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Three
commercially-available peptide-based IgG and IgA ELISA assays performed as
well as the microimmunofluorescence assay for the serological detection of
C. trachomatis infections.
Comparison of three
commercially available peptide-based IgG and IgA assays to
microimmunofluorescence assay for detection of C. trachomatis
antibodies.
Morre SA, Munk C, Persson K, Kruger-Kjaer
S, van Dijk R, Meijer CJLM, van den Brule AJC.
Journal of Clinical
Microbiology 2002;40:584-587.
Summary:
Question
Do commercially available peptide-based ELISA assays perform as well as
the "gold standard" assay, the microimmunofluorescence (MIF)
assay, for the detection of serum IgG and IgA antibodies specific for C.
trachomatis?
Design
This study describes independent comparisons of 3 peptide-based
serological assays with an in-house microimmunofluorescence assay using
the same sera. Discrepancy analysis was performed on those samples for
which there was not concordance with the peptide-based assays by repeating
the in-house MIF and by testing with a second MIF.
Participants
The study was performed on sera from 149 women, aged 20 to 30 years, who
were part of an HPV case control study. Cervical scrapings from these 149
women were previously screened for asymptomatic C. trachomatis
infection by PCR. Forty-three women were PCR positive for C.
trachomatis and 106 were negative.
Description of Tests and Diagnostic
Standard
Serum samples were tested according to the manufacturers' instructions
using the following 3 assays: 1) Chlamydia trachomatis IgG and IgA
EIA (new version, Labsystems, Helsinki, Finland), 2) SeroCT IgG and IgA (Savyon
Diagnostics Ltd., Ashdod, Israel), and 3) Chlamydia trachomatis IgG
and IgA pELISA (Medac, Wedel, Germany). The results were compared to those
of an in-house MIF assay. Slides with antigens of C. trachomatis, C
psittaci, and C. pneumoniae (Labsystems) were used for this
assay. A titer of >16 was considered diagnostically significant. Repeat
analyses by the in-house MIF and a second, commercially available MIF (MRL-MIF,
MRL Diagnostics, Santa Barbara, CA) were used for discrepancy analysis on
samples that gave discordant results on the 3 ELISA assays. A true
positive result was defined as either a confirmed positive by repeat MIF
(in-house or commercial assay) or negative by MIF but positive by at least
2 of the 3 ELISA assays.
Main Outcome Measures
The sensitivity, specificity, positive predictive value (PPV), and
negative predictive value (NPV), as calculated after discrepancy analysis,
for the detection of C. trachomatis antibodies.
Main Results
36 of 78 samples positive by at least one test were positive by all 4
tests, whereas 13 were positive by all 3 peptide assays but not by MIF,
and 10 were positive only by the MIF assay. The IgG seroprevalence rate
for the CT pELISA for the PCR-positive women (56%) was lower than that for
the other assays (about 72%). The overall IgA seroprevalence rate for the
CT-pELISA (3%) was also lower than that for the other assays (7%). The
performance of the 4 assays as observed for IgG and IgA detection is shown
in the table.
| Test
performance for detection of C. trachomatis antibodies in 149
asymptomatic women |
|
Test |
IgM
Detection |
IgA
Detection |
| Positive |
Grey
Zone |
Negative |
Positive |
Grey
Zone |
Negative |
| CT-EIA |
62 |
4 |
83 |
10 |
6 |
133 |
| SeroCT |
62 |
7 |
80 |
10 |
7 |
132 |
| CT
pELISA |
52 |
5 |
92 |
5 |
2 |
142 |
| MIF |
58 |
2 |
89 |
11 |
0 |
138 |
Authors' Conclusions
Based on the results of discrepancy
analysis, the peptide-based assays performed as well as the in house MIF
assay. (The sensitivity and specificity of both the CT-EIA and the SeroCT
assays were 84.7 and 98.7%, respectively, vs 79.2 and 83.1%, respectively,
for the in-house MIF.) Since these tests are easier to perform, less
expensive, and able to be read more objectively than the MIF assay, they
might be good alternatives to the MIF assay for the detection of C.
trachomatis IgG antibodies.
Source of funding: In part, ZON
(Prevention Fund), Den Haag, The Netherlands, Labsystems, Savyon, and
Medac.
For correspondence: Adriaan van den
Brule, Department of Pathology, University Hospital Vrije University, De
Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands. E-mail address: vandenbrule@vumc.nl.
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