Gut Decontamination In Pediatric Allogeneic Hematopoietic: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Gut Decontamination In Pediatric Allogeneic Hematopoietic (NCT02641236), a randomized phase 2 study. The primary outcome is Gut Microbiome Description.

2. Clinical Question

3. Trial Design

This was a randomized phase 2 study with a parallel-group design and no masking. The registry lists Dana-Farber Cancer Institute as the sponsor. Its title describes an examination of gut decontamination and intestinal microbiome composition in pediatric allogeneic HSCT patients. The study status is completed; the recorded start is 2016-03, and primary completion is dated 2021-04-15.

Eligible participants were assigned to one of two groups. The gut-decontamination group received non-absorbable oral vancomycin-polymyxin B according to institutional standard practice. The no-gut-decontamination group did not receive that oral antibiotic, while the arm description says other HSCT supportive care was the same. Because masking was listed as none, participants and study personnel were not described as masked to group assignment in the registry record. The record does not report further details about allocation procedures or concealment.

The primary endpoint was the Shannon diversity index measured two weeks after HSCT. The reported endpoint summaries include 10 participants in each arm. The registry also lists enrollment of 24, but the reason that the endpoint counts differ from the enrollment figure is not reported in the registry record. The record lists secondary outcomes concerning diarrhea frequency, immune-cell subsets measured by flow cytometry, acute GVHD incidence, overall survival at 12 months, and relapse-free rate at 12 months. It lists six outcome measures in total, but no analyses are posted. Details of the protocol, sample-size justification, interim analyses, and the planned statistical analysis 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.

Overall Study

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 Gut Microbiome Description, measured over 2 Weeks post HSCT.

The primary endpoint is the Shannon diversity index, a summary measure of microbial diversity in a community. The registry describes it as reflecting both richness, such as the number of species, and evenness, or how relatively abundant different organisms are. It also notes that the measure is sensitive to loss of rare taxa and assumes that all species in a sample are represented and sampled at random. The stated scale ranges from 0 to 6; a value of 0 indicates a community with only one species.

The endpoint was measured two weeks after stem cell transplantation, giving a specified post-transplant time point for describing intestinal microbiome diversity. A diversity index can condense a complex community into a single summary, which makes groups easier to describe, but it cannot show which organisms account for the value or how individual taxa changed. Nor does a group median describe every participant’s microbiome.

The registry reports the measure as a median with full range. The gut-decontamination arm has a median of 2.4 and a range from 0.03 to 5.32. The no-gut-decontamination arm has a median of 3.1 and a range from 2.1 to 3.7. These summaries describe the observed endpoint values at the stated time point. The registry record does not report a statistical comparison, confidence interval, or an interpretation of the clinical importance of a difference in this index.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the study as randomized, phase 2, parallel-group, and unmasked. Randomization assigns participants to groups by chance, which is intended to reduce systematic differences between groups at the start of a study. In general, randomization does not guarantee that groups will be identical, particularly in a small study. The record does not describe the specific allocation procedure or concealment method, so those details cannot be assessed from the registry record.

What does a median describe?

The primary outcome is reported as a median. In general, the median is the central observation after values are ordered, or the midpoint between central observations when there is an even number of values. It is less influenced by unusually high or low values than an arithmetic mean. This can be useful for biological measures whose distributions may be skewed. Here, the reported medians are 2.4 for gut decontamination and 3.1 for no gut decontamination. The registry does not post a test or estimate comparing those medians.

How should the ranges be read?

The outcome is described using the full range. A range reports the lowest and highest observed values, rather than a measure of typical distance from the median. The gut-decontamination group’s range is 0.03 to 5.32, and the no-gut-decontamination group’s range is 2.1 to 3.7. In general, ranges help show the extent of observed variation but do not indicate where most observations lie. They can also change substantially when a small number of observations are added or removed. The registry does not report a separate estimate of uncertainty around either median.

What does the diversity index measure?

The Shannon diversity index combines information about richness and evenness. Richness concerns how many types of organisms are present; evenness concerns their relative abundance. The registry states that the measure is sensitive to loss of rare taxa, assumes species are represented and sampled randomly, and has a stated range of 0 to 6. It identifies 0 as the value for a community with only one species. In general, a single index is a compact description, not a complete account of community composition. Two communities can have similar index values while differing in which organisms they contain.

What can be inferred without a comparison analysis?

The posted endpoint values allow descriptive comparison, but the registry lists zero analyses. There is no reported p-value, confidence interval, or model-based estimate for the between-group comparison. In general, a confidence interval describes a range of values compatible with an estimate under a specified statistical procedure and its assumptions. Without one, the precision of a group contrast cannot be evaluated from the record. A p-value, if reported, would address compatibility with a statistical null model; it would not by itself measure clinical importance. Neither type of result is posted for this endpoint.

The sample-size planning illustration is described as based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. It considers planning scenarios based on portions of the observed effect. Those assumptions describe an illustration, not the trial’s own design justification, which is not reported in the registry record. A planning calculation is not observed power and does not add inferential evidence to the trial’s outcome results. The record does not report a sample-size justification or interim analyses.

Why does multiplicity matter?

When a study examines multiple outcomes or makes multiple comparisons, the chance of at least one apparently unusual result can increase if each is assessed separately. In general, a statistical plan may specify how to address this, for example by prioritizing an endpoint or adjusting inference across tests. The registry lists a primary endpoint and several secondary outcomes, but it posts no analyses and does not report a multiplicity plan. It is therefore not possible to determine whether any adjustment was intended or used.

Finally, analysis populations and missing-data methods matter because the estimate can depend on which randomized participants are included and how unavailable measurements are treated. The record does not report whether the primary endpoint analysis used all randomized participants, a subset defined by treatment received, or another population. It also does not describe missing endpoint values or their handling. Those omissions limit assessment of the analysis beyond the reported group summaries.

10. Multiplicity, Missing Data and Analysis Populations

The registry identifies one primary endpoint, the Shannon diversity index at two weeks after HSCT, and lists secondary outcomes concerning diarrhea frequency, immune-cell subsets, acute GVHD, overall survival at 12 months, and relapse-free rate at 12 months. It reports six outcome measures in total and five secondary outcomes. However, it lists no analyses. No multiplicity procedure, hierarchy for interpreting secondary outcomes, or adjustment for multiple comparisons is reported in the registry record.

Multiplicity is a general statistical concern when many outcomes or comparisons are examined: interpreting each result as if it were the only planned test can make chance findings more likely to attract attention. A prespecified analysis plan can clarify which result is primary and whether secondary findings are confirmatory or exploratory. The registry identifies the primary endpoint, but does not report how multiple outcomes were handled in analysis. With no posted analyses, there are no inferential findings to evaluate for multiplicity.

The primary endpoint results list 10 participants in each treatment arm, while the study enrollment is listed as 24. The registry record does not explain why endpoint counts differ from enrollment or report the number or reasons for missing endpoint measurements. It also does not state how missing values were handled, whether any imputation was used, or which analysis population was intended. The record does not report whether analyses were based on randomized assignment, treatment received, or another inclusion rule.

These omissions matter because excluding participants with unavailable measurements can affect the groups being compared, and different approaches to missing data can yield different estimates. The posted medians and ranges remain useful descriptions of the values reported, but they do not reveal the effect of missing data or establish that the result represents every randomized participant.

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: alt increase (20.0%), blood bilirubin increased (10.0%), ast increased (10.0%), hepatobiliary disorders (10.0%), hypotension (10.0%).

The registry reports serious adverse event figures separately by group. For gut decontamination with vancopoly, 10 participants are listed as at risk for serious adverse events and 1 as affected; the other-adverse-event figures are 10 at risk and 8 affected. For no gut decontamination, the serious-event figures are 10 at risk and 3 affected, while the other-adverse-event figures are 10 at risk and 2 affected. Each treatment group has 0 deaths listed. The healthy donor control group has zero participants listed at risk in these categories and zero affected.

These are counts as recorded, not estimates adjusted for follow-up time or differences in participant characteristics. The registry also lists serious-event terms including ALT Increase at 20.0%, Blood Bilirubin Increased at 10.0%, AST Increased at 10.0%, Hepatobiliary disorders at 10.0%, Hypotension at 10.0%, and Hypokalemia at 10.0%. The record does not clarify the denominator or group attribution for each percentage in this list.

In general, adverse-event counts describe events reported under the registry’s categories; they do not by themselves show that an intervention caused an event. The record provides no comparative safety analysis, uncertainty estimates, or detailed event narratives. The figures should therefore be read descriptively and alongside the limited group sizes, not as a definitive comparison of safety between treatment assignments.

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

The posted primary results describe Shannon diversity at two weeks after HSCT. The median is 2.4 in the gut-decontamination arm and 3.1 in the no-gut-decontamination arm. The corresponding full ranges are 0.03 to 5.32 and 2.1 to 3.7. These figures show the reported central values and observed spans in the endpoint data, not a statistically tested effect of assignment.

The result does not establish whether the difference between the group medians is compatible with chance variation, because no comparison analysis or uncertainty estimate is posted. Nor does the result show that any observed difference is clinically important. The registry describes the index as a measure of microbial richness and evenness, but a single index cannot identify which organisms account for group values or fully characterize intestinal microbial communities.

The study was randomized, but it was unmasked. Random allocation is a design feature that can support a fair comparison; it does not remove all uncertainty, guarantee group balance, or address missing outcome data automatically. The record does not report the analysis population or missing-data methods. It lists enrollment of 24 and endpoint counts of 10 in each arm, without explaining the reason for those counts.

The listed secondary outcomes include diarrhea frequency, immune-cell subsets, acute GVHD, overall survival, and relapse-free rate. No analyses are posted for these outcomes. The safety figures are also descriptive, and the registry record does not provide a comparative safety analysis. Consequently, the available results do not establish effects on GVHD, survival, relapse, diarrhea, immune-cell counts, or adverse events.

In general, a trial result is strongest when its outcome definition, analysis plan, participant flow, estimates, and uncertainty are all available. This record supplies descriptive primary endpoint values but not the inferential details needed to assess the precision or statistical reliability of a group comparison. The findings should be understood within that reporting scope and should not be treated as a definitive answer about microbiome or clinical outcomes.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of a biological endpoint that compresses complex microbiome data into a single summary. The Shannon diversity index combines richness and evenness, and the registry notes its sensitivity to rare taxa. This makes the measure interpretable as a broad description of community diversity, while also reminding readers that one number cannot describe the identity or function of organisms in the gut.

The reported medians and full ranges give complementary descriptive information. A median indicates the centre of the observed values, while the range shows their extremes. The endpoint summaries are 2.4, with a range from 0.03 to 5.32, for gut decontamination, and 3.1, with a range from 2.1 to 3.7, for no gut decontamination. The difference in the span of these ranges makes clear why a central summary alone does not capture all the observed variability.

The design also illustrates why randomized allocation and transparent reporting must be considered together. Randomization is a meaningful design feature, but the registry lists no analyses for the primary comparison. Without an estimate of uncertainty, a prespecified analysis description, and information about missing values and analysis populations, readers cannot judge the precision or robustness of a group contrast from the posted summaries alone.

Finally, the record lists several secondary clinical and biological outcomes, but no analyses of them. This makes the distinction between outcomes named in a registry and outcomes with posted results important. Statistical interpretation depends not just on the presence of an endpoint, but on how it was measured, who contributed data, how comparisons were performed, and what uncertainty surrounds the estimates.

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’s primary endpoint results are limited to descriptive summaries: medians and full ranges at two weeks after HSCT. It does not post an inferential comparison, confidence interval, p-value, or adjusted estimate. The group summaries therefore cannot establish the precision of a contrast or distinguish it from sampling variation. The record does not report the analysis method, protocol, or statistical analysis plan.

The reported endpoint count is 10 in each treatment arm, while enrollment is listed as 24. The reason for the difference is not reported in the registry record. Participant flow, endpoint availability, and reasons for missing measurements are not described. There is also no reported analysis population or missing-data approach, limiting assessment of whether the posted values reflect all randomized participants.

The trial was unmasked, and the registry does not report further allocation details. The endpoint is a single diversity index, which can summarize richness and evenness but does not provide a full account of microbial composition. The measurement is specified at two weeks after HSCT, so the posted primary endpoint does not describe diversity at other time points.

The registry lists secondary outcomes but posts no analyses for them. It does not report how multiple outcomes were handled or whether a multiplicity procedure was planned. The safety record gives counts and a list of serious-event terms, but no comparative analysis, uncertainty estimates, detailed event narratives, or clear denominator and group attribution for each term percentage. These limitations constrain both efficacy-related interpretation and safety comparison.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Gut Decontamination In Pediatric Allogeneic Hematopoietic — NCT02641236.
• Registry record last updated 2023-09-15; status last verified 2023-09.
• Results first posted 2023-09-15.
• 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

This completed randomized phase 2 study examined gut decontamination in pediatric allogeneic HSCT patients at risk of acute GVHD. It used a parallel-group, unmasked design. Participants assigned to gut decontamination received oral vancomycin-polymyxin B; the comparator group did not receive it, with other HSCT supportive care described as the same.

The primary endpoint was the Shannon diversity index two weeks after HSCT. The median was 2.4, with a full range from 0.03 to 5.32, for gut decontamination, and 3.1, with a full range from 2.1 to 3.7, for no gut decontamination. The registry lists enrollment of 24 and endpoint counts of 10 in each arm. It posts no analyses of the primary comparison or listed secondary outcomes. Reasons for the endpoint counts, missing-data methods, analysis populations, and statistical analysis plan are not reported in the registry record.