• K N Simpson, R W Baran, D Collomb, E J Beck, O Van de Steen, and B Dietz.
• Department of Health Science and Research, College of Health Professions, Medical University of South Carolina, SC 29425, USA. simpsonk@musc.edu
• J Med Econ. 2012 Jan 1; 15 (4): 796-806.

BackgroundUsing a United Kingdom (UK)-based National Health Services perspective for 2011 this study first estimated the cost-effectiveness and budget impact implications for lopinavir/ritonavir (LPV/r) vs atazanavir plus ritonavir (ATV+RTV) treatment of antiretroviral therapy (ART)-naïve patients and secondly examined the long-term health-related quality-of-life (HRQoL) and economic implications for LPV/r vs ATV+RTV treatment of ART-experienced patients.MethodsA previously published Markov model that integrates epidemiological data of human immunodeficiency virus (HIV) with predictors of coronary heart disease (CHD) was modified under a clearly specified set of assumptions to reflect viral load (VL) suppression profiles and other differences for these two regimens, applying results from the CASTLE study in ART-naïve patients and using data from BMS-045 in ART-experienced patients. ART costs were referenced to current (2011) pricing guidelines in the UK. Medical care costs reflected UK treatment patterns and relevant drug pricing. Costs and outcomes were discounted at 3.5% per year. Costs are expressed in British pounds (£) and life expectancy in quality-adjusted life years (QALYs).ResultsIn the ART-naïve subjects, the model predicted a marginal improved life expectancy of 0.031 QALYs (11 days) for the ATV+RTV regimen as a result of predicted CHD outcomes based on lower increases in cholesterol levels compared with the LPV/r regimen. The model demonstrated cost savings with the LPV/r regimen. The total lifetime cost savings was £4070 per patient for the LPV/r regimen. LPV/r saved £2133 and £3409 per patient at 5 and 10 years, respectively. Referenced to LPV/r, the incremental cost-effectiveness ratio (ICER) for ATV+RTV was £149,270/QALY. For ART-experienced patients VL suppression differences favored LPV/r, while CHD risk associated with elevated total cholesterol marginally favored ATV+RTV, resulting in a net improvement in life expectancy of 0.31 QALYs (106 days) for LPV/r. Five-year costs were £5538 per patient greater for ATV+RTV, with a discounted lifetime saving of £1445 per LPV/r patient. LPV/r was modestly dominant economically, producing better outcomes and cost savings.LimitationsThe limitations of this study include uncertainty related to how well the model's assumptions capture current practice, as well as the validity of the model parameters used. This study was limited to using aggregated data in the public domain from the two clinical trials. Thus, some of the model parameters may reflect limitations due to trial design and data aggregation bias. This study has attempted to illuminate the effect of these limitations by presenting the results of the comprehensive sensitivity analysis.ConclusionsBased on 2011 costs of HIV in the UK and the published efficacy data from the CASTLE and BMS-045 studies, ATV+RTV-based regimens are not expected to be a cost-effective use of resources for ART-naïve patients similar to patients in the CASTLE study, nor for ART-experienced patients based on the only published comparison of ATV+RTV and LPV/r.

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