Heterogeneity of Randomized Controlled Trials of Fecal Microbiota Transplantation in Recurrent Clostridioides difficile Infection

INTRODUCTION: Clinical trials have demonstrated the efficacy of FMT for reduction in CDI recurrences (rCDI), but this treatment and its reporting in the literature has significant heterogeneity. Recent publications (e.g., Ramai et al. in Dig Dis Sci 2020. https://doi.org/10.1007/s10620-020-06185-7) present the clinical outcomes for different FMT methodologies. However, to understand, compare, and contextualize outcomes, this heterogeneity in methods and reporting must be understood. METHODS: We performed a literature review of randomized controlled trials (RCTs) of FMT for rCDI to evaluate heterogeneity among trials. A methodical search between January 2010 and May 2019 of Medline, Embase, and Cochrane was conducted for studies investigating FMT in adults with rCDI. RCTs were evaluated for a variety of methodological and reporting criteria. RESULTS: Eight RCTs were identified, wherein 14 different FMT preparations were considered (each with distinct protocols for processing, storage, administration, and dosing). Sample sizes were generally small, with only two studies performing FMT in more than 100 patients. Three studies used non-FMT controls (vancomycin), while the remaining compared FMT with differing routes of administration or formulations. Across the identified studies, there was no standardized manner for reporting the timing of the FMT procedure. All studies tracked adverse events; however, follow-up periods were limited. CONCLUSIONS: Considerable variability exists among RCTs, with marked differences in study design, control groups, and outcome assessment. Lack of a standard-of-care control in many trials may impact reproducibility of FMT trial outcomes in patients with rCDI. Widespread use of FMT for rCDI is still investigational; therefore, these foundational studies provide opportunities to optimize future trials.