Diagnostic relevance of simultaneous testing for Chlamydia trachomatis and Neisseria gonorrhoeae.

Background: The prevalence of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) infection in a Swiss cohort among individuals consulting for screening or symptomatic reasons is not very well known.

Methods: Between January 2009 and January 2010, diagnostic samples referred to us to test for either CT or NG or both were simultaneously analysed for both infections. Testing was performed using the commercial m2000sp and m2000rt devices from Abbott Diagnostics involving automated DNA extraction and semi-quantitative real-time polymerase chain reaction (PCR), respectively.

Results: A total of 9,245 individuals (8,009 female, 1,236 male) were tested. CT alone was found in 318 (3.97%) samples from female patients and NG infections were found in 5 (0.06%) of the female samples. Six (0.08%) women had both CT and NG infections. The numbers for males were 72 (5.83%) for CT alone, 18 (1.14%) for NG alone and 8 (0.65%) for coincident infections. Among women, a selective testing approach in which only the presence of CT was investigated missed six NG cases (0.07% prevalence, 54.55% of all NG-positive women) and the request to test only for NG missed two CT cases (0.02% prevalence, 0.62% of all CT-positive women). For the male samples, one NG case (0.08% prevalence, 3.85% of all NG-positive men) was missed when only CT was requested and three CT cases (0.24% prevalence, 3.75% of all CT-positive men) were overlooked when only NG testing was requested.

Conclusion: A sizeable number (12) of CT and NG cases is missed by physician-referred testing for only one of the two pathogens.