Measuring Effectiveness

There are three methodological challenges to measuring the effectiveness of medical interventions: the choice of good measuring instruments, the use of appropriate analytic measures, and the use of a reliable method of extrapolating measures from an experimental context to a more general context. In practice each of these challenges contributes to overestimating the effectiveness of medical interventions. These challenges suggest corrective principles. The instruments employed in clinical research should measure patient-relevant and disease-specific parameters. Effectiveness always should be measured and reported using absolute outcome measures (such as ‘risk difference’), and we should employ caution when interpreting relative outcome measures (such as ‘relative risk reduction’). Extrapolating from research settings to clinical settings should more rigorously take into account possible ways in which interventions can fail to be effective in a target population. Current regulatory standards for drug approval are insufficient to manage these problems of measurement.