Does the recent increase in HIV diagnoses among men who have sex with men in the United Kingdom reflect a rise in HIV incidence or increased uptake of HIV testing?

Objectives To determine whether the increase in HIV diagnoses since 1997 among men who have sex with men (MSM) in the UK reflects a rise in HIV incidence or an increase in HIV testing. Methods Estimates of HIV incidence were derived using data from UK HIV surveillance systems (HIV diagnoses; CD4 surveillance; unlinked anonymous surveys) for 1997-2004. Data on HIV testing were provided by KC60 statutory returns, voluntary testing and unlinked anonymous surveys in sentinel GUM clinics. Results HIV diagnoses among MSM in the UK rose by 54% between 1997 and 2004 (1,382, 2,124), with variation by age and geographic location. There was no increase in the number of HIV diagnoses among MSM <35 years in London, but in all other groups it increased. Throughout the UK, uptake of HIV testing increased significantly among MSM attending GUM clinics between 1997-2004, including among 'at-risk' MSM (p<0.001). Direct incidence estimates (STARHS assay) provided no evidence of a statistically significant increase or decrease in HIV incidence. Indirect estimates suggested there may have been a rise in HIV incidence, but these estimates were influenced by the increased uptake of HIV testing. Conclusions The number of HIV diagnoses increased among MSM in the UK between 1997 and 2004, except among younger MSM in London where there was no change. It appears that the increase in HIV diagnoses among MSM in the UK since 1997 reflects an increase in HIV testing rather than a rise in HIV incidence.