Comparing adherence to two different HIV antiretroviral regimens: an instrumental variable analysis.

The objective of this observational cohort study was to compare adherence to protease inhibitor (PI)-based regimens or non-nucleoside reverse transcriptase inhibitor (NNRTI)-based regimens. HIV-seropositive, antiretroviral-naïve patients initiating therapy between 1998 and 2006 were identified using Veterans Health Administration databases. First-year adherence ratios were calculated as proportion of days covered (PDC).