Time trends in primary resistance to HIV drugs in the United Kingdom: multicentre observational study.
OBJECTIVE
To examine whether the level of primary resistance to HIV drugs is increasing in the United Kingdom.


DESIGN
Multicentre observational study.


SETTING
All virology laboratories in the United Kingdom carrying out tests for HIV resistance as part of routine clinical care.


PARTICIPANTS
2357 people infected with HIV who were tested for resistance before receiving antiretroviral therapy.


MAIN OUTCOME MEASURE
Prevalence of drug resistance on basis of the Stanford genotypic interpretation system.


RESULTS
Over the study period (February 1996 to May 2003), 335 (14.2%, 95% confidence interval 12.8% to 15.7%) samples had mutations that conferred resistance to one or more antiretroviral drugs (9.3% high level resistance, 5.9% medium level resistance). The prevalence of primary resistance has increased markedly over time, although patterns are specific to drug class; the largest increase was for non-nucleoside reverse transcriptase inhibitors. In 2002-3, the prevalence of resistance to any antiretroviral drug to nucleoside or nucleotide reverse transcriptase inhibitors, to non-nucleoside reverse transcriptase inhibitors, or to protease inhibitors was 19.2% (15.7% to 23.2%), 12.4% (9.5% to 15.9%), 8.1% (5.8% to 11.1%), and 6.6% (4.4% to 9.3%), respectively. The risk of primary resistance was only weakly related to most demographic and clinical factors, including ethnicity and viral subtype.


CONCLUSIONS
The United Kingdom has one of the highest reported rates of primary resistance to HIV drugs worldwide. Prevalence seems still to be increasing and is high in all demographic subgroups.