4.3.2 Type of studies Randomised trials, non-randomised intervention studies, and other observational studies (including diagnostic or prognostic studies) were included in the evidence reviews as appropriate. For most intervention reviews in this guideline, parallel randomised controlled trials (RCTs) were included because they are considered the most robust type of study design that can produce an unbiased estimate of the intervention effects. Crossover RCTs were not appropriate for any of the intervention reviews . In chronic conditions there is the possibility that the initial treatment permanently alters the disease or the process being investigated. The cardiac rehabilitation review was the exception where only data from the 1st period of cross-over trials was included, unless there was formal evidence of period effects in which case data from both 1st and 2nd periods was included. If non-randomised intervention studies were considered appropriate for inclusion (for example, in prognostic risk tool and diagnostic reviews) the committee stated a priori in the protocol that either certain identified variables must be equivalent at baseline or else the analysis had to adjust for any baseline differences. If the study did not fulfil either criterion it was excluded. Please refer to the review protocols in appendix A for full details on the study design of studies selected for each review question. For diagnostic review questions, diagnostic RCTs, cross-sectional studies and retrospective studies were included. For prognostic review questions, prospective and retrospective cohort studies were included. Case control studies were not included. Where data from non-randomised studies were included, the results for each outcome were presented separately for each study or meta-analysed if appropriate. 