Table 1.

Methodological quality scoring system

	Study-specific requirements
1. Are the study design and sampling method appropriate for the research question?	Is it an observational study? And is there an adequate sample of the total population studied in the research question?
2. Is the sampling frame appropriate?	Is the ‘list for study recruitment’ from which subjects are selected (sampling frame) appropriate? (no under- or overrepresentation of the problem in the subpopulation?)
3. Is the sample size adequate?	An adequate sample size calculation in this study and/or n > 100
4. Are objective suitable and standard criteria used for measurement of the health outcome?	Are validated questionnaires used?
5. Is the health outcome measured in an unbiased fashion?	Is there a possible bias in the interpretation of the results?
6. Is the response rate adequate? Are the refusers described?	>66.6 % response rate and dropouts described and compared with the study population
7. Are the estimates of prevalence or incidence given with confidence intervals and in detail by subgroup if appropriate?
8. Are the study subjects and the setting described in detail and similar to those of interest to you?	Are the sociodemographic characteristics adequately described?
Total	0–8 Points Scoring system: 0–4 points = low; 5–8 points = high