This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for The Effect of Atorvastatin on Endothelial Cell Dysfunction in Chronic Kidney Disease (NCT02133534), a na phase 4 study. The primary outcome is Improved Counts of Endothelial Progenitor Cells.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02133534 |
| Phase | Phase 4 |
| Condition | Chronic Kidney Disease, High Cholesterol |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 1 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Duke University |
| Results posted | Yes |
2. Clinical Question
Population
The intended population was people with chronic kidney disease and high cholesterol. The registry record describes the study as examining endothelial cell function in chronic kidney disease. It does not report detailed eligibility criteria or characteristics of the participant beyond the study’s stated conditions.
Intervention
The planned intervention was atorvastatin, described as 10 mg/day for 30 days. The study description says the investigators intended to assess cholesterol and endothelial-cell-related measures before and after treatment. Because the trial terminated early and the record says the data could not be analyzed, the registry does not establish what changes occurred.
Comparator
The registered design was single-group, with allocation listed as not applicable and no masking. It does not describe a separate control group or a randomized comparison. The relevant intended contrast was therefore within the participant, comparing baseline assessments with assessments after 30 days, rather than a comparison between treatment groups.
Primary question
The primary endpoint was improvement in counts of endothelial progenitor cells, assessed at baseline and 30 days. The study asked whether those counts would indicate improvement in endothelial-cell dysfunction during atorvastatin treatment. The registry record reports insufficient accrual and says that data from the one participant could not be analyzed, so it does not answer that question with an outcome estimate.
3. Trial Design
This was a Phase 4, single-group study of atorvastatin in chronic kidney disease and high cholesterol. Duke University is listed as the sponsor. The registry gives an enrollment of one participant and identifies the study status as terminated. Its recorded start is 2008-02 and its primary completion is 2009-05. The record attributes early termination to insufficient accrual.
The intervention description specifies atorvastatin 10 mg/day for 30 days. The planned assessments included blood and urine samples at baseline before treatment and after 30 days. The description also mentions ultrasound imaging of an arm, but the available description is truncated while explaining that procedure. The registry does not report further procedural detail in the record.
There was no randomized allocation, masking, or like-for-like control comparison recorded. The planned assessment was therefore a before-and-after observation in the same participant, not a trial contrast between atorvastatin and a concurrent control. Such a design can describe measurements at successive times, but without a control group it cannot separate a treatment-associated change from other explanations for a change.
The registry lists one primary outcome measure and no analyses. It explicitly states that, because only one participant was enrolled, the data could not be analyzed. The record does not give a statistical analysis plan, a sample-size justification, or a reason for the planned enrollment beyond the study’s stated aims. Those details 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
| Stage | Atorvastatin |
|---|---|
| STARTED | 1 |
| COMPLETED | 1 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: Early termination because of insufficient accrual. With only one study participant, data could not be analyzed.
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.
| Characteristic | Unit | Atorvastatin |
|---|---|---|
| Participants analysed | 1 | |
| Age, Customized: Greater than 18 Years | participants | 1 |
| Sex: Female, Male: Female | Participants | 1 |
| Sex: Female, Male: Male | Participants | 0 |
| Region of Enrollment: United States | participants | 1 |
6. Primary Endpoint
The registry lists the primary outcome as Improved Counts of Endothelial Progenitor Cells, measured over baseline, 30 days.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint was “Improved Counts of Endothelial Progenitor Cells.” The registry describes improvement of endothelial-cell dysfunction as being assessed by improved counts of endothelial progenitor cells, with measurement time points listed as baseline and 30 days. The endpoint is therefore a biomarker count intended to represent a change related to endothelial-cell function, rather than a reported clinical event or patient-reported measure.
The study summary explains the rationale: endothelial cells line the heart and blood vessels, and their dysfunction is considered a possible marker of cardiovascular risk. The investigators intended to examine whether treatment for high cholesterol would be accompanied by changes in cholesterol and endothelial-cell function. This describes the study’s rationale and intended assessment; it does not establish that any change occurred.
In general, a prespecified primary endpoint gives a trial a principal outcome for assessing its central research question. A before-and-after endpoint can describe change over time, but interpretation depends on having analyzable measurements and a suitable analysis. Here, the registry says that the data could not be analyzed because the study had only one participant. It provides no endpoint values, estimated change, measure of uncertainty, or statistical test. The endpoint’s planned role is clear, but its result is not available in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The decisive fact for interpretation is that the trial terminated early because of insufficient accrual. The registry reports an enrollment of one participant and says the data could not be analyzed. Consequently, there is no interpretable estimate of change in endothelial progenitor cell counts, no reported comparison of baseline with 30 days, and no statistical test for the primary endpoint. The study’s stated question remains unanswered by the posted results.
This is not a finding that the endpoint did or did not change. It is an absence of an analyzable outcome result. No effect estimate, confidence interval, or p-value is reported in the registry record. Without those results, the direction and magnitude of any observed change, and the precision with which it might be estimated, cannot be assessed.
The study was single-group and unmasked, with allocation listed as not applicable. Its planned baseline and follow-up measurements would have been observations from the same participant. In general, such measurements can document a within-person difference, but a before-and-after difference alone does not establish that the intervention caused it. Changes may have other explanations, and a concurrent control group can help address some of those alternatives. This study did not register such a comparison.
The record’s safety information also requires restraint. The atorvastatin group is listed with zero participants at risk for serious and other adverse events, and the death count is null. A zero risk denominator does not provide an evaluable safety experience and should not be read as evidence that no adverse events occurred. The registry record does not provide analyzable safety results.
Any sample-size planning illustrations should also be kept separate from observed evidence. The stated assumptions describe an illustration based on an observed effect, with equal allocation between two arms and a two-sided significance level of 0.05. Yet the registered trial was single-group, and its outcome data could not be analyzed. The record does not report a usable observed primary effect on which to base interpretation. Planning illustrations do not supply a missing treatment estimate, and they are not observed power.
9. Statistical Methods Explained
What can a single-group before-and-after design show?
In general, a before-and-after design measures the same participant at an initial time and again after an intervention. Its direct descriptive quantity is the within-participant change between those observations. The registered study listed baseline and 30 days as the primary outcome time points and planned atorvastatin treatment over 30 days. This structure could have described a change if endpoint data had been available and analyzed.
A before-and-after observation does not, by itself, identify the cause of a change. Without a concurrent control group, a difference over time may reflect the intervention, ordinary variation in the measurement, changes unrelated to treatment, or other influences. Randomized allocation and a suitable control comparison can strengthen causal interpretation by helping distinguish treatment effects from those alternatives. No randomized comparison or control group is recorded for this study.
Why does the enrollment matter for analysis?
General statistical inference depends on information about variation as well as the observed outcome. An individual’s paired measurements can be compared descriptively, but a single participant cannot provide a meaningful estimate of how much the response varies across a study population. That limits assessment of uncertainty and the ability to draw conclusions beyond that participant. In this case, the registry goes further and states directly that the data could not be analyzed because only one participant was enrolled.
The record lists one primary outcome measure and zero analyses. It does not report a numerical endpoint result, an estimated change, a standard error, a confidence interval, or a test statistic. These are not merely details omitted from a statistical summary: without an analyzed outcome, the principal treatment-related quantity cannot be interpreted from the registry record.
What would an estimate and confidence interval mean?
In general, an effect estimate gives the size and direction of a contrast, while a confidence interval describes the uncertainty around that estimate under the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval, although precision does not establish that an estimate is free of bias or that a treatment caused the observed result. Neither an estimate nor an interval for the primary outcome is reported in the registry record. No conclusion about the size, direction, or precision of an endpoint change can therefore be drawn.
What role would a statistical test play?
In general, a statistical test evaluates how compatible observed data are with a specified null hypothesis under the test’s assumptions. A p-value is not the probability that a treatment works, and it does not measure the clinical importance of an effect. It must be interpreted alongside the estimated effect, its uncertainty, study design, and analysis choices. The registry lists no analyses and reports no p-value for the primary outcome, so there is no test result to interpret.
The stated sample-size assumptions refer to a planning illustration: a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of an observed effect. Those assumptions are not a description of the registered single-group design. The registry record does not give a usable analyzed observed effect for the primary endpoint, nor does it report a trial-specific sample-size justification. Any planning estimate is distinct from observed evidence and cannot replace the absent trial result.
Why can over-dispersion matter in general?
For count outcomes, analysts may use statistical models that relate the expected count to explanatory factors. Some count models assume that variability follows a particular relationship to the mean. Over-dispersion occurs when the observed variability is greater than that assumed by the model. If it is ignored, uncertainty estimates and tests can be misleading. This is a general consideration for count outcomes, not a reported feature of this trial: the registry provides no count values, model, or analysis from which to assess dispersion.
Likewise, a paired analysis could be appropriate in general for repeated measurements on the same participant, but the specific method depends on the measurement scale, distribution, study question, and analysis plan. The registry does not report a planned or completed statistical method. It would be inappropriate to infer which method investigators intended to use.
10. Multiplicity, Missing Data and Analysis Populations
The registry identifies one primary outcome measure: improvement in endothelial progenitor cell counts, assessed at baseline and 30 days. It also describes intended assessments of cholesterol and endothelial-cell function, and planned blood, urine, and ultrasound assessments. The record does not specify which additional measurements were formal secondary outcomes or how they would be analyzed.
Multiplicity arises in general when several outcomes, time points, subgroups, or statistical tests are examined. The more analyses considered, the greater the chance that at least one result may appear notable by chance if no adjustment or prespecified hierarchy is used. A statistical plan can define which outcome is primary and how other analyses will be interpreted. No multiplicity strategy or hierarchy for additional outcomes is reported in the registry record.
The registry reports no analyses and says the data could not be analyzed because the study had only one participant. It does not report missing endpoint values, the handling of missing data, an analysis population, or any imputation procedure. These details are not reported in the registry record. The stated reason for termination is insufficient accrual; it should not be recast as a particular missing-data mechanism.
For safety, the recorded risk denominators are zero and the death count is null. These entries do not establish that the participant was assessed for adverse events or that no events occurred. The record does not describe a safety analysis population or provide an interpretable adverse-event analysis. Given the early termination and absence of outcome analyses, neither outcome multiplicity nor missing-data methods can be evaluated from the registry record.
11. What the Result Does, and Does Not, Mean
The result means that the registry does not contain an analyzable primary outcome for this study. The record describes a planned assessment of endothelial progenitor cell counts at baseline and 30 days, but reports that early termination followed insufficient accrual and that data from the one participant could not be analyzed. There is no reported estimate of change to interpret.
It does not mean that atorvastatin changed the endpoint, and it does not mean that it left the endpoint unchanged. It does not establish an effect on cholesterol, endothelial-cell function, cardiovascular risk, or any clinical outcome. The study summary describes those topics as reasons for conducting the study; it does not report results supporting a conclusion about them.
The design also limits what the intended observations could have established. A single-group before-and-after assessment lacks a concurrent control comparison, so a change would not by itself demonstrate that treatment caused it. In general, causal claims require consideration of alternative explanations and the design’s ability to rule them out. Here, the registry reports no analyzable change in the first place.
The safety entries should not be interpreted as evidence of safety or absence of adverse events. With zero participants recorded at risk and a null death count, the registry does not provide an interpretable denominator-based safety result. The record likewise does not provide evidence to quantify benefits or harms.
The appropriate conclusion is limited: the study was terminated after insufficient accrual, and its primary data could not be analyzed. The unanswered question is not resolved in either direction. This distinction matters because lack of an analyzable result is different from a precise estimate showing little or no change.
12. Why This Trial Matters Statistically
This trial illustrates how accrual and analyzability are prerequisites for statistical interpretation. A study may define a biologically motivated endpoint and plan repeated measurements, yet fail to produce an estimate if too few participants enroll. Here, the registry specifically records insufficient accrual, an enrollment of one participant, and data that could not be analyzed. The consequence is not merely a wide or uncertain treatment estimate; the record reports no analyzable primary result.
It also highlights the distinction between a planned within-person assessment and a controlled treatment comparison. Baseline and follow-up measurements can describe change over time, but the single-group design cannot by itself separate treatment-associated change from other influences. Design determines what a statistical analysis can support, regardless of the plausibility of the biological question.
The record is also a reminder that a named primary endpoint is not the same as a reported endpoint result. The outcome is clearly identified as improved counts of endothelial progenitor cells, but no counts or analysis are reported. A statistical interpretation must follow the available evidence rather than infer a result from the study’s aims.
Finally, planning calculations are not evidence that a trial’s question has been answered. Assumptions for a planning illustration cannot substitute for an observed effect, especially when the registry says that outcome data could not be analyzed. Keeping design, planned outcomes, analysis, and results distinct prevents readers from treating a study’s rationale as a finding.
13. 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 principal limitation is the stated early termination because of insufficient accrual. The registry lists an enrollment of one participant and explicitly says the data could not be analyzed. As a result, there is no interpretable estimate for the primary endpoint and no basis in the registry record for assessing its direction, size, or precision.
The registered design was single-group, with allocation not applicable and no masking. It does not include a control group or randomized comparison. Even if a before-and-after outcome had been analyzable, this design would leave alternative explanations for changes difficult to separate from treatment-related change.
The record gives limited information about eligibility criteria, participant characteristics, and the statistical analysis plan. It does not report the planned sample-size justification, the handling of missing observations, the analysis population, or a multiplicity strategy. These details are not reported in the registry record. The arm description is truncated during its account of the ultrasound procedure, limiting the available procedural detail.
Safety information is also not interpretable as an absence of harm: the recorded risk denominators are zero, while the death count is null. The record does not present analyzable adverse-event results. Together, these limitations mean the registry supports a description of study intent and early termination, not an estimate of efficacy or safety.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: The Effect of Atorvastatin on Endothelial Cell Dysfunction in Chronic Kidney Disease — NCT02133534.
- Registry record last updated 2014-07-03; status last verified 2014-06.
- Results first posted 2014-07-03.
- 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.
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17. Record Summary
NCT02133534 is a Phase 4, single-group study sponsored by Duke University, titled “The Effect of Atorvastatin on Endothelial Cell Dysfunction in Chronic Kidney Disease.” The registry lists chronic kidney disease and high cholesterol as conditions, an enrollment of one participant, and terminated status. The recorded start is 2008-02 and primary completion is 2009-05.
The planned intervention was atorvastatin 10 mg/day for 30 days. The primary outcome was improvement in endothelial progenitor cell counts, assessed at baseline and 30 days. The study description also refers to cholesterol assessment, blood and urine samples, and ultrasound imaging.
The registry attributes termination to insufficient accrual and states that the data could not be analyzed. It lists no analyses. No interpretable primary outcome estimate or safety analysis is reported in the registry record.