Faecal microbiota transplantation versus placebo for moderate-to-severe irritable bowel syndrome: a double-blind, randomised, placebo-controlled, parallel-group, single-centre trial

Background Irritable bowel syndrome (IBS) is a common condition characterised by abdominal pain, bloating, and poor quality of life. IBS might be caused by a gut dysbiosis. We aimed to compare faecal microbiota transplantation (FMT) with placebo in patients with IBS. Methods In this double-blind, randomised, placebo-controlled, parallel-group, single-centre study, we enrolled patients with IBS with diarrhoea or with diarrhoea and constipation (excluding dominating constipation) defined by the ROME III criteria, scored as moderate to severe according to the IBS severity scoring system (IBS-SSS; a score of >= 175). Eligible participants were aged 18-75 years and were recruited locally by general practitioners in northern Norway. We randomly assigned participants (2: 1) in blocks of six to active or placebo FMT. Personnel not involved in the clinical performance of the trial generated the randomisation sequence using a randomisation website. Non-study personnel performed the final allocation and standardised the active and placebo transplants to make them identical in appearance and temperature. The faeces were freshly processed, and were used the same day (fresh transplant) or were stored in a freezer for later use (frozen transplant); participants' own faeces served as placebo. A dose of 8 mg loperamide was administered orally 2 h before endoscopy to retain the transplant. The transplant (50-80 g of faeces mixed with 200 mL of isotonic saline and 50 mL of 85% glycerol) was administered by a colonoscope to the caecum. The primary endpoint was symptom relief of more than 75 points assessed by IBS-SSS, 3 months after FMT. The primary analysis was done in the modified intention-to-treat population, excluding participants who did not undergo treatment or who were diagnosed with any other disease by pinch biopsies obtained during the treatment procedure. For the safety analysis, only participants who did not undergo treatment were excluded. The study is registered with ClinicalTrials. gov, number NCT02154867. The trial has been extended with an open-labelled study treating the placebo group with frozen FMT for further exploratory studies. Findings Between Jan 1, and Oct 30, 2015, we recruited 90 participants and randomly assigned them to active treatment (n=60) or placebo (n=30). Three participants did not undergo FMT and four were excluded after diagnosis of microscopic colitis, leaving 83 for final modified intention-to-treat analysis (55 in the active treatment group and 28 in the placebo group). 36 (65%) of 55 participants receiving active treatment versus 12 (43%) of 28 receiving the placebo showed response at 3 months (p=0.049). One participant had transient nausea and vertigo (active group) and was observed at the hospital for a few hours after the procedure. Two participants had soiling of transplant on their way home from treatment (one in each group) and three experienced self-limiting intermittent abdominal pain (one in the active group and two in the placebo group). No serious adverse events could be attributed to FMT. Interpretation FMT induced significant symptom relief in patients with IBS. However, larger multicentre studies are needed to confirm the results.