Today’s World AIDS Day has been greeted with some grim headlines in this week’s press. According to a Health Protection Agency report released earlier this week, more men who have sex with men (MSM) were diagnosed with HIV in 2010 than ever before. Better uptake of HIV testing is one reason for the rise but not the only one.

But what do these statistics mean, and what can be done? Professor Shelia Bird of the MRC Biostatistics Unit, Cambridge breaks down the figures for Straight Statistics.

The Need for Effective HIV Testing

Universal offering of HIV testing to men who have sex with men (MSM) accelerates treatment for those who are HIV-infected and aims to reduce the unacceptably high incidence of HIV infections in younger MSM.

The current annual incidence of new HIV infections among MSM aged between 15 and 44-years is around 1 in 100 (credible interval 0.5 to 1.3 per 100).

In fact, the UK’s HIV incidence in younger MSM may be as high in 2010 as is the HIV prevalence in injection drug users (IDUs). Yet, thirty years on from the first reports of AIDS in the USA, the UK has re-opened blood donation to MSM who have not had oral or anal intercourse in the past year, but still defers IDUs.

Those recently HIV-infected are themselves most highly infectious to others. HIV testing of MSM should therefore aim to identify the recently-infected, because their infector may himself be recently-infected and highly infectious. Diagnosis and treatment of these infectors will not only benefit them, but will reduce the risk of new HIV transmissions by decreasing viral load.

At the other extreme, infectors may have a long-standing undiagnosed HIV infection, an increasing viral load, and an urgent need for treatment.

Out of 850,000 adult MSM in UK, some 40,000 are estimated to be living with the HIV disease (1 in 20), of whom 10,000 are undiagnosed, and hence untreated.

Recognistion of recent HIV infections in newly HIV-diagnosed MSM

And so how successful is our recognition of recently HIV-infected MSM among thsoe who are newly HIV-diagnosed?

What is known is that around 780 (26 per cent) of the 3,000 MSM who were newly HIV-diagnosed in 2010 underwent additional avidity testing to determine if their HIV infection had been recently acquired. Recent HIV infections accounted for a quarter (24 per cent) of those additionally-avidity-tested.

In 2010, UK sites where additional avidity testing was available achieved only 26 per cent coverage for MSM (versus 37 per cent overall).

Why? Were more MSM refusing avidity-tests, or were fewer being offered them? Either could mean that it would be unsafe to assume that MSM who were subject to avidity-testing were representative of all newly HIV-diagnosed MSM.

If the implication truly is that a quarter of newly-HIV-diagnosed MSM were recently HIV-infected—then virus-based HIV-testing should be a priority for MSM.

Better Testing

Surely, when MSM face an HIV prevalence of 5 per cent and younger MSMs run the gauntlet of 1 per cent HIV incidence, it is critical that MSM should be offered a form of HIV testing that identifies for them, and to their doctors, whether their HIV infection was recent.

MSM need more than just HIV antibody testing; they need diagnostic testing based on the virus itself. Blood donors are, of course, subject to HIV-RNA testing for optimal detection of recent HIV infection. This week’s Health Protection Agency report, to my mind, makes a strong case for HIV-RNA testing (or other form of virus-based testing) to be offered whenever a younger MSM requests, or is offered, HIV testing.