The following 11 criteria were included: (1) Was there a clear statement of the aims of the research?; (2) Is a qualitative methodology appropriate?; (3) Was the research design appropriate to address the aims of the research?; (4) Does the study’s theoretical underpinnings (eg, ontological and epistemological assumptions; guiding theoretical framework(s)) clear, consistent and conceptually coherent?; (5) Was the recruitment strategy appropriate to the aims of the research?; (6) Were the data collected in a way that addressed the research issue?; (7) Has the relationship between the researcher and participants been adequately considered?; (8) Have ethical issues been taken into consideration?; (9) Was the data analysis sufficiently rigorous?; (10) Is there a clear statement of findings?; (11) How valuable is the research? (1: yes, 0: no).

CASP, critical appraisal skills programme.