Evaluation of a Modified Sanitary Napkin as
a Sample Self-Collection Device for the
Detection of Genital Chlamydial Infection in
Women
Michel Alary, Céline Poulin, Céline Bouchard, Michel
Fortier, Gilles Murray, Suzanne Gingras, Michel Aubé and
Carol Morin
J. Clin. Microbiol. 2001, 39(7):2508. DOI:
10.1128/JCM.39.7.2508-2512.2001.
These include:
REFERENCES
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JOURNAL OF CLINICAL MICROBIOLOGY, July. 2001, p. 2508–2512
0095-1137/01/$04.00⫹0 DOI: 10.1128/JCM.39.7.2508–2512.2001
Copyright © 2001, American Society for Microbiology. All Rights Reserved.
Vol. 39, No. 7
Evaluation of a Modified Sanitary Napkin as a Sample
Self-Collection Device for the Detection of Genital
Chlamydial Infection in Women
´ LINE POULIN,1 CE
´ LINE BOUCHARD,3 MICHEL FORTIER,3
MICHEL ALARY,1,2* CE
4
´ ,5 AND CAROL MORIN5
GILLES MURRAY, SUZANNE GINGRAS,4 MICHEL AUBE
1
´ pide´miologie de l’Universite´ Laval,
Direction Re´gionale de la Sante´ Publique de Que´bec, Groupe de Recherche en E
Centre de Recherche,2 and Departments of Obstetrics and Gynaecology,3 Microbiology,4 and Pathology,5
Ho
ˆpital du St-Sacrement du Centre Hospitalier Affilie´ Universitaire de Que´bec, Que´bec, Canada
Received 20 November 2000/Returned for modification 22 February 2001/Accepted 2 May 2001
Chlamydia trachomatis infection is the most frequently reported sexually transmitted disease in the industrialized countries. The association of this infection with transmission of
human immunodeficiency virus infection, pelvic inflammatory
disease, infertility, ectopic pregnancy, and chronic pelvic pain
(10, 20, 30) constitutes a major public health concern. Because
most infected women have no specific symptoms or are asymptomatic, screening programs represent one of the main approaches to control this infection (20, 21).
The current literature provides very good information on the
value of gene amplification techniques, such as PCR or ligase
chain reaction, for the detection of C. trachomatis in the lower
genital tracts of women. Both technologies have been evaluated in depth using endocervical swab or urine samples. With
a specificity higher than 98%, the sensitivity of PCR on either
cervical specimens or urine samples varies from 80.0 to 100%
(4, 12, 18, 19, 27, 28).
More recently, detection of chlamydial infection by these
techniques has also been assessed on secretions recovered
from vaginal introitus collected by clinicians or patients themselves (2, 5, 9, 15, 16, 22, 26, 31, 33) or from vaginal tampons
(13, 23–25). Urine and self-collected samples represent easy
and noninvasive techniques compared to the usual cervical
swabbing, which necessitates vaginal speculum insertion and a
gynecologic examination. In a study, as many as 60% of chlamydia-infected adolescents would have been missed if the
urine screening program had not been in place, because they
refused the gynecologic examination (14). In addition, specimens may be collected in nontraditional medical settings, such
as community centers and schools, and eventually at home (6,
11, 15, 17). Although these methods have been shown to be
relatively easy to use and sensitive for the detection of C.
trachomatis, some women failed to collect adequate specimens
or did not feel at ease with the technique (2, 16, 31). The
objective of the present study was to evaluate a modified sanitary napkin (Ezy-Detek [EDI] Inc., Sillery, Canada) as a specimen self-collection device for detection of chlamydial infection in women. Results of PCR tests on sanitary napkin
specimens were compared with those for endocervical and
urine specimens obtained from the same women.
MATERIALS AND METHODS
Study population and specimen collection. The study population consisted of
women at different medical or community settings in Quebec City. Women were
recruited through family-planning clinics, teen clinics, and a public juvenile
facility health service. Each of these women had a gynecologic examination, and
an endocervical swab specimen was taken for C. trachomatis detection as part of
the medical visit. In order to include a sufficient number of infected women,
physicians from private medical clinics who received positive chlamydia test
results for their patients were also invited to collaborate by asking infected
women to participate in the study before treatment.
After giving written informed consent, participants were asked to complete an
anonymous short questionnaire on risk behavior and medical history and to
* Corresponding author. Mailing address: Centre de Recherche,
Ho
ˆpital du Saint-Sacrement du CHA, 1050, chemin Ste-Foy, Que´bec
(Qc), Canada G1S 4L8. Phone: (418) 682-7387. Fax: (418) 682-7949.
E-mail: [email protected].
2508
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A modified sanitary napkin was compared with endocervical swab and urine specimens for the detection of
urogenital Chlamydia trachomatis infection. Endocervical swabs and/or first-catch urine were collected from 510
women at medical or community settings in Quebec City. Participants were also asked to wear a modified
sanitary napkin (Ezy-Detek) during 4 consecutive hours and to bring it back to the clinic or mail it to the
laboratory. Endocervical and urine specimens were tested using the Cobas Amplicor CT/NG assay (Roche
Diagnostic Systems) according to the manufacturer’s instructions, as were specimens collected with the napkin
after adequate preparation. If the PCR test result was positive on the endocervical sample or on any two
samples, a woman was considered to be infected. PCR testing results on paired samples were identical for 493
(96.6%) of 510 women. According to the definition given above, 58 (11.3%; 95% confidence interval [CI], 8.7 to
14.5%) women were infected with C. trachomatis. The sensitivity and specificity of PCR testing on modified
sanitary napkin specimens were, respectively, 93.1% (54 of 58; 95% CI, 83.3 to 98.1%) and 98.9% (447 of 452;
95% CI, 97.4 to 99.6%) compared to 81.0% (47 of 58; 95% CI, 68.6 to 90.1%) and 100% (451 of 451; 95% CI, 99.2
to 100%) for urine specimens. The positive and negative predictive values were, respectively, 91.5% (54 of 59)
and 99.1% (447 of 451) for the sanitary napkin specimens compared to 100% (47 of 47) and 97.6% (451 of 462)
for urine samples. These results suggest that a modified sanitary napkin represents an effective noninvasive
device for self-collection of specimens to detect urogenital C. trachomatis infection.
VOL. 39, 2001
C. TRACHOMATIS DETECTION IN SANITARY NAPKIN SPECIMENS
assume any gold standard (29). According to each definition, relative sensitivity
and specificity, 95% confidence intervals (95% CI), and the positive and negative
predictive values for PCR tests on sanitary napkin, urine, and endocervical swab
specimens were calculated. The sensitivity and specificity of PCR on each type of
specimen were also calculated according to the latent class model.
RESULTS
From September 1999 to May 2000, 510 women participated
in the study: 246 (48.2%) were recruited through medical clinics, among whom 24 were enrolled after laboratory-diagnosed
but untreated chlamydial infection; 157 (30.8%) were high
school students; and 107 (20.9%) were incarcerated adolescents or street youth. Another 54 women (39 from medical
clinics, 10 from high school, and 5 street youth or incarcerated
adolescents) who provided endocervical and/or urine specimens were excluded because they did not mail or bring back
the sanitary napkin. Most (90.6%) participants were less than
25 years old. A history of sexually transmitted disease (STD)
was reported by 23.9% (122 of 510) of participants, while 4.3%
(22 of 510) reported having had a sexual partner infected with
an STD in the previous 6 months. In addition, 12.6% (64 of
510) of women reported genital symptoms at their enrollment,
such as vaginal discharge, abdominal pain, and a variety of
other complaints.
A total of 294 women provided matched endocervical, urine,
and sanitary napkin specimens, and 215 participants provided
only urine and sanitary napkin specimens, whereas cervical
swab and sanitary napkin specimens were collected from 1
woman. Three hundred forty-two women (67.1%) sent in their
sanitary napkins by mail, while 168 (32.9%) brought them back
to the recruitment site. According to the information on the
label, 96.1% women wore the sanitary napkin for at least 4 h.
While cervical and urine specimens were tested within 5 days
of collection, sanitary napkin specimens were processed from 1
to 82 days of collection (median, 9 days; 98.7% within 30 days).
Overall, 64 (5.0%) of 1,286 PCR specimens were found to be
inhibitory at initial testing (this information was missing for 20
endocervical, 5 urine, and 3 sanitary napkin samples). The
inhibition rates were 4.4% (12 of 275), 4.4% (22 of 504) and
5.9% (30 of 507) for endocervical, urine, and sanitary napkin
specimens, respectively. PCR inhibitors were removed after
dilution in 61 of 64 initially inhibitory samples, while the three
other samples (one urine and two sanitary napkin specimens)
required heating at 100°C after dilution to eliminate the inhibition. Retested samples confirmed positive results for eight
endocervical and seven sanitary napkin specimens and yielded
additional positive results for two endocervical, one urine, and
five sanitary napkin specimens. Altogether, PCR test results on
paired samples were identical for 96.6% (493 of 510) of participants (94.9 and 99.0% of those who provided three and two
samples, respectively) (Table 1). This proportion was similar
for women who mailed their sanitary napkins in and those who
brought them back to the recruitment site (96.5 versus 97.0%)
and for the sanitary napkin specimens analyzed within 10 days
of collection versus the others (97% in each instance).
The PCR test results were positive on two or three paired
samples (accordingly) from 46 women (Table 1). In addition,
12 of 17 women with discrepant PCR test results were considered infected because the endocervical swab specimen or at
least two specimen types tested positive by PCR. Overall, 39
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provide a urine specimen. First-catch urine (15 to 30 ml) was collected in a
screw-cap plastic jar, placed in plastic bags, and refrigerated until transport to the
laboratory (within 4 days of collection). The modified sanitary napkin comprises
a conventional sanitary napkin which was modified by adding a removable sampling filter between the upper porous and lower impermeable sheets. This device
was provided to women with a postage-paid, preaddressed envelope. Women
were asked to wear the modified sanitary napkin for a period of 4 consecutive
hours during their usual activities (determined by a pretest study among 15
women with recently diagnosed chlamydial infections and 4 uninfected women)
and then to put it in the plastic bag provided, writing the date and the times at
which they put on and took off the napkin on the label. They could bring the
envelope back to the recruitment site or mail it to the laboratory. Infected
women who were enrolled at a medical visit at which they received a drug
prescription were asked to provide a urine specimen and to wear the sanitary
napkin before taking their treatment.
In order to assess the specimen self-collection device in a nonmedical context,
a community-based organization providing services to street youth and a highschool-based clinic were asked to collaborate in the study. In these settings, C.
trachomatis screening was performed on urine specimens. In the context of the
present study, these young women were also asked to wear the sanitary napkin
as described above. In these groups, women with positive PCR test results were
invited to visit their physicians for adequate follow-up and treatment. A gynecological examination was performed and a cervical swab specimen was taken
before treatment. Exclusion criteria were being younger than 14 years, under
antibiotherapy, or menstruating. Those with active severe vulvitis or known
intolerance of sanitary napkins were also excluded.
Questionnaires and specimens were coded. The code number was written on
the consent form in order to identify the subject. Only the medical team had
access to name information. Medical examination and free treatments were
available at recruitment sites or at local community health clinics. The study
protocol was approved by the Ethics Committee of the Ho
ˆpital du St-Sacrement
du Centre Hospitalier Affilie´ Universitaire and the Centre Hospitalier Universitaire de Que´bec-CHUL.
Laboratory procedures. The Amplicor PCR assay (Roche Diagnostic Systems,
Inc., Branchburg, N.J.) was performed on both cervical and urine specimens
within 5 days of collection. The sanitary napkins were kept at room temperature
until their preparation. At the time of testing, the filter of the sanitary napkin was
transferred into a 50-ml polypropylene tube containing 2 ml of Amplicor collection transport medium and vigorously agitated for 15 min. This preparation was
done in a separate room from that used for PCR analysis. All samples were then
processed by the Cobas Amplicor system according to the manufacturer’s instructions.
Chlamydial DNA detection with the Amplicor diagnostic kit is based on three
different steps: (i) PCR amplification, (ii) hybridization with a C. trachomatisspecific probe, and (iii) detection of amplified material by a colorimetric reaction
secondary to enzymatic reaction. The internal control DNA included in the
Cobas Amplicor system was used to monitor the inhibition of amplification.
Optical density (OD) was read on a spectrophotometer at 450 nm. OD values
below 0.2 meant a negative result if the internal control was positive. Values
equal to or greater than 0.8 meant a positive result, regardless of the internal
control result. In order to avoid ambiguity, specimens interpreted as positive and
those with OD values between 0.2 and 0.8 interpreted as equivocal results were
reprocessed and reanalyzed, and their results were established according to the
above definition. When the internal control was negative, indicating the presence
of DNA inhibitors, aliquots of the original specimens were retested after 1:10
dilution or heating at 100°C for 15 min. Paired specimens with discordant results
were retested by processing another aliquot of each original specimen.
Statistical analysis. With the advent of DNA amplification tests which have
better sensitivity than culture, different combinations of alternative tests were
used as an expanded reference standard for the calculation of the performance
characteristics of a new technique, because no “gold standard” has been defined
yet (1). Different methods used to resolve discrepant results have also been
criticized (7, 8). In the present study, the performance characteristics of PCR in
different specimens was calculated in three ways. First, only women with a
positive PCR test result on the endocervical swab specimen were considered
truly infected. This definition was based on the fact that, from a clinical point of
view, PCR testing on endocervical swab specimens is currently used for the
diagnosis of C. trachomatis infection in Quebec City. Because PCR testing on
urine samples is available for specific groups of women, such as street youth and
prostitutes, who are often reluctant to attend traditional medical settings, women
with positive PCR test results on both urine and sanitary napkin specimens were
also considered truly infected in the second analysis. Finally, PCR testing on the
three types of specimens was assessed using a latent class model which did not
2509
2510
ALARY ET AL.
J. CLIN. MICROBIOL.
TABLE 1. Results of C. trachomatis testing by PCR on
endocervical swab, urine, and modified sanitary napkin specimens
collected from 510 women in Quebec City, Canada
Resulta by PCR test on specimen type
Endocervical
Urine
Sanitary napkin
239
207
1
3b,c
2b,c
40
6
7b,d
4b,d
1b,d
⫺
NA
⫺
⫺
NA
⫹
NA
⫹
⫹
⫺
⫺
⫺
NA
⫺
⫺
⫹
⫹
⫺
⫺
⫹
⫺
⫺
⫺
⫹
⫹
⫹
⫹
⫹
⫺
⫹
295
509
510
Total
a
⫺, negative; ⫹, positive; NA, not available.
These samples produced discrepant results on one or two specimen types.
These women were classified as not infected with C. trachomatis because they
had a negative PCR test result on the endocervical swab specimen or they had a
positive PCR test result on only one specimen.
d
These women were classified as infected with C. trachomatis because they
had a positive PCR test result on the endocervical swab specimen or on at least
two specimens.
b
c
(15.9%) of 246 women recruited through medical clinics were
infected with C. trachomatis (of whom 24 were enrolled after a
recent positive test result), as were 2 (1.3%) of 157 high school
students and 17 (15.9%) of 107 incarcerated adolescents or
street youth. A minority (18 of 58) of infected women reported
symptoms such as vaginal discharge (10 women), abdominal
pain (3 women), and different other complaints (5 women).
Forty-seven (92.2%) of 51 women who were C. trachomatis
positive by PCR on the endocervical swab specimen also had a
positive PCR test on the sanitary napkin specimen. In symptomatic and asymptomatic women, these rates were, respectively, 94.4% (17 of 18) and 90.9% (30 of 33). For seven
participants, both urine and sanitary napkin specimens were C.
DISCUSSION
The results of the present study suggest that a modified
sanitary napkin may represent an effective specimen self-collection device for the detection of C. trachomatis infection by
PCR. Using a positive PCR test on endocervical swab specimens exclusively or in combination with positive results from at
least two specimens to identify infected patients, or using the
latent class model that does not assume any gold standard (29),
the relative sensitivity and specificity of PCR on sanitary napkin specimens were 92 to 100% and 98 to 99%, respectively.
These values are similar to those reported with vaginal swab
specimens obtained by health care providers (22, 26, 31, 33)
and are similar to or slightly higher than those reported with
self-collected vaginal swab specimens (2, 5, 9, 15, 16, 31) or
vaginal tampon specimens (13, 23–25).
In the present study, the results show that C. trachomatis
TABLE 2. Performance characteristics for detection of C. trachomatis by PCR in each type of specimen, according to the definition of
infection used as a reference standard, among women from Quebec City, Canada
Reference standard and specimen
Positive PCR on endocervical swab
Sanitary napkin (n ⫽ 295)
Urine (n ⫽ 294)
Endocervical swab
Positive PCR on endocervical swab or on at least 2
specimens
Sanitary napkin (n ⫽ 510)
Urine (n ⫽ 509)
Endocervical swab (n ⫽ 295)
No reference standard (latent class, model) (n ⫽ 294
for all specimens)
Sanitary napkin
Urine
Endocervical swab
a
Sensitivitya (95% CI)
Specificityb (95% CI)
PPVc
NPVd
92.1; 47/51 (81.1–97.8)
78.4; 40/51 (64.7–88.7)
NAe
98.4; 240/244 (95.9–99.6)
99.6; 242/243 (97.7–100)
NA
92.1 (47/51)
97.6 (40/41)
NA
98.4 (240/244)
95.7 (242/253)
NA
93.1; 54/58 (83.3–98.1)
81.0; 47/58 (68.6–90.1)
97.9; 47/48 (88.9–99.9)
98.9; 447/452 (97.4–99.6)
100; 451/451 (99.2–100)
100; 247/247 (98.5–100)
91.5 (54/59)
100 (47/47)
100 (47/47)
99.1 (447/451)
97.6 (451/462)
99.6 (247/248)
NA
NA
NA
NA
NA
NA
100
85.2 (75.0–95.4)
97.6 (92.8–97.7)
98.8 (97.4–99.8)
100
98.4 (96.8–100)
Values are percentages. Where a second value is listed, it is the number of specimens that were true positive/(number true positive plus the number true negative).
Values are percentages. Where a second value is listed, it is the number of specimens that were true negative/(number true negative plus the number false positive).
PPV, positive predictive value. Values are percentages, with the number of specimens that were true positive/(the number true positive plus the number false
positive) given in parentheses.
d
NPV, negative predictive value. Values are percentages, with the number of specimens that were true negative/(the number true negative plus the number false
negative) given in parentheses.
e
NA, not applicable.
b
c
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No. of women
with profile
trachomatis positive; one of these had a negative PCR test on
the endocervical swab specimen. Unfortunately, the other six
women did not provide endocervical swab specimens (Table
1). Four women had a positive PCR test on the endocervical
swab specimen and a negative PCR test on urine and sanitary
napkin specimens, while three others had a positive PCR test
on the sanitary napkin sample and a negative PCR test on
urine and endocervical swab specimens (Table 1).
The performance characteristics of PCR for each type of
specimen, calculated by using either a positive endocervical
swab specimen exclusively or at least two positive specimens as
a standard, are presented in Table 2, as well as the sensitivity
and specificity obtained with the latent class model. The sensitivity of PCR on sanitary napkin specimens was higher than
that on urine samples (92 to 100% versus 78 to 85%), whereas
the relative specificities were comparable (98 to 99% and 99 to
100%, respectively). These results did not change significantly
when symptomatic and asymptomatic infected women were
compared (data not shown).
VOL. 39, 2001
C. TRACHOMATIS DETECTION IN SANITARY NAPKIN SPECIMENS
presented symptoms clinically consistent with C. trachomatis
infection. False-positive results with sanitary napkins are possible, but false-negative results from endocervical swab specimens related to inadequate specimen collection may also explain these discrepant results (1, 3). Sanitary napkin specimens
from two women who did not provide endocervical swab specimens were positive, whereas urine samples was negative.
These women were considered noninfected in the calculation
of the performance characteristics of PCR on sanitary napkin
specimens.
The results of the present study suggest that a modified
sanitary napkin represents an easy, noninvasive, and efficient
specimen self-collection device for C. trachomatis testing by
PCR. It may be particularly useful for screening programs in
nonclinical settings, allowing for the provision of STD services
to high-risk groups, such as incarcerated adolescents, street
youth, and persons involved in prostitution who are not inclined to attend traditional medical settings. Since this device
allows very easy self-collection of specimens, it could also be
useful to increase the accessibility of C. trachomatis screening
for women in general. Further studies are required to evaluate
whether this specimen self-collection device may represent an
accurate and cost-effective approach to the detection not only
of C. trachomatis but also of other STDs.
ACKNOWLEDGMENTS
We thank the collaborating physicians as well as the directors and
staff of collaborating organizations: Les Oeuvres de la Maison Dauphine Inc.; the Centre-Jeunesse de Que´bec, I’Escale; the Colle`ge StFranc¸ois-Xavier Garneau; the CEGEP Ste-Foy; the Clinique de Planification des Naissances of the Ho
ˆpital St-Franc¸ois d’Assise and of the
Centre Hospitalier Universitaire Laval du Centre Hospitalier Universitaire de Que´bec; the CLSC Haute-Ville, Basse-Ville/Limoilou; and
CLSC La Source, Quebec City, Canada. We also acknowledge Roche
Diagnostic Systems, Inc. for providing AMPLICOR CT/NG test kits
and EZY-Detek (EDI) Inc. for providing modified sanitary napkins.
This study was supported by the Division of STD Prevention &
Control, Bureau of HIV/AIDS, STD & TB, Laboratory Centre for
Disease Control, Health Canada. M. Alary is a research scholar of the
Fonds de la Recherche en Sante´ du Que´bec (970097-103).
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Ridgway. 1999. Evaluation of self-taken samples for the presence of genital
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and M. Roger. 2000. An important proportion of genital samples submitted
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assay. J. Clin. Microbiol. 35:1536–1540.
5. Domeika, M., M. Bassiri, I. Butrimiene, A. Venalis, J. Ranceva, and V.
Vasjanova. 1999. Evaluation of vaginal introital sampling as an alternative
approach for the detection of genital Chlamydia trachomatis infection in
women. Acta Obstet. Gynecol. Scand. 78:131–136.
6. Gaydos, C. A., K. A. Crotchfelt, M. R. Howell, S. Kralian, P. Hauptman, and
T. C. Quinn. 1998. Molecular amplification assays to detect chlamydial
infections in urine specimens from high school female students and to monitor the persistence of chlamydial DNA after therapy. J. Infect. Dis. 177:
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infection was more likely to be detected in sanitary napkin
specimens than in urine specimens. As previously reported, the
sensitivity of DNA techniques on female urine samples may be
suboptimal because C. trachomatis infection is localized in the
uterine cervix in most women (21). Conversely, some infected
women may harbor C. trachomatis only in the urethra, and this
infection may be missed by testing only endocervical or vaginal
swab specimens (4, 6, 15, 18, 19, 27, 28). Thus, testing on single
specimens (either urogenital or urine samples) may fail to
identify all infected women (4, 15, 18, 19, 32).
It has been suggested that vaginal swabs may collect biologic
material from both the cervix and the urethra (31). However,
when the performance of different self-collected samples had
been assessed, the sensitivity of PCR on combined urine and
vaginal swab specimens was 96%, compared to 83% when PCR
was performed only on vaginal swab specimens and 74% when
it was performed only on first-catch urine samples (15). In the
same way, the sensitivity of a C. trachomatis PCR test on a
combined urine and cervical swab specimen was higher compared to testing on separate samples (32). It would be interesting to assess the performance of the sanitary napkin specimen compared to that of the corresponding self-collected
vaginal swab specimen in detecting C. trachomatis infection in
women. Unfortunately, self-taken vaginal introitus swab specimens were not collected in the present study because the
requirement for too many types of samples to be provided by
the women could have led to low participation rates. Further
studies would be needed to assess women’s attitudes to these
different sampling methods and to evaluate whether sanitary
napkin specimens represent an efficient alternative to sampling
of multiple sites and may thus improve the cost-effectiveness of
urogenital C. trachomatis infection diagnosis in women. Sanitary napkins represent additional important advantages. They
are a common product previously used by almost all women,
and they have less-stringent transport criteria than urine or
endocervical and vaginal swab specimens. Indeed, in the pretest study, sanitary napkin samples were kept at room temperature for up to 6 weeks before being tested without alteration
in the PCR testing results (data not shown).
For four women the PCR test was positive on the endocervical swab specimen but negative on urine and sanitary napkin
samples. The test results of these specimens were confirmed by
retesting of the original samples, and the negative samples had
no evidence of PCR inhibitors. Cross-contamination in these
endocervical samples is unlikely because of the consistent results in separate analyses and the strict use of a contamination
prevention protocol. These results may reflect the fact that
these infections would be missed by testing only on modified
sanitary napkin specimens. However, three of these four
women were from the same recruitment site, and they presented multiple behavior problems according to the health
care provider who recruited them. These results may indicate
an improper use of the sanitary napkin that we could not
identify as well as a lack of detection of the infection, possibly
related to a insufficient number of copies of organisms present
in the aliquot tested.
On the other hand, two out of three women with negative
PCR test results on endocervical swab and urine samples but
positive results on the sanitary napkin specimen, confirmed by
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