Timing and frequency of chlamydia and gonorrhoea testing in a cross-sectional study of HIV postexposure prophylaxis recipients

Objectives: Australian HIV postexposure prophylaxis (PEP) guidelines recommend Chlamydia trachomatis (CT) and Neisseria gonorrheae (NG) testing at both baseline and 2-week postexposure visits. We aimed to determine the diagnostic yield of testing at one or more visits, and predictors of infection.

Methods: Data were collected from patients prescribed PEP at RPA Sexual Health over a 4-year period from January 2008 to December 2011. Predictors of CT/NG were assessed by logistic regression.

Results: 282 individuals presented for PEP on 319 occasions during the study period. The majority (94.3%) were male and over 90% of presentations followed unprotected anal sexual exposures. Most (279, 87.5%) had CT/NG testing at least once. Almost half (153, 48.0%) of baseline presentations, two-thirds (214, 67.1%) of 2-week presentations and over a quarter (88, 27.6%) of both presentations included CT/NG testing. CT/NG was diagnosed at baseline in eight (5.2%, 95% CI 2.3% to 10.0%) presentations. A new CT/NG diagnosis occurred at the 2-week visit in 18 (8.4%, 95% CI 5.1% to 13.0%) presentations, of whom 7 tested negative and 11 were not tested at baseline. Over one-quarter (28.1%) of PEP recipients reported sexual contact between baseline and 2-week visits. Independent predictors of CT/NG at baseline were recent sex work (OR 48.0, 95% CI 3.77 to 611.94); and at 2 weeks a known HIV-positive PEP exposure source (OR 3.54, 95% CI 1.04 to 12.06) and sex between baseline and 2-week visits (OR 3.63, 95% CI 1.10 to 11.96).

Conclusions: Our findings suggest that screening PEP recipients for CT/NG at both baseline and 2 weeks may be warranted.