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Education > Clinical Updates

Clinical Update #13 - 6^th European HIV Drug Resistance Workshop

Budapest, Hungary
March 26-28, 2008

The emergence of drug-resistant HIV strains is one of the key factors associated with suboptimal virologic response to antiretroviral therapy. Understanding trends in HIV resistance can help influence overall patient management and in the development of new antiretrovirals. Researchers at Virco reported that the prevalence of clinically relevant resistance continues to decline. Prakash Sista and colleagues from Virco presented an oral talk and poster at the 6^th European HIV Drug Resistance Workshop showing that the prevalence of any resistance detected among routine clinical samples submitted to Virco, fell from 82% to 66.5% over a 9-year period (December 1998 to June 2007). Equally encouraging was the decline in the rate of triple-class resistance (≥1 drug in each of NRTI, NNRTI and PI classes) from 30.5% to 15.7% during the same time period.

This study used the most recent version of virco®TYPE HIV-1 system (version 4.2.01) to retrospectively determine fold-change values for 242,003 routine clinical samples in Virco's genotypic database. Reduced susceptibility was defined as a fold-change value greater than the lower clinical cut-off (or biological cut off for emtricitabine, efavirenz and nevirapine) value for each drug. To reduce potential bias, clinical samples from patients participating in clinical trials or specific research collaborations were excluded from the analysis.

Among the drug classes, overall prevalence of resistance to NRTIs and PI declined from approximately 70% to 40% and 60% to 40%, respectively, over 9 years. The rate of resistance to NNRTIs remained relatively steady at about 40%. The large size of the Virco Genotypic database also allowed the investigators to monitor trends of individual drugs and drug-associated mutations. For example, nelfinavir, lamivudine, and abacavir consistently had the highest rates of resistance among routine clinical samples analyzed. The absolute prevalence of signature mutations associated with lopinavir (I47V and I47V), fosamprenavir and darunavir (I50V), and atazanavir (I50L) resistance remained low (below 10% of routine clinical samples analyzed) although they increased over the study period.

If you are interested in viewing the complete poster, please click here.

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