False-positive enzyme immunoassay test results for Chlamydia trachomatis because of contact of the collection swab with agar.
BACKGROUND
We noted an increased incidence of false-positive Chlamydia trachomatis enzyme immunoassay results using the Abbott IMx SELECT C. trachomatis EIA test when a single swab was used for urethral sampling for both gonococcal culture inoculation and chlamydial detection.


OBJECTIVE
To evaluate if contact of the enzyme immunoassay collection swab with an agar produces false-positive chlamydial enzyme immunoassay results.


METHODS
Samples containing agar-based culture media were tested by two enzyme immunoassays and a ligase chain reaction technique.


RESULTS
We report false-positive chlamydial enzyme immunoassay results using the Abbott IMx SELECT C. trachomatis EIA test if the collection swabs are in contact with gonococcal culture media (Modified New York City agar, chocolate, Thayer-Martin, or GC-lect) before insertion of the swab in the transport media of the enzyme immunoassay. The other assay results were negative.


CONCLUSIONS
Using a single collection swab to screen for genital infections with gonococcal cultures and chlamydial enzyme immunoassay is inappropriate because it may lead to false-positive chlamydial enzyme immunoassay results, at least with the Abbott IMx SELECT C. trachomatis EIA test, incurring public health and financial consequences.
Department of Microbiology, Sir Mortimer B. Davis-Jewish General Hospital, Montréal, Canada.
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Sales
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Miller
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Libman
D000362:Agar; D002690:Chlamydia Infections / Q000175:diagnosis*; D002692:Chlamydia trachomatis; D003470:Culture Media; D005189:False Positive Reactions; D005784:Gene Amplification; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D011792:Quebec
D003470:Culture Media; D000362:Agar