Table 1.

Summary of seven randomized controlled trials of fecal microbiota transplantation for irritable bowel syndrome

Study	IBS subtypes	Number of patients (% female)	Intervention (number of patients)	Route of administration	Primary endpoint	Results	Microbiota assessment
Johnsen et al[22], 2018	53.0% IBS-D, 47.0% IBS-M	83 (66.3%)	50-80 g of single FMT (2 donors) (55) vs autologous stool (28)	Colon via a colonoscope	Decrease in IBS severity scoring system of ≥ 75 points at 12 wk and 12 mo	Response rate: 12-wk FMT 65% vs placebo 43% (P < 0.05); 12-mo 56% in FMT vs placebo 36% (P > 0.05)	Unkown
Halkjær et al[23], 2018	37.3% IBS-M, 33.3% IBS-C, 29.4% IBS-D	52 (68.6)	50 g ofdonor stool per dayfor 12 d (4 donors) (26) vs placebo capsules (26)	Oral capsules	Decrease in IBS severity scoring system of ≥ 50 points at 12 wk	Response rate: FMT 36.4% vs placebo 79.2%, P < 0.05	FMT increased microbiota biodiversity shift to the donor
Aroniadis et al[24], 2019	100% IBS-D	24 (37.5) Crossover after 12 wk	9.5 g of donor stool per day for 3 d (4 donors involved but each participant received from 1 donor) (24) vs placebo capsules (24)	Oral capsules	Decrease in IBS severity scoring system of ≥ 50 points at 12 wk	FMT-first 50% vs placebo-first 61%, (P = 0.46)	Prevotella abundance did not change after FMT; Similar diversity between responders and non-responders
Holster et al[25], 2019	56% IBS-D, 25.0% IBS-C, 19% IBS-M with a low amount of butyrate producing bacteria in their fecal samples	17 (50.0%)	30 g of single FMT (1 donor) (8) vs autologous stool (8)	Colon via a colonoscope	Decrease in gastrointestinal symptom rating scale-IBS of ≥ 30%	Symptom and QoL improved from baseline only in FMT arm (P < 0.05) but not different between arms	Trend of fecal and mucosal microbiota shift to the donor. No significant change in diversity and butyrate-producing bacteria
Lahtinen et al[26], 2020	51% IBS-D, 28.6% IBS-U. 14% IBS-M, 6% in remission	49 (59.2%)	30 g of single FMT (1 donor) (23) vs 30 g of autologous stool (26)	Colon via a colonoscope	decline in the IBS-SSS score of ≥ 50 points throughout 52 wk	Primary endpoint was not achieved in both arms. Only transient improved in FMT arm vs baseline at week 12	Significant shift in the microbiota profile and richness increased in FMT group
El-Salhy et al[11], 2020	38.4% IBS-D, 37.8% IBS-C, 23.8% IBS-M	164 (81%)	single 30 g FMT (54) vs 60 g (55) vs autologous stool (55)	Distal duodenum via a gastroscope	total IBS-SSS score decreased by ≥ 50 points at 3 mo	Response rate: 30 g FMT 76.9%, 60 g FMT 89.1%, control 23.6% P < 0.05; response independent of gender, IBS subtype	At 1 mo: Dysbiosis index/prevalence were not different at baseline vs post FMT (P > 0.05), Responder had higher signals forEubacterium biforme, Lactobacillus spp. and Alistipes spp. After FMT, and lower signals for Bacteroides spp
Holvoet et al[27], 2021	100% IBS-D or IBS-M with predominant bloating	62 (64.7)	Single FMT (2 male donors, each participant received from 1 donor) (43) vs autologous stool (19)	Small intestine via a nasojejunal tube	Self-reported adequate relief of symptoms at 12 wk and 1 yr	Response rate: FMT 56% vs control 26% (P < 0.05); Good response predictor: women (69% vs 29%), patients with high baseline diversity, distinct composition (P < 0.05) 1 yr response FMT 21% vs control 6%; Second FMT restored response in 67% of patients with prior response	Unknown

IBS-D: Diarrhea-predominant irritable bowel syndrome; IBS-M: Mixed-diarrhea-and-constipation irritable bowel syndrome; IBS-C: constipation-predominant irritable bowel syndrome; FMT: Fecal microbiota transplantation; IBS-SSS: Irritable bowel syndrome severity scoring system.