Table 1.

Selected fecal microbiota transplantation studies.

Author	Study Design	Methods	FMT Administration	Results
El-Salhy [146]	Single-center, double-blind, placebo-controlled RCT	165 patients: placebo (n = 55), 30 g FMT (n = 54), 60 g FMT (n = 55)	Gastroscope to the distal duodenum	Clinical response * 23.6%, 76.9% and 89.1% for placebo, 30 g, and 60 g
Johnsen [147]	Single-center, double-blind, placebo-controlled RCT	83 patients: placebo (n = 28) and 50–80 g FMT(n = 55)	Colonoscope to the cecum	Clinical response ** 65% (FMT) vs. 43% (placebo)
Holvoet [148]	Single-center, double-blind, placebo-controlled RCT	62 patients: placebo (n = 19) and FMT (n = 43)	Nasojejunal probe	Clinical response *** 56% (FMT) vs. 26% (placebo)
Halkjær [149]	Single-center, double-blind, placebo-controlled RCT	45 patients: placebo (n = 23) and FMT(n = 22)	Capsule form	Clinical response ** 79% (placebo) vs. 36% (FMT)
Madsen [150]	Single-center, double-blind, placebo-controlled RCT	51 patients: placebo (n = 26) and FMT (n = 25)	Capsule form	No difference in clinical response **** during treatment or one, three or six months post-treatment

Studies examining the efficacy of FMT in patients with IBS are not standardized, relying on different dosage and administration methods of FMT, and overall have had conflicting results. While El-Salhy et al. and Johnsen et al. found a favorable clinical response with FMT vs. placebo, Halkjær and colleagues found a significant improvement in IBS symptoms in the placebo group compared to FMT. A complete compilation of registered clinical trials with the NIH is provided in the Supplementary Materials (NIH website clinicaltrials.gov, accessed on 9 March 2023). Abbreviations: RCT (randomized control trial); FMT (Fecal microbiota transplantation). * defined by IBS symptom score. ** defined by IBS severity score. *** defined by a daily symptom diary. **** defined by abdominal pain and stool frequency (daily symptom diary) and stool form (weighted stool score).