Table 2.

Class/Level/Strength of Evidence.24,25

Class of Evidence	Study Designs
I=Strong evidence	Good quality (well designed), randomized clinical trial*
II=Moderate evidence	Moderate quality RT Good quality cohort study (CS) Good quality case control study (CCS)
III=Weak evidence	Poor quality RCT Moderate/poor quality CS or CCS Case Series, case reports, anatomical studies, expert opinion