Abstract

Surveillance of recently acquired HIV infections among newly diagnosed individuals in the UK

Presented by Samuel Lattimore (United Kingdom).

S. Lattimore¹, G. Murphy², R. Smith¹, J. Tosswill², D. Pillay^2,3, N. Gill¹, V. Delpech<sup>1

1</sup>Health Protection Agency, Centre for Infection, Microbiology and Epidemiology of STIs and HIV, London, United Kingdom, ²Health Protection Agency, Centre for Infection, Virus Reference Department, London, United Kingdom, ³University College London, Department of Infection, London, United Kingdom

Background: Recent Infection Testing Algorithms (RITA) makes it possible to distinguish recently acquired HIV infections (RHI) from long standing infections. We report findings from the first year of RITA testing as part of routine public health monitoring of newly diagnosed HIV in England in 2009.
Methods: Aliquots of remnant diagnostic specimens were submitted to the Health Protection Agency for RITA testing using the Abbott AxSYM HIV avidity method. Specimens with an avidity index (AI) of < 80% were classified as RHI (within previous 4-5 months). Those with an AI of < 70% were retested once to confirm results, specimens with an AI between 70-85% duplicated tested; final result based on the retest mean.
Results: During 2009, a third (2191) of newly diagnosed infections were RITA tested. Epidemiological information was available for 77% samples between Jan-June 2009. Among men who have sex with men (MSM), 18% (68/375) were classified as RHI. The proportion was similar across age groups, accounting for 19% among those aged < 25, 18% aged 25-39 and 16% over 40. Where available, median CD4 count among those with RHI was 532, compared to 400 among those infected more than 5 months previously.Among Heterosexuals, 9% (27/303) were classified as RHI - more common among younger age groups, accounting for 13% among those aged < 25, 9% aged 25-39 and 7% aged over 40. Where available, the median CD4 count among those with RHI was 401, compared to 271 among those infected more than 5 months previously.
Conclusions: Approximately one in five MSM and one in ten heterosexuals diagnosed with HIV in 2009 had recently acquired their infection. Continued RITA testing among all newly diagnosed infections will provide further insights into the ongoing transmission of HIV in the UK and provide the bases for monitoring and evaluating prevention programmes.