The systematic collation of HIV resistance data from HIV infected drug-naïve individuals is crucial to understanding the epidemiology of transmitted drug resistance, whilst data from those already receiving antiretroviral drugs provides indirect evidence of the contribution drug resistance makes to virological failure. All findings are based upon genotypic reports received by the MRC held UK HIV Drug Resistance Database founded in 2001, which aims to collect all tests conducted as part of routine clinical care across the UK.
The number of resistance tests performed on drug-naïve individuals each year has rapidly increased from 528 tests in 2000 to 2760 in 2005, due in part to the change in the BHIVA guidelines, recommending a baseline resistance test for all newly diagnosed individuals . This increase has been accompanied by a dramatic and sustained fall in the proportion of samples harbouring resistance mutations. Prior to the revised BHIVA guidelines, HIV resistance testing was generally focused on specific risk groups or centers where testing was routine, generating potential bias within the dataset. Therefore the data presented here for more recent years are likely to better reflect the national pattern of HIV drug resistance. Also accounting for the reduction in resistance in drug naïve patients is the fact that heterosexual transmission now accounts for the largest proportion of newly diagnosed infections in the UK . In 2005 there were 3194 heterosexually acquired infections out of a total 7645 newly diagnosed infections . Almost 3000 of these new infections were probably acquired in Africa where antiretroviral exposure is much more limited, and the presence of pre-existing resistance is therefore lower than for those infected in the UK. Analyses are planned to examine trends in transmitted drug resistance within each key exposure category within the UK.
Resistance mutations are common in those who experience ART failure, however much of this resistance arises from a subgroup of people who initially started nucleoside mono- or dual- therapy between 1987 and 1996. In 2004, over a third of tests performed showed no evidence of resistance: by 2005 this proportion had reached almost a half, suggesting that there are other increasingly important causes of virological failure. However, of those treatment-experienced individuals who experienced virological failure in 2005 and harboured a resistant mutation, 10.7% were resistant to all three classes of antiretroviral agents. Surveillance of HIV drug resistance is required not only to monitor time trends in transmitted resistance, but also to assess the likely requirement for new classes of antiretroviral agents in highly drug experienced patients.
The data indicate that the proportion of individuals, both drug-naive and drug-experienced, with evidence of drug resistance (among those tested) is decreasing. Furthermore, when resistance is detected it is frequently to a single drug class only. However, the levels of transmitted drug resistance remain significantly high; highlighting the importance of targeted health promotion campaigns at both HIV uninfected and infected individuals, reinforcing safe sex messages.
Full article from the Health protection Report
HIV Drug resistance in the United Kingdom: data to end of 2005
Published 3 August, Volume 1 Number 31 (PDF file 435KB)