Endothelial Hyperpolarization in Humans: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Endothelial Hyperpolarization in Humans (NCT00166166), a non-randomized phase 2 study. The primary outcome is Percent Change in Forearm Blood Flow (FBF) After Tetraethylammonium (TEA) Administration.

2. Clinical Question

3. Trial Design

The registry classifies this as a phase 2 study with non-randomized allocation, no masking and a single-group model. It lists two described groups, Healthy Controls and Risk Factors. The latter is described as non-hypertensive subjects with cardiovascular risk factors. Because allocation is recorded as non-randomized, the group labels do not establish a randomized comparison, and differences between groups could reflect characteristics other than the procedures or agents studied.

Enrollment was 174. The primary endpoint was assessed in only 62 subjects from the original enrollment. The registry record does not explain why this subset was treated for that portion, how participants were selected for it, or how the enrolled participants were distributed across the primary endpoint analysis. Those details are important when judging how representative the endpoint population may be.

The described procedure used venous occlusion plethysmography after intra-arterial infusions of saline and several agents, including TEA. The primary endpoint concerns FBF after TEA. The record also lists secondary measures involving FBF responses to other agents and changes in tissue plasminogen activator (t-PA) release. These descriptions identify measurements of interest, but do not establish which comparisons were formally planned or how they were analyzed.

The study is recorded as terminated. The reason for termination, the timing and circumstances of that decision, and whether it affected data collection or analysis are not reported in the registry record. The record does not report a statistical analysis plan, protocol details, or a sample-size justification for the study itself.

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: Only 62 of the original 174 subjects were treated for this portion of the 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.

Population: Baseline characteristics represent subjects that completed the study.

6. Primary Endpoint

The registry lists the primary outcome as Percent Change in Forearm Blood Flow (FBF) After Tetraethylammonium (TEA) Administration, measured over Baseline, 5 minutes.

The primary endpoint is percent change in forearm blood flow after tetraethylammonium (TEA) administration. The registry describes FBF measurements taken at baseline and after TEA, with the timeframe listed as baseline and 5 minutes. Measurements were obtained in both arms using a dual-channel venous occlusion strain gauge plethysmograph. Flow was recorded for approximately 7 seconds, every 15 seconds up to eight times, and a mean FBF value was computed. The endpoint is defined as the difference from baseline FBF after TEA administration, expressed as a percent change.

As a general statistical concept, a continuous endpoint such as FBF can describe the magnitude and direction of a physiological response rather than reducing it to a yes-or-no event. Repeated readings can help characterize a measurement, while a mean can provide a concise summary of those readings. The registry specifies the endpoint’s measurement procedure, but does not report the resulting mean, its standard error, or an estimated effect with a confidence interval. It therefore does not establish how large or precise the observed response was.

The registry identifies the endpoint’s dispersion as a standard error. A standard error describes the precision of an estimated mean, not the spread of individual participants’ measurements. The endpoint population was 62 subjects from the original 174, so the stated population for this measure is narrower than total enrollment.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical interpretation is limited by the distinction between a measurement description and a reported analysis. The registry gives a definition of the primary endpoint and describes how FBF was measured, but lists zero analyses. A planned or described endpoint is not itself a result: without an estimate, its uncertainty, or a test result, the magnitude and precision of the response cannot be assessed.

What does the endpoint estimate represent?

The primary outcome is a mean-based continuous measure: percent change in FBF after TEA relative to baseline. The record identifies the dispersion measure as a standard error. As a general concept, the mean summarizes the central value of a set of measurements, while the standard error describes uncertainty in an estimated mean. It is not the same as the standard deviation, which describes variation among individual observations. The registry record does not report either numerical summary for this endpoint.

The measurement description says FBF was recorded in both arms and that a mean FBF value was computed from repeated readings. It does not explain how measurements from the two arms were incorporated into the endpoint estimate, whether the endpoint was calculated separately for each arm, or how dependence between measurements was handled. Those details are not reported in the registry record. They matter because observations from the same participant are generally not independent; a statistical analysis should account for such structure when estimating uncertainty.

What would a confidence interval add?

As a general statistical concept, a confidence interval communicates uncertainty around an estimated effect. Its width reflects precision under the assumptions of the analysis; it does not tell whether an effect is clinically important, and it does not eliminate potential bias in the design or data collection. The registry record does not report a confidence interval for the primary endpoint, and it does not report a p-value or another test result. No conclusion about statistical significance or precision can be drawn from the endpoint description alone.

Continuous outcomes are often analyzed with methods that model an average response. The choice of method depends on the design, measurement distribution, repeated-measures structure and intended comparison. The registry record does not report which model or test was used, whether assumptions were checked, or whether analyses were adjusted for participant characteristics. These methods therefore cannot be attributed to the study.

How should the groups be understood?

The record labels groups Healthy Controls and Risk Factors, while classifying the study as non-randomized and single-group. The allocation label is important: it means the group descriptions should not be read as randomized treatment arms. As a general concept, randomization can help balance measured and unmeasured baseline characteristics, whereas non-randomized groups may differ for reasons related to how participants entered them. The record does not report a method for controlling such differences or a formal between-group estimate.

The intervention descriptions list intra-arterial infusions of saline, L-NMMA, TEA, fluconazole, bradykinin, sodium nitroprusside and acetylcholine. The record does not report the order of administration, washout procedures, dose details, or whether the order was standardized or randomized. Those procedural details can affect interpretation of repeated physiological measurements, but they are not reported in the registry record.

What does the planning illustration mean?

The sample-size assumptions describe an illustration computed from an observed effect, not the trial’s own design. They specify 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 calculations use a total number of events. The record does not report numerical sample-size estimates in the information available for this analysis.

As a general concept, a sample-size calculation estimates how many observations would be needed to detect a specified effect under stated assumptions. Its output depends on the assumed effect, variability, allocation and statistical threshold. A planning calculation based on an observed effect is not the same as a prespecified design justification, and it is not observed power. Observed power is not a substitute for examining an effect estimate and its confidence interval. The registry record does not report a prospective sample-size justification or enough outcome information to evaluate such assumptions independently.

The record does not report how missing measurements were handled, whether participants were excluded from any endpoint analysis, or whether the analysis followed an intention-to-treat or other defined population. It also does not report diagnostics, sensitivity analyses, or adjustment for multiple endpoints. These omissions prevent a fuller assessment of the statistical methods.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Healthy Controls", "Risk Factors")
n   <- c(37, 25)
m   <- c(-18, -24)
sp  <- c(16, 13)
sd  <- sp * sqrt(n)      # standard errors converted to SDs
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Healthy Controls  37  -18.000  97.324  -50.450  14.450
CARM  Risk Factors  25  -24.000  65.000  -50.831  2.831

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 11 outcome measures, including the primary FBF endpoint, several secondary FBF measures after different agents or combinations, a sodium nitroprusside FBF measure, and measures of t-PA release. It lists zero analyses. The registry record does not report which outcomes were analyzed, which comparisons were primary to the statistical plan, or whether any multiplicity adjustment was used.

As a general statistical concept, testing multiple outcomes or comparisons can increase the chance of at least one apparently unusual result arising by chance. Prespecifying a primary outcome and an analysis plan helps distinguish confirmatory questions from exploratory ones. Methods that adjust for multiple testing can address some of this issue, but the choice depends on the questions and analysis structure. No such plan or adjustment is reported in the registry record, so the status of the listed outcomes as confirmatory or exploratory is unclear.

The registry identifies 62 subjects as treated for the primary endpoint portion, compared with total enrollment of 174. It does not report how many had complete primary endpoint data, the reasons for any missing measurements, or how missingness was handled. The analysis population and exclusions are not reported in the registry record. As a general concept, missing data can affect both the precision and the validity of an estimate, particularly if the chance of a missing measurement is related to participant characteristics or response.

The record does not report an intention-to-treat population, a per-protocol population, or another prespecified analysis population. It also does not report sensitivity analyses examining alternative assumptions about missing data. These gaps limit the ability to judge how robust any endpoint analysis might be; in this case, outcome estimates themselves 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.

The registry lists serious adverse event figures separately for Healthy Controls and Risk Factors. For Healthy Controls, 103 participants are listed as at risk for serious events and zero as affected. For Risk Factors, 71 are listed as at risk and zero as affected. The figures for other events likewise list 103 and 71 at risk, respectively, with zero affected in each group. These are registry-recorded counts, not evidence that every possible event was assessed or reported in the same way.

The deaths field is null for both groups. A null entry is not a numerical count and should not be interpreted as zero deaths; deaths are not reported in the registry record. No serious event terms are listed among the top serious terms.

As a general statistical concept, an adverse-event count needs context, including the duration and completeness of follow-up, how events were defined and collected, and the number of participants observed. The record does not report those details here, nor does it provide comparative safety analyses. The at-risk figures should not be used to infer the reason for termination, and the zero affected entries do not establish that no adverse events occurred outside the reported registry fields.

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

The record describes a physiological study intended to investigate EDHF’s role in blood-vessel dilation, possible differences between healthy people and people with high cholesterol, and the identity of EDHF. It documents a primary endpoint based on percent change in FBF after TEA, along with multiple secondary outcome measures. These details establish the questions and measurements recorded in the registry, but they do not establish the study’s findings.

The primary endpoint result is not reported in the registry record. The record lists zero analyses, so there is no reported estimate or uncertainty measure to interpret. It is not possible to describe whether FBF increased or decreased after TEA, how large any change was, or how precisely it was estimated. No conclusion about the study’s scientific questions follows from the endpoint name or measurement procedure alone.

The study’s design also limits what group comparisons could establish. The record classifies allocation as non-randomized and the model as single-group, despite describing Healthy Controls and Risk Factors groups. Any observed group difference, if one were reported, could not be assumed to result from the group distinction itself. The registry record does not report a formal comparative analysis or adjustment strategy.

As a general principle, a physiological response measured under a study procedure is not automatically evidence about a clinical outcome. The record does not list a clinical endpoint or report results linking the measured FBF response to patient benefit or harm. It therefore cannot support a claim about clinical effectiveness.

The study status is terminated, but the reason is not reported in the registry record. Termination alone does not reveal whether it was related to recruitment, feasibility, safety, administrative circumstances, or any other cause. The posted information supports a description of the study’s stated aims, design labels, endpoint procedures and recorded adverse-event counts. It does not support a conclusion about the primary result or the reason the study ended.

14. Why This Trial Matters Statistically

This study is statistically notable for the gap between a detailed physiological measurement description and the absence of reported outcome analyses. The registry specifies how FBF was measured and defines a primary endpoint, yet lists zero analyses. That distinction is important: knowing what a study intended to measure does not reveal what the data showed, how uncertain an estimate was, or whether a result was consistent across participants.

The relationship between total enrollment and the primary endpoint population is also relevant. The record reports enrollment of 174, while stating that only 62 subjects were treated for the primary endpoint portion. It does not explain how that subset was selected or how many measurements contributed to an analysis. Statistical precision and generalizability depend not only on the enrolled count but also on which observations are available for each outcome and how participants enter the analysis.

The record’s design classifications should guide interpretation of its group labels. Non-randomized allocation and a single-group model do not support treating Healthy Controls and Risk Factors as randomized comparison arms. This is a useful reminder that labels such as “control” do not by themselves establish the properties of a randomized controlled trial.

Finally, the planning assumptions should be kept distinct from the actual design. An illustrative calculation based on an observed effect is not a prospective sample-size justification and cannot replace reported estimates and uncertainty. The statistical importance of this record lies in identifying what is documented and where the inferential gaps remain, rather than in estimating an effect that is not reported.

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 most direct limitation is that the registry record lists zero analyses and does not report the primary endpoint result. Without an estimate and measure of uncertainty, the magnitude, direction and precision of the FBF response after TEA cannot be evaluated. The same limitation applies to the listed secondary outcomes.

The primary endpoint applies to only 62 of the original 174 subjects. The record does not explain why this subset was treated for the endpoint, how it was selected, how many participants had usable measurements, or whether inclusion differed by group. This makes it difficult to assess selection effects or how well the endpoint population represents the enrolled participants.

The study is classified as non-randomized and single-group, although it describes Healthy Controls and Risk Factors groups. The registry record does not report a formal group comparison, an adjustment method, or sufficient details to determine how group characteristics were addressed. The risk-factor group is described as non-hypertensive subjects with cardiovascular risk factors; it should not be assumed to represent only people with high cholesterol.

Other relevant information is not reported in the registry record: the reason for termination, a statistical analysis plan, a prospective sample-size justification, handling of missing data, the defined analysis populations, multiplicity procedures, and details such as dosing and infusion order. The adverse-event fields record zero affected participants but do not report deaths as a numerical value, follow-up duration, or the completeness of event ascertainment. Together, these limits constrain both efficacy-oriented and safety-oriented interpretation.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Endothelial Hyperpolarization in Humans — NCT00166166.
• Registry record last updated 2018-08-15; status last verified 2018-07.
• Results first posted 2015-05-13.
• 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

The registry record describes a phase 2, non-randomized study with no masking and a single-group model, enrolled 174 participants, and records the study as terminated. Its stated aims concern EDHF, blood-vessel dilation, differences between healthy people and those with high cholesterol, and the identity of EDHF. Described groups are Healthy Controls and non-hypertensive subjects with cardiovascular risk factors.

The primary endpoint is percent change in FBF after TEA, measured from baseline to 5 minutes. The record states that 62 of the original 174 subjects were treated for this portion. It lists 11 outcome measures and zero analyses; the primary result and reason for termination are not reported in the registry record. Serious and other adverse-event fields list zero affected participants in both groups, while deaths are not reported as a numerical value.