A Patient-Centered Strategy for Improving Diabetes Prevention in Urban American Indians: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Patient-Centered Strategy for Improving Diabetes Prevention in Urban American Indians (NCT02266576), a randomized na study. The primary outcome is Change From Baseline in Body Mass Index (BMI) Through Month 12.

2. Clinical Question

The clinical question is about whether a patient-centered enhancement is associated with a different pattern of BMI change than the standard program in this high-risk population. It is not a question about diabetes incidence: although diabetes prevention motivates the study, the listed primary outcome is BMI change. The registry record also lists changes in diet choices, physical activity, depression symptoms, and empowerment as secondary outcomes. The available record does not establish how those measures relate to the primary outcome or whether they were intended to explain any BMI changes.

Because the primary outcome spans multiple time points, a useful interpretation would need to distinguish the time-specific estimates and their uncertainty, as well as clarify the comparison being made. Those numerical results and details are not reported in the registry record. The clinical question can therefore be described from the study design, but the posted results do not support a conclusion about the direction or size of any difference between the programs.

3. Trial Design

The registry record describes a randomized, single-masked, parallel-group behavioral trial. Its stated goal was to compare an enhanced Diabetes Prevention Program addressing psychosocial stressors with a standard version in a high-risk population of urban American Indian and Alaska Native people in a primary care setting. Enrollment is recorded as 207. The sponsor is Stanford University. The study is listed as completed; its recorded start is 2015-06 and its primary completion date is 2017-08-30.

Participants in the Standard DPP group received the standard program over 20 weeks. Participants in the Enhanced DPP group received Standard DPP plus Enhanced DPP over 20 weeks. The registry record does not describe the specific enhancement in enough detail to characterize its content beyond the stated attention to psychosocial stressors. It also does not identify which people or groups were masked, or describe how random allocation was generated or concealed. Those details are not reported in the registry record.

The primary outcome was change from baseline in BMI through month 12, with assessments at baseline, 6 months, and 12 months. The primary-outcome population description states that one participant from each group was excluded at baseline due to safety concerns and that participants with available data at subsequent time points were included in the analysis. It does not give further details about the timing or reasons for missing later observations.

The record lists 12 outcome measures and 4 analyses. Secondary outcomes include change in FFQ score as a measure of healthy and unhealthy diet choices, physical activity measured in MET per week, CES-D as a measure of mental health symptoms, and empowerment. A complete statistical analysis plan, including model specification, treatment of repeated measurements, and adjustment for multiple comparisons, is not reported in the registry record. The randomized design describes how the comparison was organized; without outcome estimates and analysis details, it does not by itself establish the size or precision of any observed difference.

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

Analysis population for the primary outcome, as defined in the registry: One participant from each group was excluded at baseline due to safety concerns; participants with available data at subsequent time points were included in the analysis.

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 Change From Baseline in Body Mass Index (BMI) Through Month 12, measured over Change through month 12, with assessments at baseline, 6 months, and 12 months.

The primary endpoint is change from baseline in body mass index through month 12. BMI is defined in the registry record as weight in kg divided by the square of height in meters, and the unit is kg/m^2. The endpoint is a continuous measure, with the primary parameter identified as a mean and the stated dispersion as a 95% confidence interval. Assessments were planned at baseline, 6 months, and 12 months, so the endpoint concerns change over time rather than a single measurement at enrollment.

BMI is used in this trial as a measure of body size and as an outcome of a diabetes-prevention program. In general, a continuous endpoint can describe both the direction and magnitude of change, while an estimate of uncertainty helps readers judge how precisely that change is known. Those are general statistical considerations, not findings about this trial.

The record does not report the group means, mean changes, confidence limits, or a numerical contrast between groups. It also does not reduce the multiple assessment times to one comparison. Consequently, the endpoint’s definition is clear, but its observed results and the precision of any between-group difference are not reported in the registry record. BMI change should not be treated as equivalent to a direct measure of diabetes onset, which is not the listed primary endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The trial is described as randomized, single-masked, and parallel. In general, randomization aims to create groups that are comparable at the start with respect to measured and unmeasured characteristics. It does not ensure perfect balance in any particular trial, especially when groups are limited in size. The registry record does not report the method used to generate the allocation sequence, how allocation was concealed, or who was masked. Those details are not reported in the registry record and should not be inferred from the design labels.

What does the primary measure represent?

BMI is a continuous measure defined as weight in kg divided by height in meters squared. The registry record identifies the mean as the parameter of interest and a 95% confidence interval as the dispersion measure. General explanation: a mean summarizes the center of a set of continuous measurements. A confidence interval conveys uncertainty around an estimate under the assumptions of the analysis. Neither is a substitute for knowing the actual estimate, which is not reported in the registry record.

The assessment schedule includes baseline, 6 months, and 12 months. Repeated observations from the same participant are generally related rather than independent. General statistical practice is to account for this within-person dependence when estimating changes over time. The registry record does not report the statistical model used, whether the analysis compared changes within groups or differences between groups, or how the repeated measurements were handled.

What does a comparison between groups require?

A group-specific change and a between-group contrast answer different questions. A change within one group describes what happened over time among participants in that group; a contrast compares the changes or measurements between the two randomized groups. General explanation: interpreting a treatment comparison usually requires the contrast itself, an estimate of its uncertainty, and clarity about the time point or overall trajectory being compared. The registry record does not report a single primary comparison or the estimates needed to evaluate one.

The record specifies the primary parameter as a mean and gives a 95% confidence interval as the dispersion measure, but it does not state whether the primary contrast is adjusted for baseline BMI or other variables. It also does not describe assumptions or diagnostics for the model. These analysis details are not reported in the registry record. No particular model or adjustment strategy should be presumed.

How should missing observations be considered?

The primary-outcome description says one participant from each group was excluded at baseline due to safety concerns, with participants who had available data at later time points included in the analysis. General explanation: analyses based on available observations can be affected if participants with missing measurements differ systematically from those measured. The consequences depend on why observations are missing and on the analytic approach. The registry record does not report the amount of missing data at each follow-up, reasons for missingness, or any imputation or sensitivity analyses.

The record does not say whether all randomized participants were analyzed in their assigned groups. It also does not describe a per-protocol analysis or another analysis population. These distinctions matter because excluding participants or using only observed measurements can alter the balance achieved by randomization. No specific bias can be concluded from the record alone.

What can planning calculations establish?

The planning assumptions describe an illustration using the observed effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation; the effect to detect is expressed as a fraction of the observed effect. Such calculations are planning illustrations, not observed power and not evidence that the trial was adequately or inadequately designed. They do not replace the results or uncertainty estimates. The numerical planning values and the trial’s own sample-size justification are not reported in the registry record.

General explanation: sample-size planning depends on assumptions about the effect of interest, variability, significance threshold, allocation, and analysis. A calculation based on an observed effect can be especially dependent on that effect estimate. Planning results should be interpreted as conditional on the stated assumptions, not as a measure of the certainty of the trial’s findings.

How do multiple outcomes affect interpretation?

The registry record lists 12 outcome measures and 4 analyses, including diet, physical activity, mental health symptoms, and empowerment as secondary outcomes. General explanation: when many outcomes or comparisons are tested, the chance of finding at least one apparently notable result by chance can increase. Methods for handling multiplicity can be used, but the record does not report whether an adjustment or other strategy was used. It also does not report which outcomes were included in each analysis. Therefore, no inference about multiplicity control or the selection of reported analyses can be made.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists 12 outcome measures and 4 analyses. It names secondary measures concerning diet choices, physical activity, depression symptoms, and empowerment, in addition to the primary BMI outcome. A larger set of outcomes can provide a broader description of a trial, but it also creates more opportunities for statistical comparisons. General statistical explanation: without a plan for interpreting multiple tests, isolated findings can be difficult to distinguish from chance variation. The registry record does not report whether multiplicity was addressed through adjustment, hierarchy, or another strategy, and numerical results for the listed secondary outcomes are not reported.

The primary outcome includes assessments at baseline, 6 months, and 12 months, and the record indicates that it was not reduced to a single comparison. It does not specify which time-specific or overall contrast was considered primary for inference. It also does not report whether analyses were prespecified in a statistical analysis plan or whether any analyses changed after the study began. Those details are not reported in the registry record.

For the primary outcome, the record says one participant from each group was excluded at baseline due to safety concerns; participants with available data at later assessments were included in the analysis. It does not report follow-up completeness at each visit, reasons for later missing observations, or whether missing values were imputed. The handling of missing data beyond using participants with available data is not reported in the registry record.

The record also does not state whether analyses retained all participants in their randomized groups or describe alternative analysis populations. As a general matter, missing data and exclusions can affect the interpretation of randomized comparisons if the analyzed participants differ from those not analyzed. The information available is insufficient to determine whether that occurred in this trial.

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.

The registry record reports zero participants affected by serious adverse events in the Standard DPP group, with 102 at risk, and zero in the Enhanced DPP group, with 105 at risk. It also reports zero participants affected by other adverse events in both groups, with 102 and 105 at risk, respectively. Deaths are recorded as zero in each group. These are the recorded figures for the safety categories presented; they do not provide a detailed account of all possible symptoms or events.

General explanation: an adverse-event count describes what was recorded under the trial’s reporting definitions and observation procedures. A zero count in a category means that no affected participants were recorded in that category; it does not establish that no event of any kind occurred or that an intervention is free of risk. The registry record does not provide serious-event terms, and the listed top serious terms are empty. Further details about event definitions, follow-up duration for safety, and completeness of reporting are not reported in the registry record.

The safety counts should be read separately from the primary BMI outcome. They do not show whether BMI changed, and they do not resolve the missing numerical efficacy results. The record’s baseline exclusion due to safety concerns is described for one participant from each group, but additional details about those concerns are not reported in the registry record.

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

The record describes a randomized comparison of Standard DPP with Enhanced DPP over 20 weeks, in a high-risk urban American Indian and Alaska Native population. Its primary outcome is change from baseline in BMI through month 12, with measurements at baseline, 6 months, and 12 months. These registry entries explain what the trial was designed to study. They do not reveal what the comparison found.

The primary group estimates, between-group contrast, confidence interval values, and p-value are not reported in the registry record. As a result, the posted results do not establish the direction, magnitude, or precision of any BMI difference. The absence of numerical results must not be interpreted as evidence of no difference, just as the trial’s stated prevention goal must not be interpreted as evidence that either program changed diabetes risk.

The listed secondary measures address diet, physical activity, mental health symptoms, and empowerment. Numerical results for these measures are not reported in the registry record. The primary outcome is BMI, not diabetes incidence. No conclusion about diabetes onset, the proposed psychosocial pathway, or the relationship between secondary measures and BMI can be drawn from the record as described.

General statistical explanation: a randomized design can support a fair comparison when allocation and follow-up are appropriately conducted, but inference also depends on the actual estimates, uncertainty, missing-data handling, and analysis choices. Those details are not sufficiently reported to assess the strength or precision of a finding. The safety record lists zero affected participants for the serious and other adverse-event categories shown, but those counts do not replace a fuller safety description.

The narrow conclusion is that the registry record documents a completed trial design and a defined primary outcome, but does not report the numerical outcome evidence needed to judge the result. Any stronger claim about which program produced a greater BMI change, whether a difference was meaningful, or whether diabetes was prevented would go beyond what is reported.

13. Why This Trial Matters Statistically

This trial is statistically notable for asking a comparative question about two behavioral program approaches in a high-risk urban American Indian and Alaska Native population. The randomized parallel design provides a structure for comparing groups, and the primary outcome is a continuous measure assessed over multiple visits. These features make clarity about the estimand—the particular group contrast the analysis is intended to estimate—important for interpretation.

Multiple assessment times can provide information about the course of an outcome, rather than only a single endpoint. At the same time, they make it necessary to specify whether the target is a change at a particular visit, an average pattern over follow-up, or another summary. The registry record does not identify a single comparison across the baseline, 6-month, and 12-month assessments, and it does not report numerical results. Thus the trial’s statistical question is identifiable, but its answer cannot be evaluated from the posted results.

The record also highlights the importance of understanding the analysis population. It describes baseline exclusions for safety concerns and later inclusion when data were available. Without details on follow-up completeness and missing-data methods, readers cannot fully assess how the analyzed observations relate to the randomized groups. This is a general interpretive issue for longitudinal clinical research, not a finding that bias occurred in this trial.

Finally, the record lists a range of secondary outcomes and analyses. A statistical plan for handling multiple outcomes would help readers understand how confirmatory claims were distinguished from exploratory findings, but such a plan is not reported in the registry record. The value of the trial’s design therefore cannot be translated into a conclusion about efficacy or precision without its estimates and analytic detail.

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 main limitation for interpreting this trial from the registry record is that numerical results for the primary BMI outcome are not reported. The record defines the endpoint and its assessment schedule, but does not provide group means, changes, a between-group contrast, confidence interval limits, or a p-value. The direction and precision of the primary finding cannot be assessed.

The primary outcome spans baseline, 6 months, and 12 months, and the record indicates it was not reduced to one comparison. It does not specify the contrast used for the primary inference or the model used to account for repeated measurements. The analysis plan, including any baseline adjustment, is not reported in the registry record.

The population description reports that one participant from each group was excluded at baseline due to safety concerns and that participants with data at subsequent time points were included. Later follow-up counts, reasons for missing data, and methods for handling missing observations are not reported. The record does not explain whether analyses retained all participants in their randomized groups.

The record describes the enhanced program as Standard DPP plus Enhanced DPP, and the study summary says it addresses psychosocial stressors. Further intervention details are not reported in the registry record. Allocation generation, concealment, the identity of the masked parties, and the statistical analysis plan are also not reported. Secondary outcome results and multiplicity procedures are not reported. These omissions limit assessment of how the findings were generated and how broadly they can be interpreted; they do not establish that the study methods were inadequate.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Patient-Centered Strategy for Improving Diabetes Prevention in Urban American Indians — NCT02266576.
• Registry record last updated 2025-08-26; status last verified 2025-08.
• Results first posted 2020-01-02.
• 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.

18. Record Summary

NCT02266576 is a completed randomized, single-masked, parallel behavioral trial sponsored by Stanford University. It enrolled 207 participants and compared Standard DPP over 20 weeks with Enhanced DPP, described as Standard DPP plus Enhanced DPP over 20 weeks. The study focused on urban American Indian and Alaska Native people at high risk of diabetes in a primary care setting.

The primary outcome was change from baseline in BMI through month 12, with assessments at baseline, 6 months, and 12 months. The registry record describes BMI in kg/m^2 and specifies a mean with a 95% confidence interval. One participant from each group was excluded at baseline due to safety concerns; participants with available later data were included in the analysis.

Numerical primary and secondary outcome results, detailed analysis methods, and multiplicity procedures are not reported in the registry record. Safety entries list zero affected participants in the serious and other adverse-event categories shown and zero deaths in each group.