Time trends in HIV incidence among homosexually active men seen at sexual health clinics in Australia, 1993-1999

A new surveillance system for monitoring HIV infection in Victoria, Australia

Objectives: To establish a new mechanism for monitoring patterns of HIV infection, in the context of a sustained increase in HIV diagnosis among men who have sex with men (MSM) in Victoria. Methods: Between April 2004 and August 2005, a linked voluntary HIV sentinel surveillance system was implemented at five medical clinics with a high case load of MSM. Using a questionnaire, doctors collected HIV testing history, demographic and sexual risk behaviour information from all clients undergoing voluntary HIV testing. Questionnaires were linked with HIV test results. Logistic regression analysis was conducted to determine factors associated with HIV infection. Results: Of 3435 MSM tested for HIV at participating sites, 1.7%, (95% CI = 1.2–2.2) were newly diagnosed with HIV; between 2004 and 2005 the proportion increased from 1.3% (95% CI = 1.2–1.5) to 2.0% (95% CI = 1.8–2.2), P = 0.107. There was no significant change in the number of HIV tests conducted per month or in demographic characteristics, testing history and sexual behaviour characteristics between time periods. In multivariate analysis, reporting unprotected anal intercourse (UAI) with any partner, UAI with a HIV-positive partner/s and being aged 30–39 years or 40 years or greater were significantly associated with HIV infection. Conclusion: This new surveillance mechanism, based on linked testing at participating clinics, indicates that the increase in HIV notifications in 2005 was unrelated to changes in testing and data from a Melbourne sexual behavioural survey suggests the increase was more likely to be attributed to increases in transmission within the past few years. The sentinel system highlighted UAI, especially with HIV positive partner/s are important transmission factors.

Men who have sex with men (MSM) in public sex environments (Pses): a systematic review of quantitative literature

We systematically review quantitative research relating to the sexual behaviours of MSM in PSEs. We examine the methodological rigour of these studies to determine an appropriate framework for future PSE-based research and quantify sexual behavioural trends therein. Medline, BIDS, Web of Science and recent HIV/AIDS conferences were searched according to a systematic inclusion criteria. Nine papers were included for review. Recruitment of participants' outwith PSE settings, and low response rates (6%) of participants contacted in situ, question the validity and generalizability of current evidence. Most PSE users were gay or bisexually identified and half of men in the gay community reported recent PSE use. Around 10% of men reported casual status-unknown/serodiscordant unprotected anal intercourse (UAI) within PSEs. HIV testing rates amongst PSE users were similar to the wider gay community, though the proportion of men who tested positive was twice as high. Rates of casual UAI suggest that PSEs represent important sites for HIV prevention. However, since extant evidence is scant and methodologically flawed, further research is urgent. Such work must recruit participants in situ, and obtain satisfactory response rates, to be generalizable to the wider population of men who cruise.

Studies relying on passive retrospective cohorts developed from health services data provide biased estimates of incidence of sexually transmitted infections

OBJECTIVE

Passive retrospective cohorts composed of persons who have tested 2 or more times for a sexually transmitted infection (STI) of interest during clinical visits have been used to estimate STI incidence. We hypothesized that the analytic period of a passive cohort might affect the estimate of STI incidence, with shorter periods yielding higher estimates of incidences of infection.

STUDY

We analyzed data collected from women, 12 to 24 years of age, tested for chlamydia 2 or more times at 6 sites in San Francisco between January 1997 and December 2000. Incidence was calculated for 10 different analytic periods.

RESULTS

The calculated incidence of chlamydial infection during 1997 was 16.8 (95% confidence interval [CI], 10.9-24.0) per 1000 person-months of follow up. The calculated incidence dropped markedly as the analytic period lengthened, with the incidence estimated to be 9.7 (95% CI, 8.6-10.9) using a study period of 4 years (1997-2000). Estimates of incidence were similar when using the same analytic period, regardless of calendar year, and there was a similar decline in estimated incidence using longer analytic periods.

CONCLUSIONS

Estimates of STI incidence based on passive cohort data may have limited epidemiologic value because incidence measures may be highly dependent on the analytic period.