Background Chlamydia and gonorrhoea are the two most common sexually transmissible infections (STI) among men who have sex with men (MSM) worldwide. Infections at the pharynx and rectum are usually asymptomatic; however, the natural history of these infections remains unknown. The aim of this study is to estimate the duration of both infections at the extragenital sites from published epidemiological cohort studies.
Methods: English peer-reviewed articles were searched from 1 January 2000 to 12 March 2015 in three electronic databases (MEDLINE, EMBASE and Cochrane Central). The prevalence-to-incidence ratio from each study was calculated to reflect the duration of each infection. This review followed the PRISMA guidelines and was registered in PROSPERO (CRD42014007087).
Results: There were 2585 records identified, with 1721 abstracts and 52 full-text articles screened, resulting in four studies fulfilling the inclusion criteria. Pharyngeal gonorrhoea (114-138 days) had a shorter duration of infection than rectal gonorrhoea (346 days). In addition, chlamydia had a longer duration of infection at the pharynx (667 days) and rectum (579 days) compared with gonorrhoea infection.
Conclusions: Gonorrhoea has a shorter duration of infection than chlamydia, suggesting that annual STI screening will be more effective at diagnosing chlamydia than gonorrhoea. The current STI guidelines recommend screening gonorrhoea and chlamydia at least once a year in MSM; it would only detect ~30% of incident pharyngeal gonorrhoea cases, with a mean duration of 4 months.