It's about time: The association between abacavir and cardiovascular disease.

Data from the REPRIEVE trial have been used to study the association between treatment with abacavir and cardiovascular disease in people with HIV. Past exposure to abacavir before the trial was found to be just as risky as exposure during the trial. This calls into doubt the widely accepted hypothesis that recent exposure to abacavir increases the risk of cardiovascular disease but that risk rapidly attenuates after exposure ends. The evidence for this hypothesis is weak while evidence for an alternative hypothesis has been neglected. An alternative hypothesis is that risk from exposure to abacavir is not immediate but increases as exposure cumulates, plateauing after about three years. Confusion over the likely effect of abacavir has arisen partly because overly simplistic methods have been used to model the exposure outcome relationship in observational cohort data. Better methods are available and should be used in future to avoid misdirected research effort.