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The leukocyte
esterase dipstick test could be a useful case finding tool for
sexually transmitted infections in high risk, asymptomatic men in
developing countries.
Sexually transmitted infections in
male clients of female sex workers in Benin: risk factors and reassessment
of the leukocyte esterase dipstick for screening of urethral infections.
Alary M, Lowndes CM, Mukenge-Tshibaka L,
Gnintoungbe CAB, Bedard E, Geraldo N, Jossou P, Lafia E, Bernier F,
Baganizi E, Joly JR, Frost E, Anagonou S.
Sexually
Transmitted Infections 2003;79:388-392.
Summary:
Question
What are the risk factors for urethral infections caused by C.
trachomatis, N. gonorrhoeae, or T. vaginalis among male
clients of female sex workers (FSW) in Benin, and how valid is the
leukocyte esterase dipstick (LED) test of male urine samples compared to
PCR detection for the diagnosis of urethral infection with any of these
three agents?
Design
This study describes a comparison of the results of the LED test with
those of PCR assays performed on urine specimens for the diagnosis of C.
trachomatis, N. gonorrhoeae, and T. vaginalis in male clients
of FSW in Cotonou, Benin.
Participants
Four hundred four male clients of FSWs were recruited at 13 diverse
prostitution venues in Benin, Cotonou. All men provided urine specimens,
330 submitted questionnaires, and 298 had a physical examination. The
median age was 25.5 years (range = 17 to 53 years). C. trachomatis, N.
gonorrhoeae, and/or T. vaginalis was detected in 10.1% of the
men; 8.4% of the urine samples were positive for HIV antibody.
Description of Tests and Diagnostic
Standard
A urine sample obtained from each participant was tested immediately using
a leukocyte esterase dipstick test (Chemstrip 10A, Boehringer Mannheim,
Quebec, Canada). Specimens with results greater than trace were considered
positive. Frozen urine aliquots were PCR tested for C. trachomatis
and N. gonorrhoeae using the Amplicor CT/NG detection kit (Roche
Diagnostics) and for T. vaginalis using an in-house assay targeting
the 650 bp repetitive sequence.
Main Outcome Measures
The sensitivity, specificity, positive predictive value (PPV), and
negative predictive value (NPV) of the LED test in comparison with the
gold standard PCR results for the diagnosis of C. trachomatis, N.
gonorrhoeae, and T. vaginalis infections were calculated.
Main Results
Among the 31 (7.7%) of 404 men with C. trachomatis and/or N.
gonorrhoeae infections, 81.3% were asymptomatic (reported no urethral
discharge or dysuria and had no urethral discharge on physical
examination). In multivariate analysis of risk factors, history of
previous STI and condom use were significantly associated with chlamydial
or gonococcal infection. No variables were associated with T. vaginalis
infection.
The LED test was positive in 34 (8.4%) of
404 men. The performances of the LED test compared to detection of C.
trachomatis and/or N. gonorrhoeae, or of T. vaginalis
by PCR are shown in the table.
Authors' Conclusions
In this study, the LED test had a much
better specificity and higher positive predictive value than when
previously evaluated in comparison with non-NAAT tests. The LED test,
which is rapid, inexpensive, and can be administered at the point of care,
could be useful to detect asymptomatic infection by either C.
trachomatis or N. gonorrhoeae in high risk men.
Source of funding:
In part by the project "Appui a la lutte contre le sida en Afrique de
l'ouest" executed by CCISD Inc and funded by CIDA Canada
For correspondence:
Michel Alary, Unite de recherché en sante des populations, Centre
hospitalier affilie universitaire de Quebec, 1050, chemin Sainte-Foy,
Quebec, G1S 4L8, Canada. E-mail address: michel.alary@uresp.ulaval.ca
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