HIV prevention studies in Africa: it's important to ask about anal sex

Individuals enrolled on HIV prevention trials in Africa should be asked if they have had anal sex, suggest investigators in a article published in the online edition of Sexually Transmitted Infections. Their study found that 18% of women enrolled in their study had recently had receptive anal sex and that undiagnosed anal sexually transmitted infections were present in many of these individuals.

Studies into sexual behaviour in Africa have often neglected to enquire about anal sex, and sex between men. There has either been an assumption that such behaviour was not prevalent, or a sensitivity to cultural taboos and prejudices means that investigators are reluctant to enquire about such behaviour. But studies are now suggesting that anal intercourse is common in Africa in both heterosexual and homosexual contexts and is an important mode of HIV transmission.

The study also showed that relying on patient report of symptoms will lead to many sexually transmitted infections remaining undiagnosed, and that simple microscope examinations of genital and anal swabs can lead to more infections being diagnosed.

Numerous HIV prevention studies are underway around the world. Investigators involved in one such study in Mombasa, Kenya, wanted to demonstrate the value of introducing routine sexual health screens involving basic laboratory tests, and the value of asking individuals about anal sex so that they could be offered appropriate tests and treatment.

The study ran between 2005 and 2007 and recruitment was focused on individuals with a high risk of HIV, including 334 commercial sex workers, 316 men who have sex with men, 169 individuals with multiple sexual partners, 59 patients with recent symptomatic sexually transmitted infections, and 28 HIV-negative individuals with an HIV-positive partner.

Initially the investigators did not ask about receptive anal intercourse. It was only in 2006, after the study had been running for over a year, that questions about anal intercourse were included because participants were frequently reporting this behaviour or symptoms suggestive of a sexually transmitted infection in the anus.

It became clear to the investigators that they could not rely on self-report of symptoms to diagnose sexually transmitted infections. The majority of women (60%, 20 of 32) with trichomoniasis did not have any discharge, and their infection was only diagnosed after genital swabs were examined under a microscope. Of the 13 women with laboratory-confirmed pelvic inflammatory disease, only three had any symptoms. Similarly, 67% of urethritis cases were only diagnosed after microscope analysis of samples.

Another important finding of the study was a high prevalence of receptive anal intercourse, which was reported by 36% of the men who have sex with men and by 18% of the women. Most (89%), but not all of these women were sex workers. Symptoms suggestive of an anal infection were reported by a third of patients reporting receptive anal sex. A total of 69 patients agreed to have an anal examination using a proctoscope, and 20% of these patients had visible discharge, 20% inflammation, and 7% ulcers. Proctitis was diagnosed in 7% of patients after microscope examination of rectal swabs.

Amongst men, recent receptive anal sex was strongly associated with HIV infection (adjusted odds ratio, 3.8; 95% CI, 2.0 – 6.9), however this was not the case in women. But the investigators did note that two-thirds of syphilis cases in women were in individuals reporting anal sex (adjusted odds ratio, 12.9; 95% CI: 3.4 – 48.7).

The investigators also found that men infected with HIV were also more likely to have anogenital ulcers and warts and have urethritis. HIV infection in women was associated with anogenital warts and pelvic inflammatory disease.

“Given that anal sex is not uncommon among high-risk adults, we recommend that STI screening include questions on receptive anal intercourse and the diagnosis of proctitis when symptoms are present”, write the investigators.

The investigators also make recommendations regarding the recruitment of high-risk individuals to HIV prevention studies, including vaccine trials.

• Focus on risk behaviour rather than risk group.
• Individuals reporting recent receptive anal sex should be screened for infections with appropriate management.
• Incorporating sexual health screens and treatment can reduce the risk of HIV infection for individuals and could help recruitment to prevention studies in resource limited settings.

This study raises some significant issues about the design and robustness of HIV prevention studies in Africa. In particular, it is notable that although this study recruited men who have sex men from the outset, the study protocol did not initially include questions on anal sex. It was only after the study had been running for over a year that reports of anal sex from participants lead to a change in the protocol and the inclusion of questions about anal intercourse.

Furthermore, there is a continuing reluctance in some African contexts to acknowledge the prevalence of anal intercourse in both heterosexuals and homosexuals. The investigators note, “questions on receptive anal intercourse in the recently conducted national AIDS survey in Kenya were rejected as being too offensive to ask…unfortunately, data on the general population practice of anal sex in Kenya remains elusive."