Serosorting and 'strategic positioning' used by HIV-positive US gay men to reduce HIV transmission risks, shows meta-analysis

Michael Carter
Published: 21 August 2009

Over 40% of gay and other men who have sex with men diagnosed with HIV in the US have unprotected anal intercourse, according to the results of a meta-analysis published in the August 24th edition of AIDS. However, there was evidence that those engaging in unprotected sex were attempting to limit the risk of HIV transmission to partners by employing strategies such as "serosorting" (sex with other HIV-positive men) or “strategic positioning” (adopting the receptive role during unprotected sex). There was no evidence that clinical factors such as adherence to HIV treatment, or an undetectable viral load affected unprotected sexual activities.

Gay and other men who have sex with men in the US are disproportionately affected by HIV and other sexually transmitted infections. Many men reduce their HIV risk behaviour after their diagnosis with HIV, but others continue to have unprotected sex which and this may involve a risk of HIV transmission to others, or exposure to sexually transmitted infections.

Several studies have examined the prevalence of unprotected anal intercourse amongst gay and other men who have sex with men in the US who have been diagnosed with HIV. To obtain a synthesis of the findings of this research, investigators performed a meta-analysis of the results of 30 studies conducted between 2000 and 2007 that examined unprotected sexual behaviours in this population.

To avoid over-estimating the prevalence of unprotected anal sex, the researchers excluded studies that exclusively recruited men with behaviours that could inflate the proportion such activity (for example, users of methamphetamine, or sex workers) and studies that recruited men from settings such as “barebacking” websites, sex parties, and saunas.

The studies included in the analysis involved a total of 18,121 men. These men were recruited either from clinics or gay venues and events. All these studies were cross-sectional (a “snap-shot”), and 21 included men recruited as a convenience sample, the other nine used random sampling methods.

The median age of the study participants was 38 years. The median duration of diagnosed HIV infection was 70 months, and the proportion of individuals taking antiretroviral therapy ranged from 23% to 89% (median, 77%). The percentage of individuals who reported taking at least 90% of their treatment doses ranged from 26% to 76% (median, 67%), and the proportion of patients with an undetectable viral load ranged from 39% to 57% (median, 42%).

Overall, the combined results of the studies showed that 43% of men reported unprotected anal sex. This behaviour was reported most frequently with other men known to be HIV-positive (in other words, serosorting). However, 26% of men reported unprotected sex with a man who was HIV-negative or of unknown HIV status.

There was evidence that men were attempting to reduce the risk of HIV transmission to HIV-negative partners by adopting a receptive role during unprotected sex (9% receptive vs. 5% insertive). Similarly, men were more likely to be receptive when their partner was of unknown HIV status (12% receptive vs. 8% insertive).

In the investigators’ first set of statistical analysis, the prevalence of unprotected sex was lower in studies that:

  • Recruited before 2000.
  • Included men of colour rather than white men.
  • Recruited participants from medical settings rather than gay venues or events.
  • Used a random sampling technique rather than a convenience sample.
  • Had the questionnaire administered by an interviewer rather than being self-completed.

In “multivariate” analysis, only sampling method and how the questionnaire was administered remained significant. The investigators suggest that further research is needed to identify why method of sampling was significant.

They also note “the fact that unprotected anal intercourse prevalence was significantly higher in studies with self-administered questionnaires than in studies with interviewer-administered questionnaires suggests that HIV-seropositive men who have sex with men may have underreported socially undesirable behaviours when the questionnaire was administered by an interviewer.”

“We found that a sizeable percentage of HIV-diagnosed men who have sex with men engaged in unprotected anal intercourse with male partners”, write the investigators.

They add, “this is an important public health concern, given the high prevalence of HIV and sexually transmitted infections among men who have sex with men in the United States.”

However, they also found evidence that “some HIV-diagnosed men who have sex with men engage in behaviours that may lessen the probability of infecting others.”

The investigators believe that their results are “useful for targeted prevention efforts” and suggest that a priority for such work should be “the safety of serosorting and strategic positioning.”


Crepaz N et al. Prevalence of unprotected anal intercourse among HIV-diagnosed MSM in the United States: a meta-analysis. AIDS 23: 1617-1629, 2009.

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