4/28/2010 Scoring Systems for severity of illness: Why and what Mohan Mysore, MD, FCCM Children’s Hospital & Medical Center Omaha, Nebraska USA Why do we need scoring systems ? Large randomized control trials are gold standard d d Expensive Might not always be feasible Alternative is observational methods/studies Need to consider patient characteristics before any inferences can be drawn Need to “adjust for case mix” 1 4/28/2010 Need a common language Outcome: Definition A measurable change in health or other relevant status Outcome should be tied to something of interest Outcomes could be: Short-term Short Intermediate Long Long--term 2 4/28/2010 Outcomes determined/impacted by: Input I t (equipment, ( i t staff) t ff) Processes of care (type, skill and timing of care) Case mix of patients Type of facility Underlying y g disease processes (eg Bone marrow transplant) Another way to classify: E i Environmental t l factors f t Unit characteristics Provider characteristics Organizational characteristics Inter--organizational Inter g charactersitics Outcomes - categories Perceptual outcomes: P ti t-family PatientPatient f il satisfaction ti f ti Clinical outcomes: Change in clinical parameters Morbidity Mortality Functional outcomes Financial outcomes: Effi i Efficiency Length of stay Cost Resource utilization 3 4/28/2010 A word about mortality….. Mortality in a particular disease might be low (with py), but morbidityy might g be significant g intensive therapy), and have longlong-term impact Outcome measures other than mortality might need to be looked at: Ventilator free days Organ failure Days of vasopressor use Disability metrics: Pediatric Overall Performance Category (POPC) and Pediatric Cerebral Performance Category (PCPC) scores Reference: Fiser DH: Assessing the outcome of pediatric intensive care. J Peds 1992;121;681992;121;68-74 Scoring systems Aimed at quantifying case mix and using resultant l score to estimate i outcome Provide a standard by which patient severity of illness can be gauged Permits stratification of patients to determine outcomes – such as riskrisk-adjusted mortality Particularly beneficial if large and diverse patient populations are being studied 4 4/28/2010 Types of scoring systems Specific or Generic Anatomical: Extent of injury; usually fixed Physiological: Impact of injury on function; score may change based on effect of injury Physiology--based systems: Physiology Neonatal: APGAR, CRIB Pediatric: PRISM, PIM Cardiac: CCOS Adult: APACHE, TISS, MPM etc. Each system is designed for a specific patient population. No “one size fits all” Glasgow Coma Scale Motor Obeys y commands Localizes to pain Flexes to pain Abnormal flexion Abnormal extension No response 6 5 4 3 2 1 Score Ranges from 33--15 Has been studied extensively and validated – corresponds to outcome. Verbal Oriented Confused Words only Sounds only No response 5 4 3 2 1 Eye Opening Spontaneous To speech To pain No response 4 3 2 1 5 4/28/2010 TISS Therapeutic Intervention Scoring System (TISS): 1974 Q Quantify if severity i off illness ill among ICU patients i b based d on type and amount of treatment recd. Sicker the patient, greater the complexity of treatment Provides a proxy measure of the severity of illness for a patient Simplified version based on 28 therapeutic activities (TISS 28) APACHE score Acute Physiology and Chronic Health Evaluation Mid--1970s Mid 1970 – Dr.William D Willi K Knaus 34 Physiological variables which impact outcome APACHE II (1985): Narrowed down to 12 parameters. Points assigned to each variable according to its most abnormal value in first 24 hours. Score range: 00-71 Updated to APACHE III (1991) 6 4/28/2010 0 Pediatric Trauma Score Variables (help) Value Points Weight (kg) Systolic BP (mmHg) Mental status Airway Skeletal Open wounds Score . .............. References TEPAS JJ et coll. The Pediatric Trauma Score as a predictor of injury severity in the injured child. J. Pediat. Surg. 1987;22:14-8. RAMENOFSKY M et coll. The Predictive Validity of the Pediatric Trauma Score. J. Trauma 1988;28:1038-42. PRISM – Pediatric Risk of Mortality Data collected during first 24 hours in the PICU Age in months Post--operative state Post Revised to PRISM III (proprietary) Reference: Pollack MM et al: Pediatric Risk of Mortality score: Crit Care Med 1988:16:1110--6 1988:16:1110 Systolic BP Diastolic BP HR RR PaO2/FiO2 PaCO2 PT/PTT Total bilirubin Calcium Potassium Glucose HCO3 Pupillary reaction GCS 7 4/28/2010 PRISM III and PICUEs PRISM III and PICUEs 8 4/28/2010 PIM – Pediatric Index of Mortality A new pediatric-specific score introduced in 1997 PIM2 (Pediatric Index of Mortality) • Systolic Blood Pressure * • Pa02 * • Fi02 * • Base Excess * • Weight (kg) * • Height (cm) * • Pupillary Reactions * • Mechanical Ventilation * • Elective Admission to ICU * • Recovery from Surgery or a Procedure is the Main Reason for ICU Admission * • Admitted Ad itt d Following F ll i Cardiac C di Bypass B * • High Risk Diagnosis * • Low Risk Diagnosis * Shann F, Pearson G, Slater A, et al: Paediatric index of mortality (PIM): A mortality prediction model for children in intensive care.Intensive Care Med 1997; 23:201–207 Variables (help) Values (1 if Yes, 0 otherwise) Beta Elective admission Recovery post procedure Cardiac bypass High risk diagnosis Low risk diagnosis No response of pupils to bright light (> 3 mm and both fixed) Mechanical ventilation (at any time during first hour in ICU) Systolic Blood Pressure (mmHg) 0.01395 Base Excess (mmHg) (arterial or capillary blood) 0.1040 FiO2*100/ PaO2 (mmHg) 0.2888 .. Predicted Death Rate : . ... .. . Logit = (-4.8841) + (values * Beta) + (0.01395 * (absolute(SBP-120))) + (0.1040 * (absolute base excess)) + (0.2888 * (100*FiO2/PaO2)) Predicted death rate = eLogit/ (1+eLogit) Reference A. Slater et al. PIM 2 : a revised version of the Paediatric Index of Mortality. Intensive Care Med 2003 ;29:278-85. 9 4/28/2010 PRISM and PIM Studies have compared the two systems in the same ggroups p of patients p 303 pts. over 9 month period PRISM III at 12h and 24h and PIM Expected mortality: 6.96% by PRISM III at 12h and 6.95% at 24h versus 7.5% based on PIM Showed them to be adequate indicators of mortality pr b bilit in probability i a PICU population p p l ti Reference: Gemke RJ and vanVught J in Intensive Care Medicine 2002 Feb 28(2): 204204-7 PRISM and PIM 2-phase prospective observational study conducted in 10 PICUs in Australia and NZ Phase 1: 1997 1997--99: PIM, PRISM and PRISM III Phase 2: 2000 2000--01: PIM 2 26,966 patients (<16 yrs) Compared number of observed to predicted deaths in different diagnostic and risk groups Results: PIM 2 was most accurate with no difference between observed and predicted mortality. P PIM M ((116%), 6%), PRISM PR SM III (130%) and PRISM (189%) all overestimated mortality Reference: Slater A, Shann F and ANZICS Pediatric study group in Pediatric Crit Care Med 2004 Sep; 5(5): 447447-54 10 4/28/2010 SAPS and MPM Simplified Acute Physiology Score Updated to SAPS II in 1993 Mortality Prediction Model (MPM) Organ Failure scoring systems Take into account severity of dysfunction in each organ system and its effect on prognosis of dysfunction in several organ systems Need constant updating since therapies and outcomes evolve and improve PLOD: Pediatric Logistic Organ Dysfunction score. Looks L k at 6 organ systems andd gives i each ha score based on physiologic/lab data. Refrence: Leteurtre S. et al. Validation of the paediatric logistic organ dysfunction (PELOD) score: prospective, observational, multicentre study. Lancet. 2003 Jul 19;362(9379):19219;362(9379):192-7 11 4/28/2010 P-MODS Pediatric Multiple Organ Dysfunction Score Looks at 5 parameters: PaO P O2/FiO2 Lactic Acid Bilirubin BUN Fibrinogen Reference: Graciano AL et al: The Pediatric Multiple Organ Dysfunction Score (P(P-MODS): development and validation of an objective scale to measure the severity of multiple organ dysfunction in critically ill children. Crit Care Med 2005 Jul;33(7):1484Jul;33(7):1484-91 Composite Clinical Outcome Score New score developed by Children’s Hospital, Boston Predictive validity of CCOS to predict LOS and Psychomotor Development Index at 1year after cardiac surgery 711 infants from 19881988-2004 Patients placed into 4 groups: D-TGA ggroup p Conotruncal group VSD group High--risk diagnoses (HLHS) High 12 4/28/2010 Composite Clinical Outcome Score (CCOS) Clinical Variable Score 0 1 2 Time Ti untilil first fi negative i fluid fl id balance b l <3 44-5 >6 Time until sternal closure <2 33--4 >5 Time until first extubation <4 55-8 >9 Death/Use of ECMO 7 Results: I Increase in i CCOS by b 1 increased i d LOS andd likelihood lik lih d off still ill being in the hospital at any point in time by 62% CCOS significantly predictive of 1 year PDI Yerlagadda V et al: Pediatr Crit Care Med.2006 Vol 7 No 6 Selecting a scoring system Main criteria: Proposed use Accuracy Validity of score Reliability of score G d Goodness off fit fi Discrimination of scoring system Calibration of scoring system 13 4/28/2010 Roles of scoring systems Evaluative research Outcome prediction* Clinical management of individual patients* Comparative studies of efficiency, outcomes In concluding… Scoring systems are getting more sophisticated while at the same time, becoming simpler to apply Newer systems are more accurate in predicting outcome The calculation of a risk assigned to a measured score is an epidemiologic tool. Still only provide probabilities and do not accurately predict whether an individual patient will survive Should not be used alone to determine outcome of critical care Scoring systems will need to be dynamic and require updating/recalibration Inter--observer variability remains an issue and is an important Inter factor which needs to be taken into consideration (Ref: Keulen J, Polderman K: Reliability of PRISM and PIM scores in paediatric intensive care) 14 4/28/2010 Shukran 15
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