We consider a method for extending instrumental variables methods in order to estimate the overall effect of a treatment or exposure. The approach is designed for settings in which the instrument influences both the treatment of interest and a secondary treatment also influenced by the primary treatment. We demonstrate that, while instrumental variables methods may be used to estimate the joint...

WHO standard of care for failure of a first regimen, usually 2N(t)RTI's and an NNRTI, consists of a ritonavir-boosted protease inhibitor with a change in N(t)RTI's. Until recently, there was no evidence to support these recommendations which were based on expert opinion. Two large randomized clinical trials, SECOND LINE and EARNEST both showed excellent response rates (>80%) for the WHO standar...