Health benefits, costs, and cost-effectiveness of earlier eligibility for adult antiretroviral therapy and expanded treatment coverage: a combined analysis of 12 mathematical models

July 24, 2014

Abstract: 

Background: New WHO guidelines recommend initiation of antiretroviral therapy for HIV-positive adults with CD4 counts of 500 cells per μL or less, a higher threshold than was previously recommended. Country decision makers have to decide whether to further expand eligibility for antiretroviral therapy accordingly. We aimed to assess the potential health benefits, costs, and cost-effectiveness of various eligibility criteria for adult antiretroviral therapy and expanded treatment coverage.

Methods: We used several independent mathematical models in four settings—South Africa (generalised epidemic, moderate antiretroviral therapy coverage), Zambia (generalised epidemic, high antiretroviral therapy coverage), India (concentrated epidemic, moderate antiretroviral therapy coverage), and Vietnam (concentrated epidemic, low antiretroviral therapy coverage)—to assess the potential health benefits, costs, and cost-effectiveness of various eligibility criteria for adult antiretroviral therapy under scenarios of existing and expanded treatment coverage, with results projected over 20 years. Analyses assessed the extension of eligibility to include individuals with CD4 counts of 500 cells per μL or less, or all HIV-positive adults, compared with the previous (2010) recommendation of initiation with CD4 counts of 350 cells per μL or less. We assessed costs from a health-system perspective, and calculated the incremental cost (in US$) per disability-adjusted life-year (DALY) averted to compare competing strategies. Strategies were regarded very cost effective if the cost per DALY averted was less than the country's 2012 per-head gross domestic product (GDP; South Africa: $8040; Zambia: $1425; India: $1489; Vietnam: $1407) and cost effective if the cost per DALY averted was less than three times the per-head GDP.

Findings: In South Africa, the cost per DALY averted of extending eligibility for antiretroviral therapy to adult patients with CD4 counts of 500 cells per μL or less ranged from $237 to $1691 per DALY averted compared with 2010 guidelines. In Zambia, expansion of eligibility to adults with a CD4 count threshold of 500 cells per μL ranged from improving health outcomes while reducing costs (ie, dominating the previous guidelines) to $749 per DALY averted. In both countries results were similar for expansion of eligibility to all HIV-positive adults, and when substantially expanded treatment coverage was assumed. Expansion of treatment coverage in the general population was also cost effective. In India, the cost for extending eligibility to all HIV-positive adults ranged from $131 to $241 per DALY averted, and in Vietnam extending eligibility to patients with CD4 counts of 500 cells per μL or less cost $290 per DALY averted. In concentrated epidemics, expanded access for key populations was also cost effective.

 

Incremental cost per DALY averted for expanding eligibility criteria for antiretroviral therapy, by country and model Results calculated over 20 years, with all costs and health benefits discounted at 3% per year. All costs are in 2012 US$. Values below the upper dashed line (three-times per-head gross domestic product [GDP]) are defined as cost effective; those below the lower dashed line (per-head GDP) are defined as very cost effective. The Menzies model (South Africa) and all models for India simulated only expanding eligibility to all HIV-positive adults. For the Goals model in Zambia, the estimated incremental cost-effectiveness ratio (cost per disability-adjusted life-year [DALY] averted) is negative because over 20 years the strategy produces health benefits and is estimated to be cost-saving because of the reduced treatment and care burden, including savings due to averted cost of tuberculosis treatment. *Indicates that eligibility for patients with CD4 counts of 500 cells per μL or less is dominated by the other strategy (ie, produces fewer health benefits at higher cost).

Results: We first examined whether it would be cost effective to change antiretroviral therapy eligibility criteria for adults in generalised-epidemic settings (ie, South Africa and Zambia). In South Africa, the ICER for changing the CD4 count threshold from 350 cells per μL to 500 cells per μL ranged from $273 to $1691 per DALY averted over 20 years (results from six models; figure 1). The cost per DALY averted for changing eligibility to all HIV-positive adults compared with eligibility for those with CD4 counts of 350 cells per μL or less ranged from $438 to $3790 (seven models). In Zambia, the ICER for expanding eligibility to patients with CD4 counts of 500 cells per μL or less ranged from improving health outcomes while reducing costs (ie, dominating the previous guidelines) to $749 per DALY averted (four models). For expanding eligibility to all HIV-positive adults compared with eligibility for those with CD4 counts of 350 cells per μL or less, results ranged from dominating the previous guidelines to $790 per DALY (four models).