Abacavir and cardiovascular disease: A critical look at the data.

Most HIV-infected subjects will receive a treatment regimen including abacavir or tenofovir. Therefore, clarifying if there is an increased risk of acute myocardial infarction (AMI) among those exposed to abacavir is of the utmost importance. Due to the low frequency of AMI in this young population (2-5 per 1000 patients/year), efforts to clarify this have been quite controversial. While some observational cohorts have found a statistically significant association, others have not. Meta-analysis of randomized clinical trials offering the highest scientific evidence found no association at all, but with a limited statistical power to definitely rule out a small effect. A channelling or selection bias has been demonstrated in cohort studies, favouring the prescription of abacavir to subjects with or at risk for chronic kidney disease, and therefore, with an intrinsic increased cardiovascular risk. The recent NA-ACCORD cohort study does not identify an increased risk for AMI associated with recent abacavir use in a fully adjusted model (HR 1.33; 95%CI:0.96, 1.88). However, it does find an association in a second analysis restricted to treatment-naïve persons, with higher differences in baseline characteristics among compared arms. A critical review of the compiled available evidence is therefore mandatory, particularly in light of the first single-tablet regimen to receive approval that does contain abacavir.