appendix II.

Quality assessment form (modified form of STROBE)

Items		Yes=1	No=0	Unclear=0
Abstract	1. Clearly defined study design and main results of the study
Objectives	2. State specific objectives, including any prespecified hypotheses
Study design	3. Present key elements of study design early in the paper
Setting	4. Describe the setting
	5. Locations
	6. Including periods of recruitment
	7. Case definition/ exposure
Participants	8. Give the eligibility criteria
	9. The sources and methods for the selection of participants
	10. Describe methods of follow-up/ Give the rationale for the choice of cases and controls
	11. For matched studies, give matching criteria and the number of exposed and unexposed/ controls per case
Variables	12. Clearly define all outcomes
	13. Clearly define potential confounders and effect modifiers
Data sources/measurement	14. Give sources of data and details of methods of assessment
Bias	15. Address potential sources of bias
Study size	16. Explain how the study size was derived
Statistical methods	17. Describe all statistical methods
	18. Including those used to control for confounding
	19. If applicable, explain how lost to follow-up/matching of cases and controls was addressed
	20. Describe any sensitivity analyses
Total