Discussion

Between 2005 and 2008, there was a substantial increase in the proportion of men reporting ever and recent HIV testing in community-based surveys in Scotland (in continuation of a trend noted previously).4 Collection of oral fluid specimens in 2005 and 2008 provided the unique opportunity to assess the association of this increase with undiagnosed infection in this population for the first time. There are some limitations to note when considering our results. This was a venue-based sample so caution should be exercised when generalising to the wider population. The oral fluid specimen response rate was relatively low, and may not be representative. However, the overall survey response rate was higher (66% in 2005 and 71% in 2008), and there were few differences between the men who did and did not provide oral fluid specimens;7 8 suggesting that the men who provided these were representative of the larger venue-based sample. It should also be noted that the question used to derive recent HIV testing, and therefore the period defined as recent testing, was different in 2005 and 2008 (16 months in 2005 and 12 months in 2008). However, if this had affected the results then reported recent testing would almost certainly have been higher in 2005 than in 2008, which was not the case. Finally, caution should be exercised in interpreting our findings on the recency of HIV testing and undiagnosed infection, given the small numbers involved. This could also have limited power to detect a difference between years.

Although testing rates have traditionally been lower in the Scottish surveys than those observed in other UK cities,4 9 the rates are now more similar to those reported in comparable venue-based surveys in London, Manchester and Brighton.10 Almost half of the men surveyed in Glasgow and Edinburgh reported having tested in the past year. It is encouraging that recent HIV testing has continued to increase among MSM in Scotland; strong evidence of an impact beyond the clinical setting of the opt-out testing policy, now recommended throughout the UK.11 However, although there was a concurrent, albeit non-significant, reduction in undiagnosed HIV, our results cannot address whether the two are causally linked and do not suggest the two are directly correlated, with no difference in undiagnosed infection between men who had and had not tested recently. This raises the question of what more can be done to reduce undiagnosed HIV in this population?

Estimates suggest one in five UK MSM newly diagnosed with HIV are diagnosed within 6 months of infection.3 Here, just under half of undiagnosed HIV-positive men reported having had a (negative) HIV test in the past year. With high viral loads immediately after seroconversion,12 the risk of onward HIV transmission is apparent. Lower proportions of undiagnosed infection among the most recent HIV-positive testers (in the past 6 months) are consistent with even more frequent (than annual) testing playing a role in reducing undiagnosed HIV. However, the decline in recent testing with age (noted here and in our previous analysis of trends between 1996 and 2005)4 suggests that men may not test regularly. This implies that the challenge now is to increase the frequency of HIV testing, and essentially ‘normalise’ regular testing among gay men at risk of HIV. Current policy recommends annual testing,11 but there is a case for testing the acceptability of greater frequencies of 6, 3 or even 1-monthly intervals. This is no easy task, and as much attention must be given to why men would want (and therefore be willing) to increase the frequency of testing,13 as to achieving this.

There is growing interest and debate around the use of treatment for HIV transmission prevention.14–17 The premise for this is that if new HIV infections are predominantly transmitted from HIV-infected individuals not on treatment, treating all HIV-infected individuals regardless of CD4 cell counts could ultimately reduce HIV transmission at the community level.14 For new infections to be promptly identified and treated, frequent, regular HIV testing among at-risk groups is central to this approach. Although the evidence is mainly limited to modelling or ecological and observational studies,14 18–21 a ‘test and (immediate) treat’ approach has been adopted in San Francisco.22 The Strategic Timing of Antiretroviral Treatment (START) study (clinicaltrials.gov NCT00867048) will inform us whether earlier treatment initiation is of individual benefit. If demonstrated to be the case, increasing the frequency of HIV testing will be vital.

There is also still some question as to whether treatment does reduce sexual transmission of HIV.23 Although there is evidence to suggest this could be the case within heterosexual partnerships,24 there is not currently the same evidence for MSM. There are further concerns about the development of drug resistance, the interaction of other sexually transmitted infections, and the possible impact of increasing risk behaviours.14 15 17 Studies have shown that most HIV-positive MSM reduce sexual risk behaviour after diagnosis;25–27 however, a recent review reported that the prevalence of unprotected anal intercourse with a partner of unknown or discordant HIV status in the past 12 months was 26% among diagnosed HIV-positive MSM in the USA.28 We previously found similarly high rates of sexual risk among this group in the UK,29 not all of which could be accounted for by risk-reduction strategies, and there was some suggestion that it was maintaining safer sex behaviour that men find difficult (with higher risk among men diagnosed over a year earlier). Therefore, behaviour change, particularly during the period immediately after seroconversion when HIV transmission could be more likely,12 remains a necessary goal of any HIV prevention strategy.

The UK policy change to opt-out HIV testing appears to have had a significant impact on the testing rates of MSM. However, with only one in five UK MSM newly diagnosed with HIV diagnosed within 6 months of infection,3 and high viral loads immediately after seroconversion,12 increasing earlier diagnosis is imperative. Further expansion of HIV testing in clinical and community settings has been recommended to reduce undiagnosed HIV further,3 but beyond providing additional testing opportunities, there is little to suggest this would have any great impact on the frequency with which MSM test for HIV. It is the latter that remains the challenge to be met and may have the greatest chance of reducing the undiagnosed fraction and having a real impact on the HIV epidemic among MSM in the UK.