Five RCTs were included for review (n=262). On the Jadad scale, one RCT scored 4, one scored 3 and three scored 2. Intention to treat analysis was used in three trials.
AZA was not associated with significantly greater treatment success in patients with UC when all five studies were included. Significant statistical heterogeneity was found (p=0.048). Sensitivity analyses of steroid dependent versus not steroid dependent patients and of studies with an active versus placebo control arm did not alter the results. There was evidence of significant statistical heterogeneity for these outcomes (p<0.05). But, when only the two high-quality studies were considered, AZA was associated with significantly increased treatment success compared to placebo or 5-ASA (n= 107, RR 2.05, 95% CI: 1.30, 3.23, p=0.002). There was no evidence of statistical heterogeneity.
Stratified analysis showed that there was greater efficacy of AZA in maintaining clinical remission of UC in steroid dependent patients (RR 1.57, 95%CI: 1.08, 2.28, p=0.0185), in the high quality studies (RR 2.17, 95% CI: 1.39, 3.41, p=0.0007), in studies with a placebo control (RR 1.41, 95% CI: 1.02, 1.95, p=0.0357) and in studies with an endoscopic score (RR 1.43, 95% CI: 1.07, 1.90, p=0.0146).
There was no evidence of publication bias from inspection of the funnel plot or using Begg's statistic.