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.