Two-Way Sensitivity Analysis on Effectiveness and Cost of Directly Observed Therapy.

Each diagonal curve represents a different estimate of effectiveness (log₁₀ reduction in viral load) of directly observed therapy: −0.5 log₁₀ (thick line, squared); −0.8 log₁₀ (thin solid line, diamonds); or −1.5 log₁₀ (dashed line, triangles). Incremental cost-effectiveness of directly observed therapy relative to self-administered antiretrovirals appears on the Y-axis. At each level of effectiveness, increasing the cost of directly observed therapy increases the cost-effectiveness ratio associated with this intervention; however, only under the most unfavorable cost and effectiveness assumptions does this ratio exceed $50,000 per quality-adjusted life-year (QALY) gained, a commonly cited cost-effectiveness threshold (horizontal dashed line). Values falling below the X-axis indicate that directly observed therapy is cost-saving.