Niacin and Endothelial Function in Early CKD: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Niacin and Endothelial Function in Early CKD (NCT00852969), a randomized phase 4 study. The primary outcome is Change in the Flow Mediated Dilation From Baseline.

2. Clinical Question

3. Trial Design

The registry describes a randomized, triple-masked, parallel-group, phase 4 study. Its status is completed, and the listed enrollment is 30. The sponsor is Tufts Medical Center. The study start is recorded as 2008-08 and primary completion as 2012-04. These registry entries identify the design and timeline, but do not specify the practical arrangements for allocation or masking.

The two intervention arms are Niacin and Placebo. The niacin arm summary reports n=15; the placebo arm summary reports n=13. The adverse-event record separately lists 15 participants at risk in each group. These figures belong to different registry summaries and should not be treated as interchangeable descriptions of the analysis population. Reasons for differences between the arm summaries are not reported in the registry record.

The primary endpoint is the change in flow-mediated dilation from baseline, with a timeframe of 14 weeks since baseline. The registry describes measurement by brachial artery reactivity and gives the unit as absolute percent change. Change in HDL-C from baseline to 14 weeks is listed as a secondary outcome. Numerical results for that secondary outcome are not reported in the registry record.

The record does not report the randomization sequence method, allocation concealment, the identities of the people included in triple masking, treatment dose, adherence, or details of follow-up. It also does not report a protocol or a fuller account of eligibility criteria. The labels randomized, triple-masked, and parallel describe important design features, but they do not answer those additional questions.

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: There was no washout period. Patients receiving Niacin were excluded from the study.

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.

Population: These were the number of individuals who agreed to be randomized for the study

6. Primary Endpoint

The registry lists the primary outcome as Change in the Flow Mediated Dilation From Baseline, measured over 14 weeks since baseline.

The primary endpoint is change in flow-mediated dilation from baseline, assessed 14 weeks since baseline. The registry describes flow-mediated dilation measured by brachial artery reactivity and reports the unit as absolute percent change. The posted group summaries are means with 95% confidence intervals.

In general, flow-mediated dilation is used as a physiological measure of how an artery responds to a stimulus. It provides an indicator of endothelial function, the capacity of the inner lining of blood vessels to participate in vascular responses. In this trial, the measure addresses a biological question about endothelial function in chronic kidney disease; it is not itself a direct measure of clinical events such as heart attack, stroke, or kidney failure. Such clinical outcomes are not identified as the primary endpoint in the registry record.

The endpoint is expressed as change from baseline rather than as a final measurement alone. A change measure describes how the recorded value moved over the specified study period, while the between-group comparison addresses whether the mean changes differed. The registry record does not provide participant-level values, baseline group summaries, or additional measurement details. Consequently, the posted endpoint gives a summary of the recorded changes and their uncertainty, not a detailed account of individual trajectories or measurement variability.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry reports a two-sided t-test for the mean difference between the niacin and placebo groups. A t-test evaluates whether the observed difference in group means is compatible with a null model of no difference, given the test assumptions. “Two-sided” means the test considers departures in either direction, rather than testing only whether one named group is greater. The registry does not report further details about the test implementation, such as whether any adjustment was made or how assumptions were assessed.

What does the mean describe?

The primary endpoint is continuous: it records a quantity on a scale rather than assigning participants to event categories. The arm summaries report means of the change in flow-mediated dilation. A mean represents the average recorded change within a group; it does not show the distribution of individual changes. Participants may have values far from the mean, and the mean alone does not show whether values were concentrated or widely dispersed.

The registry gives confidence intervals for each arm mean and for the net mean difference. In general, a confidence interval communicates the precision of an estimate under the method used to construct it. A narrower interval indicates greater statistical precision, while a wider interval leaves more uncertainty about the range of values compatible with the data and method. The intervals in the record are broad and include zero. That feature is relevant to the uncertainty of the mean changes and the between-group contrast, but it does not establish that the groups are equivalent.

How should the reported contrast be read?

The reported analysis labels its estimate “Mean Difference (Net)” and gives -1.69, with a 95% confidence interval from -10.79 to 7.41. It reports p = 0.71 from a two-sided t-test. The confidence interval describes uncertainty in the contrast according to the reported method; the p-value summarizes the test against its null hypothesis. Neither should be interpreted alone as a measure of clinical importance. The record does not state the contrast sign convention, so the negative sign cannot safely be assigned to a particular arm as the higher-change group.

The arm-level means and intervals are useful context, but they are not a substitute for the reported between-group analysis. In general, inference about a difference depends on the variability and structure of the data, not just on comparing the displayed point estimates. The record does not provide participant-level data or a separate variance estimate in the arm summaries. No new contrast should be calculated from those summaries when the registry already reports its own analysis.

Why does variability matter?

For a continuous outcome, the precision of a mean and of a difference in means depends in part on how variable participant measurements are. Greater variability makes it harder to estimate a group mean or contrast precisely. The registry reports confidence intervals but does not give a separate standard deviation or other dispersion measure for the arm summaries. The interval width conveys uncertainty in the estimates, while the underlying participant-level spread cannot be reconstructed from the listed values alone.

In general, departures from a model’s assumptions can affect the calibration of a test and interval. For continuous outcomes, relevant considerations may include the shape of the outcome distribution, independence of observations, and the treatment of missing measurements. These are general statistical considerations, not reported findings about this trial. Whether assumptions were checked, whether any transformations were considered, and whether missing data were handled with a particular method are not reported in the registry record.

What can a planning illustration tell readers?

The registry describes sample-size illustrations as planning calculations based on the observed effect, not as the trial’s original design. It states that the illustrations use a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation, with the effect to detect set as a stated fraction of the observed effect. Such calculations illustrate how planning requirements would vary with the assumed effect and target power. They are not observed power and do not show the probability that the trial’s result is true.

The registry record does not report the original sample-size justification or the assumptions used when the study was planned. The planning illustrations therefore cannot establish whether the trial was designed to detect a particular clinically meaningful difference, and they should not be used as evidence that the study had adequate or inadequate power. The numerical results of those illustrations are not repeated in this interpretation.

What is not specified about the analysis?

The record identifies the primary endpoint, timeframe, group summaries, and reported t-test. It does not report an analysis plan, adjustment for baseline values, covariate adjustment, handling of missing primary-outcome data, or the population used for the primary analysis. It also does not state whether interim analyses occurred. Those omissions constrain assessment of how closely the posted results follow an intended plan and how analysis choices might affect the reported uncertainty.

In general, a statistical result is best interpreted together with its prespecified estimand, analysis population, missing-data strategy, and model assumptions. Those details clarify what comparison is being estimated and which participants contribute to it. Without them, the reported contrast remains interpretable as the registry’s posted analysis, but its full analytic context is not available from the registry record.

10. Analyses Reported by the Sponsor

The registry reports the sponsor’s own primary comparison as a two-sided t-test, with a net mean difference of -1.69, a 95% confidence interval from -10.79 to 7.41, and p = 0.71. That analysis is the posted inferential result for the primary endpoint. The record does not flag a discrepancy between the reported analysis and a recalculation, and it does not report a separate recalculated estimate in the registry record.

A recalculation from posted summary statistics, when available, is a simple unadjusted check. It may not reproduce the sponsor’s analysis if the latter uses participant-level data, a different analysis population, or details not captured by the summary values. The registry record does not describe such additional analytic details. Accordingly, the reported sponsor analysis should be read as the registry’s stated result, while any summary-statistic recalculation should be treated as a check rather than as a replacement estimate. No independent recalculated numerical contrast is stated in the registry record.

The sponsor’s reported interval spans zero and is broad, and the reported p-value is 0.71. These results indicate substantial uncertainty in the estimated contrast under the stated analysis. They do not establish equivalence, and they do not determine the clinical importance of all differences compatible with the interval.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists change in flow-mediated dilation from baseline as the primary outcome and change in HDL-C from baseline to 14 weeks as a secondary outcome. It reports two outcome measures and one posted secondary outcome. A numerical result for the secondary HDL-C outcome is not reported in the registry record.

When a study examines multiple outcomes or multiple analyses, the chance of obtaining at least one apparently notable result can increase. Statistical methods for addressing multiplicity may adjust thresholds or otherwise account for the family of questions being tested. This is a general principle; it does not establish that multiplicity affected the findings in this trial. The registry record does not report a multiplicity strategy, a hierarchy among secondary outcomes, or an analysis plan defining which results were confirmatory.

The primary result is reported with a confidence interval and a p-value, but the record does not say whether these were adjusted for other outcomes or analyses. The meaning of the p-value is therefore the one attached to the reported two-sided t-test, not a stated family-wise conclusion across every outcome. The secondary outcome’s listing alone does not show that it was analyzed, and the absence of its numerical result in the registry does not explain why it is missing.

The arm summaries report n=15 for niacin and n=13 for placebo, while the adverse-event record lists 15 participants at risk in each group. The record does not explain these differences. It does not identify the primary analysis population, state whether all randomized participants were included, or report how missing endpoint measurements were handled. Reasons for unavailable observations, if any, are not reported in the registry record.

These omissions matter because analysis populations and missing-data decisions can influence the estimate and its uncertainty. Without a reported strategy, readers cannot determine whether the primary analysis followed an intention-to-treat, per-protocol, or other approach. These labels should not be assigned by inference. The posted results should be interpreted with the available group summaries and stated test, while recognizing that the analysis population, missing-data handling, and multiplicity plan are not reported in the registry record.

12. Safety Results

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

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 lists zero serious adverse events among 15 participants at risk in the niacin group and zero among 15 participants at risk in the placebo group. No top serious-event terms are listed. Death counts are not reported in the registry record.

For other adverse events, the record lists 10 affected participants among 15 at risk in the niacin group and 5 affected participants among 15 at risk in the placebo group. These counts are presented under the registry’s “other” adverse-event category. The record does not provide further definitions or event-level descriptions in the registry record for this analysis.

These figures describe events recorded during the trial; they do not by themselves establish a comparative safety profile. In general, a count of zero observed serious events does not prove that serious events cannot occur, especially when the record concerns a limited study population and follow-up. The registry does not report exposure time, event severity details beyond the serious/other categories, or a statistical comparison of adverse events. The counts should therefore be read descriptively, not as proof of safety or harm.

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

The posted result describes the mean change in flow-mediated dilation over 14 weeks since baseline and the registry’s comparison of that change between niacin and placebo. The group means are 3.07 for niacin and 1.37 for placebo. The reported net mean difference is -1.69, with a 95% confidence interval from -10.79 to 7.41 and p = 0.71. The uncertainty interval spans zero and permits values in either direction under the reported analysis.

This result does not establish that the groups are equivalent. A test that does not provide strong evidence against its null hypothesis is not an equivalence test, and the registry does not identify an equivalence margin or a non-inferiority objective. Nor does the result prove that there is no effect. Its confidence interval is compatible with a range of possible differences, and the record does not define which differences would be clinically important.

The endpoint is a physiological measure of endothelial function, not a reported clinical event. The result therefore does not establish an effect on cardiovascular disease, kidney outcomes, or other long-term health outcomes. The registry’s stated purpose concerns raising HDL-cholesterol and endothelial function, but the numerical HDL-C result is not reported in the registry record. No conclusion about the secondary HDL-C outcome can be drawn from its listing alone.

The finding also applies only to the endpoint, study population, and timeframe represented in the registry. The record identifies chronic kidney disease and describes the study as concerning early CKD, but detailed eligibility criteria and participant characteristics are not reported in the registry record. The available information does not establish how well the results apply to people outside the studied population or to other treatment schedules and settings.

In general, a trial result is one estimate subject to sampling variation and design and analysis limitations. The posted confidence interval helps communicate that uncertainty; it does not resolve the unreported details about analysis populations, missing data, or prespecified methods. The most defensible reading is therefore a broadly uncertain estimate for the specified physiological endpoint, rather than a definitive statement about treatment benefit, absence of effect, or clinical outcomes.

14. Why This Trial Matters Statistically

This trial illustrates an important distinction between a point estimate and the precision of an estimate. The primary comparison has a reported value of -1.69, but its 95% confidence interval extends from -10.79 to 7.41. The point estimate is only one location within a much broader range of values compatible with the reported analysis. Reading the point estimate without its interval would obscure that uncertainty.

It also illustrates why a non-small p-value should not be translated into proof of no difference. The reported p-value is 0.71, but the result is not an equivalence test. The confidence interval’s breadth matters: it does not isolate a narrow range around zero. Without a prespecified clinically meaningful margin, the result cannot be used to conclude that any possible difference is too small to matter.

The study asks a biological question using a physiological endpoint. Flow-mediated dilation offers a way to study endothelial function, but it is distinct from clinical outcomes. This distinction is central to interpreting the scope of a result: a measured change in a vascular response does not itself establish a change in cardiovascular events or long-term kidney outcomes.

The record also demonstrates the value of transparent analysis reporting. The endpoint and test are identified, but the analysis population, missing-data handling, multiplicity approach, and detailed analysis plan are not reported in the registry record. Those details help readers understand exactly which comparison the estimate represents and how robust the inference may be. The listed arm sizes and adverse-event risk groups also differ in presentation, with no explanation in the record.

Finally, the planning illustrations must be distinguished from the original design and from observed power. They are described as calculations based on the observed effect under stated assumptions, not as the trial’s own design justification. This distinction prevents retrospective planning exercises from being mistaken for evidence that the study was prospectively sized for a particular effect.

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 registry record contains limited information about the population beyond chronic kidney disease and the title’s description of early CKD. Eligibility criteria, baseline participant characteristics, disease severity, and other details that could clarify the population are not reported in the registry record. This limits assessment of how closely the study population matches other clinical settings.

There is also incomplete information about the conduct of treatment and measurement. The record identifies niacin and an active placebo but does not report the dose, treatment schedule, adherence, or further details about the placebo. Although the study is described as triple-masked, the people masked and the procedures used to maintain masking are not reported in the registry record.

The primary endpoint is described as flow-mediated dilation by brachial artery reactivity, but the registry does not provide additional measurement procedures, assessor details, or quality-control information. The baseline group values and participant-level outcome data are also not reported. As a result, readers cannot examine the distribution of changes, influential observations, or measurement variability directly.

The arm summaries report n=15 for niacin and n=13 for placebo, while the adverse-event summaries report 15 at risk in each group. The registry record does not explain the difference between these figures. It also does not report the primary analysis population, missing-data strategy, or reasons for any unavailable endpoint values. These omissions make it difficult to assess whether the posted comparison represents all randomized participants or another analysis set.

Finally, the registry reports the primary t-test but does not provide a full statistical analysis plan, multiplicity strategy, or details of interim analyses. The numerical result for the listed HDL-C secondary outcome is not reported in the registry record. The study’s relatively limited posted information therefore supports interpretation of the reported primary comparison, but not a complete reconstruction of trial conduct or a broad assessment of all planned outcomes.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Niacin and Endothelial Function in Early CKD — NCT00852969.
• Registry record last updated 2014-05-06; status last verified 2014-04.
• Results first posted 2014-05-06.
• 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

This completed phase 4 study is titled “Niacin and Endothelial Function in Early CKD.” It was randomized, triple-masked, and parallel-group, with Tufts Medical Center listed as sponsor. The registry records enrollment of 30, a start date of 2008-08, and primary completion in 2012-04.

The primary outcome was change in flow-mediated dilation from baseline at 14 weeks since baseline, measured by brachial artery reactivity and reported as absolute percent change. The niacin arm mean was 3.07, and the placebo arm mean was 1.37. The reported net mean difference was -1.69, with a 95% confidence interval from -10.79 to 7.41 and p = 0.71 from a two-sided t-test.

Change in HDL-C was listed as a secondary outcome, but its numerical result is not reported in the registry record. Serious adverse events were recorded as zero in each group; other adverse-event counts were 10 in the niacin group and 5 in the placebo group. The record does not report a detailed analysis plan, analysis population, or missing-data strategy.