Analytical approach:
The analysis was based on a Markov micro-simulation model, with a lifetime horizon. The authors stated that it was carried out from the perspective of the third-party payer.
Effectiveness data:
The clinical data were from a selection of studies. Most evidence for the efficacy and safety of the two treatments was from the Comparison of Atazanavir/ritonavir in naive Subjects in combination with Tenofovir-emtricitabine versus Lopinavir/ritonavir in combination with Tenofovir-emtricitabine to assess Safety and Efficacy (CASTLE) trial. This trial directly compared once daily atazanavir and ritonavir with twice daily lopinavir and ritonavir. It had a 96-week follow-up and it provided the patients’ characteristics. Treatment adherence, disease progression, and mortality were from published literature, including the Data Collection on Adverse Events of Anti-HIV Drugs Study. A key input for the model was the rate of adverse events, such as diarrhoea and hyperbilirubinaemia.
Monetary benefit and utility valuations:
The utility values for combination ART were from a published study that used the European Quality of life (EQ-5D) instrument in patients with HIV. Values for hyperbilirubinaemia were estimated by an infectious disease clinical specialist.
Measure of benefit:
Quality-adjusted life-years (QALYs) were the summary benefit measure and were discounted at an annual rate of 3%. Outcomes, such as the coronary heart disease events, opportunistic infections, diarrhoea, and hyperbilirubinaemia were reported, but were not combined with costs.
Cost data:
The economic analysis included the costs of first- and second-line ART (drugs, physician visits, and laboratory tests), non-drug treatment for HIV states defined by the patient's cluster of differentiation (CD) 4 cell count, and the management of adverse events, such as coronary heart disease, diarrhoea, hyperbilirubinaemia, and opportunistic infections. The resource quantities were from published literature and the drug costs were their average wholesale prices. Other costs were from published studies, including an economic evaluation conducted in the USA. The costs of opportunistic infections were from the Multicenter AIDS Cohort Study (MACS). All costs were in US dollars ($) and were discounted at a rate of 3% per annum. The price year was 2008.
Analysis of uncertainty:
One-way sensitivity analyses were carried out to consider nine alternative scenarios for selected inputs. A probabilistic sensitivity analysis was performed to assess the impact of simultaneously varying all 47 parameters of the model. Conventional distributions were used for each group of inputs and these were from the same source as each baseline input.