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Influence of patient baseline clinical and demographic characteristics on choice of initial antiretroviral therapy regimen: evidence of channeling bias in HIV clinical care
E. Brouwer1,2, S. Napravnik1,2, J. Eron Jr.2
1University of North Carolina Gillings School of Global Public Health, Epidemiology, Chapel Hill, United States, 2University of North Carolina at Chapel Hill, Medicine, Chapel Hill, United States
Background: Observational clinical cohort studies complement randomized clinical trials by assessing combination antiretroviral therapy (cART) effectiveness and unintended long-term and rare outcomes. However, antiretrovirals (ARVs) may be differentially prescribed by pre-treatment patient characteristics, giving rise to ARV channeling bias, and possibly confounding by indication. Therefore we evaluated initial cART prescribing choice.
Methods: Study population included all UNC HIV Clinical Cohort participants initiating cART after 09/2004 (FDA TDF/FTC combination approval) (N=150). We evaluated use of the most commonly prescribed nucleoside reverse transcriptase inhibitors (NRTIs): lamivudine or emtricitabine (3TC/FTC), abacavir (ABC), tenofovir (TDF), and zidovudine (AZT); non-nucleoside reverse transcriptase inhibitor (NNRTI): efavirenz (EFV); and protease inhibitors (PIs): atazanavir (ATV[RTV]), and lopinavir (LPV/RTV). Multivariable logistic regression models were fit to identify independent predictors of ARV use, including: demographic characteristics; comorbidities (diabetes, hypertension, and coronary artery disease); and laboratory measures (cholesterol, liver function tests, calculated glomerular filtration rate, CD4 cell count and HIV RNA level).
Results: One-third of patients were women (31%), 51% African American, with median age of 41 years (IQR: 32, 50). Patients received: 3TC/FTC (100%), TDF (75%), ABC (11%), AZT (11%), EFV (45%), LPV/RTV (30%), ATV (3%) and ATV/RTV (11%). Elevated cholesterol level (LDL-C≥100 mg/dL) and hypertension predicted greater ABC versus TDF use (all P< 0.05). Elevated liver function tests (ALT≥35 units/L) predicted greater TDF versus ABC use (P=0.002). MSM predicted AZT versus TDF use (P=0.02). Being a woman and having a lower CD4 predicted LPV/RTV versus EFV use (P=0.03 and 0.01). Lower CD4 and elevated ALT predicted ATV/RTV versus EFV use (P=0.04 and 0.004). Elevated ALT predicted LPV/RTV versus ATV/RTV use (P=0.02).
Conclusions: Patient clinical and demographic characteristics predict choice of initial cART regimen, including NNRTI versus PI, and NRTI backbone use. Advanced analytic techniques are available and needed to account for ARV channeling bias in observational clinical studies.
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