Randomised controlled trials (RCTs) that compared antibacterial agents (including combination regimens) to placebo in patients with Crohn's disease were eligible for inclusion. Treatment duration had to be at least three months. Studies needed to report sufficient data to calculate odds ratios (ORs). Studies that administered other drugs were included if regimens were identical in the two treatment groups. Studies of patients with exclusive perianal Crohn's disease were excluded. Outcomes of interest were remission in patients with active disease and relapse in patients with inactive disease.
Most included studies enrolled patients with active disease, some studies enrolled patients with inactive disease and one study enrolled both types of patients. Where reported, in most studies diagnostic criteria for Crohn's disease were standard clinical findings with typical radiologic, endoscopic or histological lesions. Studies used a disease activity index (most commonly the Crohn's Disease Activity Index) to assess outcomes. One study assessed recurrence of lesions. Studies assessed a variety of treatment regimens that consisted of up to four different drugs and covered the categories of anti-tuberculosis drugs, nitroimidazoles, clarithromycin and clofazimine. In some studies patients also received steroid treatment; this was not permitted in others. Median study duration was six months (range three to 24 months).
Two reviewers independently assessed studies for inclusion. Disagreements were resolved by consensus or referral to a third reviewer.