Prevalence, incidence and risk factors for pharyngeal chlamydia in the community based Health in Men (HIM) cohort of homosexual men in Sydney, Australia.
OBJECTIVE
To determine the prevalence, incidence and risk factors for pharyngeal Chlamydia trachomatis in the community based Health in Men (HIM) cohort of HIV negative homosexual men in Sydney, Australia.


METHODS
From January 2003, all HIM participants were offered annual screening for pharyngeal chlamydia using BD ProbeTec nucleic acid amplification testing (NAAT). Detailed sexual behavioural data were collected every 6 months, and risk factors for infection and hazard ratios were calculated using Cox regression.


RESULTS
Among 1427 participants enrolled, the prevalence of pharyngeal chlamydia on initial testing was 1.06% and the incidence rate was 0.58 per 100 person-years. More than 50% of all infections were identified on baseline testing and 68% of men with pharyngeal infection had no evidence of concurrent anogenital chlamydia. There was no association of pharyngeal chlamydia with sore throat. Infection was significantly associated with increasing frequency of receptive penile-oral sex with ejaculation with casual partners (p = 0.009), although approximately half of infections occurred in participants not reporting this risk behaviour. Neither kissing nor oro-anal practices were associated with infection.


CONCLUSIONS
The incidence of pharyngeal chlamydia infection in the HIM study was relatively low; however, the relatively high prevalence on baseline testing compared to incidence suggests a long duration of infection. Occasional screening for pharyngeal chlamydia in homosexual men who frequently practise receptive oral sex with ejaculation may be warranted.
Templeton
D J
DJ
National Centre in HIV Epidemiology and Clinical Research, The University of New South Wales, Level 2, 376 Victoria Street, Sydney NSW 2010, Australia. dtempleton@nchecr.unsw.edu.au
Jin
F
F
Imrie
J
J
Prestage
G P
GP
Donovan
B
B
Cunningham
P H
PH
Kaldor
J M
JM
Kippax
S
S
Grulich
A E
AE
D000293:Adolescent; D000328:Adult; D000368:Aged; D002690:Chlamydia Infections / Q000453:epidemiology* / Q000209:etiology; D002692:Chlamydia trachomatis; D018451:Homosexuality, Male; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009517:New South Wales / Q000453:epidemiology; D010608:Pharyngeal Diseases / Q000453:epidemiology*; D015995:Prevalence; D012307:Risk Factors; D047568:Unsafe Sex / Q000706:statistics & numerical data*