Cost-effectiveness of HIV monitoring strategies in resource-limited settings: a southern African analysis

Abstract

Background: Although the number of infected persons receiving highly active antiretroviral therapy (HAART) in low- and middle-income countries has increased dramatically, optimal disease management is not well defined.

Methods: We developed a model to compare the costs and benefits of 3 types of human immunodeficiency virus monitoring strategies: symptom-based strategies, CD4-based strategies, and CD4 counts plus viral load strategies for starting, switching, and stopping HAART. We used clinical and cost data from southern Africa and performed a cost-effectiveness analysis. All assumptions were tested in sensitivity analyses.

Results: Compared with the symptom-based approaches, monitoring CD4 counts every 6 months and starting treatment at a threshold of 200/muL was associated with a gain in life expectancy of 6.5 months (61.9 months vs 68.4 months) and a discounted lifetime cost savings of US $464 per person (US $4069 vs US $3605, discounted 2007 dollars). The CD4-based strategies in which treatment was started at the higher threshold of 350/microL provided an additional gain in life expectancy of 5.3 months at a cost-effectiveness of US $107 per life-year gained compared with a threshold of 200/microL. Monitoring viral load with CD4 was more expensive than monitoring CD4 counts alone, added 2.0 months of life, and had an incremental cost-effectiveness ratio of US $5414 per life-year gained relative to monitoring of CD4 counts. In sensitivity analyses, the cost savings from CD4 count monitoring compared with the symptom-based approaches was sensitive to cost of inpatient care, and the cost-effectiveness of viral load monitoring was influenced by the per test costs and rates of virologic failure.

Conclusions: Use of CD4 monitoring and early initiation of HAART in southern Africa provides large health benefits relative to symptom-based approaches for HAART management. In southern African countries with relatively high costs of hospitalization, CD4 monitoring would likely reduce total health care expenditures. The cost-effectiveness of viral load monitoring depends on test prices and rates of virologic failure.

Figure 1. Health and Cost Outcomes of Monitoring Strategies

Open symbols represent strategies that were dominated by other strategies either through strict dominance (less effective and more costly than another strategy) or extended dominance (less effective and more costly than a mix of other strategies). All CD4-based strategies were more effective and less costly than the symptom-based strategies. Starting HAART at CD4 350/μl was always more effective than starting at 200/μl, regardless of viral load monitoring. More frequent monitoring was generally more effective than less frequent, but was dominated in most cases. The squares represent the symptom-based strategies, circles represent the CD4-based strategies, and diamonds represent the CD4-viral load strategies.

Figure 2. Effect of Inpatient Costs on Cost-Effectiveness of CD4 Monitoring

The incremental cost-effectiveness ratio of monitoring CD4 and starting HAART at 200 cells/μl compared to a symptom-based strategy is represented on the Y axis. A negative ratio suggests that monitoring CD4 was cost saving. The symptom-based approach is cheaper than monitoring CD4 when inpatient stay costs less than $120 per day. At $20 per day, the incremental cost-effectiveness ratio is a little under $700 per life-year gained.

Figure 3. Sensitivity Analysis of Viral Load Monitoring

The incremental cost-effectiveness ratio (ICER) is sensitive to both the rate of virologic failure and the cost per test of viral load monitoring. The squares represent the relationship between per-test costs and the ICER when the rate of virologic failure was halved compared with the base case, while the triangles represent the relationship when the rate of virologic failure was doubled, highlighting the importance of viral load monitoring in settings with high rates of virologic failure.