Table 1.

Methodological quality criteria for prevalence studies.

A. Representatives of population	1. At least one of the following should apply for the study: an entire target population, randomly selected sample, or sample stated to represent the target population (two points)
	2. At least one of the following: reasons for nonresponse described, non-responders described, comparison of responders and non-responders, or comparison of sample and target population (two points)
	3. Response rate ≥90% (two points) Response rate 70–90% (one point) Response rate ˂70% (zero points)
B. Quality of data	4. Were the primary data from a prevalence study (two points) or were they taken from a survey not specifically designed for the purpose (one point)?
	5. The same mode of data collection should be used for all subjects (two points), if not (zero points).
	6. The data have been collected directly from the patient by means of a validated questionnaire/interview (three points), no validated questionnaire/interview (two points), data have been collected from proxies or retrospectively from medical record (zero points)
C. General description of method and results	7. Description of the target population and setting where patients were found (two points)
	8. Description of stage of disease (one point)
	9. Description of type of cancer, gender, and age: all (two points), 2 of 3 (one point), 1 of 3 (zero points)
	10. Final sample size (one point)
D. Definition of pain prevalence	11. Prevalence recall periods should be stated (one point)