The first data from new systems of detecting recent HIV infection in the UK have shown that among those diagnosed, one in six gay men were infected in the past few months, whereas only one in 16 heterosexuals were. Sam Lattimore of the Health Protection Agency presented the results to the Eighteenth International AIDS Conference today.
A Recent Infection Testing Algorithm (RITA, sometimes also known as Serological Testing Algorithm for Recent HIV Seroconversion, or STARHS) works by looking for specific antibody markers, which give different results in the months immediately following infection. If a test gives a result below a pre-determined cut-off point, it is deemed to be a recent infection (approximately the last six months).
Nonetheless, because of person-to-person variability in the development of immune response, RITA cannot give definitive date for an individual’s infection. They are only able to suggest rough timings.
In 2008, the Health Protection Agency began the roll-out of STARHS, with the objective of it becoming part of the routine public health monitoring of all newly diagnosed HIV infections in the country.
The data presented the conference are based on samples from 2099 individuals, whom the HPA believe to be broadly representative, demographically and geographically, of people newly diagnosed in the UK. Samples were collected between February 2009 and May 2010.
Amongst gay and bisexual men, 16.1% of diagnoses were judged to be of recent infections. Similar proportions of recent infections were seen across all age groups.
Amongst heterosexual men and women, 6.2% and 6.8% respectively of diagnoses were of recent infections.
There appears to be a trend for recent infections to be more commonly identified in younger women (probably due to antenatal testing), but the age variations were not statistically significant. It is possible that when a larger number of samples can be analysed, statistically significant data will be available. Curiously, in women aged 50 or over, there was a relatively high proportion of recent infections, but this is based on a small number of cases and could be due to chance.
The cases of recent infection in heterosexuals were largely in people born in the UK, suggesting that new cases of heterosexual HIV acquired in the UK are mostly in people born in the UK. Heterosexual people born in Africa tend to have their infection diagnosed at a later stage.
View abstract and slides from this session on the official conference website.
Lattimore S et al. Surveillance of recently acquired HIV infections among newly diagnosed individuals in the UK. Eighteenth International AIDS Conference, Vienna, abstract FRAX0101, 2010.