Examining the Efficacy of Fecal Microbiota Transplantation (FMT) and Dietary Fiber in Patients With Ulcerative Colitis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Examining the Efficacy of Fecal Microbiota Transplantation (FMT) and Dietary Fiber in Patients With Ulcerative Colitis (NCT03998488), a randomized phase 2 study. The primary outcome is Clinical Response.

2. Clinical Question

3. Trial Design

This phase 2 study is listed as randomized, triple-masked, placebo-controlled, and crossover. Its official title describes a clinical trial examining FMT and subsequent dietary fiber in patients with moderate ulcerative colitis. The brief summary describes active mild to moderate ulcerative colitis. The registry record lists an enrollment of 27 and a completed status.

The three reported groups were investigational FMT, investigational FMT plus psyllium fiber, and placebo FMT with or without psyllium fiber. The primary results list 9 participants in each group. The arm descriptions specify a single dose of the assigned FMT treatment during the week 0 colonoscopy. They also describe a single dose at week 8, delivered by flexible sigmoidoscopy, with the active and placebo assignments switched in some groups. The description for one group is truncated in the registry record, so its full treatment sequence is not reported there.

The primary endpoint is clinical response at week 8 post-FMT, recorded as a participant count. The registry describes the analysis as intent to treat and says that missing week 8 primary-endpoint data would be handled by carrying forward the participant’s baseline Mayo score. The record lists three secondary outcomes: clinical remission, endoscopic response or remission, and the number of treatment- or disease-related adverse events. The specific results for those secondary outcomes are not reported in the registry record.

The study start date is 2020-01-31, and the primary completion date is 2023-06-09. Details such as the sequence-generation method, allocation concealment, masking procedures, crossover period structure, and any washout procedure are not reported in the registry record.

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.

Week 8 Colonoscopy

Follow Up

Analysis population for the primary outcome, as defined in the registry: Analysis will be performed based on intent to treat. Therefore, any subjects with missing primary endpoint data at week 8 will have their baseline Mayo score carried forward to remain the same for the week 8 primary endpoint.

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 Clinical Response, measured over Week 8 post-FMT.

The primary endpoint is the count of participants meeting the trial’s definition of clinical response at week 8 post-FMT. A participant qualified by having a Mayo score reduction of >3 points (+30% reduction), together with a decrease of at least 1 point in the rectal-bleeding sub-score. The endpoint is therefore a binary classification at the participant level—response or no response—presented as counts within each group.

A composite clinical definition can capture improvement across more than one aspect of a condition. Requiring both a specified Mayo-score reduction and improvement in rectal bleeding makes the endpoint more specific than relying on one score component alone. The measure is intended to represent a clinically relevant response during the period named in the registry record; it is not a direct measure of every symptom, disease feature, or longer-term outcome.

Because the outcome is reported as counts, it should be read alongside each group’s stated number of participants. Counts alone do not convey uncertainty or establish that apparent differences between groups exceed what could arise from sampling variability. The registry record does not post an inferential analysis or an uncertainty interval for this endpoint. Clinical remission and endoscopic outcomes are listed as secondary outcomes, but their results are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is binary at the participant level: each participant either met the clinical-response definition at week 8 or did not. The registry reports counts, with 5 responses among 9 participants for investigational FMT, 2 among 9 for investigational FMT plus psyllium fiber, and 1 among 9 for placebo FMT with or without psyllium fiber. A count is a direct description of observed classifications. It is not itself a measure of the size or precision of a treatment effect.

For a binary endpoint, an analysis might compare response probabilities between groups or estimate an effect measure with an uncertainty interval. Which measure and model are appropriate depends on the design, analysis population, and prespecified plan. The registry record does not report a model, effect estimate, confidence interval, or p-value for the primary endpoint. It lists zero posted analyses and notes that values for a two-arm comparison of the binary endpoint were missing or not estimable. The counts should consequently be read descriptively, not as the output of a reported hypothesis test.

General explanation: a confidence interval expresses the uncertainty associated with an estimated quantity under a specified statistical method and its assumptions. It is not a guarantee that the true value lies in the interval, and its interpretation depends on the method and study design. No confidence interval is reported for the primary response results in the registry record, so the precision of a between-group effect cannot be assessed from a reported interval.

The trial is listed as crossover, a design in which participants may receive more than one treatment condition in a planned sequence. General statistical explanation: crossover analyses often need to account for within-participant correlation, treatment order, and possible carryover from an earlier treatment period. Those issues can affect both the analysis and the interpretation of observations. The registry record gives some week 0 and week 8 treatment descriptions but does not report the full sequence structure, a washout procedure, or an analysis accounting for period or sequence. The week 8 response counts should not be treated as if they demonstrate that these design features were handled in a particular way.

The record describes the primary analysis as intent to treat. It says that any missing primary-endpoint data at week 8 would be handled by carrying forward the baseline Mayo score so that it remains the same for the week 8 primary endpoint. This is a stated missing-data rule, not a report of how many outcomes were missing or whether the rule was applied to any participant. The number of missing primary outcomes and the sensitivity analyses, if any, are not reported in the registry record.

General explanation: carrying a baseline score forward assumes that the score would remain unchanged for a participant with a missing follow-up assessment. That assumption can be consequential if missingness is related to clinical status or if the score would otherwise change over time. Such a rule may be easy to describe, but it does not remove uncertainty about outcomes that were not observed. Analyses under alternative assumptions can help assess sensitivity to the missing-data rule; whether such analyses were planned or conducted is not reported in the registry record.

The registry’s sample-size assumptions describe a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is described as a stated fraction of the observed effect. For non-time-to-event outcomes, the stated convention is participants per arm; time-to-event illustrations use total events. These are planning assumptions, not the trial’s own design justification and not observed power. The registry record does not report the trial’s sample-size justification or a prespecified target effect.

General explanation: sample-size planning asks how much information a future study might need to detect a chosen effect under selected assumptions. A calculation that uses an effect observed in a small trial can be unstable, because that estimate may be imprecise. A planning result is not evidence that the current trial had a particular probability of detecting an effect, and it does not replace an uncertainty interval or a valid analysis of the observed data. The registry record does not report a full statistical analysis plan, including the planned method for the three-group or crossover structure.

Multiplicity is relevant when several outcomes or treatment comparisons are examined. The record lists one primary outcome and three secondary outcomes, but it does not report how multiple comparisons were to be handled. General explanation: testing multiple hypotheses without an appropriate strategy can increase the chance of at least one apparently notable result arising by chance. No adjustment method or hierarchy of secondary analyses is reported in the registry record. Since no inferential analyses are posted, the response counts should not be presented as statistically significant or nonsignificant findings.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Investigational FMT", "Investigational FMT + Psyllium Fiber", "Placebo FMT +/- Psyllium Fiber")
n      <- c(9, 9, 9)
events <- c(5, 2, 1)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Investigational FMT  9  5  55.6  21.2  86.3  26.7  81.1  26.2  81.3
ARM  Investigational FMT + Psyllium Fiber  9  2  22.2  2.8  60.0  6.3  54.7  6.7  55.6
ARM  Placebo FMT +/- Psyllium Fiber  9  1  11.1  0.3  48.2  2.0  43.5  2.5  44.5

11. Multiplicity, Missing Data and Analysis Populations

The registry identifies clinical response at week 8 post-FMT as the primary endpoint. It lists three secondary outcomes: clinical remission, endoscopic response or remission, and the number of treatment- or disease-related adverse events. Results for those secondary outcomes are not reported in the registry record. The record does not describe a hierarchy among outcomes, a multiplicity adjustment, or a plan for selecting which comparisons to report. Those details are not reported in the registry record.

The primary analysis is described as intent to treat. For any missing week 8 primary-endpoint data, the registry says the baseline Mayo score would be carried forward and remain the same at week 8. This states a rule for handling missing scores, but the number of missing endpoint assessments and the number of participants affected are not reported in the registry record. Whether the rule was applied, or whether other missing-data approaches were examined, is also not reported.

General statistical explanation: an analysis population defines which participants contribute to an estimate, while a missing-data method addresses outcomes that were not observed. The intent-to-treat label alone does not describe every population detail, especially in a crossover trial. The registry does not report additional population definitions, exclusions, or a sensitivity analysis of the baseline-carry-forward assumption. It also lists no posted analyses for the primary outcome, so there are no reported inferential results with which to evaluate multiplicity or the consequences of missing data.

12. 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: worsening ulcerative colitis disease activity (11.1%).

The registry reports serious adverse events for 1 participant in the investigational FMT group and none in either the investigational FMT plus psyllium fiber group or the placebo FMT with or without psyllium fiber group. Each group lists 9 participants at risk. The most frequently listed serious-event term is worsening ulcerative colitis disease activity, reported as 11.1%. The record does not give further detail linking that term to a particular group.

Other adverse events are reported for 4 participants in the investigational FMT group, 7 in the FMT-plus-psyllium-fiber group, and 6 in the placebo group. The registry reports zero deaths in each group. These counts are descriptive; they do not establish that an intervention caused an event or that the groups differ in underlying risk. The record does not provide event-level timing, severity beyond the serious classification, exposure-adjusted rates, or a causal assessment.

General statistical explanation: adverse-event counts depend on how events are defined, collected, and attributed, as well as on the amount of observation time. Small group counts can be particularly imprecise. The registry’s serious and other adverse-event counts should therefore be interpreted as reported safety observations, not as proof of safety or harm. Further details are not reported in the registry record.

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

The posted primary results describe how many participants met a prespecified clinical-response definition at week 8 post-FMT: 5 in the investigational FMT group, 2 in the investigational FMT plus psyllium fiber group, and 1 in the placebo FMT with or without psyllium fiber group. Each group lists 9 participants. This is a descriptive account of the endpoint classifications in the registry record.

The counts do not establish a statistically significant difference, a causal effect, or the size of an effect in a broader population. The registry record does not report a p-value, confidence interval, or model-based comparison for the primary outcome. It also does not report the detailed analysis plan needed to assess how the randomized crossover design was incorporated into an inferential analysis. The record lists no posted analyses for the endpoint.

The group structure further limits what can be attributed to any one component. One active group received FMT and psyllium fiber, while the comparator group could receive fiber or not. The reported results therefore do not, on their own, isolate the effect of FMT from the effect of fiber. The record’s treatment descriptions include active and placebo FMT at different visits, but full details of treatment sequence and analysis are not reported.

The secondary outcomes could add information about remission, endoscopic findings, or adverse events, but their results are not reported in the registry record. The available safety counts are not a substitute for comparative statistical analysis and do not establish causation. Likewise, the listed planning assumptions describe an illustration for sample-size planning, not observed power or a conclusion about the trial’s ability to detect an effect.

In short, the registry provides group-level response counts and some safety counts, alongside a stated missing-data rule. It does not provide enough reported inferential detail to quantify uncertainty in a treatment contrast or to draw a definitive comparative conclusion. The findings should be understood as the posted results for this trial, with the design, small group counts, missing-data information, and absent analysis details kept in view.

14. Why This Trial Matters Statistically

This trial raises statistical questions that are common in clinical studies combining interventions and using repeated treatment periods. It is listed as randomized, triple-masked, and crossover, while its arms combine FMT and, in some cases, psyllium fiber. The interpretation of a group comparison can depend on treatment sequence, period effects, within-participant correlation, and whether the comparator group’s fiber exposure is consistent. The registry record does not report enough detail to establish how those features were handled analytically.

The endpoint is clinically framed but operationally specific: it combines a Mayo-score reduction with improvement in rectal bleeding. That definition makes the classification rule explicit, while also underscoring why the underlying endpoint and missing-score handling matter. The record’s baseline-carry-forward rule is stated, but the extent of missingness and the results of any sensitivity analyses are not reported.

The reported counts also show why descriptive results and inferential conclusions should be kept separate. There are 9 participants listed in each group, and the response counts vary across groups. Without an uncertainty interval or a reported analysis, the degree of precision around a comparative effect cannot be judged. The registry lists secondary outcomes but does not report their results or a multiplicity strategy.

These features make the record useful for understanding how outcome definitions, intervention combinations, crossover structure, missing data, and analysis reporting interact. The reported information identifies the questions a reader would need an analysis plan and fuller results to answer, without turning raw counts into stronger conclusions than the record supports.

15. 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 group sizes are small, with 9 participants listed in each of the three groups. Counts from groups of this size provide limited information about the range of outcomes that might occur in a broader population. The registry does not report confidence intervals or other uncertainty estimates for the primary response results.

The record describes the study as crossover but does not provide a complete account of treatment sequence, period structure, washout, or the statistical approach to repeated observations. The week 8 treatment descriptions are partly truncated, and the full treatment sequence is not reported in the registry record. These gaps limit interpretation of how the reported endpoint relates to each treatment exposure.

The placebo group is described as receiving psyllium fiber or not, while another group received FMT plus fiber. This means the reported groups do not straightforwardly isolate FMT and fiber components. The record does not provide separate outcome results by fiber exposure.

The missing-data rule is stated, but the amount of missing primary-endpoint data and whether the rule was used are not reported. No sensitivity analyses, prespecified statistical analysis plan, or sample-size justification are reported. The registry lists three secondary outcomes, but their results and any multiplicity approach are not reported. Finally, the record does not report participant-level data or detailed event timing and attribution for safety outcomes.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Examining the Efficacy of Fecal Microbiota Transplantation (FMT) and Dietary Fiber in Patients With Ulcerative Colitis — NCT03998488.
• Registry record last updated 2025-01-03; status last verified 2024-12.
• Results first posted 2024-04-02.
• 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.

19. Record Summary

NCT03998488 is a completed phase 2 randomized, triple-masked, placebo-controlled crossover trial sponsored by Weill Medical College of Cornell University. The registry lists an enrollment of 27, a study start date of 2020-01-31, and a primary completion date of 2023-06-09. The study examined FMT and psyllium fiber in participants with ulcerative colitis.

The primary endpoint was clinical response at week 8 post-FMT, defined through a Mayo-score reduction and improvement in rectal bleeding. The registry reports response counts of 5 for investigational FMT, 2 for investigational FMT plus psyllium fiber, and 1 for placebo FMT with or without psyllium fiber; each group lists 9 participants. It reports a baseline-score carry-forward rule for missing primary data, but no inferential analysis for the endpoint.

Serious and other adverse-event counts are reported by group, as are zero deaths in each group. The registry lists clinical remission, endoscopic response or remission, and adverse events as secondary outcomes, but their results are not reported in the registry record. Details of the analysis plan, sample-size justification, and full crossover analysis are also not reported.