Table 3 The critical appraisal tool utilized to assess the quality of the included studies

Part I

Is the final sample representative of the target population?

1. At least one of the following must apply in the study: an entire target population, randomly selected sample, or sample stated to represent the target population.

2. At least one of the following: reasons for non-response described, non-responders described, comparison of responders and non-responders, or comparison of sample and target population

3. Response rate and, if applicable, drop-out rate reported

Part II

Quality of the data?

4. Were the data primary data of low back pain or was it taken from a survey not specifically designed for that purpose?

5. Were the data collected from each adult directly or were they collected from a proxy?

6. Was the same mode of data collection used for all subjects?

7. At least one of the following in case of questionnaire: a validated questionnaire or at least tested for reproducibility.

8. At least one of the following in the case of an interview: Interview validated, tested for reproducibility, or adequately described and standardized.

9. At least one of the following in the case of an examination: Examination validated, tested for reproducibility, or adequately described and standardized.

Part III

Definition of low back pain (LBP)

10. Was there a precise anatomic delineation of the lumbar area or reference to an easily obtainable article that contains such specification?

11. Was there further useful specification of the definition of LBP, or question(s) put to study subjects quoted such as the frequency, duration or intensity, and character of the pain. Or was there reference to an easily obtainable article that contains such specification?

12. Were recall periods clearly stated: e.g., 1 week, 1 month or lifetime?