The impact of disease stage on direct medical costs of HIV management: a review of the international literature.

The global prevalence of HIV infection continues to grow, as a result of increasing incidence in some countries and improved survival where highly active antiretroviral therapy (HAART) is available. Growing healthcare expenditure and shifts in the types of medical resources used have created a greater need for accurate information on the costs of treatment. The objectives of this review were to compare published estimates of direct medical costs for treating HIV and to determine the impact of disease stage on such costs, based on CD4 cell count and plasma viral load. A literature review was conducted to identify studies meeting prespecified criteria for information content, including an original estimate of the direct medical costs of treating an HIV-infected individual, stratified based on markers of disease progression. Three unpublished cost-of-care studies were also included, which were applied in the economic analyses published in this supplement. A two-step procedure was used to convert costs into a common price year (2004) using country-specific health expenditure inflators and, to account for differences in currency, using health-specific purchasing power parities to express all cost estimates in US dollars. In all nine studies meeting the eligibility criteria, infected individuals were followed longitudinally and a 'bottom-up' approach was used to estimate costs. The same patterns were observed in all studies: the lowest CD4 categories had the highest cost; there was a sharp decrease in costs as CD4 cell counts rose towards 100 cells/mm³; and there was a more gradual decline in costs as CD4 cell counts rose above 100 cells/mm³. In the single study reporting cost according to viral load, it was shown that higher plasma viral load level (> 100,000 HIV-RNA copies/mL) was associated with higher costs of care. The results demonstrate that the cost of treating HIV disease increases with disease progression, particularly at CD4 cell counts below 100 cells/mm³. The suggestion that costs increase as the plasma viral load rises needs independent verification. This review of the literature further suggests that publicly available information on the cost of HAART by disease stage is inadequate. To address the information gap, multiple stakeholders (governments, pharmaceutical industry, private insurers and non-governmental organizations) have begun to establish and support an independent, high quality and standardized multicountry data collection for evaluating the cost of HIV management. An accurate, representative and relevant cost-estimate data resource would provide a valuable asset to healthcare planners that may lead to improved policy and decision-making in managing the HIV epidemic.