ATLANTA – A large proportion of minority men with early syphilis who have sex with men, as well as those who have sex with both men and women, acquired the infection through behaviors that are not likely to be detected during routine risk evaluations, according to an analysis of cases throughout Los Angeles County.
Latent class analysis – a statistical procedure for identifying clusters of individuals in a population – identified five relevant risk behavior subgroups among 4,178 cases of syphilis reported in men who have sex with men (MSM) and men who have sex with men and women (MSMW) between 2010 and 2012, Ryan Murphy, Ph.D., reported at a conference on STD prevention sponsored by the Centers for Disease Control and Prevention. The subgroups included individuals who:
CDC
Routine risk evaluations may not be enough to detect early syphilis in minority men.
• had no identified risk (33% of cases).
• were at risk for having sex with anonymous or many partners without substance use (48%).
• were at risk for being high or intoxicated during sex, as well as having sex with many partners (11%).
• were at risk for being high or intoxicated during sex and having sex with anonymous partners (7%).
• reported all of these risk factors as well as having sex in exchange for drugs or money or trading drugs or money for sex (2%).
Once the clusters were identified, additional analysis was performed to identify variables associated with each cluster, said Dr. Murphy of the Los Angeles Department of Public Health.
"We found quite a few associations," he said.
For example, compared with whites, blacks and hispanics were more likely to be in the "no identified risk" and "substance use during sex and having sex with anonymous partners" risk groups, Dr. Murphy said.
Also, MSMW with early syphilis were more likely than MSM with early syphilis to report trading sex for drugs or money.
Geographical differences were also identified, and were very highly correlated with race/ethnicity. Those living in the metro area of Los Angeles were less likely than those in other areas to be in the "no identified risk" group, Dr. Murphy noted.
Perhaps most surprising was the finding that a third of cases had no "identified" risk, he said.
"We put ‘identified’ in quotation marks, because these are all men with early syphilis, so we know everybody’s high risk. It’s just that in that first cluster, they aren’t reporting any of the risk behaviors," he said.
Cases analyzed for this study included all cases of early syphilis – meaning cases that were still in the infectious stages – that were reported to the Los Angeles Department of Public Health Division of HIV and STD Programs from 2010 through 2012.
The findings underscore the importance of recognizing the wide range of risk behaviors that can contribute to early syphilis, Dr. Murphy said.
Also, the finding that many MSM and MSMW – particularly those living outside the metro Los Angeles area – acquire syphilis through patterns of behavior that aren’t likely to be detected during routine screening emphasizes the need to recognize that some patients at risk won’t be easily identified and raises questions about whether that group is getting less screening, and whether there are infections going untreated, he said.
This point underscores the importance of "looking at messaging to providers and making sure we are really driving home the importance of routine syphilis screening for MSM, even in the absence of reported risk behaviors," he said.
The data also highlight the value of latent class analysis for identifying particular risk groups and suggest that targeted interventions based on the risk profiles might be useful in those groups, he said.
"So we could look at those clusters and see, for example, who was reporting drug use, and then maybe that’s part of your intervention for that group or geographic area," he said.
Dr. Murphy reported having no disclosures.