Twenty RCTs (n=1,404) that comprised 23 probiotic interventions were included in the review. Median sample size was 54 (range 25 to 363). There were some minor discrepancies in reported sample sizes between text and tables. Study quality was variable. Quality scores ranged from 3 to 6 points (median 4 points). None of the studies performed ITT analysis or adequately accounted for withdrawals and dropouts.
Global IBS symptoms were statistically significantly reduced in the probiotic groups compared with the placebo groups (RR 0.77, 95% CI 0.62 to 0.94, NNT=7.3; 14 RCTs; I2=68%). Probiotics were also associated with lower incidence of abdominal pain (RR 0.78, 95% CI 0.69 to 0.88, NNT=8.9; 11 RCTs; I2=73%). There was no evidence of statistically significant publication bias in either analysis.
Fourteen RCTs stated that there were no serious adverse reactions reported; three reported no safety data and three provided limited data on reactions including increased intestinal symptoms, epistaxis, aftertaste, anxiety and angina.