title: Rectal chlamydia--a reservoir of undiagnosed infection in men who have sex with men.
abstract: OBJECTIVE
  To determine the prevalence of rectal chlamydia infection in a cohort of men who have sex with men (MSM) and the proportion of infection that would be missed without routine screening.
  
  
  METHODS
  MSM presenting to four HIV/GUM outpatient clinics at the Chelsea & Westminster Hospital NHS Foundation Trust between 1 November 2005 and 29 September 2006 were offered testing for rectal chlamydia infection in addition to their routine screen for sexually transmitted infections (STIs). Chlamydia trachomatis (CT) tests were performed using the Beckton-Dickinson Probe-Tec Strand Displacement Assay. Positive samples were re-tested at the Sexually Transmitted Bacteria Reference Laboratory, to confirm the result and identify lymphogranuloma venereum (LGV)-associated serovars.
  
  
  RESULTS
  A total of 3076 men were screened. We found an 8.2% prevalence of infection with CT (LGV and non-LGV serovars) in the rectum and 5.4% in the urethra. The HIV and rectal chlamydia co-infection rate was 38.1%. The majority of rectal infections (69.2%, (171/247)) were asymptomatic and would have been missed if routine screening had not been undertaken. Of the samples re-tested, 94.2% (227/242) rectal and 91.8% (79/86) urethral specimens were confirmed CT positive and 36 cases of LGV were identified.
  
  
  CONCLUSIONS
  Our data show a high rate of rectal chlamydia infection, in the majority of cases it was asymptomatic. We recommend routine screening for rectal chlamydia in men at risk, as this may represent an important reservoir for the onward transmission of infection.
authors.affiliation: GUM/HIV Directorate, Chelsea & Westminster Hospital NHS Foundation Trust, London, UK. torshie.annan@fph-tr.nhs.uk
authors.forename: N T
authors.initials: NT
authors.lastname: Annan
authors.forename: A K
authors.initials: AK
authors.lastname: Sullivan
authors.forename: A
authors.initials: A
authors.lastname: Nori
authors.forename: P
authors.initials: P
authors.lastname: Naydenova
authors.forename: S
authors.initials: S
authors.lastname: Alexander
authors.forename: A
authors.initials: A
authors.lastname: McKenna
authors.forename: B
authors.initials: B
authors.lastname: Azadian
authors.forename: S
authors.initials: S
authors.lastname: Mandalia
authors.forename: M
authors.initials: M
authors.lastname: Rossi
authors.forename: H
authors.initials: H
authors.lastname: Ward
authors.forename: N
authors.initials: N
authors.lastname: Nwokolo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002690:Chlamydia Infections / Q000175:diagnosis* / Q000453:epidemiology; D002692:Chlamydia trachomatis / Q000302:isolation & purification*; D015331:Cohort Studies; D003955:Diagnostic Tests, Routine; D015658:HIV Infections / Q000453:epidemiology; D018451:Homosexuality, Male; D006801:Humans; D008131:London / Q000453:epidemiology; D008219:Lymphogranuloma Venereum / Q000175:diagnosis / Q000453:epidemiology; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D015995:Prevalence; D012002:Rectal Diseases / Q000175:diagnosis / Q000453:epidemiology*; D012007:Rectum / Q000382:microbiology; D014521:Urethra / Q000382:microbiology; D014522:Urethral Diseases / Q000175:diagnosis / Q000453:epidemiology*; D055815:Young Adult