Table 2.

Level of evidence rating criteria

Level	Rating	Criteria
Strong	+ or −	Consistent findings in multiple studies of good methodological quality OR in one study of excellent methodological quality
Moderate	+ or −	Consistent findings in multiple studies of fair methodological quality OR in one study of good methodological quality
Limited	+ or −	One study of fair methodological quality
Conflicting	+ or −	Conflicting findings
Unknown	?	Only studies of poor methodological quality or no studies

 + : positive rating, ?: indeterminate rating, −: negative rating