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Effectiveness of ART may be improving
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A 12-fold decrease in the incidence of resistance to antiretroviral therapy may have occurred over a 12 year period among a large population of patients with HIV in British Columbia, according to results of a recent study. This indicates that the effectiveness of antiretroviral therapy may be improving at the population level, researchers said.
British Columbian researchers conducted a longitudinal analysis of plasma viral load and genotypic resistance data from patients receiving ART at the British Colombia Drug Treatment Program from July 1996 to December 2008.
There were 24,652 resistance tests from 5,422 patients available for analysis. The researchers calculated the incidence of successful plasma viral load suppression and resistance to each of three categories of ART regimens, including, nucleoside/nucleotide reverse transcriptase inhibitors, nonnucleoside reverse transcriptase inhibitors and protease inhibitors.
The incidence of newly detected resistance was 1.73 cases per 100 person-months of therapy in 1997. By 2008, there was a decrease in the incidence rate of >12 fold, to 0.13 cases per 100 person-months of therapy.
The researchers wrote that the decrease in incidence of resistance has occurred exponentially, “with half-times on the order of 2-3 years.”
A linear rate of increase over time was observed in the proportion of individuals with plasma viral load suppression. In 2000, HIV RNA levels <50 copies/mL were observed in 64.7% of patients; by 2008, that proportion had increased to 87.0% (P<.001).
Gill VS et al. Clin Infect Dis. 2009;50:98-105.