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Journal of Clinical Microbiology, January 1999, p. 74-80, Vol. 37, No. 1
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Multicenter Evaluation of the Fully Automated COBAS
AMPLICOR PCR Test for Detection of Chlamydia trachomatis in
Urogenital Specimens
Jean
Vincelette,1,*
Jurjen
Schirm,2
Marc
Bogard,3
Anne-Marie
Bourgault,1
Dirk S.
Luijt,2
Anne
Bianchi,4
Pieter C.
van
Voorst Vader,5
Ann
Butcher,6 and
Maurice
Rosenstraus6
Centre Hospitalier de l'Université de
Montréal, Campus Saint-Luc, Montréal,
Canada1;
Regional Public Health
Laboratory,2 and
Department of
Dermatology, University Hospital,5 Groningen,
The Netherlands;
Unité de Biologie Moléculaire,
Centre Hospitalier de Meaux, Meaux,3 and
Laboratoire de Virologie, Institut Alfred Fournier,
Paris,4 France; and
Roche Molecular
Systems, Branchburg, New Jersey6
Received 26 June 1998/Returned for modification 3 August
1998/Accepted 2 October 1998
 |
ABSTRACT |
The fully automated COBAS AMPLICOR CT/NG test for the detection of
Chlamydia trachomatis was evaluated in a multicenter trial. Test performance was evaluated for 2,014 endocervical swab and 1,278 urine specimens obtained from women and for 373 urethral swab and 254 urine specimens obtained from men. Culture served as the reference
test. Culture-negative, COBAS AMPLICOR-positive specimens that tested
positive in a confirmatory PCR test for an alternative target sequence
within the C. trachomatis major outer membrane protein gene
were resolved as true positives. The overall prevalence of chlamydia
was 4.3% in cervical swabs and 11.0% in urethral swabs from men. When
the results for each specimen type were considered separately, the
resolved sensitivities were 96.5% (83 of 86) for endocervical swab
specimens, 95.1% (39 of 41) for urine specimens from women, 100.0%
(41 of 41) for urethral swab specimens from men, and 94.4% (17 of 18)
for urine specimens from men; the resolved specificities were 99.4%
(1,912 of 1,924) for endocervical swab specimens, 99.8% (1,204 of
1,207) for urine specimens from women, 98.5% (325 of 330) for urethral
swab specimens from men, and 100.0% (236 of 236) for urine specimens
from men. For the subset of patients from whom both swab and urine
specimens were collected, the combined results for both specimen types
were used to identify all infected patients. Using these combined
reslts as criteria, the resolved sensitivities for the COBAS AMPLICOR test were 82.6% (38 of 46) for endocervical swab specimens, 84.4% (38 of 45) for urine specimens from women, 84.2% (16 of 19) for urethral
swab specimens from men, and 89.5% (17 of 19) for urine specimens from
men. In comparison, the sensitivity of culture was only 56.5% (26 of
46) for endocervical specimens and 63.2% (12 of 19) for urethral
specimens from men. The internal control provided in the COBAS AMPLICOR
test revealed that 2.9% of specimens were inhibitory when they were
initially tested. Nevertheless, valid results were obtained for 99.1%
of specimens because 68.7% of the inhibitory specimens were not
inhibitory when a second aliquot of the original sample was tested. Two
additional COBAS AMPLICOR-positive specimens were detected by retesting
inhibitory specimens. The COBAS AMPLICOR CT/NG test for the detection
of C. trachomatis exhibited equally high sensitivities and
specificities with both urogenital swab and urine specimens and, thus,
is well-suited for use in screening.
| |
INTRODUCTION |
With an estimated 89 million new
cases occurring annually worldwide (36), Chlamydia
trachomatis infections are a major public health problem.
Untreated C. trachomatis infections can cause pelvic
inflammatory disease, cervicitis, urethritis, infertility, ectopic
pregnancy, epididymitis, infant pneumonia, and infant conjunctivitis
(for a review, see reference 4). Untreated
individuals serve as a reservoir for the transmission of infections to
their sexual partners. Chlamydia screening programs have been shown to
decrease the prevalence of chlamydia infection (5, 21) and
reduce the incidence of pelvic inflammatory disease
(31). Economic modeling studies based on decision-tree
analysis suggest that screening programs are cost-effective; the
savings resulting from the prevention of long-term sequelae more than
compensate for the cost of screening patients for infections and
treating infections (20, 24).
Diagnosis remains a challenge because C. trachomatis
infections are asymptomatic in up to 80% of infected women and 50% of infected men. Culture is relatively insensitive (for a review, see
reference 4). Antigen-based tests such as enzyme
immunoassay have limited sensitivities and specificities (for a review,
see reference 4). Furthermore, asymptomatic
individuals are reluctant to seek medical attention, especially because
of the discomfort associated with collecting a swab specimen from the
endocervix or urethra. Recent studies have shown that nucleic acid
amplification-based tests are ideally suited for screening because they
exhibit high sensitivities and specificities for the detection of
C. trachomatis in noninvasively collected urine specimens
(1, 2, 6, 7, 9, 11, 14, 18, 23, 25-28, 30, 33). The
availability of urine testing should encourage asymptomatic individuals
in at-risk populations to undergo screening and should reduce the costs
associated with specimen collection.
The availability of a fully automated test method will also reduce the
cost of screening. Roche Molecular Systems has developed a PCR-based
test for the detection of C. trachomatis that is performed on the COBAS AMPLICOR system, an integrated unit that automatically amplifies RNA or DNA targets and that detects the resulting amplicon (12, 16). The COBAS AMPLICOR CT/NG test for C. trachomatis uses a master mixture containing one pair of primer
oligonucleotides specific for C. trachomatis DNA and a
second pair specific for Neisseria gonorrhoeae DNA to
simultaneously amplify both organisms in a single processed specimen
(11). The master mixture also contains an internal control
(IC) DNA that monitors the amplification for each clinical specimen.
The IC contains primer binding regions identical to those of the
C. trachomatis target sequence, a randomized internal
sequence with a length and base composition similar to those of the
target sequence, and a unique probe binding region that differentiates
the IC from the amplified target nucleic acid (29). The
C. trachomatis, N. gonorrhoeae, and IC
amplification products can be detected separately in the same amplified
specimen with different target- and IC-specific oligonucleotide
capture probes.
Here, we describe the results of a multicenter evaluation of the COBAS
AMPLICOR CT/NG test for the detection of C. trachomatis. Test performance was evaluated for endocervical swab specimens, urethral swab specimens from men, and urine specimens from women and men.
| |
MATERIALS AND METHODS |
Patient population.
In Montreal, Quebec, Canada, specimens
were collected from individuals visiting general practitioners and
family-planning clinics. In Groningen, The Netherlands, specimens were
collected from individuals visiting general practitioners,
dermatologists, gynecologists, sexually transmitted disease clinics,
and family-planning centers. In Meaux, France, specimens were obtained
from men and women consulting the outpatient clinic of Institut Alfred
Fournier, Paris, France. Most of the individuals studied in Groningen
and Meaux were symptomatic. Information on symptomatology was not available for individuals from Montreal.
Specimen collection and processing.
Endocervical swab
specimens and urethral swab specimens from men were collected by
standard procedures and inoculated into 2SP transport medium (0.2 M
sucrose-0.02 M phosphate). These specimens were stored at 2 to 8°C
until they were transported to the laboratory; all specimens were
transported within 24 h. An aliquot of the specimen was used for
Chlamydia culture on cycloheximide-treated McCoy cells
(Montreal and Groningen) or cycloheximide-treated HeLa 229 cells
(Institut Fournier). Chlamydial inclusions were detected by
immunofluorescence with monoclonal antibodies specific for the major
outer membrane protein (MOMP; Micro Trak; Syva Co.). When a specimen
was toxic for cell culture, a passage was performed. If the toxicity
persisted the specimen was excluded from analysis. A second aliquot was
processed and tested with the COBAS AMPLICOR system. A 100-µl sample
of specimen was mixed with 100 µl of CT/NG Lysis Buffer, and the
mixture was incubated for 10 min at room temperature. The resulting
mixture was combined with 200 µl of CT/NG Specimen Diluent, and this
mixture was incubated for an additional 10 min at room temperature.
A total of 10 to 50 ml of first-catch urine was also collected from
each subject. The urine was shipped to the laboratory at room
temperature and was stored at 2 to 8°C for up to 7 days (Montreal and
Meaux) or at 
20°C (Groningen) until it was processed and tested
with the COBAS AMPLICOR system. A 500-µl sample of urine was combined
with 500 µl of CT/NG Urine Wash Buffer, and the mixture was incubated
at 37°C for 15 min. The mixture was then centrifuged at 12,500 × g for 5 min. The supernatant was discarded and the pellet
was resuspended in 250 µl of CT/NG Lysis Buffer. After a 15-min
incubation at room temperature, 250 µl of CT/NG Specimen Diluent was
added to the lysate. The specimens were centrifuged at 12,500 × g for 10 min, and the resulting supernatant was tested.
Amplification and detection.
A 50-µl sample of processed
specimen was added to 50 µl of Master Mix containing IC and was
amplified by using the thermal cycler onboard the COBAS AMPLICOR
system. The thermal cycling conditions were automatically performed by
the COBAS AMPLICOR system (12, 16). Upon the completion of
amplification, the COBAS AMPLICOR system automatically denatured the
amplified DNA, hybridized the amplicon to target-specific
oligonucleotides bound to magnetic microparticles, and colorimetrically
detected the captured amplicon by using an avidin-horseradish
peroxidase complex (12, 16). The C. trachomatis
target and the IC were detected in separate reactions with separate
C. trachomatis- and IC-specific oligonucleotide capture probes.
Interpretation of results.
Specimens yielding C. trachomatis signals above the test cutoff were interpreted as
positive, regardless of the IC result. Specimens yielding C. trachomatis signals below the test cutoff were interpreted as
negative, provided that the IC signal was above the assigned cutoff.
Specimens with signals below the cutoffs for both the C. trachomatis and IC signals were interpreted as inhibitory.
Specimens with inhibitory activity were retested by processing another
aliquot of the original specimen. The repeat test results were
classified by the criteria presented above.
Sensitivity and specificity were calculated by comparing PCR results to
the resolved results because culture is not 100% sensitive. Results
for specimens with discrepant results (positive by PCR but negative by
culture) were resolved by performing PCR for an alternative target DNA
sequence, a portion of the MOMP gene (13). The results for
the specimens were resolved as being positive for infection if the
culture was positive or if the specimen was PCR positive for both the
primary and the alternative targets.
Sensitivity and specificity were calculated in two ways. The
calculation on a sample basis showed the results that would have
been
obtained if only one specimen type had been tested by PCR.
Culture-negative infections were identified by using the PCR results
for only one specimen type (swab or urine). Samples were classified
as
positive for infection if the reference test was positive or
if the
specimen type being evaluated was PCR positive for both
the primary and
the alternative
targets.
The calculation on a patient basis considered the results for both the
swab and urine specimens to identify all infected patients.
This
analysis was performed for the subset of patients from whom
both
specimen types were collected. Culture-negative infections
were
identified by using PCR results for both the swab and urine
specimens
from a single patient. Patients were classified as positive
for
infection if the culture was positive or if either specimen
type was
PCR positive for both the primary and the alternative
targets.
| |
RESULTS |
Frequency of inhibition.
Only 1 of 114 specimens (0.9%)
obtained from culture-positive patients was inhibitory when it was
initially tested; this specimen yielded a true-positive result when it
was retested (Table 1). The frequency of
inhibition was somewhat higher for specimens from culture-negative
patients, ranging from 0.9% for endocervical swab specimens to 6.7%
for urine specimens from women (Table 1). The frequency of inhibition
did not vary substantially between laboratories.
Approximately 68.7% (79 of 115) of inhibitory specimens were not
inhibitory when another aliquot of the specimen was processed
and
tested (Table
1). The frequency of successful retesting did
not vary
between specimen types or between laboratories. The conversion
of
specimens from inhibitory to noninhibitory could indicate that
inhibitors were labile, nonuniformly distributed, or present at
a low
concentration (
29). Regardless of the mechanism, the absence
of inhibition during retesting enables the laboratory to generate
valid
test results without having to collect a second
specimen.
Performance with specimens from women.
A total of 2,014 endocervical swab specimens were evaluated, 49 (2.4%) of which were
positive for C. trachomatis by culture. The COBAS AMPLICOR
test yielded positive results for 46 of the 49 endocervical swab
specimens obtained from culture-positive women (Table
2). One of these 46 positive specimens
was inhibitory when it was initially tested and would have been
interpreted as false negative if the IC had not been used. An
additional 49 specimens obtained from culture-negative women generated
positive results by the COBAS AMPLICOR test. Thirty-seven of these 49 specimens were confirmed to be positive by performing PCR for an
alternative target sequence within the C. trachomatis MOMP
gene (Table 2). Thus, 12 specimens yielded false-positive COBAS
AMPLICOR test results. When performed with endocervical swab specimens,
the prevalence of chlamydia was 4.3% (86 of 2,014), the resolved
sensitivity and specificity of the COBAS AMPLICOR test were 96.5 and
99.4%, respectively, and the corresponding positive and negative
predictive values were 87.4 and 99.8%, respectively (Table
3). Test performances were similar in all
three laboratories.
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TABLE 3.
Resolved sensitivity, specificity, and positive and
negative predictive values of the COBAS AMPLICOR test calculated
separately for
each specimena
|
|
To assess the impact of using the IC, we also calculated the test
sensitivity and specificity by ignoring the IC results and
interpreting
all PCR results as positive or negative on the basis
of the initial
test result. If the IC had not been used, the sensitivity
would have
decreased to 95.3% and the specificity would not have
changed (data
not
shown).
A total of 1,278 urine specimens were evaluated; 26 (2.0%) of these
were obtained from women who were positive by culture
of endocervical
swab specimens. The COBAS AMPLICOR test yielded
positive results for 24 of the 26 urine specimens obtained from
culture-positive women (Table
2). An additional 18 specimens
obtained from
culture-negative women generated positive results
by the COBAS
AMPLICOR test. Fifteen of these 18 specimens were
confirmed to be
positive by performing the MOMP PCR (Table
2);
1 of these specimens
confirmed to be positive was inhibitory when
it was initially tested
and would have been incorrectly interpreted
as negative if the IC had
not been used. Thus, three specimens
yielded false-positive COBAS
AMPLICOR test results. When performed
with urine specimens from women,
the resolved sensitivity and
specificity of the COBAS AMPLICOR test
were 95.1 and 99.8%, respectively,
and the corresponding positive and
negative predictive values
were 92.9 and 99.8%, respectively (Table
3). Test performances
were similar in all three laboratories. If the IC
had not been
used, the sensitivity would have decreased to 95.0% and
the specificity
would not have changed (data not
shown).
Because two COBAS AMPLICOR tests were performed for each patient, we
were able to identify infections that would not have
been detected had
we tested only a single specimen. Matched urine
and endocervical swab
specimens were available for 1,253 women,
46 of whom were infected with
C. trachomatis. Twenty-six of the
46 infections were
detected by culture (Table
4). The COBAS
AMPLICOR
test was positive for 25 of the endocervical swab specimens
and
24 of the urine specimens from culture-positive patients (the
false-negative swab specimen and one of the two false-negative
urine
specimens came from the same patient). The COBAS AMPLICOR
test detected
20 infections in culture-negative patients. For
seven of these 20 infections, both the endocervical swab and urine
specimens were
positive by the COBAS AMPLICOR test. For 6 of the
20 infected patients,
only the endocervical swab specimen was
positive, and for the remaining
7 patients only the urine specimen
was positive. Consequently, when the
results for the infected
patient were used as the "gold standard,"
the resolved sensitivities
were 56.5% for endocervical swab specimen
culture and 82.6% for
endocervical swab specimens and 84.4% for urine
specimens by the
COBAS AMPLICOR test (Table
4).
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TABLE 4.
Resolved sensitivity of the COBAS AMPLICOR test and
culture calculated on the basis of patient
infection statusa
|
|
Performance with specimens from men.
A total of 373 urethral
swab specimens were evaluated; 27 (7.2%) of these were positive for
C. trachomatis by culture. The COBAS AMPLICOR test yielded
positive results for all 27 urethral swab specimens obtained from
culture-positive men (Table 2). An additional 19 specimens obtained
from culture-negative men generated positive results by the COBAS
AMPLICOR test. Fourteen of these 19 specimens were confirmed to be
positive by the MOMP PCR (Table 2). Thus, five specimens yielded
false-positive COBAS AMPLICOR test results. When performed with
urethral swab specimens from men, the prevalence of chlamydia was
11.0% (41 of 373), the resolved sensitivity and specificity of the
COBAS AMPLICOR test were 100.0 and 98.5%, respectively, and the
corresponding positive and negative predictive values were 89.1 and
100.0%, respectively (Table 3). The same sensitivity and specificity
would have been obtained had the IC not been used because none of the
positive specimens gave negative IC results when they were initially
tested. Test performances were similar in all three laboratories.
A total of 254 urine specimens were evaluated; 12 (4.7%) of these were
obtained from men who were positive by culture of urethral
swab
specimens. The COBAS AMPLICOR test yielded positive results
for 11 of
the 12 urine specimens obtained from culture-positive
men (Table
2). An
additional six specimens obtained from culture-negative
men generated
positive results by the COBAS AMPLICOR test, and
all of these were
confirmed to be positive by performing the MOMP
PCR (Table
2). Thus,
there were no false-positive COBAS AMPLICOR
test results. When
performed with urine specimens from men, the
sensitivity and
specificity of the COBAS AMPLICOR test were 94.4
and 100.0%,
respectively, and the corresponding positive and negative
predictive
values were 100.0 and 99.6%, respectively (Table
3).
The same
sensitivity and specificity would have been obtained
had the IC not
been used. Test performances were similar in all
three
laboratories.
Matched urine and urethral swab specimens were available for 251 men,
19 of whom were infected with
C. trachomatis. Twelve
of the
19 infections were detected by culture (Table
4). The
COBAS AMPLICOR
test was positive for all 12 urethral swab specimens
and 11 of the
urine specimens from culture-positive patients.
The COBAS AMPLICOR test
detected infections in seven culture-negative
patients. For three of
these seven patients, both the urethral
swab and urine specimens were
positive by the COBAS AMPLICOR test,
for one of these seven infected
patients, only the urethral swab
specimen was positive, and for the
remaining three patients only
the urine specimen was positive.
Consequently, when the results
for the infected patient were used as
the gold standard, the resolved
sensitivities were 63.2% for urethral
swab specimen culture and
84.2% for urethral swab specimens and 89.5%
for urine specimens
by the COBAS AMPLICOR test (Table
4).
| |
DISCUSSION |
The results of this study demonstrate that the COBAS AMPLICOR
CT/NG test for the detection of C. trachomatis exhibited
excellent sensitivity and specificity. Our data do not allow us to
contrast the performance of the test among symptomatic and asymptomatic subjects. A transport medium other than 2SP may result in a different performance. When performance was calculated as if only one specimen from each patient had been tested, the sensitivity ranged from 94.4 to
100.0%, the specificity ranged from 98.5 to 100.0%, and the positive
and negative predictive values ranged from 89.1 to 100.0% and 99.6 to
100.0%, respectively. While the manuscript was being prepared, two
other studies reported similar results for the COBAS AMPLICOR test
(14, 26). These values are similar to those reported for the
nonautomated AMPLICOR C. trachomatis test (2, 6,
25-28, 30, 35) and other amplification-based C. trachomatis tests (1, 6, 7, 9, 14, 18, 23, 25, 26, 30,
33). Virtually identical performance was observed for urine and
endocervical swab specimens from women. Similarly, the test performed
equally well with urethral swab specimens from men and urine specimens
from men. Thus, the COBAS AMPLICOR CT/NG test for the detection of
C. trachomatis is well-suited for the screening of
noninvasively collected specimens.
When two specimens were evaluated from each patient, for some patients
positive results were obtained for only one specimen type. Thus, the
total number of infections detected was greater than the number that
would have been detected if only a single specimen had been tested. As
a result, the estimate of test sensitivity for each specimen type was
more stringent, but also more realistic, than it would have been in the
absence of a test result for the second specimen. Actually, the
combination of testing of both urine and swab specimens by PCR
increased the rate of detection of C. trachomatis infection
by 17% (64 versus 54 when only swab specimens were tested or 64 versus
55 when only urine specimens were tested). Other recent studies
(8, 14) have also demonstrated that the estimate of the
sensitivity of each test is lower when multiple tests are performed for
each patient to identify all infected patients (i.e., the results for
the infected patient served as the gold standard). When COBAS AMPLICOR
test results were compared to the results for the infected patient used
as a gold standard, the test sensitivities for the individual specimen types ranged from 82.6 to 89.5%. In contrast, the sensitivities of
culture were only 56.5 to 63.2%. Thus, the COBAS AMPLICOR CT/NG test
for C. trachomatis performed with any one specimen type
detected approximately 40% more infections than cell culture (Table
4). Enhancement of the rate of detection appears even greater (50 to
80%) when the rate is estimated from the results for all specimens (Table 2). The low sensitivity of culture has been reported previously (7). Delay between specimen collection and initiation of
culture may have contributed to the low culture sensitivity in our
study. Because a loss of sensitivity during transport is unavoidable in
most clinical settings, amplification tests that do not depend on
maintenance of specimen viability will offer a large improvement in
sensitivity over that of culture for routine testing.
When evaluating the positive predictive value of a test, one must take
disease prevalence into account. Even a test with a sensitivity of 95%
and a specificity of 99.5% will yield a positive predictive value of
below 90% for a population with a prevalence of less than 4.5%. The
positive predictive values of the COBAS AMPLICOR CT/NG Test for the
detection of C. trachomatis with swab and urine specimens
from women and swab and urine specimens from men were 87.4, 92.9, 89.1, and 100.0%, respectively. When specimens with false-positive results
at one site (Groningen) were retested, nearly all of them became
negative, increasing the positive predictive value to >99%. Given
this observation, laboratories that test populations with a low
prevalence of C. trachomatis infection may want to evaluate
whether positive predictive value could be significantly enhanced by
retesting all positive specimens.
Use of the IC increased the test sensitivity for urine and swab
specimens from women because two initially inhibitory specimens were
found to be true positive upon retesting. Numerous studies have
demonstrated that a small but significant proportion of clinical specimens contain substances that inhibit PCR, the ligase chain reaction, transcription-mediated amplification (TMA), and nucleic acid
sequence-based amplification (1-3, 6, 8-10, 15, 17, 19, 22, 25,
32-35). Use of the IC enabled us to determine definitively that
the overall frequency of inhibition for the COBAS AMPLICOR CT/NG test
for C. trachomatis was 2.9% (115 of 3,919) and that female
urine specimens from women were somewhat more inhibitory than
endocervical swab specimens and urethral swab and urine specimens from
men. We cannot directly compare the frequencies of inhibition for
different amplification technologies because the commercially available
LCx assay and TMA tests for C. trachomatis lack an IC,
making it impossible to assess inhibition for reference test-negative
specimens. The frequency of inhibitory, positive specimens can be
estimated from the number of reference test-positive, amplification
test-negative specimens that give positive results when they are
retested (29). This analysis indicates that the inhibition
rates for positive specimens were 1 to 30% for the LCx assay for
C. trachomatis (1, 3, 8-10, 15, 26, 33) and 8%
for the TMA for C. trachomatis (25). The
inhibition rate for all specimens is probably higher since weak
inhibition may go undetected for positive specimens that contain
relatively high concentrations of target (29). Indeed, the
results for the IC obtained in this study demonstrated that the
observed frequency of inhibition was higher for culture-negative specimens than for culture-positive specimens.
Use of the IC ensures the integrity of negative results and maximizes
test sensitivity by monitoring amplification for specimens with
negative test results for C. trachomatis. The added cost of
using the IC corresponds to the cost for reagents, but the workload is
almost identical whether or not the IC is used with the COBAS AMPLICOR
system. This cost can be minimized by programming the system to detect
the IC only for those specimens that test negative for C. trachomatis (12). When inhibition is found to be rare,
the IC may be omitted or used selectively, for instance, to monitor
proficiency as part of a quality control program or to validate the
results for specimens more likely to be inhibitory.
The COBAS AMPLICOR system improves laboratory productivity by fully
automating amplification and detection. After laboratory personnel
process clinical specimens and load the samples onto the COBAS AMPLICOR
system, they are free to perform other tasks. One technician can
process 24 swab specimens in 30 min or 24 urine specimens in 1 h.
Results for these specimens are available approximately 5 h after
the technician starts the COBAS AMPLICOR system. While these specimens
are being amplified, the technician can process a second set of
specimens, which can be loaded into the system and amplified while any
amplicon in the first set are being detected. Results for the second
set of specimens are available approximately 7 h after the start
of the first run. A third set of specimens can be processed while the
first two sets are being tested and can be loaded into the system at
the end of the workday. The system will run unattended overnight, and
the results will be available the next morning. Thus, a single operator
performing 3 to 4 h of hands-on work can test 96 specimens in a
single workday.
In summary, the fully automated COBAS AMPLICOR CT/NG test for the
detection of C. trachomatis exhibited high sensitivity and specificity with both urogenital swab and urine specimens and used an
IC to ensure the integrity of negative results. Because the test can
detect C. trachomatis in noninvasively collected urine
specimens from men and women without sacrificing sensitivity, it is
well-suited for use in screening.
| |
ACKNOWLEDGMENTS |
We thank Camillia Beaudin and Ginette Breton (Montreal), Ludo
A. B. Oostendorp and Petra Bos (Groningen), and Mireille Louvet and Mathieu Landu (Meaux) for technical assistance and D. H. Bogchelman, Department of Gynecology, University Hospital,
Groningen, for providing clinical specimens.
This work was supported by Roche Molecular Systems.
| |
FOOTNOTES |
*
Corresponding author. Mailing address:
Département de Microbiologie Médicale et Infectiologie,
Centre Hospitalier de l'Université de Montréal, Campus
Saint-Luc, 1058 Saint-Denis, Montréal, Québec, Canada H2X
3J4. Phone: (514) 281-2100. Fax: (514) 281-2443. E-mail: vincelej{at}magellan.umontreal.ca.
| |
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Abstract
Introduction
