This article by Roger Pebody first appeared on aidsmpa.com here.
A case-control study, examining the sexual behaviour of German gay men receiving HIV-negative and HIV-positive test results, identified two key factors which distinguish the groups – consistent condom use with casual partners and discussing HIV status with partners.
The results, recently published in BMC Public Health, lend some support to the idea of serosorting (choosing a partner who has the same HIV status), but only when HIV status is ascertained through a clear and unambiguous conversation. Men who didn’t use condoms because they assumed their partner was HIV negative had a greater risk of acquiring HIV than other men.
This was a case-control study – in other words, an observational study in which a group of people with an infection (called ‘cases’) are compared with a group of people without the infection (called ‘controls’). The past events and behaviour of the two groups are compared in order to help us understand the risk factors for acquiring the infection.
Cases were gay men who attended one of a variety of HIV testing facilities in Germany, were diagnosed with HIV and who were determined to have acquired their HIV infection within the previous five months (based on a Recent Infection Testing Algorithm or RITA). Controls were gay men who took an HIV test and received a negative result, matched to the cases on the basis of their age and country of birth.
Information about the sexual behaviour of cases and controls was collected before receiving HIV test results.
Data were collected between 2008 and 2010. There were 105 cases and 105 controls, who had an average age of 34 years. Nine out of ten were born in Germany and they were generally well educated.
There were numerous variables for which no differences were observed between cases and controls:
- Knowledge of HIV transmission risks during different sexual acts.
- Recent HIV testing.
- Recent diagnosis of a sexually transmitted infection.
- Being single.
- Inconsistent condom use in a primary relationship.
However some behavioural factors did distinguish cases (men who acquired HIV) from controls (men who did not) in the first analysis.
More cases (22 men) than controls (10 men) reported having been in a relationship of less than six months duration, and cases were also less likely to be in a relationship lasting more than a year. This points to the risks of HIV transmission during the early stages of romantic relationships.
While equal numbers of cases and controls had only had one sexual partner in the past six months (14 men in each group), average partner numbers were higher for cases (mean 11.8 partners, median 5) than controls (mean 6.6, median 4).
Whereas 60 cases reported having unprotected anal intercourse with a partner of unknown HIV status, this was only reported by 36 controls. There was a marked difference in terms of having unprotected receptive anal intercourse with a partner of unknown status (reported by 43 cases and 18 controls). Cases were also more likely to report inconsistent condom use outside of a primary relationship, with partners met online and with acquaintances.
Moreover, cases were less likely to report ‘always being safe’ with non-primary partners – in other words, consistent condom use or no anal sex. This was reported by 9 cases and 30 controls.
As can be seen only a minority of participants – including the controls – reported consistent condom use. When asked why condoms hadn’t been used on the last occasion of unprotected sex, many responses did not differ between cases and controls. For example, men in both groups said that they hoped nothing would happen, that condoms would have disturbed the mood, or that condoms caused erection problems.
However not using a condom because the respondent had assumed his partner was HIV negative was reported by more cases (25 men) than controls (8 men). Furthermore, while relatively few men said that they didn’t use condoms because they had talked to their partner about HIV status, this was reported much less frequently by cases (3 men) than controls (16 men).
The key results come from the multivariable analysis, which uses statistical techniques to identify the most important factors associated with HIV infection. Only two variables remained statistically significant. Demonstrating the continued relevance of consistent condom use, men who reported ‘always being safe’ were less likely to be diagnosed with HIV (odds ratio 0.23, 95% confidence interval 0.08 – 0.62).
In addition, men who did not use condoms having previously talked to their partner about HIV status were less likely to be diagnosed with HIV (odds ratio, 0.18, 95% confidence interval 0.05 – 0.71).
“One of the key findings was that having an explicit conversation about HIV serostatus before sexual activity reduces the risk of acquiring HIV,” conclude the researchers. “This might be attributable to the mode of serostatus communication: namely a direct and explicit conversation might be protective, whereas other ways of serosorting, such as relying on online profiles, or guessing/assuming HIV status based on appearance, might be much less effective.”
Santos-Hövener C et al. Conversation about Serostatus decreases risk of acquiring HIV: results from a case control study comparing MSM with recent HIV infection and HIV negative controls. BMC Public Health 14:453, 2014. (Full text available freely available here).