TABLE 2

Critical Appraisal Tool Criterion

Control for bias
 1. Defined sample
 2. Representative sample
 3. Blind outcome rating
Appropriate measurement of variable
 4. Methods of assessment (a) face validity
 5. Methods of assessment (b) evidence of psychometrics
 6. Outcome data reported
 7. Adequate power calculation
Control for confounding
 8. Statistical adjustment: multivariable or regression analysis conducted, with adjustment for potentially confounding factors.
Each of these criterions was explicitly judged by using: Yes = criterion clearly satisfied; No = criterion clearly not satisfied or unclear if criterion is satisfied. A quality score (maximum score = 8) was allocated to each individual study.