Table 1. Recommendation and Evidence Levels.

Recommendation levels
	Strongly recommended
	Conditionally recommended
Evidence levels
	I: Systematic review of cross-sectional studies with consistently applied reference standard and blinding
	II: Individual cross sectional studies with consistently applied reference standard and blinding
	III: Non-consecutive studies, or studies without consistently applied reference standards
	IV: Case-control studies or poor or non-independent reference standard