Table 2: Grading of Recommendations Assessment, Development and Evaluation (GRADE) summary of findings.

Outcome	No. of participants (studies); length of follow-up	Quality of evidence (GRADE)	Anticipated effects
Incidence of surgical-site infections	4036 (4 trials); follow-up ≤ 2 yr	Very low (owing to risk of bias, imprecision and inconsistency)	The pooled absolute risk difference for surgical-site infections between postoperative antibiotic prophylaxis and placebo or no treatment was 0.01 (95% CI 0.00 to 0.02)

Note: CI = confidence interval.