Evaluation of Atorvastatin on Atherosclerosis Composition: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of Atorvastatin on Atherosclerosis Composition (NCT00576576), a na na study. The primary outcome is Change in Necrotic Core Volume.

2. Clinical Question

The study’s stated purpose was to evaluate the effects of atorvastatin on coronary atherosclerosis plaque morphology. Its primary endpoint was change in necrotic core volume, measured in mm^2 using Virtual Histology-Intravascular Ultrasound (VH-IVUS). The registry description says that necrotic core cross-sectional area was measured in each VH-IVUS frame and averaged over the length of the studied vessel. Change was defined as the follow-up value minus the baseline value.

This question is about change within a treated group, not a contrast between treatment and control. Without a separate comparator, a change over time cannot by itself distinguish a treatment-associated change from changes that might also occur without the intervention. The registry record does not report a numerical primary outcome estimate, its variability, or a statistical test result. It also does not report the number of participants with complete primary outcome data. Therefore, the clinical question can be described from the registered design and endpoint, but the magnitude and precision of the observed change cannot be assessed from the registry record.

3. Trial Design

The study, titled “Evaluation of Atorvastatin on Atherosclerosis Composition,” was sponsored by Emory University and is listed as completed. Its start is recorded as 2007-07, and its primary completion as 2010-03. Enrollment was 27. The condition listed is atherosclerosis, and the official title specifies patients with moderate coronary disease.

The registry describes a single-group model with atorvastatin as the intervention. All patients in the arm are described as receiving atorvastatin therapy. Allocation is listed as NA, and masking is listed as NONE. The record therefore does not describe a randomized, masked comparison or a separate control arm. Its own note cautions that the arms are not a like-for-like control comparison. The phase is listed as NA.

The primary outcome is change in necrotic core volume, with a timeframe of 6 months. The endpoint description defines the change as the follow-up measurement minus the baseline measurement. The primary population is described as all enrolled patients with a complete data set. Change in atheroma volume and change in fibrous plaque volume are also listed as secondary outcomes, but their numerical results are not reported in the registry record.

Although enrollment is recorded as 27, the number contributing complete data to the primary endpoint is not reported in the registry record. The record also does not report the treatment regimen, the frequency or timing of study visits beyond the primary outcome timeframe, eligibility details, or the statistical plan. These omissions limit how fully the design and conduct can be reconstructed from the registration information alone.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All enrolled patients with complete data set

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 in Necrotic Core Volume, measured over 6 months.

The primary endpoint is change in necrotic core volume, expressed in mm^2, at 6 months. The registry’s operational description uses VH-IVUS to measure necrotic core cross-sectional area in each imaging frame, then averages these measurements over the length of the studied vessel. The change is calculated by subtracting the baseline value from the follow-up value. A positive change would therefore mean that the follow-up measurement was larger than baseline, while a negative change would mean it was smaller; this is a general interpretation of the stated subtraction direction, not a reported study result.

In general, a continuous endpoint retains the magnitude of measured change rather than reducing it to a yes-or-no category. Reporting its mean can describe the average direction and size of change across the analysis population, while a measure of dispersion can show how variable individual changes are around that average. The registry specifies the mean and standard deviation as the summary measures for this endpoint.

Necrotic core volume is used in this study as a measure of plaque morphology. The registry record does not report the numerical mean change, its standard deviation, a confidence interval, or an analysis result. It also does not give a numerical baseline or follow-up value. Consequently, the endpoint’s definition is available, but the observed magnitude and precision are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the mean summarize?

The registry specifies the mean as the summary parameter for the primary continuous outcome. The outcome is a participant-level change: the follow-up necrotic core measurement minus the baseline measurement. In general, the mean of such changes describes the average observed change in the analysis population. It does not show whether every participant changed in the same direction, and it can be influenced by unusually large or small observations.

The registry also specifies the standard deviation as the dispersion measure. In general, the standard deviation describes how spread out the observed changes are around their mean. It is not the same as the uncertainty in the estimated mean. A confidence interval for the mean would address estimation uncertainty, but a confidence interval is not reported in the registry record.

How is the imaging endpoint defined?

The registry describes VH-IVUS measurements of necrotic core cross-sectional area in each imaging frame, averaged over the length of the studied vessel. The resulting baseline and follow-up measurements are used to calculate change by subtracting baseline from follow-up. This direction matters when interpreting the sign of a change: positive and negative values correspond to opposite directions of change under the registered definition. The registry does not report the numerical measurements or a numerical change estimate.

In general, any measurement-based endpoint depends on how consistently the measurement is obtained and processed. The registry record does not report details about image-reading procedures, reader masking, reproducibility, or quality-control procedures. These details should not be assumed from the endpoint description alone.

What can a single-group analysis estimate?

The study is listed as a single-group model, with all patients in the arm receiving atorvastatin. Allocation is NA, masking is NONE, and no separate comparator is described. In general, a single-group analysis can estimate the observed average change within the group. It cannot, without a comparator or additional assumptions, isolate the effect of the intervention from other changes over time. The registry record does not report an adjusted comparison or a control-group estimate.

The outcome population is described as all enrolled patients with a complete data set. Enrollment is 27, but the number included in the primary analysis is not reported in the registry record. The registry also does not report whether the analysis used all available measurements, how incomplete data were handled, or whether any participants were excluded from the endpoint analysis.

What do the analysis and planning details establish?

The registry lists zero analyses. A numerical primary outcome estimate, standard deviation, confidence interval, and p-value are not reported in the registry record. Without these quantities, statistical significance and estimation precision cannot be assessed. This absence does not establish that no analyses were performed; it means their results are not reported in the registry record.

The record describes a sample-size planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. Such calculations are planning illustrations rather than observed trial results, and they are not observed power. The record does not supply numerical planning results. It also does not report the trial’s own sample-size justification or design assumptions. The illustration’s two-arm assumptions do not change the registered study’s single-group design, and should not be mistaken for evidence that a randomized comparison took place.

In general, statistical interpretation of a continuous endpoint benefits from an estimate, a measure of dispersion, and an uncertainty interval, alongside a clear account of who was analyzed. Here, the endpoint definition and intended summary measures are available, but the numerical outcome and analysis details needed to assess those elements are not reported in the registry record.

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("Atorvastatin")
n   <- c(20)
m   <- c(0.07)
sp  <- c(0.06)
sd  <- sp      # posted standard deviations
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  Atorvastatin  20  0.070  0.060  0.042  0.098

11. Multiplicity, Missing Data and Analysis Populations

Change in necrotic core volume is identified as the primary outcome. Change in atheroma volume and change in fibrous plaque volume are listed as secondary outcomes. The registry record does not report a multiplicity adjustment, a hierarchy for testing outcomes, or a plan for interpreting several statistical tests together. It also does not report numerical results for the listed secondary outcomes.

In general, when several outcomes or statistical tests are considered, the chance of at least one apparently notable result can increase if no plan accounts for the number of comparisons. Whether and how that issue was handled in this study is not reported in the registry record. The record lists zero analyses, so it does not provide test-specific results that could be assessed for multiplicity.

The primary population is described as all enrolled patients with a complete data set. Enrollment was 27, but the number with complete data is not reported in the registry record. Missing-data rules, reasons for missing measurements, and any imputation or sensitivity analyses are also not reported in the registry record. In general, complete-case analysis uses participants with the measurements needed for an endpoint; if completeness is related to participant characteristics or outcome values, the analyzed group may not represent everyone enrolled. Whether this concern applies cannot be determined from the registration information.

The registry record does not report a protocol-based analysis population, an intention-to-treat approach, exclusions from analysis, or interim analyses. Those procedures should not be inferred from the study status or the listed enrollment. The available information identifies the intended complete-data population but does not establish how many participants contributed to each outcome or how incomplete observations affected the analyses.

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 adverse-event summary lists 27 participants at risk for serious adverse events and 0 affected. For other adverse events, it likewise lists 27 at risk and 0 affected. The serious-event terms list is empty. Deaths are not reported in the registry record.

These are counts in the registry summary, not a comparison of event rates between treatment and control groups. The study has a single atorvastatin group and no separate comparator arm described. The counts therefore cannot establish whether the frequency of events differed from what would have occurred without treatment. They also do not quantify risk beyond the reported participants and study record.

In general, a zero count means that no affected participants are recorded in that summary; it does not prove that an event is impossible or that there is no risk. Interpretation also depends on the completeness and duration of safety observation and on how events were collected. Those details are not reported in the registry record. The listed counts should therefore be read as the registry’s reported safety figures, with the stated limitations, rather than as evidence of comparative safety.

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

The registry record establishes that this completed study enrolled 27 participants in a single group receiving atorvastatin and focused on plaque morphology in patients with moderate coronary disease. It defines a primary endpoint based on VH-IVUS measurement of necrotic core cross-sectional area, averaged along the studied vessel, with change calculated from baseline to follow-up at 6 months. It also identifies change in atheroma volume and fibrous plaque volume as secondary outcomes.

What the record does not establish is the observed size or direction of the primary endpoint change. The numerical mean, standard deviation, confidence interval, and p-value are not reported in the registry record. The number of participants with complete outcome data is also not reported. The secondary outcome results are not reported either. As a result, the magnitude and precision of any observed change cannot be judged from this information.

Even if a within-group change were available, the design would not provide a direct treatment-versus-control contrast. In general, observed change during follow-up may reflect treatment as well as other influences that change over time. A single-group result is therefore distinct from a randomized estimate of the treatment effect.

The safety summary records zero affected participants among 27 at risk for both serious and other adverse events, while deaths are not reported. These figures should be understood as the registry’s counts, not as proof of no risk or as a comparison with another treatment group.

The appropriate statistical reading is consequently bounded: the registration provides a defined research question, intervention, endpoint, and broad study structure, but does not report numerical outcome analyses sufficient to quantify change or its uncertainty. No conclusion about the size, precision, or comparative effect of treatment can be drawn from the registry record alone.

14. Why This Trial Matters Statistically

This study is statistically notable for the distinction between measuring change and estimating a treatment effect. Its primary endpoint is explicitly a change from baseline to follow-up, which can describe what happened within the enrolled group. Because the registry describes a single-group study with no separate comparator, that within-group change is not the same estimand as a contrast between treated and untreated participants.

The endpoint also illustrates why a clear measurement definition matters. The registry identifies the imaging method, the vessel-level averaging approach, the unit, and the subtraction direction. Those details make the intended outcome interpretable. At the same time, the numerical result, dispersion, and uncertainty are not reported in the registry record, so the defined measure cannot be evaluated quantitatively.

The distinction between enrollment and analysis population is also important. Enrollment was 27, while the primary population is described as participants with complete data. The number meeting that description is not reported in the registry record. For a change endpoint that requires baseline and follow-up measurements, knowing how many observations contribute is essential to assess the basis of the estimate.

Finally, the record lists secondary outcomes and safety counts but does not report outcome analyses or a multiplicity plan. This highlights a general statistical principle: outcome definitions and descriptive counts are not substitutes for estimates with uncertainty and a transparent account of analysis choices. The record offers useful design and measurement context, while leaving those result-level details unreported.

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 main limitation for statistical interpretation is that numerical results for the primary endpoint are not reported in the registry record. The mean change and standard deviation specified for the outcome are unavailable, as are a confidence interval and p-value. There is therefore no estimate whose direction, magnitude, or precision can be assessed.

The single-group design has no separate comparator described. A within-group change, even if reported, would not by itself isolate the effect of atorvastatin from other influences on measurements over time. The registry lists allocation as NA and masking as NONE; it does not describe randomization or a masked comparison.

Enrollment was 27, but the number of participants with a complete data set is not reported in the registry record. The record does not describe missing-data handling, exclusions, participant flow, or analysis populations beyond the complete-data description. These omissions prevent assessment of how missing measurements may have affected the primary endpoint estimate.

Secondary outcomes are named, but their numerical results are not reported. A multiplicity approach, detailed statistical analysis plan, and interim analyses are not reported in the registry record. The record also does not give details of imaging reproducibility or quality control, treatment regimen, eligibility criteria, or the duration and methods of safety observation. These are specific gaps in the information available for assessing this study; they should not be filled by assumptions about standard practice.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Evaluation of Atorvastatin on Atherosclerosis Composition — NCT00576576.
• Registry record last updated 2013-12-24; status last verified 2013-11.
• Results first posted 2013-10-18.
• 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

NCT00576576 is a completed Emory University study titled “Evaluation of Atorvastatin on Atherosclerosis Composition.” The record lists 27 enrolled participants, a single-group model, atorvastatin therapy, allocation NA, and masking NONE. The primary outcome is change in necrotic core volume, measured with VH-IVUS and defined as follow-up minus baseline at 6 months. The primary population is described as enrolled patients with a complete data set.

Change in atheroma volume and change in fibrous plaque volume are listed as secondary outcomes. Numerical outcome analyses are not reported in the registry record. The safety summary lists 0 affected among 27 at risk for serious adverse events and 0 affected among 27 at risk for other adverse events; deaths are not reported. The study record supplies design and endpoint definitions but not the numerical outcome estimates needed to assess the magnitude or precision of change.