Table 2.

The quality assessment criteria

Domain	Criteria
Sample	1- Source of the sample were clearly defined
	2- Enough description of the sample
Prognostic variables	3- Clear definition and description of the used prognostic factor
	4- Measured appropriately (reliable and valid)
Follow-up	5- Completeness rate (>80%)
	6- Adequate description of the completeness
Outcome	7- Clear definition and description of the used outcomes
	8- Measured appropriately (reliable and valid)
Analysis	9- Enough description of the analysis
	10- Appropriate analysis
Confounding	11- Account for potential confounders with appropriate analysis