Chlamydia infection laboratory findings
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
The diagnosis of genital chlamydial infections evolved rapidly from the 1990s through 2006. Nucleic acid amplification tests (NAAT), such as polymerase chain reaction (PCR), transcription mediated amplification (TMA), and the DNA strand displacement assay (SDA) now are the mainstays.
Laboratory Findings
As of January 2007, the most commonly used and widely studied chlamydia NAATs in the US and many other industrialized countries are Aptima (Gen-Probe), Probe-Tec (Becton-Dickinson), and Amplicor (Roche). The Aptima Combo II assay tests simltaneously for C. trachomatis and Neisseria gonorrhoeae, the cause of gonorrhea. NAAT for chlamydia may be performed on swab specimens collected from the cervix (women) or urethra (men), on self-collected vaginal swabs, or on voided urine. Urine and self-collected swab testing facilitates the performance of screening tests in settings where genital examination is impractical. At present, the NAATs have regulatory approval only for testing urogenital specimens, although rapidly evolving research indicates that the Aptima test may give reliable results on rectal specimens. Because of improved test accuracy, ease of specimen management, convenience in specimen management, and ease of screening sexually active men and women, the NAATs have largely replaced culture, the historic gold standard for chlamydia diagnosis, and the non-amplified probe tests, such as Pace II (Gen-Probe). The latter test is relatively insensitive, successfully detecting only 60-80% of infections in asymptomatic women, and often giving falsely positive results. Culture remains useful in selected circumstances and is currently the only assay approved for testing non-genital specimens.