Evaluation is essential for all types of intervention

Editor—Clark's plea for home visits by health visitors to be excluded from evaluation by randomised controlled trials cannot be accepted.¹ His objections—the limitations of meta-analyses, the problems of confounding particularly where complex social factors are involved, and the selection of outcome measures—apply to many other interventions. The acceptance of randomised controlled trials does not preclude other methods of evaluation.

Complex social interventions can be and have been evaluated despite the difficulties as Oakley described in her review of the rise and fall of evaluation of social interventions.² She noted that one of the main reasons for the decline in evaluation was the apparent ineffectiveness (and in some cases adverse effects) of some of the favoured interventions, and concluded that experts in the social domain, like those in medicine, have resisted the notion that rigorous evaluation of their work is more likely to give reliable answers than their own individual preferences. When randomised controlled trials find that new “treatments” are no better than old ones, a retreat to other methods of evaluation is particularly likely, as though the prime task is not to identify whether anything works but to prove that something does.

It would not be right to discontinue every intervention for which evidence of effectiveness is lacking. If, as Clark says, however, home visits to elderly people have almost disappeared by default, then it is reasonable to ask for evidence—from randomised controlled trials or otherwise—before reintroducing them.