Background:
The clinical and preventive care of MSM seen in STD clinics is currently relatively uniform, with little specific follow-up directed toward those at greatest risk. Intensified interventions will require identification of the highest risk MSM.

Objective:
To estimate HIV incidence in MSM STD clinic patients, and devise criteria to identify the highest risk men for potential intensified intervention.

Method:
We identified MSM serially HIV tested in the PHSKC STD clinic between 2001 and 2005, calculated HIV incidence in the population, and developed criteria to identify high-risk men for intensified follow-up.

Result:
A total of 2698 MSM were seen in the clinic, of whom 954 tested for HIV more than once. Forty-six seroconversions were identified over 1715 person-years (incidence=2.9 per 100 person-years, 95%CI: 1.96-3.58). On multivariate analysis, incident HIV infection was associated with the following factors identified at initial testing visit: methamphetamine use (HR=1.87), syphilis (HR=3.38), gonorrhea (HR=3.49), and sex with a partner of discordant or unknown HIV status (HR=2.33). The 45% of men with one or more of these risk factors accounted for 73% of the cases of HIV and 40% of the total person-time. Men with any of the associated risk criteria experienced an incidence of 6.4 per 100 person-years (95%CI: 4.6-8.7), while men with none of the identified risk factors had an incidence of 2.1 per 100 person-years (95%CI: 1.2-3.5).

Conclusion:
Easily ascertained risk factors can identify MSM STD clinic patients at very high risk of acquiring HIV.

Implications:
Seroconversion risk criteria can be used to identify candidate populations for intensified prevention interventions, such as scheduled follow-up HIV/STD testing and methamphetamine treatment interventions.