Comparison of transcription-mediated amplification and PCR assay results for various genital specimen types for detection of Mycoplasma genitalium

Mycoplasma genitalium is now recognized as a possible cause of several idiopathic sexually transmitted disease (STD) syndromes. However, due to the difficulty of culture of this fastidious bacterium, nucleic acid amplification tests (NAATs) are necessary for its detection in patient specimens. In the current study we compared a newly developed research-only transcription-mediated amplification (TMA) assay (Gen-Probe Incorporated) to our in-house DNA-based PCR assay for detection of M. genitalium. The relative performance characteristics of these two NAATs were assessed with genital specimens from 284 women and 352 men reporting to an STD clinic in Seattle, WA. Among the women, M. genitalium was detected by the TMA and PCR assays in 36 (13%) and 39 (14%) vaginal swab specimens, respectively (kappa = 0.923); 26 (9%) and 23 (8%) cervical swab specimens, respectively (kappa = 0.843); and 25 (9%) and 28 (10%) urine specimens, respectively (kappa = 0.687). Among the M. genitalium-positive women, the relative sensitivities of detection for the TMA and PCR assays were 84% and 91%, respectively, for vaginal swab specimens; 60% and 53%, respectively, for cervical swab specimens; and 58% and 65%, respectively, for urine specimens. By using an infected patient (a woman positive at any site by TMA assay and at any site by PCR) as a proxy for a "gold standard," the specificities of detection were >99.5% for both the TMA and the PCR assays. Among the men, M. genitalium was detected in 24 urine specimens (6.8%) by the TMA assay, 26 (7.4%) urine specimens by PCR assay, and 32 urine specimens (9%) by either test (kappa = 0.791). We conclude that the M. genitalium TMA and PCR assays are highly specific and that vaginal swab specimens are the most sensitive specimen type for the detection of M. genitalium in women.