There was a large increase in the number of HIV diagnoses among MSM across the UK between 1997 and 2004, except for younger (<35 years) MSM in London, in whom there was no change. Among all groups of MSM, a substantial increase in the uptake of HIV testing was observed, with the biggest increase being among those most at‐risk of HIV infection. Increased uptake of HIV testing will have contributed substantially to the rise in HIV diagnoses. However, no evidence of a statistically significant increase or decrease in HIV incidence was observed among MSM in E,W&NI using the STARHS assay which provides a direct estimate of incidence. Indirect estimates of HIV incidence, using CD4 cell count at diagnosis, indicated an increase in incidence, as the proportion of MSM diagnosed earlier during the course of infection increased in all groups. However, this increase could also reflect a corresponding increase in the uptake of HIV testing. Outside London, in E,W&NI, improvements in the HIV diagnoses reporting system may have also contributed to the increase in the number of diagnoses among MSM.
The fact that HIV diagnoses among younger MSM in London did not increase at all is particularly interesting, given that there has been a substantial increase in HIV testing among this group. Increased uptake of HIV testing among HIV‐infected MSM and those with an acute STI indicates that the increase in testing has not just been among low‐risk younger MSM. Taken together, there is no evidence of an increase in HIV incidence among younger MSM in London, despite an increase in STIs and high‐risk behaviour in this group.1,5,7,8,9
This is the first time that changing patterns of HIV incidence and testing among MSM in the UK have been systematically investigated to explain the recent increase in HIV diagnoses. The strength of this analysis is that data on HIV diagnoses, incidence and testing are all presented in the same paper, although disentangling a rise in incidence from an increased uptake of testing is methodologically challenging.
The only direct estimate of incidence was based on data collected from 16 sentinel GUM clinics in E,W&NI participating in the unlinked anonymous survey. Clinics were not randomly selected, and so these estimates may not be generalisable to all GUM clinic attendees, particularly outside London. Estimates will also be raised, as GUM clinic attendees tend to be at higher risk of acquiring HIV than other MSM.
The indirect estimates of HIV incidence were based on an increase in early diagnoses, or a decrease in late diagnoses. However, these indices may also reflect an increase in HIV testing, as well as earlier presentation by MSM. The influence of reporting changes on the increase in HIV diagnoses is difficult to assess, as some centres changed their reporting patterns after the introduction of clinical HIV reporting in 2000.
Whereas increased migration to the UK by HIV‐infected MSM may have also had an effect on the number of HIV diagnoses, there are as yet no discernible trends in selective migration of HIV‐infected MSM to the UK.26
Unlinked anonymous data show an increasing HIV prevalence among MSM in the UK born in other world regions, although absolute numbers are small.27
Demographic changes within the UK MSM population itself may have also contributed to the stable number of diagnoses of HIV among younger MSM in London. However, interpreting census data on all men in relation to the changes in the MSM population is difficult and merits further examination.28
In Amsterdam, increasing HIV incidence (measured using STARHS) was observed among MSM >35 years of age, but not <34 years attending STI clinics (1991–2001), accompanied by an increase in STI incidence and high‐risk sexual behaviour.3,29
Similar trends in HIV incidence has been observed in Australia.2
In E,W&NI, we did not observe an increase in HIV incidence among MSM using the STARHS assay on samples from GUM clinics participating in the unlinked anonymous GUM clinic survey. However, a similar increase was observed in STIs among MSM in the UK to The Netherlands.1,5
The reason for the differences in HIV incidence trends between MSM in Amsterdam and London is not clear. They might be due to differences in the sample populations or changes in the E,W&NI STARHS denominator over time.16,17
Our analysis shows that the number of HIV diagnoses increased among MSM in the UK between 1997 and 2004, except among younger MSM in London, in whom there was no change. A substantial increase in the uptake of HIV testing seems to explain the rise in HIV diagnoses. Direct estimates of HIV incidence among MSM in E,W&NI provided no evidence of a statistically significant change in HIV incidence between 1997 and 2004, indicating that HIV transmission continued at a steady rate among MSM in the UK between 1997 and 2004.
Taken in concert with STI data, our analysis points towards a need for additional investment in targeted sexual health promotion if the goal of reducing HIV transmission among MSM is to be met.12,13,14
This should be coupled with a further understanding of sexual risk behaviour among MSM.30
In terms of surveillance, further examination of the relationship between HIV diagnoses, testing and HIV incidence data is required to explain trends among younger MSM in London and differences in trends between the UK and other countries. Finally, the substantial increase in the uptake of HIV testing among MSM in recent years highlights the recent success of sexual health promotion in reducing the number of MSM with undiagnosed HIV.