UK: one in six gay men testing HIV-positive were infected recently

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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.

Glossary

statistical significance

Statistical tests are used to judge whether the results of a study could be due to chance and would not be confirmed if the study was repeated. If result is probably not due to chance, the results are ‘statistically significant’. 

trend

In everyday language, a general movement upwards or downwards (e.g. every year there are more HIV infections). When discussing statistics, a trend often describes an apparent difference between results that is not statistically significant. 

representative sample

Studies aim to give information that will be applicable to a large group of people (e.g. adults with diagnosed HIV in the UK). Because it is impractical to conduct a study with such a large group, only a sub-group (a sample) takes part in a study. This isn’t a problem as long as the characteristics of the sample are similar to those of the wider group (e.g. in terms of age, gender, CD4 count and years since diagnosis).

seroconversion

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.

 

antenatal

The period of time from conception up to birth.

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.

Further information

View abstract and slides from this session on the official conference website.

References

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.