Criteria for evaluating evidence on public health interventions.

Public health interventions tend to be complex, programmatic, and context dependent. The evidence for their effectiveness must be sufficiently comprehensive to encompass that complexity. This paper asks whether and to what extent evaluative research on public health interventions can be adequately appraised by applying well established criteria for judging the quality of evidence in clinical practice. It is adduced that these criteria are useful in evaluating some aspects of evidence. However, there are other important aspects of evidence on public health interventions that are not covered by the established criteria. The evaluation of evidence must distinguish between the fidelity of the evaluation process in detecting the success or failure of an intervention, and the success or failure of the intervention itself. Moreover, if an intervention is unsuccessful, the evidence should help to determine whether the intervention was inherently faulty (that is, failure of intervention concept or theory), or just badly delivered (failure of implementation). Furthermore, proper interpretation of the evidence depends upon the availability of descriptive information on the intervention and its context, so that the transferability of the evidence can be determined. Study design alone is an inadequate marker of evidence quality in public health intervention evaluation.