title: Comparing adherence to two different HIV antiretroviral regimens: an instrumental variable analysis.
abstract: 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). Multivariable regressions were run with an indicator for PDC >95, 90, 85, and 80 % as the dependent variable and an indicator for a PI-based regimen as the key independent variable. We controlled for residual unmeasured confounding by indication using an instrumental variable technique, using the physician's prescribing preference as the instrument. Out of 929 veterans on PI-based and 747 on NNRTI-based regimens, only 19.7 % of PI patients had PDC >80 %, compared to 35.1 % of NNRTI patients. In multivariable analysis, starting a PI regimen was significantly associated with poor adherence for all 4 adherence thresholds using conventional regressions and instrumental variable methods.
authors.affiliation: George E. Whalen Department of Veterans Affairs Medical Center, 500 Foothill Drive, GRECC-182, Salt Lake City, UT 84148, USA. richard.nelson@utah.edu
authors.forename: Richard E
authors.initials: RE
authors.lastname: Nelson
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Nebeker
authors.forename: Candace
authors.initials: C
authors.lastname: Hayden
authors.forename: Larry
authors.initials: L
authors.lastname: Reimer
authors.forename: Karen
authors.initials: K
authors.lastname: Kone
authors.forename: Joanne
authors.initials: J
authors.lastname: LaFleur
mesh_terms: D000328:Adult; D019380:Anti-HIV Agents / Q000008:administration & dosage*; D023241:Antiretroviral Therapy, Highly Active; D018791:CD4 Lymphocyte Count; D004334:Drug Administration Schedule; D005260:Female; D005500:Follow-Up Studies; D015658:HIV Infections / Q000188:drug therapy*; D017320:HIV Protease Inhibitors / Q000008:administration & dosage* / Q000627:therapeutic use; D006801:Humans; D008297:Male; D055118:Medication Adherence; D008875:Middle Aged; D015999:Multivariate Analysis; D012042:Registries; D012044:Regression Analysis; D018894:Reverse Transcriptase Inhibitors / Q000008:administration & dosage* / Q000627:therapeutic use; D012307:Risk Factors; D014481:United States; D014493:United States Department of Veterans Affairs; D019562:Viral Load
chemical_list: D019380:Anti-HIV Agents; D017320:HIV Protease Inhibitors; D018894:Reverse Transcriptase Inhibitors