The prevalence of rectal chlamydial infection amongst men who have sex with men attending the genitourinary medicine clinic in Edinburgh.

Little is known about the prevalence of rectal chlamydial infection amongst men who have sex with men (MSM). Previous studies using culture methods reported this to be between 4-6%. The emergence of nucleic acid amplification tests has significantly increased the sensitivity and specificity for chlamydial detection, making it possible to estimate the prevalence of rectal infection more accurately. A prospective cross sectional study involving 443 MSM who were screened for sexually transmitted infections (STIs) between May 1999 and January 2002. Rectal swabs for chlamydiae were obtained in addition to specimens for routine STI screening. Rectal chlamydiae were detected by ligase chain reaction (LCR) utilizing the Abbott LCX Amplicor with confirmation by COBASE amplicor for the majority of cases. Those with rectal chlamydial infection were treated with azithromycin. The characteristics of men with rectal chlamydial infection were compared with those who were not infected at this site. Rectal chlamydia was detected in 32 (7.2%) of 443 patients. Those with rectal chlamydial infection were more likely to have rectal symptoms (12/32) or having a partner with confirmed chlamydial (2/32) or gonococcal (3/32) urethritis than those MSM without rectal chlamydial infection. They were also more likely to have a history of receptive anal sex (25/32) in the previous three months compared to those MSM without rectal chlamydial infection (263/411). The most common symptoms of patients with rectal chlamydial infection were pruritus ani and peri-anal pain. Eight (25%) of those with rectal chlamydial infection were known to be HIV seropositive. Rectal chlamydial infection is common amongst MSM and is effectively diagnosed by LCR. The test should be included in the routine STI screening offered to MSM.