ANTIRETROVIRAL STRATEGIES AND TREATMENT MONITORING IN RESOURCE-LIMITED SETTINGS – A COST-EFFECTIVENESS ANALYSIS

Background: Current World Health Organization (WHO) guidelines for treatment of HIV in sub-Saharan Africa call for a sequence of two antiretroviral regimens.  As patients develop resistance to the recommended Highly Active Antiretroviral Therapy (HAART) regimens, they may need additional treatment options.

Methods: We developed a computer simulation model to compare survival and costs of three HAART strategies: the WHO 2-regimen strategy; initial treatment with  an inexpensive but less effective regimen of three nucleoside reverse transcriptase inhibitors (NRTI); and the standard 2-regimen WHO strategy followed by a third regimen based on a second-generation protease inhibitor (PI).  In the base case, only CD4 count monitoring was used, and we evaluated scenarios where viral load counts were also available.  We used data from Cape Town’s region to determine costs of care.  All assumptions were tested in sensitivity analyses.

Results: Over the lifetime of the cohort, 25.6% of individuals failed 1^st and 2^nd line regimens by virologic criteria.  However, only 8.1% had detectable failure when only CD4 counts were available for monitoring due to a long lag in diagnosing treatment failure and higher rates of mortality compared to virologic monitoring.  The incremental cost-effectiveness ratio of adding a second-generation PI was $7,356/year-of-life gained.  The strategy where a triple-NRTI was used as the initial regimen was associated with worse survival and higher costs compared to the present WHO strategy when CD4 monitoring alone was available.  With virologic monitoring, the triple NRTI regimen was beneficial, and cost $3,924/year-of-life gained compared to the standard WHO strategy.   Use of a second generation PI cost $6,950/year-of-life gained compared to the triple NRTI strategy.  Results were sensitive to current prices of antiretrovirals, and to the rates of treatment failure.

Conclusions: A substantial portion of individuals on HAART in sub-Saharan Africa may fail both existing regimens.  At a threshold of about $7,500/year-of-life gained, adding a third regimen, based on a second-generation PI, was cost-effective with either CD4 or viral load monitoring.  At a threshold of about $4,000/year-of-life gained, an initial triple NRTI-strategy was cost-effective only if viral load monitoring was used.  At lower thresholds, the current WHO 2-regimen strategy is preferred.