Fecal Microbiota Transplantation for the Treatment of Obesity: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Fecal Microbiota Transplantation for the Treatment of Obesity (NCT02741518), a randomized phase 1, phase 2 study. The primary outcome is Adverse Event Frequency.

2. Clinical Question

The clinical question concerns both safety and the effects of assigning participants to FMT rather than placebo in a small pilot study. The listed primary outcome is adverse-event frequency, measured as the number of participants reporting adverse events. A secondary outcome concerns change in the area under the curve of GLP-1 from baseline to week 12, described as a therapeutic biomarker for clinical response. The registry record does not provide a result for that secondary outcome.

The study is described as randomized and triple-masked, with a parallel-group model and a 1:1 allocation plan. Random assignment is intended to make the groups comparable on average, while masking is intended to limit influences from knowing the assigned treatment. The registry record does not say who was masked or describe how allocation was generated or concealed. As a pilot with recorded enrollment of 22, its results are primarily descriptive in the available record; no formal estimate of the treatment effect on adverse events is reported.

3. Trial Design

This completed study was registered as a randomized, parallel-group pilot trial in obesity. Its phase is listed as Phase 1 and Phase 2. Brigham and Women's Hospital is the sponsor. The registry record gives a start date of 2017-04-01 and a primary completion date of 2018-10-18. Recorded enrollment was 22.

The registry summary describes a plan to prospectively enroll 20 adults with obesity and a body mass index of 35kg/m2 or higher. Participants were to be assigned in a 1:1 ratio to FMT or placebo. The recorded enrollment is 22, rather than the planned enrollment stated in the summary. The record does not explain this difference, and it does not report how many participants completed treatment or follow-up.

The treatment arm received an induction dose of FMT capsules and monthly maintenance oral capsules at week 4 and week 8. The placebo arm received placebo capsules for induction and oral placebo capsules at week 4 and week 8. The brief summary describes treatment as lasting 12 weeks total. The treatment description also mentions an induction dose via capsules (30), but the registry record does not clarify the meaning of that parenthetical number. It says donor stool and placebo material were obtained from OpenBiome; no further detail about preparation or administration is available in the record.

Masking is listed as triple, but the record does not identify which groups of people were masked or describe whether masking was maintained throughout follow-up. It also does not report the randomization method, allocation concealment, eligibility criteria beyond the summary description, or the statistical plan. These omissions limit how fully the design and conduct can be assessed from the registry record alone.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Adverse Event Frequency, measured over 6 months.

The primary endpoint is adverse-event frequency, expressed as the number of participants reporting adverse events over a six-month timeframe. The registry describes the measure as the number of patients reporting adverse events and gives the unit as participants. This is a participant-level count: it concerns whether participants were recorded as having events, rather than the total number of individual event episodes.

Adverse-event frequency is used to describe the occurrence of unwanted events during a study. In a randomized comparison, counts from the two assigned groups can provide a descriptive view of the safety experience recorded in each arm. A formal comparison would need to specify how events and follow-up were defined and how differences between groups were to be estimated. The registry record does not report such an analysis or an effect estimate for this endpoint.

The record separately lists serious adverse events and other adverse events, including participants at risk and participants affected. These categories should be read as the registry reports them; they are not interchangeable with a single overall count of all event episodes. The available entry does not explain event ascertainment, grading, attribution to treatment, or whether participants could contribute to more than one category. The secondary outcome is change in GLP-1 area under the curve from baseline to week 12, but no result for it is reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Randomization assigns participants to study groups by chance. General statistical rationale: random assignment can reduce systematic differences between groups at the point of assignment, although it does not ensure that groups will be identical, especially in a small study. This record says participants were randomized in a 1:1 allocation plan, but it does not report the sequence-generation method or allocation concealment. Those details are important for evaluating how assignment was carried out.

The trial is listed as triple-masked. General statistical rationale: masking can reduce the influence of treatment knowledge on participant reports, clinical care, and outcome assessment, depending on who is masked and how outcomes are measured. The registry record does not identify the masked parties or describe how masking was implemented. The label alone therefore does not show which potential sources of bias were addressed.

The parallel-group design means participants were assigned to one of the two groups rather than being described as crossing between treatments. The recorded arms are FMT and placebo. The outcome timeframe is six months, while the intervention summary describes a 12-week course and the GLP-1 secondary outcome is specified from baseline to week 12. These timeframes refer to different parts of the record; no further schedule for adverse-event collection is reported.

The primary endpoint is a count of participants with adverse events, not a count of all event episodes. General statistical rationale: participant-level counts can be analyzed as binary outcomes, with each participant classified according to whether the defined event occurred. A statistical analysis would need a clear outcome definition and a specified method for comparing the arms. The registry record does not report the method, an adjusted or unadjusted estimate, a confidence interval, or a p-value. The listed adverse-event numbers can be described, but they should not be treated as a completed inferential analysis.

General explanation of uncertainty: a confidence interval gives a range of values compatible with the observed data under the statistical model and its assumptions. Its width conveys the precision of the estimate; a wider interval indicates greater uncertainty. Because no confidence interval is reported for this endpoint, the precision of a between-arm effect cannot be assessed using the registry entry. A p-value, if reported, would address how unusual the data are under a specified null model; it would not by itself measure the size or importance of an effect. No p-value for the primary comparison is reported.

General explanation of multiplicity: when many outcomes, time points, or statistical comparisons are examined, the chance of finding an apparently notable result by chance can increase. A statistical plan may address this by identifying a primary comparison in advance or by adjusting interpretation for multiple testing. The registry lists two outcome measures and indicates that the primary outcome includes several categories or time points and was not reduced to one comparison. It does not report a multiplicity strategy or explain how the outcome categories were handled.

General explanation of missing data: missing outcomes can affect interpretation when participants do not provide information at every planned assessment. The consequences depend on how much information is missing and why it is missing, as well as the analysis method. The registry record does not report missing-data counts, reasons for missingness, imputation methods, or sensitivity analyses. It also does not specify whether analysis followed assignment regardless of treatment received or was restricted to participants with available observations.

The record reports 22 participants enrolled and 11 participants at risk in each adverse-event group. It does not provide a participant-flow account connecting enrollment, randomization, follow-up, and the at-risk counts. General statistical rationale: an analysis should make clear which participants contribute to each result and how follow-up time is handled. Without that information, it is not possible to determine from the registry entry whether all enrolled participants contributed to each listed outcome.

The registry record does not report an interim-analysis plan, stopping rules, or a sample-size justification. Any sample-size calculations elsewhere associated with the posted results are planning illustrations based on an observed effect, not evidence of the trial's original design assumptions or observed power. Such illustrations are not a substitute for a reported analysis plan, and they do not establish the precision or reliability of the trial's results.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists adverse-event frequency as the primary outcome and change in GLP-1 area under the curve from baseline to week 12 as a secondary outcome. It also notes that the primary outcome has several categories or time points and was not reduced to one comparison. No analysis is listed. The record does not explain which categories or time points were intended for formal testing, whether any were prioritized, or how multiple comparisons were to be handled.

General statistical context: testing multiple outcomes or comparisons can increase the chance of a result appearing noteworthy by chance. A prespecified analysis plan can clarify which tests are primary and whether adjustment or another interpretive strategy is used. The registry record does not report a multiplicity procedure or a complete statistical analysis plan. Therefore, the listed outcome categories should be read descriptively, not as evidence of a prespecified set of tested hypotheses.

The record does not report the amount or pattern of missing outcome data, reasons for missingness, imputation, or sensitivity analyses. It also does not describe the analysis population, such as whether participants were analyzed according to randomized assignment or according to treatment received. The recorded enrollment is 22, while the registry summary describes a plan to enroll 20; the record does not explain the difference. Participant flow and completion by arm are not reported.

These omissions prevent assessment of whether the posted counts represent all randomized participants, all participants with available data, or another analysis set. They also make it difficult to judge whether missing follow-up or outcome definitions could have influenced the counts. No conclusions about the direction or size of those influences can be drawn from the registry record.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: er visit for vomiting and diarrhea (9.1%).

The registry lists serious adverse events separately from other adverse events. In the treatment arm, 1 of 11 participants at risk was affected by a serious adverse event, and in the placebo arm, 0 of 11 was affected. For other adverse events, 11 of 11 participants at risk were affected in each arm. The registry reports 0 deaths in both arms.

The serious-event term listed as a top term is “ER Visit for Vomiting and Diarrhea,” with 9.1%. The record does not provide event-level timing, severity details beyond the serious classification, attribution, or an explanation of the percentage. It is not possible to determine from that entry alone whether the term refers to one episode, how it was assessed, or whether it was considered related to treatment.

These are counts of participants reported as affected, not necessarily counts of distinct event episodes. General statistical context: a participant may experience more than one event, and participant counts do not describe the total number or duration of episodes. The registry record does not explain whether participants could appear in both the serious and other categories. The counts should therefore be read as the registry's category-specific participant summaries, not as a complete account of event burden or causation.

12. What the Result Does, and Does Not, Mean

The registry record establishes that this randomized pilot compared FMT capsules with placebo in adults with obesity and recorded adverse-event information in both arms. It reports a serious adverse event among participants in the treatment arm and none among participants in the placebo arm; it reports other adverse events for all participants at risk in both arms, and no deaths in either arm. These are descriptive entries for the six-month adverse-event timeframe.

The record does not establish that FMT caused or prevented any event. Event attribution is not reported, and the registry gives no formal statistical comparison, effect estimate, confidence interval, or p-value for the primary outcome. The counts alone do not show whether any apparent difference is compatible with chance, nor how precisely a treatment effect could be estimated. They also do not show that the arms are equivalent.

The study's recorded enrollment was 22, and the registry describes it as a pilot. A pilot can provide information about study procedures and generate descriptive observations, but the record does not report a sample-size justification or a threshold for a definitive conclusion. No claims about efficacy or clinical benefit follow from the adverse-event counts. The listed GLP-1 outcome is secondary, and its result is not reported.

Important details remain unavailable: participant flow, follow-up completeness, missing-data handling, the analysis population, event ascertainment, masking implementation, and the statistical analysis plan. The registry record also does not explain the difference between its stated enrollment plan of 20 and recorded enrollment of 22. These gaps limit interpretation of both the outcome counts and the conduct of the trial. The appropriate reading is a narrow one: the posted results describe recorded event categories and participant counts, while leaving comparative effects and their uncertainty unreported.

13. Why This Trial Matters Statistically

This trial illustrates why endpoint definitions and analysis details matter alongside raw counts. The primary outcome is framed as the number of participants reporting adverse events over a six-month timeframe, while the registry separately lists serious and other adverse events. Those categories answer related but distinct descriptive questions. Without an explicit analysis and clear event definitions, the reported counts cannot be turned into a precise comparative estimate.

The randomized, triple-masked design indicates an effort to structure the comparison and limit some sources of bias. At the same time, the registry record does not describe the randomization procedure, who was masked, or how masking was maintained. A design label is useful context, but it is not a substitute for details that allow readers to assess implementation.

The enrollment record also highlights the value of distinguishing planned enrollment from recorded enrollment. The summary describes a plan for 20 participants, while recorded enrollment is 22. The record does not explain why. A participant-flow account would help readers understand how enrollment relates to the numbers at risk and the outcome counts.

Finally, the registry identifies several outcome categories or time points but does not report a formal analysis. General statistical context: prespecified outcomes, analysis populations, missing-data methods, and multiplicity plans shape what a result can support. Their absence makes it especially important to keep interpretation descriptive. This record is useful for understanding what was registered and which adverse-event counts were posted, but it does not provide the inferential detail needed to quantify a treatment effect or its precision.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The registry record leaves key features of trial conduct and analysis undescribed. It does not report the randomization method, allocation concealment, the identities of the masked parties, or how masking was implemented. It also does not provide participant flow, completion by arm, or an explanation of how the recorded enrollment relates to the summary's planned enrollment.

The primary outcome is described as the number of participants reporting adverse events, but event ascertainment, definitions, severity grading, and attribution are not reported. The record gives a six-month timeframe without a detailed schedule for collecting adverse-event information. It does not clarify whether participants could be counted in more than one category, or how the listed serious-event term relates to the participant-level counts.

No formal primary-outcome analysis is reported. The registry does not provide an effect estimate, confidence interval, p-value, analysis population, statistical method, or a complete analysis plan. It does not report missing-data counts, reasons for missingness, imputation, sensitivity analyses, or an approach to multiplicity. The GLP-1 secondary outcome is listed without a result.

The record identifies the study as a pilot and records enrollment of 22, but it does not report a sample-size justification or interim-analysis plan. It does not explain the difference between the planned enrollment of 20 described in the summary and the recorded enrollment. The treatment description includes a parenthetical “30” after the induction dose, but the meaning of that number is not stated. Together, these omissions restrict interpretation to the posted descriptive information and prevent a full assessment of precision, missingness, and potential bias.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Fecal Microbiota Transplantation for the Treatment of Obesity — NCT02741518.
• Registry record last updated 2020-01-07; status last verified 2019-12.
• Results first posted 2020-01-07.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

NCT02741518 is a completed randomized, triple-masked, parallel-group pilot study of FMT for obesity, sponsored by Brigham and Women's Hospital. The registry lists Phase 1 and Phase 2, recorded enrollment of 22, a start date of 2017-04-01, and a primary completion date of 2018-10-18.

Participants were assigned to FMT capsules or placebo. The treatment description specifies an induction dose and maintenance capsules at week 4 and week 8; the brief summary describes a 12-week treatment course. The primary outcome is adverse-event frequency over six months. The registry posts category-specific participant counts, including serious and other adverse events, and reports no deaths in either arm.

No formal primary-outcome comparison or result for the listed GLP-1 secondary outcome is reported. The record does not provide a statistical analysis plan, participant-flow details, or missing-data methods. Its results therefore support a descriptive reading of the posted counts, not a quantified estimate of comparative effect.