Analytical approach:
The analysis was based on the AntiRetroviral Analysis by Monte Carlo Individual Simulation (ARAMIS) model, which was adapted to the Mexican setting. A lifetime horizon was adopted. The authors stated that the perspective of the health care system was taken.
Effectiveness data:
Most clinical inputs had been already incorporated in the published simulation model and were taken from published studies. Baseline characteristics of patients and treatment effect (the key clinical input) were taken from the MOTIVATE 1 and 2 trials, which directly compared the two options. Data were pooled in some circumstances. A 48-week follow-up was used in the clinical trials, so long-term extrapolations were based on observational studies and assumptions. Adverse events were obtained from these two trials. Mortality and other epidemiological data were taken from Mexican sources.
Monetary benefit and utility valuations:
Utility valuations were based on published sources, except for the quality of life associated with adverse events, which was based on expert option.
Measure of benefit:
Quality-adjusted life-years (QALYs) and life-years were used as the summary benefit measures. A 5% annual discount rate was applied.
Cost data:
The direct medical costs for HIV care included active antiretroviral therapy, tropism testing, adverse events associated with antiretroviral therapy, acute and prophylactic treatment of opportunistic infections, CD4+ cell count tests, HIV RNA tests, treatment for adverse events, and HIV-related or opportunistic infection-related palliative care preceding death. Patterns of resource consumption and most unit costs were based on a review of patient records from nine hospitals in Mexico City. Costs were in presented in Mexican pesos and US $. The price year was 2008. Costs were discounted at an annual rate of 5%.
Analysis of uncertainty:
A secondary analysis considered only the subgroup of CCR5-tropic HIV-1 detectable after tropism testing. Various one-way and multi-way sensitivity analyses were carried out on inputs including treatment efficacy, accuracy of the tropism test, cost of treatment, utility values, and discount rate (no discounting). Data from the MOTIVATE trial were used to calculate genotypic, phenotypic, and overall susceptibility scores for the optimised background therapy activity in each patient.