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.
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
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.
about the sexual behaviour of cases and controls was collected before receiving HIV test results.
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.
numerous variables for which no differences were observed between cases and
- Knowledge of HIV transmission
risks during different sexual acts.
- Recent HIV testing.
- Recent diagnosis of a sexually
- Being single.
- Inconsistent condom use in a
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
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
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.”