Level I | Good quality evidence |
Systematic review of RCTs with consistent findings High quality individual RCT |
Level II |
Limited quality patient orientated evidence |
Systematic review of lower quality studies or studies with inconsistent findings Low quality clinical trial Cohort studies Case-control studies |
Level III | Other |
Consensus guidelines, extrapolations from bench research, usual practice, opinion, disease-oriented evidence (intermediate or physiologic outcomes only), or case series |
[2] Steinberg JP, C et. al. Timing of antimicrobial prophylaxis and the risk of surgical site infection: results from the Trial to Reduce Antimicrobial Prophylaxis Errors. Ann Surg. 2009; 250:10-6.