Quality appraisal
The CASP (critical appraisal skills programme, 2006) frame- work was used and adapted to appraise the quality of the research. However, relevance to the study rather than any clinical service or organisation was a minor but neces- sary adaptation of the framework. The key questions asked when reviewing the studies are included in Table 2. The studies were initially reviewed by one author (LRC). Sub- sequently peer scrutiny of study reviews and the