The usefulness of ratios for allocation decisions: the case of stroke

Economic evaluation is becoming increasingly important in the field of stroke as well. The results of economic evaluation can be expressed in cost per quality-adjusted life years (QALY) gained, which enables policy makers to compare the relative efficiency of different interventions regarding different diseases. Although using the concept of QALY is preferable from a theoretical point of view, in medical practice more often cost-effectiveness analysis (CEA), and not cost-utility analysis, is applied for practical reasons. One of the main limitations of CEA is that the results may be compared only with results of other CEAs, using the same effect parameter. The calculation of cost-effectiveness ratios (CERs) in many cases is misleading for resource allocation. Effects should be expressed in interval or ratio scales in order to calculate CERs, which is rarely the case. The calculation of a CER in a CEA should only be performed if, and only if, the investigator is convinced that there is a constant relation between the specific effect parameter and the ultimate gain in health.