El‐Sefi 1986 C.

Methods	Randomised controlled trial. Randomisation based on a table of random numbers. Patient blinded. Unclear blinding of surgeon and outcome assessor.
Participants	480 eligible patients. 80 patients excluded after randomisation. 400 enrolled in the study. Patients with perforated appendix were excluded after randomisation. The study has 4 subgroups (see El‐Sefi 1986 A & B). In El‐Sefi 1986 C 200 patients enrolled in the study.
Interventions	Treatment group: Metronidazole 500 mg i.v preoperatively and eight‐hourly for the next 3 days. (When the patient tolerated oral medication converted to 250 orally) Placebo group: Not specified same regime as above.
Outcomes	Wound infection (Presence of pus or a purulent exudate of the wound).
Notes	No comments on drain treatment Wrote to author to specify subgrouping on drop‐outs.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment?	Low risk	A ‐ Adequate