Patterns and predictors of the use of different antiretroviral drug regimens at treatment initiation in the UK

Background We describe the patterns of antiretroviral drug use at treatment initiation from 1996 to 2005 in a large UK multicentre cohort. Methods We examined trends over time and across 10 clinical sites in stage of disease and type of antiretroviral therapy (ART). Multivariable regression was used to identify factors associated with the CD4 cell count at ART initiation, and with the choice of a protease inhibitor (PI) over a nonnucleoside reverse transcriptase inhibitor (NNRTI), and use of nevirapine over efavirenz. Results A total of 14 252 patients initiated ART, of whom 54% had a CD4 count <200 cells/mu L. The most important predictors of starting ART at a lower CD4 cell count were being male, nonwhite, and heterosexual or an injecting drug user (P<0.0001). Among those starting ART, the use of highly active ART increased from 23% in 1996 to >96% from 2000 onwards. There were differences over time and across the clinics in the use of PIs vs. NNRTIs, in the choice of specific PIs, NNRTIs and nucleoside reverse transcriptase inhibitor (NRTI) backbone, and in the rate at which prescribing practices changed. Conclusions Clinic site and calendar year were important determinants of choice of drug at ART initiation, whereas clinical and demographic characteristics were more important in influencing the CD4 cell count at initiation of ART.