Twenty-one studies were included in the review (n=2,134). There were 19 randomized controlled trials (RCTs) (n=1,898), one observational study (n=9) and one questionnaire-based retrospective study (n=227). The mean raw MQ score was 0.91 for the primary prevention studies and 0.81 for the secondary studies. It was reported that the prevention studies were of the highest quality.
Prevention trials (six trials): Probiotics significantly reduced the incidence of PAD two years after intervention, when compared to placebo, RR 0.66 (95% CI: 0.49, 0.89). Details of heterogeneity were not provided for this random-effects analysis, but the I2 value was 55% for the fixed-effect analysis. Exclusion of the one prevention trial which administered probiotics only postnatally resulted in a fixed effect I2 of 0%.
Treatment trials (four trials): There were no statistically significant changes in either intra- or inter-group SCORAD scores. In trial subgroup analyses, four trials detected significant therapeutic effect in sensitised (immunoglobulin E status) patients.