Re-evaluating the evidence for fecal microbiota transplantation “super-donors” in inflammatory bowel disease

SUMMARY Background Fecal microbiota transplantation (FMT) is a recommended treatment for recurrent Clostridioides difficile infection, and there is promise that FMT may be effective for conditions like inflammatory bowel disease (IBD). Previous FMT clinical trials have considered the possibility of a “donor effect”, that is, that FMT material from different donors has different clinical efficacies. Aim & Methods Here we re-evaluate evidence for donor effects in published FMT clinical trials for IBD. Results In 7 of 9 published studies, no statistically significant donor effect was detected when rigorously re-evaluating the original analyses. One study had statistically significant separation of microbiota composition of pools of donor stool when stratified by patient outcome. One study reported a significant effect but did not have underlying data available for re-evaluation. When quantifying the uncertainty on the magnitude of the donor effect, confidence intervals were large, including both zero donor effect and very substantial donor effects. Conclusion Although we found very little evidence for donor effects, the existing data also cannot rule out the possibility that donor effects are clinically important. Large clinical trials prospectively designed to detect donor effects are likely necessary to determine if donor effects are clinically relevant for IBD.