This review investigated medical treatment for prevention of postoperative recurrence of Crohn's disease and concluded that it had a beneficial effect on clinic recurrence. The conduct of this review was good and its conclusions appear reliable.

To compare clinical and endoscopic postoperative recurrence from medical treatment for Crohn's disease.

MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), Science Direct and Ingenta Connect database and Ovid search engine were searched from inception to April 2008 without language restrictions. Handsearches of reference lists and related articles were performed. Search terms were reported.

Randomised placebo-controlled trials of any medical treatment given for postoperative prophylaxis after operative resection of the bowel in Crohn's disease were eligible for inclusion. Primary outcomes were clinical recurrence, endoscopic and severe endoscopic recurrence. Clinical recurrence was defined as a Crohn's Disease Activity Index (CDAI) score of more than 150 or an increase from baseline of between 60 and 100 points. Endoscopic recurrence was an endoscopy score (using Rutgeerts scoring system) of 1 or more and severe recurrence was a score of 3 or more.

Included studies compared mesalamine, interleukin 10, budesonide, 6-MP, probiotics, metronidazole or ornidazole with placebo. Duration of follow-up ranged from three to 72 months. Where reported, mean age ranged from 29 to 39 years, duration of disease from 24 months to 10 years, 51% of patients were male and the most common involvement sites were ileum and ileocolon.

Studies were selected by two reviewers independently. Disagreements were resolved by consensus.

The authors used the Jadad scale to assess adequacy of reported randomisation, allocation concealment, blinding and withdrawals and allocate scores between zero and 5 points. Studies that scored 2 or less were classed as low quality and those that scored 3 or more were classed as high quality.

Study validity was assessed by two reviewers independently. Disagreements were resolved by consensus.

Relative risks (RR) for each type of outcome, with 95% confidence intervals (CI), were calculated on both an intention-to-treat (ITT) and per protocol basis.

Data were extracted by two reviewers independently. Disagreements were resolved by consensus. Authors were contacted for further information where necessary.

Results were pooled in meta-analyses using a fixed-effect model. Heterogeneity was assessed using a Q test (p<0.10 was considered significant) and a random-effects model was used in the presence of significant heterogeneity. Sensitivity analyses explored the impact on the pooled results of removing individual studies from the analysis. Subgroup analyses compared results for disease duration of 75 months or less with more than 75 months and follow-up of 12 months or less with more than 12 months. Publication bias was assessed using a funnel plot and Egger's regression test.

Fourteen studies (n=1,497) were included in the review. All studies were double-blind and they were considered to be good quality (six scored 5 and eight scored 4).

Clinical recurrence: ITT analyses showed that medical treatment reduced the risk of clinical recurrence compared with placebo (RR 0.74, 95% CI 0.64 to 0.87; 13 studies). There was no evidence of statistical heterogeneity (p=0.614). Subgroup analyses showed similar risk reductions for most groups (≤ or >12 months follow-up and >75 months disease duration) apart from three studies where disease duration was 75 months or less, which showed no significant difference. Overall results from the per protocol analysis were similar, but only the subgroup of studies with 12 months or less follow-up showed a significant risk reduction. There was no evidence of publication bias (Egger's test p=0.752).

Endoscopic recurrence: There was no evidence of a difference between medical treatment and placebo in risk of endoscopic recurrence for either ITT or per protocol analyses (12 studies). However, subgroup analyses showed a significant risk reduction for studies with disease duration of 75 months or less (RR 0.78, 95% CI 0.63 to 0.97; four studies) in the ITT analysis with similar reductions in risk for this group and also the group with a follow-up of 12 months or less in the per protocol analysis. There was no evidence of statistical heterogeneity for any analysis.

Severe endoscopic recurrence: There was no evidence of a difference between medical treatment and placebo in the risk of endoscopic recurrence for either ITT or per protocol analyses (seven studies) or any of the subgroup analyses. There was no evidence of statistical heterogeneity for any analysis.

Medical treatment had a beneficial effect on decreased risk of postoperative recurrence in patients with Crohn's disease.

This review clearly stated the inclusion criteria in terms of study design, interventions, participants and outcomes. A number of sources were searched without language restrictions, but (as the authors pointed out) a limitation was that they did not try to find unpublished studies. All steps of the review were performed by two people, which reduced risks of errors and bias. Full details of the validity assessment were presented for each study. Methods of meta-analysis were appropriate. Heterogeneity was assessed. But, it was unclear whether subgroup analyses were pre-specified. In summary, the conduct of this review was generally good and its conclusions appear reliable.

The authors did not state any implications for practice and research.

Not stated.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.