Aufenacker 2004.

Study characteristics
Methods	Double‐blind RCT Country: the Netherlands Enrolment period: November 1998 to May 2003 Multicentre (4) study
Participants	N: 1040 participants Age: (years; mean ± SD) PG: 58.3 ± 12.9; CG: 58.2 ± 13.2 % Men: PG: 95.6%; CG: 97.0% Inclusion criteria: primary uni‐ or bilateral inguinal hernia and an indication for Lichtenstein hernia repair Exclusion criteria: age under 35, the need for antibiotics for a different reason, immunosuppressive disease (diabetes mellitus, malignancy, HIV) or medication (glucocorticoid therapy), allergy to the given antibiotic, recurrent hernia, or the inability to get an informed consent. BMI: not reported Skin antiseptic: PG: povidone iodine 98% of patients; CG: povidone iodine 98.4% of patients Operative time (minutes, median (IQR)) PG: 40 (30 to 50) / CG 40 (28 to 51) Method of repair: Lichtenstein technique with polypropylene mesh (hernioplasty). Drain use: PG: n = 11 (2.2%); CG: n = 4 (0,8%) ASA class: not reported Anaesthesia method: PG: local n = 10 (2%); spinal n = 180 (35.8%); general n = 311 (61%); unknown n = 2 (0.4%); CG: local n = 7 (1.4%); spinal n = 191 (37.8%); general n = 330 (60%); unknown n = 4 (0.8%). Hospitalisation method: PG: outpatients n = 231 (46.1%); CG: outpatients n = 232 (45.9%) Length of hospital stay: not reported Surgeon: PG: resident n = 212 (42.1%), certified surgeon n = 291 (57.9%); CG resident n = 225 (44.6%), certified surgeon n = 280 (55.4%)
Interventions	Prophylactic group (PG): N: 503 antibiotic: cefuroxime dose: 1500 mg number of doses: 1 route of administration: intravenous timing of administration: induction of anaesthesia. The exact timing of administering was not standardised, thereby copying daily practice. Control group (CG): N: 505 substance: equal volume of sterile saline.
Outcomes	Wound infection definition: CDC criteria. Follow‐up: 1, 2, 12 weeks SSSI N infected/N patients (%) PG: 7/503 (1.4%); CG: 7/505 (1.4%) DSSI N infected/N patients (%) PG: 1/503 (0.2%); CG 2/505 (0.4%) Adverse effects: not reported
Notes	Staphylococcus aureus, Enterococcus faecalis, Corynebacterium, Streptococcus group G/ Aspergillus fumigatus and skin bacteria were isolated from the wound infection Funding was not reported.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: “….according to a computer generated list in blocks of 10 patients with stratification for each hospital.”
Allocation concealment (selection bias)	Low risk	Quote: “The patients were double‐blinded randomly assigned to either intravenous placebo or antibiotic prophylaxis. A pharmacist carried out randomization….” and “A pharmacist prepared the trial medication under laminar airflow condition, and it was packed in nontransparent material to exclude optical differences. The anesthesiologist administered the trial medication at the induction of anesthesia.”
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: “A pharmacist prepared the trial medication under laminar airflow condition, and it was packed in nontransparent material to exclude optical differences. The anesthesiologist administered the trial medication at the induction of anesthesia.”
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "In most cases, the surgeon who performed the operation did not perform the follow‐up. In case of missing observations, the patients were contacted and a standardized telephone interview was performed." In the few cases that the surgeon who performed the operation also performed the follow‐up, it should be kept in mind that Quote: " trial medication ...was packed in nontransparent material to exclude optical differences" and that therefore the surgeon was unaware whether participant was part of intervention or control group.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Missing data were balanced between intervention groups. PG n = 17 (17/520 = 3.2%) and CG n = 15 (15/520 = 2.9%). The proportion of missing outcomes was considered not enough to have had a clinically relevant impact on the intervention effect estimate Available case analysis was performed 1 death in placebo‐group due to operation‐related complication (Quote: "One patient died of pulmonary complications and a bleeding gastric ulcer".)
Selective reporting (reporting bias)	Low risk	Study protocol was not registered, but report contains all expected outcomes, including specification of SSSI and DSSI
Other bias	Low risk	The study appears to be free of other sources of bias