The Blueberry Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Blueberry Study (NCT04421950), a randomized na study. The primary outcome is Phenolic Acid Metabolites Measured in Plasma and Urine After Dietary Intervention.

2. Clinical Question

The clinical question is primarily about the appearance and characterization of blueberry-derived compounds in biological samples. It is not framed in the registry record as a question about a clinical illness or a patient-centered health outcome. The listed secondary outcomes concern immune-cell counts and percentages, T-lymphocyte responsiveness to immune stressors, and endothelial function by brachial artery flow-mediated dilation. Those outcomes extend the investigation to biological measures, but their numerical results are not reported in the registry record.

3. Trial Design

The Blueberry Study (NCT04421950) is recorded as a completed, randomized, triple-masked, parallel-group study sponsored by Arkansas Children's Hospital Research Institute. The registry lists an enrollment of 44 and identifies the participants as healthy children with typically low fruit and vegetable consumption. The recorded study dates are 2021-04-23 for the start and 2022-08-18 for primary completion. The phase is listed as NA.

Participants were assigned to wild-blueberry supplement foods or placebo supplement foods. The wild-blueberry arm description specifies 30 grams of wild blueberry powder per day in provided food items. The placebo foods were provided without wild blueberry powder. The registry also describes a single-dose visit: after fasting blood and urine collection at visit two and visit three, children consumed a single dose of the study product at visit three, followed by plasma and urine collection. The record does not explain how the daily provision related to the timing of that collection visit or provide further details about the intervention schedule.

Randomization is intended to support comparable groups at the start of a trial, while masking is intended to limit the influence of treatment knowledge on participants, study personnel, or outcome assessment. The record labels the study triple masked but does not identify the masked parties or describe how masking was maintained. A parallel design means the registry describes separate intervention arms rather than a crossover comparison. The record does not report the randomization method, allocation concealment procedures, or the planned statistical analysis in enough detail to assess those features.

Four outcome measures and 1 analysis are recorded. The registry lists a primary metabolite outcome and secondary biological outcomes, but it does not report a single numerical primary-outcome contrast. The absence of that result limits interpretation of the randomized comparison, even though the trial's design and intervention groups are described.

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.

Before assignment: After enrollment, the children were placed on a low-polyphenol diet for 48 hours. Following this period, they were assigned to consume either wild-blueberry products (n = 22) or placebo-containing products (n = 22).

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Phenolic-derived metabolites were characterized in the samples using an ultra-high performance liquid chromatography method coupled with mass-spectrometry/mass spectrometry multiple reactions monitoring

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 Phenolic Acid Metabolites Measured in Plasma and Urine After Dietary Intervention, measured over Measurements were conducted hourly for 5 hours; the cumulative number of metabolites characterized over the 5 hours is reported.

The primary endpoint is the number of phenolic acid metabolites measured in plasma and urine after dietary intervention. The registry describes fasting blood and urine collection at visit two and visit three. At visit three, children consumed a single dose of the study product, and plasma and urine were collected. Measurements were conducted hourly for 5 hours; the reported endpoint is intended to be the cumulative number of metabolites characterized over that period.

Metabolites were characterized using an ultra-high performance liquid chromatography method coupled with mass-spectrometry/mass spectrometry multiple reactions monitoring. In general, measuring compounds in plasma and urine can help establish whether compounds associated with a food exposure are detectable in biological samples. A count of characterized metabolites describes how many distinct compounds the assay identified under the study's measurement procedures; it does not, by itself, describe their concentrations, the amount absorbed, or a clinical effect.

The record does not report the observed metabolite counts by arm, the identities of the metabolites, or a statistical comparison. It also does not specify how the cumulative count was defined if a metabolite was detected at more than one hourly measurement. These omissions mean the endpoint's measurement goal is clear, but its numerical findings and the precision of any group difference cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Interpretation of a randomized trial begins by identifying the assigned groups, the outcome definition, and the planned comparison. In this study, the groups are wild-blueberry supplement foods and placebo supplement foods. The primary outcome is a count of phenolic acid metabolites characterized in plasma and urine. The registry describes hourly measurements over 5 hours and defines the reported measure as cumulative across that period. It does not provide arm-specific values or a treatment-effect estimate, so the main statistical comparison cannot be reconstructed from the record.

What does randomization contribute?

In general, random assignment is used to reduce systematic differences between groups at the beginning of a study. If allocation is implemented as planned and follow-up and measurement are handled appropriately, differences in outcomes can be interpreted as evidence about the assigned interventions more credibly than differences in a nonrandomized comparison. Randomization does not guarantee that every measured or unmeasured characteristic will be balanced, especially in a study with limited enrollment. The registry record says the study was randomized but does not describe the sequence-generation method, allocation concealment, or baseline characteristics, so those details cannot be assessed.

What does masking contribute?

Masking can reduce the chance that knowledge of assignment affects behavior, care, or outcome assessment. The registry labels the trial triple masked. It does not state who was masked or how the masking worked for the food products and metabolite measurements. Therefore, the label identifies the recorded design feature, but the record does not permit an assessment of whether masking was maintained or whether the laboratory assessment was conducted without knowledge of group assignment.

How should a count endpoint be understood?

A count records how many qualifying items were observed, rather than measuring a continuous quantity such as concentration. Count outcomes are often nonnegative and can have distributions that differ from the symmetric, bell-shaped pattern assumed by some standard methods. In general, the appropriate analysis depends on the count distribution, the frequency of zeros, whether observations vary more than a basic count model expects, and how repeated measurements are handled. Over-dispersion means that the observed variability exceeds what a chosen count model assumes; if ignored, uncertainty estimates can be too small. These are general considerations, not descriptions of analyses confirmed for this trial. The record does not identify a count-data model or explain how repeated hourly measurements contributed to the cumulative endpoint.

Why do repeated measurements matter?

Measurements taken from the same participant over time are generally related. Treating them as independent observations can misstate uncertainty because the repeated values share information about the same person. An analysis may instead use a participant-level summary, a repeated-measures model, or another approach appropriate to the outcome and design. The registry describes hourly collection for 5 hours and a cumulative metabolite count, but it does not report the analysis method, the exact aggregation procedure, or whether the hourly values were also analyzed separately. No particular method should be assumed.

What can a confidence interval and p-value tell a reader?

In general, a confidence interval gives a range of effect estimates compatible with the data under the model and its assumptions. Its width conveys precision: wider intervals indicate greater uncertainty, while narrower intervals indicate greater precision. A p-value assesses how unusual data at least as incompatible with a specified null hypothesis would be under that hypothesis and the analysis assumptions. Neither measure, on its own, establishes clinical importance. The registry record does not report a confidence interval or p-value for the primary comparison, so neither statistical precision nor a test result can be evaluated.

How should planning calculations be read?

A sample-size planning illustration uses assumptions about the significance level, allocation, statistical approximation, and effect to detect to explore what a future study might require. The stated illustration uses a two-sided significance level of 0.05, equal allocation between arms, a normal approximation, and an effect defined as a stated fraction of the observed effect. These are planning assumptions, not evidence that the trial was designed using those assumptions. The registry record does not report the trial's own sample-size justification. A planning calculation is not observed power and does not reveal whether the completed trial had a statistically significant result.

Any recalculation from summary statistics would be an unadjusted calculation and would not replace the sponsor's analysis if the two differed. No recalculated estimate is available from the registry record because the necessary arm-specific outcome summaries are not reported. More generally, calculations based on group summaries may not reproduce a model-based analysis that adjusts for baseline variables, repeated measurements, or other design features. The analysis method and its assumptions must be known before a recalculation can be interpreted.

Finally, the number of outcome measures and analyses does not by itself define the statistical plan. The registry records 4 outcome measures and 1 analysis, but it does not describe which outcomes were included in that analysis, how repeated time points were handled, or what multiplicity strategy was used. Those details are not reported in the registry record and should not be inferred from the outcome list.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 4 outcome measures, including the primary metabolite outcome and secondary measures of immune-cell counts and percentages, T-lymphocyte responsiveness to immune stressors, and endothelial function by brachial artery flow-mediated dilation. It records 1 analysis, but does not explain which outcome or outcomes that analysis covers, whether there were additional analyses, or how the analysis addressed repeated hourly measurements. The primary outcome itself is described over measurements conducted hourly for 5 hours, with a cumulative count reported. The record does not state whether individual hourly results were also treated as separate tests.

When a study examines multiple outcomes or multiple time points, the chance of finding at least one apparently unusual result can increase if each is tested separately without accounting for the multiplicity. In general, a prespecified hierarchy, an adjustment method, or a clearly stated distinction between confirmatory and exploratory analyses can help readers interpret results. No multiplicity strategy is reported in the registry record, so it is not possible to tell whether or how this issue was addressed.

Missing-data handling is not reported in the registry record. The record does not say whether all randomized participants contributed primary outcome data, how incomplete samples or failed metabolite measurements were handled, or whether any imputation was used. The analysis population is also not described: there is no stated intention-to-treat, per-protocol, or other population definition. These gaps matter because exclusions and missing measurements can affect both the estimated group comparison and its uncertainty. They also prevent a reader from assessing whether the analysis preserved the intended randomized comparison.

These are reporting gaps, not proof that the study lacked a plan or that data were missing. The available registry information does not support a more specific account.

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 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports serious adverse events for the wild-blueberry supplement group with 22 at risk and 0 affected, and for the placebo supplement group with 22 at risk and 0 affected. Deaths are recorded as 0 in each group. No serious-event terms are listed. The registry also records other adverse events, with 22 at risk and 2 affected in each group.

These are event counts recorded for the trial groups, not a complete description of the nature, timing, severity, or relatedness of each event. The record does not provide further detail about the other adverse events or indicate whether they were judged related to a study product. It also does not provide a statistical comparison of adverse-event rates. The count of 0 serious events in each group should therefore be read as the registry's reported observation during this study, not as evidence that serious events are impossible or that risk is absent.

Safety interpretation is constrained by the number of participants at risk in each group and by the lack of detailed event descriptions. A trial's adverse-event record can identify events observed during the study, but the absence of recorded events does not rule out uncommon events or establish safety in populations beyond those studied. These figures should not be treated as a substitute for a fuller safety assessment.

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

The registry record shows that a randomized, triple-masked, parallel study compared wild-blueberry supplement foods with placebo foods in healthy children described as having typical low fruit and vegetable consumption. It also describes a laboratory outcome intended to characterize phenolic acid metabolites in plasma and urine after a single dose at visit three, with measurements conducted hourly for 5 hours. These details establish the question the study set out to examine and the general form of its primary measurement.

The registry record does not report the primary outcome values, identities of the characterized metabolites, or a numerical comparison between the randomized groups. It therefore cannot show whether the metabolite count differed, the magnitude of any difference, or the precision of an estimate. The record also does not report numerical findings for the listed secondary outcomes. No conclusion about a biological effect or clinical benefit can be drawn from the outcome descriptions alone.

A metabolite count is evidence about what the study's assay characterized under its procedures. It is not equivalent to a concentration, a measure of health status, or a clinical outcome. Even a reported difference in such a count would require interpretation alongside the assay methods, uncertainty, and a clear account of how the repeated measurements were analyzed. Those numerical and analytical details are not reported in the registry record.

The safety figures report 0 serious adverse events and 0 deaths in each arm, and 2 other adverse events in each arm. These observations are limited to the trial record and do not establish that the intervention is free of risk. The record does not provide sufficient descriptions to interpret the other events or their possible relationship to the study products.

In short, the study record describes a randomized biological-measurement investigation, but it does not include the outcome results needed to judge the primary comparison. The design and measurement plan can be described; the numerical findings and their uncertainty cannot be determined from the posted results.

13. Why This Trial Matters Statistically

This trial illustrates why a clearly defined outcome and a reported treatment contrast are both necessary for statistical interpretation. The primary measure is described as a cumulative count of metabolites characterized in plasma and urine, using a specified analytical approach and a collection schedule. That information helps readers understand what was measured. Without arm-specific counts and an estimate of the between-group difference, however, it does not answer whether the randomized groups differed or how precisely any difference was estimated.

The study also brings together a food intervention, biological samples, and repeated measurements. In general, repeated observations can contain information about how a measurement changes over time, but they require analysis that accounts for their relationship within participants. A cumulative summary may answer a different question from a comparison at each hourly measurement. The registry record does not explain which form of comparison was used, underscoring the value of reporting both the estimand and the analytical method.

The outcome list spans metabolite characterization and biological measures related to immune function and endothelial function. Multiple outcomes can broaden scientific inquiry, but they also make a prespecified analysis plan and transparent reporting important. The record gives no multiplicity strategy or missing-data approach. Readers consequently cannot determine how the reported analysis relates to the full outcome set.

Finally, the trial's planning assumptions should be distinguished from evidence about its observed result. A sample-size illustration based on an assumed fraction of an observed effect is a planning exercise; it is not observed power and does not substitute for an effect estimate and confidence interval. Overall, the record highlights the difference between describing a trial's design and reporting enough statistical results to evaluate its findings.

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 most consequential limitation for interpreting this trial from the registry record is that the primary outcome result is not reported. There are no arm-specific metabolite counts, no treatment-effect estimate, and no measure of uncertainty. The record therefore does not permit a quantitative assessment of the central randomized comparison. The same limitation applies to the listed secondary outcomes: their numerical results are not reported in the registry record.

The outcome description leaves important measurement details unclear. It states that metabolites were measured hourly for 5 hours and that a cumulative number characterized over the period is reported, but does not define how repeated detections of the same metabolite were counted. It does not list metabolite identities or provide assay performance details that would help evaluate detection and characterization. The record also does not provide the statistical method for analyzing the count or the repeated measurements.

Further design and analysis details are absent. The registry does not describe the randomization procedure, allocation concealment, masked parties, analysis population, missing-data handling, or multiplicity strategy. It does not report baseline characteristics or explain how the daily food provision relates to the single-dose collection visit. These omissions do not establish that the trial lacked procedures; they mean those procedures cannot be evaluated from this record.

The safety information is also limited to aggregate event counts. Serious-event terms are not listed, and the record does not describe the other adverse events, their timing, or their relationship to the study products. The findings are specific to the recorded study population and should not be generalized beyond the information reported.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: The Blueberry Study — NCT04421950.
• Registry record last updated 2025-08-22; status last verified 2024-09.
• Results first posted 2025-08-22.
• 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

NCT04421950, The Blueberry Study, is recorded as completed. It was randomized, triple masked, and parallel, with an enrollment of 44. The sponsor was Arkansas Children's Hospital Research Institute. The recorded study dates are 2021-04-23 to 2022-08-18.

The study compared food items containing 30 grams of wild blueberry powder per day with placebo food items without wild blueberry powder. Its primary outcome concerned the cumulative number of phenolic acid metabolites characterized in plasma and urine over measurements conducted hourly for 5 hours. The registry lists 4 outcome measures and 1 analysis.

Numerical primary and secondary outcome results, the statistical analysis details, missing-data handling, analysis populations, and multiplicity procedures are not reported in the registry record. Serious adverse events and deaths are recorded as 0 in each arm; other adverse events are recorded for 2 participants in each arm.