Fig. 3.

The effect of antibiotic prophylaxis on the risk of surgical site infection within 30 days after surgery was assessed using unadjusted univariable logistic regression and multivariable regression before and after propensity score matching. Propensity score matching was repeated using several caliper requirements, which limit the permissible difference in propensity scores between matched patients to improve the closeness of match. Statistical significance was assessed at a significance level of p = 0.05.