OBJECTIVES : Quality-Adjusted Life Years (QALYs) and Disability-Adjusted Life Years (DALYs) are commonly used in cost-effectiveness analysis (CEA) to measure health benefits. While several studies have explored their conceptual differences, there is little data on how they differ empirically. We sought to quantify and explain differences between QALY- and DALY-based cost-effectiveness ratios when both were reported in the same evaluation, and whether using one versus the other would materially affect conclusions about an intervention’s cost-effectiveness.

METHODS : We identified CEAs using both QALYs and DALYs from the Tufts Medical Center CEA Registry (CEAs with primary results reported as cost-per-QALY) and Global Health CEA Registry (CEAs with primary results reported as cost-per-DALY), and a supplemental search to ensure comprehensive literature coverage. We calculated absolute and relative differences between the QALY- and DALY-based ratios, the latter defined as the absolute difference divided by the QALY-based ratio, and compared ratios to common benchmarks (e.g., 1x GDP per capita). We converted reported ratios into US dollars.

RESULTS : Among the eleven studies, seven focused on pharmaceuticals and infectious disease, nine were published within the last three years, and five were conducted in high-income settings. Four studies concluded the intervention was “cost-saving.” Among the eleven intervention-specific QALY- and DALY-based ratios reported from seven remaining studies, six DALY-based ratios exceeded QALY-based ratios. While relative differences ranged from 6% to 120% (median 39%), and absolute differences from approximately $2 to $15,000 (median $366), the differences were small relative to each ratio’s magnitude. Utility and/or disability weights explained most differences between ratios. The QALY-based and DALY-based ratios were consistent (both above or both below the benchmark) in 10 of 11 cases.

CONCLUSIONS : Our results suggest that while QALY-based and DALY-based ratios for the same intervention can differ, differences tend to be modest and are unlikely to materially affect resource allocation recommendations.