| 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 |
[13] Surgical antibiotic prophylaxis (re-dosing):Ohge H, Takesue Y, Yokoyama T, Murakami Y, Hiyama E, Yokoyama Y, Kanehiro T, Itaha H, Matsuura Y. An additional dose of cefazolin for intraoperative prophylaxis. Surg Today. 1999;29(12):1233-6.http://www.ncbi.nlm.nih.gov/pubmed/16039702
Surgical antibiotic prophylaxis (re-dosing): National Institute for Health and Care Excellence. Surgical site infections: prevention and treatment clincal guideline, 22 October 2008. https://www.nice.org.uk/guidance/cg74