Pre-exposure prophylaxis (PrEP) is a highly effective HIV prevention tool but does not protect against sexually transmitted infections (STIs). The US CDC recommends that men who have sex with men (MSM) on PrEP be screened for STIs every 6 months. Among a cohort of participants in a PrEP demonstration project, we assessed: 1) the number and percent of gonorrhea (GC) and chlamydia (CT) infections that would have been missed if extra-genital screening had not been conducted and 2) The number and percent of participants infected with GC, CT or syphilis for whom treatment would have been delayed without quarterly screening.
MSM and transgender women participating in an open-label PrEP demonstration project were tested for syphilis and urethral (U), pharyngeal (P) and rectal (R) GC and CT at screening and at weeks 12, 24, 36 and 48, and treated promptly if positive. Participants were considered asymptomatic if they denied STI symptoms on a structured review of symptoms and did not have any signs on physical examination. To determine the number of infections that would have been missed without extra-genital screening, we calculated the number and proportion of R and P GC and CT infections in which there was not a concurrent U GC or CT infection. To determine the number of participants with GC, CT or syphilis for whom treatment would have been delayed without quarterly screening, we tabulated the number of participants diagnosed with GC, CT or syphilis at weeks 12 and 36 who were asymptomatic at all potential sites of infection.
Between October 2012 and January 2014, 557 participants were enrolled. Overall, 50.9% of participants were diagnosed with ≥1 STI during follow-up. The number of GC, CT and early syphilis infections by visit week, anatomic site (for GC and CT) and symptom status are shown in the Table. A total of 150 (82.9%) GC infections and 159 (75.7%) CT infections would have been missed if extra-genital screening had not been conducted. If screening had been conducted only semi-annually or based on symptoms, 62 (34.3%) of participants with GC, 86 (41.0%) of participants with CT and 11 (20.4%) of participants with syphilis would have been missed, extending the period of infectivity by up to 3 months/case.
Quarterly STI screening, including testing at extra-genital sites, significantly increases detection of GC, CT and syphilis, providing opportunities for prompt treatment, partner therapy, and prevention of STI related morbidity.