A meta-analysis of randomized controlled trials evaluating the effectiveness of fecal microbiota transplantation for patients with irritable bowel syndrome
Authors: Wang Yu , Hu Yongmei , Shi Ping 
Published: July 2024

Abstract
Objective
Multiple randomized controlled trials (RCTs) have investigated the efficacy of fecal microbiota transplantation (FMT) for irritable bowel syndrome (IBS), but have yielded inconsistent results. We updated the short-term and long-term efficacy of FMT in treating IBS, and performed a first-of-its-kind exploration of the relationship between gut microbiota and emotions.

Methods
We conducted a comprehensive search of PubMed, Embase, Web of Science, and the Cochrane Library using various search strategies to identify all eligible studies. The inclusion criteria for data extraction were randomized controlled trials (RCTs) that investigated the efficacy of fecal microbiota transplantation (FMT) compared to placebo in adult patients (≥ 18 years old) with irritable bowel syndrome (IBS). A meta-analysis was then performed to assess the summary relative risk (RR) and corresponding 95% confidence intervals (CIs).

Results
Out of 3,065 potentially relevant records, a total of 10 randomized controlled trials (RCTs) involving 573 subjects met the eligibility criteria for inclusion in the meta-analysis. The meta-analyses revealed no significant differences in short-term (12 weeks) (RR 0.20, 95% CI -0.04 to 0.44), long-term (52 weeks) global improvement (RR 1.38, 95% CI 0.87 to 2.21), besides short-term (12 weeks) (SMD − 48.16, 95% CI -102.13 to 5.81, I2 = 90%) and long-term (24 weeks) (SMD 2.16, 95% CI -60.52 to 64.83, I2 = 68%) IBS-SSS. There was statistically significant difference in short-term improvement of IBS-QoL (SMD 10.11, 95% CI 0.71 to 19.51, I2 = 82%), although there was a high risk of bias. In terms of long-term improvement (24 weeks and 54 weeks), there were no significant differences between the FMT and placebo groups (SMD 7.56, 95% CI 1.60 to 13.52, I2 = 0%; SMD 6.62, 95% CI -0.85 to 14.08, I2 = 0%). Sensitivity analysis indicated that there were visible significant effects observed when the criteria were based on Rome IV criteria (RR 16.48, 95% CI 7.22 to 37.62) and Gastroscopy (RR 3.25, 95%CI 2.37 to 4.47), Colonoscopy (RR 1.42, 95% CI 0.98 to 2.05). when using mixed stool FMT based on data from two RCTs, no significant difference was observed (RR 0.94, 95% CI 0.66 to -1.34). The remission of depression exhibited no significant difference between the FMT and placebo groups at the 12-week mark (SMD − 0.26, 95% CI -3.09 to 2.58), and at 24 weeks (SMD − 2.26, 95% CI -12.96 to 8.45). Furthermore, major adverse events associated with FMT were transient and self-limiting.

Discussion
Based on the available randomized controlled trials (RCTs), the current evidence does not support the efficacy of FMT in improving global IBS symptoms in the long term. The differential results observed in subgroup analyses raise questions about the accurate identification of suitable populations for FMT. Further investigation is needed to better understand the reasons behind these inconsistent findings and to determine the true potential of FMT as a treatment for IBS.