Over 40% of gay men with HIV in UK are undiagnosed, 60% believing they do not have HIV

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More than 40% of gay men who were found to be HIV-positive during anonymous testing in five UK cities were unaware of their positive HIV antibody status, according to the results of a UK study published in the May 31st edition of the journal, AIDS. This makes for “a perfect storm” for HIV transmission, argues an accompanying editorial. Both the study authors and the editorial call for better HIV testing strategies, as well as renewed promotion of behaviour change, such as lower risk sexual practices, condom use, and partner number reduction.

In order to better understand the links between sexual risk behaviour, HIV testing status and HIV prevalence in five major UK cities – London, Brighton, Manchester, Glasgow, and Edinburgh – investigators from the Medical Research Council's Social and Public Health Sciences Unit in Glasgow and the Centre for Sexual Health and HIV Research, at UCL, London, conducted cross-sectional surveys along with anonymous HIV testing in bars, clubs and saunas frequented by gay men in London, Brighton and Manchester in 2003/4 and in Glasgow and Edinburgh in 2005.

Their headline findings, presented two years ago at the Sixteenth International AIDS Conference in Toronto, reported here, was that 41.2% of the HIV-positive gay men were undiagnosed, and this ranged from 48.1% in Glasgow to 33.3% in Brighton (with 44.1% undiagnosed in London, 36.7% in Manchester, and 36.4% in Edinburgh).


unprotected anal intercourse (UAI)

In relation to sex, a term previously used to describe sex without condoms. However, we now know that protection from HIV can be achieved by taking PrEP or the HIV-positive partner having an undetectable viral load, without condoms being required. The term has fallen out of favour due to its ambiguity.

adjusted odds ratio (AOR)

Comparing one group with another, expresses differences in the odds of something happening. An odds ratio above 1 means something is more likely to happen in the group of interest; an odds ratio below 1 means it is less likely to happen. Similar to ‘relative risk’. 


A serodiscordant couple is one in which one partner has HIV and the other has not. Many people dislike this word as it implies disagreement or conflict. Alternative terms include mixed status, magnetic or serodifferent.


The transition period from infection with HIV to the detectable presence of HIV antibodies in the blood. When seroconversion occurs (usually within a few weeks of infection), the result of an HIV antibody test changes from HIV negative to HIV positive. Seroconversion may be accompanied with flu-like symptoms.


safer sex

Sex in which the risk of HIV and STI transmission is reduced or is minimal. Describing this as ‘safer’ rather than ‘safe’ sex reflects the fact that some safer sex practices do not completely eliminate transmission risks. In the past, ‘safer sex’ primarily referred to the use of condoms during penetrative sex, as well as being sexual in non-penetrative ways. Modern definitions should also include the use of PrEP and the HIV-positive partner having an undetectable viral load. However, some people do continue to use the term as a synonym for condom use.

In this paper, investigators from Medical Research Council and University College London explored behavioural and other differences between the 187 HIV-positive men who were aware of their HIV status, and the 131 HIV-infected men who were not. This is the first time that the behaviour of undiagnosed HIV-positive gay men has been explored in such depth.

Testing history and HIV status perceptions

In total, 103 (81.1%) of the undiagnosed men reported having had a previous HIV test at any time prior to the survey – 92% reported having tested negative; the remaining 8% reported not knowing the test result.

The investigators found that undiagnosed men were more likely to report having had an HIV test in the year prior to the survey than HIV-negative men (45% vs. 36%), and were less likely to report never having tested (19% vs. 32%; p = 0.005 for both).

When asked about their perception of their HIV status, only five (3.8%) of the undiagnosed men thought that they might be HIV-positive, whereas 81 (62.3%) thought they were HIV-negative, and 44 (33.8%) said that they did not know their HIV status.

In comparison, 1.2% of the 3183 HIV-negative men thought they might be HIV-positive, 83.8% thought they were negative, and 14.9% reported that they did not know their HIV status (p < 0.001).

Sexual risk behaviours

The investigators found that both diagnosed and undiagnosed HIV-positive men reported significantly more sexual partners, more high risk sex, and more sexually transmitted infections (STIs) in the previous year than HIV-negative men.

Multivariate analysis, adjusting for city of recruitment, age, education, employment status, and HIV testing history, calculated the adjusted odds ratios (AOR) of certain risk behaviours for diagnosed and undiagnosed HIV-positive men compared with HIV-negative men.

Compared with HIV-negative men, the odds were significantly higher for both undiagnosed and diagnosed men (p < 0.001) of:


  • having ten or more sexual partners (diagnosed men, AOR 2.53; undiagnosed men, AOR 1.73);
  • having ten or more anal intercourse partners (diagnosed men, AOR 3.62; undiagnosed men, AOR 2.22);
  • having two or more unprotected anal intercourse (UAI) partners (diagnosed men, AOR 6.80; undiagnosed men, AOR 2.21);
  • and of having had an STI in the previous year (diagnosed men, AOR 7.19; undiagnosed men, AOR 3.09).


However, only diagnosed HIV-positive men were found to have significantly higher odds of having UAI with casual partners (AOR 3.29; p < 0.001), and UAI with partners of unknown or discordant HIV status (AOR 1.63; p = 0.011) compared with HIV-negative men.

Serosorting and risk

A 2006 study from London found that many diagnosed HIV-positive gay men who 'serosort' (i.e. choose to have UAI with other HIV-positive partners) are unintentionally having high-risk sex with untested and HIV-negative men, primarily due to misperceptions about the other partner’s status.

In this study, serosorting was reported by 29 men with diagnosed HIV (representing 42% of the men who reported UAI with casual partners and 18.5% of the total with diagnosed HIV). Among the 100 men who received their HIV-positive diagnosis over a year ago, 18% reported only having UAI with casual partners of the same HIV status and 32% reported UAI with partners of unknown/discordant HIV status in the year prior to the survey.

The study also found that eleven of the 75 undiagnosed men who originally reported not having UAI with partners of unknown or discordant HIV status, reported having what they perceived to be concordant UAI (i.e. they had UAI with men that they perceived to be HIV-negative). Adding these eleven men to the 31 undiagnosed men who did report UAI with partners of unknown/discordant HIV status increases the proportion of undiagnosed men who potentially had unknown/discordant partners to 40%, which also increases the adjusted odds for this high-risk behaviour (AOR 2.30) in undiagnosed men, compared with HIV-negative men.

Implications for testing

“Only one in five men with undiagnosed infection had never had an HIV test and two-thirds still perceived their status to be negative” note the investigators. “Just under half reported testing negative in the twelve months leading up to the surveys, suggesting many were recent seroconverters...[w]ith high viral loads at seroconversion, they could have been highly infectious, but were basing their sexual risk decisions on an assumption of negativity. This highlights the limits of HIV status disclosure risk reduction strategies for HIV-negative men.”

"Our findings suggest that relying on a past HIV-negative test result, even within the previous year, may be an ineffective prevention strategy without the additional interventions of condom use and reduced partner numbers," they continue. Noting the correlation between STIs and undiagnosed HIV infection they suggest that, "sexual health services...throughout the UK should assiduously offer HIV testing to [gay men] presenting with STIs.”

Implications for prevention

Although a previous meta-analysis has found that diagnosed, HIV-positive individuals take significantly fewer sexual risks than the undiagnosed, “in our study,” they write, “it was men who were aware of their HIV-positive status who reported the highest levels of sexual risk, and the higher likelihood of UAI with two or more partners among men diagnosed over a year earlier, [and this] suggests that maintenance of safer sex behaviour may be problematic for men living with HIV.”

“Our findings suggest behaviour change, including the promotion of lower risk sexual practices, condom use, and partner number reduction, should continue to be a major component of HIV prevention efforts in the UK,” they write. “There is a need for targeted prevention with different age groups, given HIV prevalence increases with age, but levels of undiagnosed infection decrease.”

They also argue that, “there is an urgent need to evaluate evidence-based behavioural interventions in the UK” and that “sexual health services are appropriate settings for such interventions, given their access to men living with HIV and those at high risk of seroconversion.”

They stress that, “[t]he opportunity to challenge low-risk perceptions and reinforce safer sex messages among men at high risk of seroconversion exists, and should be grasped, in clinical settings.”

A ‘perfect storm’ for HIV transmission

An accompanying editorial from Thomas J Coates of the University of California, Los Angeles, suggests that such a prevalence of undiagnosed HIV amongst gay men in the UK “presents a perfect storm for the spread of HIV.”

“He argues that the strategies suggested by the study authors are useful, but “they do not necessarily hit the heart of the matter... The truth is that individuals place other priorities over avoidance of HIV, and thus will engage in the highest risk activities - unprotected receptive anal intercourse - with individuals whose serostatus is declared negative, or unknown, or even positive. This is the toughest conundrum of health promotion, and HIV now faces the same difficulty as is faced when trying to prevent other health problems, especially the chronic ones caused by lifestyle,” he writes.

“Motivating individuals to forego an immediate benefit for a long-term one is never easy. We need the best minds to engage on this task to see if other more clever strategies can be developed.” He also suggests that what is missing from the gay community is a sense of collective responsibility, which characterised the early days of the HIV epidemic. “We need leadership from within the community itself to encourage concern for the collective so that the community norm, once again, can be one of balancing what the individual might want against the desire to take care of others,” he argues.

He also suggests that the increased risk-taking seen amongst gay men in the developed world may be replicated in resource-limited settings once effective treatment programmes are finally rolled out. “It would behoove us to prepare,” he concludes, “for what is to come down the road...Perhaps we can begin to prepare now, and maybe avoid the same outcomes there.”


Williamson, LM et al. Sexual risk behaviour and knowledge of HIV status among community samples of gay men in the UK. AIDS 22(9): 1063-1070, 2008.

Coates TJ. What is to be done? AIDS 22(9): 1079-1080, 2008.