| 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 |
[8] Cefazolin, IV: McDanel JS, Perencevich EN, Diekema DJ, Herwaldt LA, Smith TC, ChrischillesEA, Dawson JD, Jiang L, Goto M, Schweizer ML. Comparative effectiveness of beta-lactams versus vancomycin for treatment of methicillin-susceptible Staphylococcus aureus bloodstream infections among 122 hospitals. Clin Infect Dis. 2015 Aug 1;61(3):361-7. https://www.ncbi.nlm.nih.gov/pubmed/25900170