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Review: An
effective screening program for C. trachomatis infection in
asymptomatic young men and women requires the use of accurate
diagnostic tests.
The accuracy and
efficiency of screening tests for Chlamydia trachomatis: a
systematic review.
Watson EJ, Templeton A, Russell I, Paavonen
J, Mardh P-A, Stary A, Pederson BS.
J Med Microbiol. 2002;51:1021-31
Question:
Which of the available diagnostic tests for C. trachomatis is most
accurate and effective when used in young, asymptomatic, sexually active
populations?
Data Sources:
Studies published from 1990 onward that assessed the effectiveness of
tests used to diagnose C. trachomatis infection were identified by
searching Medline, CINAHL, and Embase, by hand searching relevant
journals, by searching the internet, Medscape, and the references of
included studies, and by contacting experts in the field.
Study Selection Criteria:
Studies were included if they evaluated
methods of detecting urogenital infection with chlamydia on asymptomatic
populations of sexually active young men or women. Papers that described
low prevalence populations (<5%), regardless of setting, and
those that were set in primary care or family planning clinics, regardless
of prevalence, were included. Only comparative studies were examined due
to the lack of randomized controlled studies available. Studies were
excluded if study design was poor, as determined by an Irwig score of
<5 out of 10
Data Extraction
Data were extracted on type of diagnostic test used for detection of C.
trachomatis, type of specimen collected, the gold standard used to
evaluate the test, the prevalence of C. trachomatis infection,
gender, sample size, and the sensitivity and specificity of the tests
being evaluated. Tests being evaluated were compared to tissue culture of
a cervical or urethral swab or to an expanded gold standard using the
results of two non-culture tests on either urine or cervical swabs.
Culture was compared with two non-culture assays.
Main Results
Thirty studies were included in the meta-analysis. The age range of the
populations in the included studies was 14-40 years. The mean prevalence
of chlamydia infection among the populations studied was 4.5% (range =
<1% to 15%). Studies were analyzed in subgroups according to specimen
type and test. A pooled sensitivity for each test type by specimen type,
calculated by summing the number of false-negative results in each study,
is shown in the figure. To compare different tests, false-negative results
were selected as a suitable measure of poor outcome. The false-negative
rate for each test, expressed as an odds ratio (OR), is shown in the
table. LCR on urine had the lowest number of false-negative results.
| Mean sensitivity by
sample for each diagnostic test. GP, gene probe; LET, leukocyte
esterase test; DFA, direct fluorescent antibody test. |
Odds ratio (OR) of a false negative result by test and sample |
| Test |
Sample |
OR
of a false-negative result |
| LCR |
urine |
0.33
(0.13-0.8) |
| PCR |
cervix |
0.26
(0.12-0.54) |
| urine |
0.84
(0.37-1.89) |
| Gene probe |
cervix |
0.84
(0.37-1.89) |
| urine |
0.44
(0.15-1.26) |
| EIA |
cervix |
4.1
(1.15-14.59) |
| urine |
1.89
(0.39-8.75) |
| DFA |
cervix |
1.05
(0.09-12.93) |
| LET |
urine |
47.02
(6.21-356) |
Conclusions
Nucleic acid amplification methods using
both urine and cervical swabs are superior to other methods for detecting
asymptomatic chlamydial infection in a young, sexually active population.
EIA will probably miss a large proportion of infections in a screening
program.
Source of funding: EU Biomed grant,
Department of Obstetrics and Gynecology, Aberdeen University, UK
For correspondence: Emma Watson,
Department of Obstetrics and Gynecology, Aberdeen University, Aberdeen,
Scotland. E-mail address: emma.watson@abdn.ac.uk.
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