(CI 0.47–0.71) and 0.54 (CI 0.42–0.66) for α-GST and π-GST, respectively.47
4.b. Alkaline Phosphatase and Gammaglutanyl Transpeptidase
Alkaline phosphatase (AP) and gammaglutanyl transpeptidase (GGT) are brush border
enzymes that as a consequence of damage to the brush border membrane together with damage to
the microvillous morphology show increased levels in urine.104,105
According to the study of Westhuyzen et al. tubular AP and GGT enzymuria on admission to
the ICU was useful in predicting AKI with estimated AUC of 0.950 and 0.863, respectively. 102
Conversely, Endre et al while evaluating the performance of several urinary biomarkers of AKI in
critically ill patients, reported feeble predictive performances for urine AP and GGT, with AUC of
0.56 and 0.57, respectively.58
4.c. N-acetyl-beta-D-glucosaminidase
N-acetyl-beta-D-glucosaminidase (NAG), is a lysosomal enzyme mainly present in proximal
tubules,106 that due to its molecular weight (130kDa) is not filtrated at the glomerulus. Increased
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Souto: Novel Biomarkers of AKI
excretion in urine has been described following contrast-induced toxicity107 and methotrexate
toxicity108 suggesting injury to tubular cells, although increased concentrations may also result from
increased lysosomal activity without cellular lesion.109,110
NAG enzymuria may indicate tubular injury, so its utility as a marker for either specific
segmental injury or early renal injury has been examined in diverse clinical settings. In a casecontrol study of pediatric CPB patients, (n=40, 20 patients with AKI diagnosis 72h post
intervention), the performance of NAG in diagnosing AKI showed an estimated AUC of 0.70 at 24h
after CPB, having increased within 6 h post-CPB and remaining elevated up to 48 h after surgery. 57
In adult CPB patients, in a study where 13 cases of developing AKI were detected, NAG's post
surgery prediction ability at the 2 hours time point was very moderate (AUC=0.62). 49 As for the
adult ICU patients, Westhuyzen and colleagues reported an AUC value of 0.845 (CI 0.639–0.955)
for NAG's ability to predict developing AKI.102
Conclusion
It is widely accepted that conventional clinical laboratory methods for detection of kidney
disease are not suitable for the early recognition of AKI. The broad spectrum of AKI entails a
heterogeneous and complex disease, that has a compelling need for further guided intervention,
monitoring of progression and recovery. This brief review compiled relevant studies on the
functions and properties of several auspicious molecules belonging to either functional markers,
low-molecular weight proteins, up-regulated proteins or tubular enzymes categories, emphasizing
their performance characteristics in different settings prone to AKI. Even though the basic and
clinical published data on this subject is substantial and supportive, the evidence was found to be
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Souto: Novel Biomarkers of AKI
insufficient as to which biomarkers should be recommended or how to use them, according to the
current clinical practice guidelines, written in 2012 by KDIGO's AKI work group.9
Beyond the recent scientific evidence gathered and associated with each individual
biomarker, there are several interpretative challenges in the early steps of validating markers for
clinical use in nephrology. The discovery and development of biomarkers for kidney injury may
benefit from large amounts of data and discussion available in cardiovascular literature. For cardiac
biomarkers validation, AUC's versatility often allowed for prediction of future events, nonetheless
it was found to be rather insensitive metric to measure the increasing predictive ability of a
biomarker relative to established predictors,111 highlighting the perils of over-relying on the AUC as
a measure of biomarker performance. Another undeniable limitation of kidney biomarker studies is
that they rely on SCr as gold standard in their evaluation. The failings of SCr have been detailed in
this review, but since it is not ethical nor feasible to rely on a more accurate benchmark (e.g. kidney
biopsy examination), the use of SCr is legitimate. Still, the potential risk of defining a marker as a
good performer for AKI detection that shares similar imperfections as SCr needs to be
acknowledged.
The heterogeneity of AKI indicates that a single marker may be inadequate to achieve high
diagnosis and prognosis specificity/sensitivity, in similarity to other complex acute diseases, such as
acute lung injury.112 Ideally, a panel of biomarkers will emerge from future studies, that combines
and enhances their clinical utility by for example targeting distinct nephron sites. Moreover, a
battery of biomarkers robustly validated that accurately identifies and risk-stratifies patients for the
need for dialysis or death could lead to improvement of therapeutics and outcomes of AKI in the
next decade.
Lastly, a major obstacle to the clinical utility of these set of markers is the fact that most
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Souto: Novel Biomarkers of AKI
available data has emerged from small single-centre studies in homogenous populations, therefore
still in the early stages of the validation process. 9,113 Large multi-centre prospective studies are
pressing for the validation of the temporal course of expression of AKI's biomarker for early
detection, posterior outcome, and defining respective cut-off values. Besides, a wider range of
patient populations needs to be included in these studies, including patients with pre-existing CKD,
that more often than not are excluded from smaller studies. Incorporation of these novel AKI
biomarkers by the scientific and clinical communities requires above all the demonstration of
increased diagnostic benefit over traditional markers, allowing for better patient care, which for the
time being remains to be ascertained.
Disclosure
The author has no relationship with any company neither any financial interest in the information
contained in the manuscript.
Acknowledgments
The author wishes to thank Professor Manuel Pestana, MD, PhD, for kindly accepting to review this
work, and also for leading by example, a dedicated team of nephrologists at the Faculdade de
Medicina da Universidade do Porto, that without exception, are willing to share their knowlegde
with their medical students.
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Souto: Novel Biomarkers of AKI
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34
Anexo
Normas da revista "Kidney International" para a formatação de artigos científicos.
GUIDE TO AUTHORS
Table of Contents
About the Journal
Preparation of Manuscripts
Content Types
Format of Manuscripts
Figures and Tables
Supplementary Information
Submission and Publication
Appendix
New Membership Category introduced for Members in Training
p1
p2
p2
p3
p4
p5
p6
p6
Trainees in nephrology up to the age of 37 years are now encouraged to apply to become ISN Members in Training at a greatly reduced annual membership rate of US$ 70 (all benefits included).
Eligible individuals must submit a copy of a valid form of identification
stating their date of birth as well as a proof of their current training
status to the ISN Global Headquarters together with their completed
application.
http://www.theisn.org/join
About the Journal
PUBLICATION CHARGES (Do not apply to invited authors)
For all articles accepted to Kidney International on or after January
1st 2013, the previously separate pricing structure for page and
color charges is now consolidated into a single processing fee
called ‘page charge’.
The page charge will be fully inclusive of color reproduction of all
color images (where deemed appropriate by the Editor) in print,
HTML and PDF formats. It covers also a proportion of the costs of
processing and producing the article for publication. After final
layout for publication, each page of an article will incur a fixed
charge of US$165 / £106 per page.
This new policy leads to a fairer distribution of costs across authors. Also, with the shift to digital publication, archiving and
preservation, these charges help support the following valuable
services, to the benefit of authors and the wider research community:
•
Manuscript Deposition Service: Currently available to
authors publishing original research articles. NPG’s automated manuscript deposition service enables authors
to meet the open access or public access policies of all
of the participating funders, making it simple and free for
researchers to comply.
•
Portico: Ensures that an author’s intellectual content is
preserved in perpetuity and secure in a carefully managed archive. Original source files of electronic journals
are converted to an archival format. Portico assumes responsibility for future content migrations. Full access to
NPG’s content is via the Portico web portal. The Portico
archive is open to a publisher’s complete list of scholarly
e-journals and e-books and to some d-collection.
•
CLOCKSS: Ensures long-term access to scholarly publications in digital format. As libraries migrate from print
to online-only publications, they expect assurances from
publishers that their shared investments are protected
and preserved for generations to come. The CLOCKSS
archive provides this assurance via its secure network of
content that can be accessed only when a trigger event
is deemed to have occurred. CLOCKSS is unique because it makes all content triggered from the archive
freely available to the world.
Offprints
Offprints may be ordered using the order form available for download with the proofs.
IMPACT FACTOR
2012 Impact Factor 7.916*
4/73 Urology and Nephrology
*2012 Journal Citation Reports (Thomson Reuters, 2013)
ISSN
ISSN: 0085-2538
EISSN: 1523-1755
FREQUENCY
Printed once a month. Advance Online Publication once a week.
SCOPE
Kidney International aims to inform the renal researcher and the
practicing nephrologist on all aspects of renal research, including:
•
The latest clinical studies on emerging developments in renal medicine.
•
The highest level of original research studies in clinical and
basic renal research.
•
In each issue, some articles will be highlighted by commentaries that aim to put these studies in the appropriate context. These will form a research tool for clinical and basic
investigators.
•
Editorials that highlight important issues in international
nephrology.
•
Nephrology sans Frontieres - occasional short articles that
discuss matters of local interest to nephrologists around the
world, but which we feel need to be known by nephrologists
world-wide.
•
Short reviews on hot topics and in depth reviews about major issues in renal research.
•
Controversial discussions on renal therapeutics or diagnosis written by two opposing authorities.
•
State of the Art teaching materials including clinicopathological conferences where eminent clinicians discuss
difficult or interesting cases illustrated by multiple pathology, imaging studies and charts.
•
Images in Nephrology which are presentations of interesting images in renal pathology, radiology chosen for their illustrative nature or simply for their esthetic qualities.
•
Issues of importance to the international renal community
including the politics of funding; of organ transplantation, of
adequacy of dialysis, of world-wide affordability of end
stage renal care and many other topical issues.
•
Journal Club are synopses that bring you the latest research highlights from across a wide spectrum of journals
in fields relevant to renal research.
•
Book Reviews.
1
G U I DE T O AU T H O R S
(3) Original Article
Subcategories: Basic Research, Clinical Investigation, Clinical
Trials
Word limit: 4,000 words (22,400 characters) maximum including
spaces and abstract but excluding references, tables and figures.
Abstract: 250 words (1,500 characters) maximum including spaces.
Results: Include headings about what is being tested in each individual experiment.
References: no limit
Figures/ tables: no limit. However, additional figures and tables
may be considered as supplements for Web-only publication.
Disclosure statement required (see page 3 for details)
Full-length reports of current research in either basic or clinical
science.
ABSTRACTED/ INDEXED IN
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Index Medicus/Medline
Science Citation Index
Current Contents/Life Sciences
Current Contents/Clinical Medicine
SciSearch
BIOSIS
Chemical Abstracts
EMBASE/Excerpta Medica
Reference Update
CABS
Biological Abstracts
Global Health
MDX Health Digest
EBSCO
Adonis
PASCAL
Preparation of Manuscripts
Manuscripts that do not adhere to the following instructions
will be returned to the corresponding author for technical
revision before undergoing peer review.
Content Types
The types of manuscripts accepted by KI are: (1) Review, (2) Minireview, (3) Original Article, (4) Commentary, (5) Technical Note,
(6) Letter to the Editor (7), Editorial (8), Nephrology Image, (9)
Make Your Diagnosis, (10) Book Review, (11) ISN Forefronts in
Nephrology, ISN Nexus, Meeting Report.
(1) Review
Word limit: 5,000 words (28,000 characters) maximum including
spaces and abstract but excluding references, tables and figures.
Abstract: 250 words (1,500 characters) maximum including spaces
References: no maximum
Figures/tables: 3 images or figures required
Disclosure statement required (see page 3 for details)
Reviews are comprehensive analyses of specific topics in nephrology that are usually solicited by the Editors. Proposals for reviews
should be submitted to the editorial office by email:
[email protected]; proposals submitted to Manuscript
Central will not be considered. Authors should only send an outline
of the proposed paper for initial consideration. Both solicited and
unsolicited review articles will undergo peer review prior to acceptance. Kidney International will cover charges for color images
for articles invited by the Editors, and for images in which color
was added by the journal.
(2) Minireview
Word limit: 3,000 words (16,800 characters) maximum including
spaces and abstract but excluding references, tables and figures.
Abstract: 250 words (1,500 characters) maximum including spaces
References: 20 maximum
Figures/tables: 2 images or figures required
Disclosure statement required (see page 3 for details) Minireviews
of topical and highly focused subjects are usually solicited by the
Editors. Proposals for minireviews should be sub- mitted to the
editorial office by email: [email protected]; proposals
submitted to Manuscript Central will not be considered. Authors
should only send an outline of the proposed paper for
initial consideration. Both solicited and unsolicited minireview articles will undergo peer review prior to acceptance. Kidney International will cover charges for color images for articles invited by the
Editors, and for images in which color was added by the journal.
Special Notice Regarding Clinical Trials:
Kidney International encourages the submission of manuscripts
reporting results of clinical trials and must be submitted under a
separate category under Original Articles - Clinical Trials. It is important to follow the recommendations of the International Committee of Medical Journal Editors (ICMJE), which requires that “any
research project that prospectively assigns human subjects to intervention and comparison groups to study the cause-and-effect
relationship between a medical intervention and a health outcome”
must be registered before the start of patient enrollment. Trials in
which the primary goal is to determine pharmacokinetics are exempt. A list of acceptable registries is available on the ICMJE website (http://www.icmje.org). Each manuscript will be checked upon
submission to determine whether the study has been appropriately
registered. All studies which began enrolling patients after July 1,
2005 must have been registered before patient enrollment. Any trial
which was still seeing patients on September 13, 2005, should
have been registered before September 13, 2005. If the trial was
complete before September 13, 2005, the study should be registered before submission.
Reporting of randomized controlled trials should follow the guidelines of The CONSORT Statement (http://www.consortstatement.org).
(4) Commentary [only by invitation of Editors]
Word limit: 1,500 words (8,400 characters) maximum including
spaces and abstract but excluding references
Title: 115 characters maximum including spaces
Abstract: 75 words (420 characters) maximum
References: 10 maximum including the article discussed
Figures/tables: 1 figure required (will be redrawn)
Commentaries discuss a paper published in a specific issue and
should set the problems addressed by the paper in the wider context of the field. Authors will not be charges for color images.
(5) Technical Note
Word limit: 1,500 words (8,400 characters) maximum including
abstract but excluding references, tables and figures.
Abstract: 250 words (1,500 characters) maximum including spaces
References: 20 maximum
Disclosure statement required (see page 3 for details)
Examples of appropriate subject matter include descriptions of new
laboratory or clinical methods, new apparatus, or critical modifications of established techniques. Organization of Technical Notes
should be the same as for regular manuscripts except that section
headings should be omitted.
(6) Letter to the Editor
Word limit: 250 words (1,500 characters) maximum including
spaces
Abstract: no abstract required for this manuscript type
References: 4 maximum
Figures/ tables: Up to 1
Letters to the Editor will be considered for publication, subject to
editing. Letters must contain information critical to a certain area or
must be confirmatory of data recently published in Kidney International. A Letter must reference the original source, and a Response
to a Letter must reference the Letter in the first few paragraphs, as
well as the original source. Letters can use an arbitrary title, but a
Response must cite the title of the Letter: e.g. Response to [title of
Letter]. All Letters must contain a title page including title, all au-
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thors’ names and affiliations, and corresponding author contact
information.
(7) Editorial [only by invitation of Editors]
Word Limit: 1,600 words (8,960 characters) maximum including
spaces
Abstract: no abstract required for this manuscript type
References: 5 maximum
Proposals for Editorials may be submitted; authors should only
send an outline of the proposed paper for initial consideration.
(8) Nephrology Image
Word limit: Title: 70 characters including spaces; text: 300 words
(1700 characters) including spaces
Figures: 2 single panel figures maximum. No multi-part figures
allowed.
References: none
Abstract: no abstract required for this manuscript type
Illustrative images that are unique or highly illustrative of specific
occurrences in Nephrology such as renal pathology, radiology,
specific skin lesions, etc. They should be accompanied by a brief
one-paragraph description of relevant clinical information. Article
must fit onto one page. You will be asked to cut text or part of your
figure in the proof if article is longer than one page.
(9) Make Your Diagnosis
Word limit: Title: 70 characters; The Case (page 1): 245 words
(1,400 characters); The Diagnosis (page 2): 405 words (2,300
characters). Word limits include spaces but exclude references,
tables and figures.
Abstract: no abstract required for this manuscript type
References: 3 maximum
Figures/tables: 1 single panel figures maximum per page
This column provides readers with an opportunity to make clinical
diagnoses based on an image accompanied by the history and
physical exam, all of which will be on the first page. The second
page will include the answers, a brief discussion and any other
relevant follow up images and laboratory data.
(10) Book Review
Word limit: 500-1000 words including spaces, excluding references
Abstract: no abstract required for this manuscript type
References: 3 maximum
Book Reviews alert readers to work that is potentially important to
the field of nephrology, and puts it in context with the nephrology
literature. Book Reviews should follow this outline: (a) exact title of
book, full name(s) of author(s), publisher’s name, publication date,
number of pages and price, (b) summary of the content (general
discussion of what the book covers and its major topics; NOT a
chapter by chapter summary), (c) discussion of author(s) (for example, background, experience, why they are qualified to write the
book and whether they present a certain view), (d) strong points of
the book, (e) weak points of the book, (f) identification of the audience of this book and the background needed for the reader to
understand its contents, (g) discussion of why one should or
should not buy the book, and if yes, for what purpose (as a text, a
reference, etc.), (h) comparison to other books in the field, and (i) if
possible, a “quotable quote” or annotation regarding the book.
(11) ISN Forefronts in Nephrology, ISN Nexus, Meeting Report
[only by invitation of Editors]
Word limit: To be determined in consultation with Editors
Abstract: 150 words (1500 characters) maximum including spaces,
excluding references and figures.
References: no maximum
Figures/tables: at least 1 image or figure
Disclosure statement required (see page 3 for details)
These authoritative proceedings of specific topics in nephrology
are usually solicited by the Editors. Proposals may be submitted;
authors should only send an outline of the proposed paper for
initial consideration. Both solicited and unsolicited articles will undergo peer review prior to acceptance. Kidney International will
cover charges for color images in articles invited by the Editors.
Format of Manuscripts
GENERAL FORMAT
Manuscripts must be typed in English and double-spaced. All text
including legends, footnotes, tables and references are to be on
one side of the page only. All manuscript pages must be numbered.
Title page
This should include (a) the complete manuscript title; (b) all authors’ full names (listed as first name, middle initial, last name),
highest academic degrees, and affiliations; (c) the name and address for correspondence, fax number, telephone number, and email address; and (d) the sources of support that require acknowledgment. A running headline of no more than 50 characters (including spaces) should be supplied.
Abstract and Keywords
The abstract should be no longer than 1500 characters including
spaces, stating the main problem, methods, results, and conclusions. There should be no subheadings in the abstract. It must be
factual and comprehensive. The use of abbreviations and acronyms should be limited and general statements (e.g. ‘‘the significance of the results is discussed’’) should be avoided. The editors
reserve the right to edit the title and abstract to conform to journal
style.
Text
The manuscript should be organized under the following nine headings:
 Title Page
 Abstract
 Introduction
 Results
 Discussion
 Methods
 Disclosure
 References
 Acknowledgements
Abbreviations
Abbreviations should be defined at the first mention in the text and
in each table and figure. For a list of standard abbreviations, please
consult the Council of Biology Editors Style Guide (available from
the Council of Science Editors, 9650 Rockville Pike, Bethesda, MD
20814) or other standard sources. Write out the full term for each
abbreviation at its first use unless it is a standard unit of measure.
Refrain from overuse of abbreviations.
Disclosure
For original articles and reviews only, the submitting author must
include a disclosure statement in the body of the manuscript. The
statement will describe all of the authors’ relationships with companies that may have a financial interest in the information contained
in the manuscript. This information should be provided under the
heading titled ‘Disclosure,’ which should appear after the ‘Methods’
section and before the ‘References’ section. The absence of any
interest to disclose must also be stated. In addition, any financial
interests must be detailed in the Financial Disclosure form, which
will be provided to the corresponding author upon acceptance for
distribution to each author.
References
References should be listed in order of appearance (Vancouver
style). In the text, number references in order of appearance using
Arabic numerals (e.g. 1, 2, 3) in parentheses for citations. The
reference list (starting on a separate page) should contain the references in the order in which they are cited in the text. Only published works (as well as manuscripts already accepted for
publication) which are referred to in the text should be listed in the
reference list. The reference list must not contain any abstract
citations, unpublished observations, personal communications, etc.
Kindly cite such sources solely within the text (in parentheses), not
in the reference list. Do not list more than three authors per reference. Should there be four or more, please include only the first
three followed by ‘‘et al.’’
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The following examples demonstrate correct reference style:
Journal articles:
Fan SL-S, Almond MK, Ball E, et al. Pamidronate therapy as prevention of bone loss following renal transplantation. Kidney Int
2000; 57: 684–690.
Supplement articles:
Fogo AB. Glomerular hypertension abnormal glomerular growth,
and progression of renal diseases. Kidney Int 2000; 57 (Suppl 75):
S15–S21.
5. Replication of the association in an independent cohort is required for new association findings.
6. Priority will be given to studies that demonstrate a specific effect
of the associated polymorphism on the expression or function of
the relevant genes. A convincing biological validation will be considered in lieu of the replication requirement.
MICROARRAY DATA
Books:
Lameire N, Mehta RL (eds.). Complications of Dialysis. Marcel
Dekker, Inc.: New York, 2000.
Authors submitting manuscripts containing microarray data must
submit the data to the Gene Expression Omnibus
(http://www.ncbi.nlm.nih.gov/geo/) or ArrayExpress
(http://www.ebi.ac.uk/arrayexpress/) databases, and provide the
accession number(s) upon submission to the journal. The data
must be MIAME-compliant, with all variables completed.
Articles in books:
Weidner N, Buckalew VM Jr. Sickle cell anemia, sickle cell trait,
and polycythemic states, in Renal Pathology (vol 2), eds. Tisher
CC, Brenner BM. JB Lippincott Company: Philadelphia, 1989, pp
1417–1436.
STYLE
ORIGINALITY
A submitted manuscript must be an original contribution not previously published (except as an abstract or preliminary report), must
not be under consideration for publication elsewhere, and, if accepted, must not be published elsewhere in a similar form, in any
language, without the consent of the ISN. Each person listed as an
author is expected to have participated in the study to a significant
extent and agrees with submission of the paper for publication.
Although the editors and referees make every effort to ensure the
validity of published manuscripts, the final responsibility rests with
the authors, not with Kidney International, its editors, the International Society of Nephrology or Nature Publishing Group.
INFORMED CONSENT AND ETHICS
When reporting experiments on human subjects, indicate whether
the procedures were in accordance with the ethical standards of
the responsible committee on human experimentation (institutional
or regional) or with the Helsinki Declaration of 1975 (and as revised in 1983) and in the case of renal transplant the Declaration of
Istanbul (as published in KI Vol. 74 No. 7 [2008]). Include any Institutional Review Board or Animal Care and Use Committee protocol
numbers as warranted by experimental design. Kidney International will not consider manuscripts containing data derived from
transplants obtained from executed prisoners. If authors wish to
submit a manuscript related to this issue such as an editorial or
review examining the consequences of such practices, they must
contact the Editorial Office to obtain permission prior to submitting
the manuscript.
GUIDELINES FOR STUDIES OF DNA POLYMORPHISMS
For case-control studies investigating associations between DNA
sequence polymorphisms and renal phenotypes the following review criteria will be considered in prioritizing manuscripts for publication:
1. Adequate sample size and explicit power calculation are required for all submitted manuscripts. Negative studies have to be
adequately powered in order to be considered for publication.
2. Appropriate correction of p-values for multiple comparisons is
also required. In many cases this will involve calculation of empiric
p-values by permutation.
3. Typing multiple markers within a locus of interest is preferred
over studies that examine a single polymorphism. Defining risk
haplotypes and performing haplotypic association tests is encouraged.
4. Assessment and correction for possible population stratification
are strongly encouraged, unless the analysis involves a method
that is robust to stratification effects (eg. transmissiondisequilibrium testing).
The American Medical Association Manual of Style (9th edition),
Stedman’s Medical Dictionary (27th edition) and Merriam Webster’s Collegiate Dictionary (10th edition) should be used as standard references. Refer to drugs and therapeutic agents by their
accepted generic or chemical name, and do not abbreviate them (a
proprietary name may be given only with the first use of the generic
name). Code numbers should be used only when a generic name
is not yet available (the chemical name and a figure giving the
chemical structure of the drug are required). Copyright or trade
names of drugs should be capitalized and placed in parentheses
after the name of the drug. Names and locations (city and state in
USA; city and country outside USA) of manufacturers of drugs,
supplies, or equipment cited in a manuscript are required to comply
with trademark law and should be provided in parentheses. Quantitative data may be reported in the units used in the original measurement, but SI units are preferred, including those applicable to
body weight, mass (weight) and temperature.
Journal style
As the electronic submission will provide the basic material for
typesetting, it is important that papers are prepared in the general
editorial style of the journal.
1. For information on labeling figures, see the artwork
guidelines: http://www.nature.com/aj/artworkguidelines.pdf
2. Do not make rules thinner than 1 pt (0.36mm)
3. Use a coarse hatching pattern rather than shading for tints
in graphs
4. Color should be distinct when used as an identifying tool
5. Use SI units throughout
6. Spaces, not commas, should be used to separate thousands
7. Abbreviations should be preceded by the words for which
they stand in the first instance of use in the text. Overuse of
abbreviations in the text is discouraged
8. No abbreviations should be used in the title or the
abstract
9. The abstract should be written as a single paragraph; do
not include headings
10. Text should be double spaced with a wide margin
11. At the first mention of a manufacturer, the town (state if
USA) and country should be provided
FILE FORMATS
Manuscripts
Use Microsoft Word for the text of your article. Files in MS Office
2007 format cannot be accepted for publication. For instructions on
how to save MS Office 2007 files in a format acceptable for publication, please see the Appendix.
Figures, Images and Tables
Figures and images should be labeled sequentially, numbered and
cited in the text. Figures should be referred to specifically in the text
of the paper but should not be embedded within the text. Each
table should be double-spaced on a separate sheet and numbered
consecutively in the order of first citation in the text. Make sure that
each table is cited in the text. Tables must be submitted as Microsoft Word documents. Do not use internal horizontal and verti-
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cal lines. The use of three-dimensional histograms is strongly discouraged when the addition of the third dimension gives no extra
information. If a table or figure has been published before, the
authors must obtain written permission to reproduce the material in
both print and electronic formats from the copyright owner and
submit the permission with the manuscript. This rule applies for
quotes, illustrations and other materials taken from previously
published works not in the public domain. The original source
should be cited in the figure caption or table footnote.
For more information on image integrity and standards, please visit
http://www.nature.com/authors/policies/image.html.
Legends and Titles
Legends must be submitted for all figures and images, and titles
for all tables. They should be brief and specific, double spaced,
and placed on a separate sheet titled ‘Titles and legends’ after the
Reference section. Use scale markers in the image for electron
micrographs and indicate the type of stain used. Place explanatory
matter of tables in the footnotes rather than in the titles.
ARTWORK GUIDELINES
Detailed guidelines for submitting artwork can be found by downloading the guidelines PDF:
http://www.nature.com/aj/artworkguidelines.pdf. Using the guidelines, please submit production quality artwork with your submission. At submission, all figures must be high enough quality (no
less than 300 dpi) to be assessed in the peer review process. We
prefer artwork to be submitted in eps, .jpg, .ppt, or .tif format. .pdf
or Corel Draw format is discouraged. If you have not followed the
artwork guidelines, we will require artwork to be resubmitted if your
paper is accepted for publication.
Minimum Resolutions: Halftone images 300 dpi (dots per
inch)
Color images 300 dpi saved as CMYK
Images containing text 400 dpi
Line art 1000 dpi
Sizes:
Figure Width – single image
86mm (Should be able to fit into a single column of the printed journal)
Figure Width – multi-part image
178mm (Should be able to fit into a double column of the
printed journal)
Text Size
8 point (Should be readable after reduction – avoid large type
or thick lines) Line Width Between 0.5 and 1 point
Supplementary Information
Supplementary information is peer-reviewed material directly relevant to the conclusion of an article that cannot be included in the
printed version owing to space or format constraints. It is posted on
the journal’s web site and linked to the article when the article is
published and may consist of data files, graphics, movies or extensive tables. The printed article must be complete and selfexplanatory without the supplementary information. Supplementary
information enhances a reader’s understanding of the paper, but is
not essential to that understanding. Supplementary information
must be supplied to the editorial office in its final form for peer
review. On acceptance, the final version of the peer-reviewed supplementary information should be submitted with the accepted
paper. To ensure that the contents of the supplementary information files can be viewed by the editor(s), referees and readers,
please also submit a ‘read-me’ file containing brief instructions on
how to use the file.
If your manuscript or any significant part of it has been under consideration for publication elsewhere, or has appeared elsewhere in
a manner that could be construed as a prior or duplication publication of the same, or very similar, work, the said material must be
included and marked appropriately as a supplemental file.
Supplying supplementary information files
Authors should ensure that supplementary information is supplied
in its FINAL format as it is not copy edited and will appear online
exactly as originally submitted. It cannot be altered, nor new supplementary information added, after the paper has been accepted
for publication. Please supply the supplementary information via
the electronic manuscript submission and tracking system, in an
acceptable file format (see below). Authors should: include a text
summary (no more than 50 words) to describe the contents of each
file; identify the types of files (file formats) submitted and include
the text ‘Supplementary information is available at Kidney International’s website’ at the end of the article and before the references.
Accepted file formats
Quick Time files (.mov), graphical image files (.gif), HTML files
(.html), MPEG movie files (.mpg), JPEG image files (.jpg), sound
files (.wav), plain ASCII text (.txt), MS Word documents (.doc),
Postscript files (.ps), MS Excel spreadsheet documents (.xls) and
PowerPoint files (.ppt). We cannot accept TeX and LaTeX.
File sizes must be as small as possible so that they can be downloaded quickly. Images should not exceed 640 x 480 pixels but we
would recommend 480 x 360 pixels as the maximum frame size for
movies. We would also recommend a frame rate of 15 frames per
second. If applicable to the presentation of the supplementary information, use a 256-color palette. Please consider the use of lower specification for all of these points if the supplementary
information can still be represented clearly. Our recommended
maximum data rate is 150 KB/s.
The number of files should be limited to eight, and the total file size
should not exceed 8 MB. Individual files should not exceed 1 MB.
Please seek advice from the editorial office before sending files
larger than our maximum size to avoid delays in publication.
Further questions about the submission or preparation of supplementary information should be directed to the editorial office.
Protocol Exchange
Kidney International encourages authors of accepted manuscripts
to upload the step-by-step protocols used in their manuscripts to
the Protocol Exchange. Protocol Exchange is an open online resource that allows researchers to share their detailed experimental
know-how. All uploaded protocols are made freely available, assigned DOIs for ease of citation and fully searchable through nature.com. By uploading your Protocols to Protocol Exchange, you
are enabling researchers to more readily reproduce or adapt the
methodology you use, as well as increasing the visibility of your
work. Further information about Protocol Exchange is available at:
www.nature.com/protocolexchange/about.
Open Access
Authors of accepted original research papers may choose to pay
an article processing charge in order for their article to be published
open access. The article processing charge is £2,000 / $3,200 /
€2,300 (plus VAT where applicable) and can be paid via credit card
or by requesting an invoice be raised. This charge is in addition to
any standard publication charges, such as those for color images.
By paying the article processing charge, authors are permitted to
post the final, published PDF of their article on a website, institutional repository or other free public server immediately on publication.
Upon acceptance, it is mandatory that authors fill out and send
back the payment form along with their license to publish form. The
license form has been amended to offer authors the choice of one
of two Creative Commons licenses to use on their paper.
The Creative Commons Attribution-Noncommercial-No Derivative
Works 3.0 Unported License allows readers to download the article
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and share it with others. Users must attribute the work to the author and link back to the original article. The article cannot be
changed in any way or used commercially.
The Creative Commons Attribution Noncommercial Share Alike 3.0
Unported License allows readers to alter, transform, or build upon
the article and then distribute the resulting work under the same or
similar license to this one. The work must be attributed back to the
original author and commercial use is not permitted.
For further information please see the FAQs
(http://www.nature.com/ki/open_access_faqs.html), payment form
(http://www.nature.com/licenceforms/ki/ki-apc-form.pdf) and
License to Publish form (http://www.nature.com/licenceforms/ki/kiltp-cc-sa-nd.pdf)
Please note that usual credit terms require payment within 30 days
of receipt of invoice. Failure to pay your invoice within the stated
credit terms will rescind the open access option for your article and
the paper will be placed behind the paywall.
Submission and Publication
SUBMISSION OF PAPERS
If you are ready to submit an article please visit the Online Submission page: http://mc.manuscriptcentral.com/ki.
All text should be submitted in Microsoft Word (.doc) and
figures as .tif or .jpg files
Figures appearing in the online version of manuscripts will be published in 72 dpi as is standard for all .pdf files on the internet. All
figures published in print are at least 300 dpi.
LICENSE TO PUBLISH
The corresponding author must complete and sign the License to
Publish form upon acceptance of the manuscript and return it to
the editorial office. Failure to do so will result in delays to the publication of your paper. A copy of the License to Publish form can be
found under “Instructions & Forms” on the online submission page:
http://mc.manuscriptcentral.com/ki
The International Society of Nephrology does not require authors of original research papers to assign copyright of their published contributions. Authors grant the International Society of
Nephrology an exclusive license to publish, in return for which
they can re-use their papers in their future printed work. Authors
are encouraged to submit their version of the accepted, peerreviewed manuscript to their funding body's archive for public release six months after publication. In addition, authors are encouraged to archive their version of the manuscript in their institution's
repositories (as well as on their personal web sites), also six
months after the original publication. Authors should cite the publication reference and DOI number on any deposited version, and
provide a link from it to the published article on the NPG website.
This policy complements the policies of the US National Institutes
of Health, the Wellcome Trust and other research funding bodies
around the world. NPG recognizes the efforts of funding bodies to
increase access to the research they fund, and strongly encourages authors to participate in such efforts.
More information is available online at the following link:
http://www.nature.com/authors/editorial_policies/license.html
ADVANCE ONLINE PUBLICATION
All original articles and reviews are published ahead of print on
Advance Online Publication. This will be the final version of the
manuscript and will subsequently appear, unchanged, in print.
PUBLIC ACCESS POLICY
Nature Publishing Group and Kidney International support the public access policy but are not able to deposit accepted manuscripts
for the authors at this time. Authors are allowed (without requesting
permission) to deposit the accepted (i.e., untypeset, uncopyedited)
version of their accepted manuscripts in PubMed Central. You can
deposit your manuscript here: http://www.nihms.nih.gov.
PROOFS
An e-mail will be sent to the corresponding author with a URL link
from where proofs can be collected. Proofs must be returned by fax
within 48 hours of receipt. Failure to do so may result in a delay to
publication. Extensive corrections cannot be made at this stage.
BUSINESS MATTERS
For contact information regarding business correspondence and
inquiries such as advertising, subscriptions, permissions, papers in
production or publishing a supplement, please visit our publisher’s
contacts page at http://www.nature.com/ki/contact_npg.html.
Alternatively, you can write to: Kidney International, Academic
Journals Division, Nature Publishing Group, 75 Varick Street, 9th
Floor, New York, NY 10013, USA.
Appendix
SAVING FILES WITH MICROSOFT OFFICE 2007
MS Office 2007 saves files in an XML format by default (file extensions .docx, .pptx and .xlsx). Files saved in this format cannot currently be
accepted for publication.
Save Word documents using the file extension .doc
•
Select the Office Button in the upper left corner of the Word 2007 window and choose “Save As”
•
Select “Word 97-2003 Document”
•
Enter a file name and select “Save”
These instructions also apply to the 2007 version of Excel and PowerPoint.
Equations in Word must be created using Equation Editor 3.0
Equations created using the new equation editor in Word 2007 and saved as a “Word 97-2003 Document” (.doc) are converted to graphics
and can no longer be edited. To insert or change an equation with the previous equation editor:
•
Select “Object” on the “Text” sections of the “Insert” tab
•
In the drop-down menu, select “Equation Editor 3.0”
Do not use the “Equation” button in the “Symbols” section of the “Insert” tab.
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