Swabs (dry or collected in universal transport medium) and semen can be used for the detection of Chlamydia trachomatis using the cobas 4800 system

In this prospective study, the fully automated cobas 4800 CT/NG and the cobas TaqMan CT tests were compared for Chlamydia trachomatis detection in urine and in genital specimens collected with Copan flocked swabs in culture media. A protocol was also established for the highly sensitive detection of C. trachomatis in semen specimens using the cobas 4800 CT/NG test. A total of 708 consecutive urogenital samples (293 male urine samples and 356 vaginal, 45 cervical and 14 urethral swabs) obtained from the Bacteriology Department, as well as 100 consecutive semen samples collected from patients attending the Reproduction Biology Department, Bordeaux University Hospital, France, from July to September 2010, were analysed. Positive and negative agreements between the cobas 4800 CT/NG and cobas TaqMan CT tests were 92.7 % [95 % confidence interval (CI), 82.7–97.1 %] and 99.2 % (95 % CI, 98.2–99.7 %), respectively, with an overall agreement of 98.7 % (699/708). The clinical sensitivity of the cobas 4800 CT/NG assay for C. trachomatis ranged from 90.9 to 100 % depending on specimen type, with an overall prevalence of 7.2 % (51/708). The clinical specificity ranged from 99.1 to 100 % depending on specimen type. Dilution of 25 µl semen samples in cobas PCR medium proved to be the most sensitive protocol with the lowest inhibition rate. In conclusion, the cobas 4800 CT/NG test was found to be an effective method for detection of C. trachomatis in semen, male urine and genital swab samples collected dry or in universal transport medium.