Endovascular Exclusion of Abdominal Aortic Aneurysms in High Risk Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Endovascular Exclusion of Abdominal Aortic Aneurysms in High Risk Patients (NCT00583414), a na na study. The primary outcome is Freedom From Aneurysm Rupture.

2. Clinical Question

Accordingly, the registered question is about the occurrence of rupture following endovascular exclusion in the studied group, not a comparison of outcomes between randomized treatment groups. Without a reported primary result or a control group, the record cannot establish a comparative effect. It also does not report additional details needed to characterize the enrolled population, such as the specific criteria used to define high risk or the distribution of aneurysm types.

3. Trial Design

The registry identifies this study as a single-group investigation of Endovascular Aneurysm Repair, a device intervention. The arm description specifies an investigational stent-graft implant intended to exclude an aneurysm. The study title refers to high-risk patients, and the listed conditions are abdominal aortic aneurysm, iliac aneurysm, and internal iliac aneurysm. The registry records enrollment of 401.

Allocation is listed as NA, masking as none, and the study model as single group. The registry record therefore does not describe a randomized allocation or a masked comparison. Its study-design note explicitly cautions that the arms are not a like-for-like control comparison. No separate control group or comparator intervention is described in the record.

The listed phase is NA. The study start is recorded as 1998-09, primary completion as 2017-10, and status as completed. These administrative details do not establish when each participant was followed or whether all participants contributed data to the primary endpoint.

The record lists one outcome measure, Freedom From Aneurysm Rupture, with a timeframe of 2 years. It also reports zero analyses. The primary outcome description gives a CT-based definition, but neither an observed count nor a statistical estimate is reported. Details of eligibility criteria, follow-up procedures, outcome adjudication, protocol deviations, and analysis populations are not reported in the registry record. The registry also does not report a sample-size justification or a statistical analysis plan. The planning assumptions described for illustrative sample-size calculations are not evidence of the study's original design or analysis plan.

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

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 Freedom From Aneurysm Rupture, measured over 2 years.

The primary endpoint is titled Freedom From Aneurysm Rupture and is measured as a count of participants. The registry defines freedom from rupture as absence of blood extravasation outside the aneurysm sac demonstrated by CT scan, with a timeframe of 2 years. This makes the endpoint a binary participant-level outcome: a participant either meets the stated freedom-from-rupture definition or does not, according to the assessment. The registry does not provide a result for this endpoint.

In general, a clearly defined clinical endpoint makes explicit what event or state is being assessed and how it is recognized. Here, the CT-based criterion specifies the evidence used to classify rupture status. A time horizon is also important because outcome status is tied to a defined period rather than an unspecified point in follow-up. However, the record does not report the details of scan timing, completeness of imaging, handling of uncertain findings, or how outcome classifications were made.

Freedom from rupture is used as the primary outcome to describe whether rupture was observed under the study's stated definition during the specified timeframe. It does not, by itself, provide a comparison with what would have happened under another intervention or without the device. The single-group design and absence of a reported primary result further limit interpretation. The registry record does not report a confidence interval, event count, or estimate of uncertainty for the primary endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

For the primary endpoint, the registry specifies a count of participants and defines the outcome as freedom from aneurysm rupture at 2 years. In general, a binary outcome classifies each participant according to whether a defined event or state occurred. Counts can describe how many participants fall into each category, while a proportion can express the count relative to an appropriate denominator. The record does not report the primary endpoint count or a proportion, so neither can be interpreted from the posted results.

What can a single-group design estimate?

In general, a single-group study can describe observed outcomes among participants who receive the intervention, provided those outcomes are measured and reported. It does not directly estimate a contrast against a concurrent control group. Without that contrast, changes or outcomes cannot be distinguished from what might have occurred due to participant characteristics, the course of disease, other care, or other influences. The registry lists a single-group model and does not describe a like-for-like control comparison. It therefore does not support a randomized comparative treatment-effect analysis.

Allocation is recorded as NA and masking as none. These entries do not establish further details about conduct or assessment. The registry record does not report whether outcome assessors were independent, whether CT scans were centrally reviewed, or what safeguards were used to limit measurement bias. Those details should not be inferred from the listed masking field.

How should uncertainty be considered?

In general, an estimate is more informative when accompanied by a measure of its uncertainty, such as a confidence interval. A confidence interval indicates a range of values compatible with the data and statistical model; it does not establish causation, eliminate bias, or resolve problems in study design. The registry record does not report an estimate or confidence interval for the primary endpoint. Its precision therefore cannot be evaluated.

For event-count outcomes, interpretation also depends on a clear denominator and complete follow-up. Participants must have an opportunity for the outcome to be assessed over the stated period, and losses or incomplete observation can affect the meaning of a count. The record does not report how follow-up was completed, how missing scans or other missing endpoint information were handled, or whether all enrolled participants were included in a primary analysis. A denominator alone would not answer these questions.

What is the role of sample-size planning?

In general, sample-size planning uses assumptions about the outcome, a target effect, variability, and a chosen statistical approach to illustrate the amount of information a future study might need. Such planning calculations are not observed outcomes and are not evidence that a study had a particular probability of detecting an effect. The planning assumptions associated with this record describe an illustrative calculation based on an observed effect, two-sided significance level 0.05, equal allocation, and a normal approximation. They do not establish the original study's design or sample-size justification. The registry record does not report the study's own sample-size rationale.

Illustrations based on a two-arm comparison are especially distinct from the recorded single-group design. They cannot be treated as an analysis of this study or as observed power. No resulting planning values are included in the registry entries described in this analysis, and no such values are needed to interpret the registry's reported outcomes.

What do the adverse-event counts represent?

The record lists serious and other adverse-event counts for the Endovascular Aneurysm Repair group, along with the number at risk for each listing. In general, an adverse-event count is meaningful only with its definition, observation period, and rules for counting participants and events. The record does not state whether the figures count participants with at least one event, individual event occurrences, or overlapping categories beyond the labels presented. It gives no timing or causal attribution. The counts should therefore be read as registry entries, not as comparative rates or proof that the intervention caused an event.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Endovascular Aneurysm Repair")
n      <- c(401)
events <- c(0)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Endovascular Aneurysm Repair  401  0  0.0  0.0  0.9  0.0  0.9  0.0  0.9

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure and reports zero analyses. It does not report a multiplicity plan, such as how multiple outcomes or statistical tests would be handled. Multiplicity is a general concern when many outcomes or comparisons are tested, because the chance of a chance finding can increase as testing expands. The record does not provide enough information to determine whether such an issue arose in the study's conduct or analysis.

Missing-data methods are not reported in the registry record. In particular, the record does not state how participants without a CT assessment at the 2-year timeframe, incomplete follow-up, or uncertain endpoint classifications were handled. It also does not report the number of participants with evaluable primary outcome data. Without those details and the endpoint count, the completeness of the primary analysis cannot be assessed.

Analysis populations are not reported in the registry record. It is therefore unclear which enrolled participants, if any, were included in an analysis of the primary endpoint, and how deviations from the intended intervention or follow-up were handled. The registry record does not report an intention-to-treat or other prespecified analysis population, and none should be assumed.

The record provides no statistical analysis plan or interim-analysis information. It also does not report whether the endpoint was adjudicated or whether analysis decisions changed over time. These omissions prevent assessment of prespecification and potential selective reporting. The completed status and the presence of adverse-event entries do not fill the gaps in primary-outcome reporting, missing-data handling, or analysis methods.

12. 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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: aneurysm growth (2.2%).

The registry lists 9 serious adverse events and 9 other adverse events for the Endovascular Aneurysm Repair group. Each listing gives 401 at risk. It separately reports 292 deaths. These are registry counts, not estimates of comparative risk: the study is recorded as single-group, and the record does not identify a like-for-like control group.

The registry also lists Aneurysm Growth among the top serious adverse-event terms, with 2.2%. The record does not state the observation period for these adverse-event figures, clarify the denominator or counting convention for the term, or describe how events were attributed. It also does not report causes of death or whether the death count overlaps with participants recorded as having adverse events. The serious and other event listings may not represent mutually exclusive groups, and the record does not explain their relationship.

In general, safety counts need context about exposure, follow-up, definitions, and attribution. Without these details, the counts do not establish why an event occurred or permit a reliable comparison with another treatment. The registry entries should be read descriptively, with these limits in mind.

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

The registry record documents a completed, single-group study of endovascular aneurysm repair using an investigational stent-graft implant. It identifies freedom from aneurysm rupture at 2 years as the primary outcome and defines the outcome using CT evidence of absence of blood extravasation outside the aneurysm sac. It also records adverse-event counts for the intervention group.

What the registry does not report is the primary outcome result. No count of participants free from rupture, count of ruptures, effect estimate, confidence interval, or analysis is recorded. Thus, the available information does not establish how participants fared on the primary endpoint or how precisely any estimate could be made. The registry's completed status is not a substitute for those results.

The study's single-group design also means that even a reported outcome count would describe the enrolled group rather than provide a randomized comparison with another course of care. In general, a single-group result cannot by itself show what would have occurred in the absence of the intervention. Other participant and care-related factors could contribute to observed outcomes, and this record does not provide a comparison that could separate them.

The adverse-event counts likewise do not establish causation or comparative safety. Their observation period, attribution, and relationship to the reported deaths are not described. The record does not report a detailed analysis population, missing-data approach, or statistical plan. Accordingly, the defensible interpretation is limited: the registry records the intervention, the study design, a CT-defined primary endpoint, and certain adverse-event entries, but does not report the primary outcome analysis needed to quantify the endpoint.

14. Why This Trial Matters Statistically

This study illustrates an important statistical distinction between describing outcomes and estimating comparative effects. A single-group study can record outcomes after an intervention, but the absence of a like-for-like control comparison limits what can be concluded about the intervention's contribution. The registry explicitly identifies the study as single group and cautions that its arms are not a like-for-like control comparison.

It also shows why a clearly specified endpoint is not the same as a reported result. The primary outcome has a stated timeframe and a CT-based definition, which make the intended measure more interpretable. Yet the registry provides no observed endpoint count or analysis. Without those, neither the outcome level nor its statistical precision can be assessed.

The record is also a reminder that study completion and outcome reporting are separate matters. A completed status does not provide missing estimates, explain missing follow-up, or reveal the analysis population. Likewise, adverse-event counts need context such as observation time and attribution before they can support safety comparisons.

These distinctions matter when readers assess clinical evidence. Statistical interpretation depends not only on the question and endpoint, but also on the design, reported data, analysis, and uncertainty. In this record, the design and endpoint are identifiable, while the primary result and key analytical details are not reported. That makes the study's registered objective clear, but leaves its primary outcome evidence unquantified in the registry record.

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 primary limitation for interpretation is that the registry does not report the primary endpoint result or any analysis. The stated outcome is freedom from aneurysm rupture at 2 years, but there is no outcome count, estimate, or measure of uncertainty. The record reports zero analyses, so the primary endpoint cannot be quantitatively assessed from this record.

The single-group model and lack of a like-for-like control comparison limit causal and comparative interpretation. Allocation is listed as NA and masking as none. The registry does not describe a control group, blinded endpoint assessment, or further procedures for reducing measurement bias. The record also does not report detailed eligibility criteria or the characteristics of participants enrolled for the primary endpoint, despite the study title's reference to high-risk patients.

Important analysis details are not reported in the registry record, including sample-size justification, statistical plan, interim analyses, analysis populations, and missing-data handling. Follow-up completeness and the handling of missing or uncertain CT assessments are also not described. These gaps prevent evaluation of whether the primary outcome was measured and analyzed consistently across participants.

For safety, the registry reports adverse-event counts but does not give their observation period, attribution, or relationship to deaths. It does not clarify all counting conventions or whether event categories overlap. These limitations apply to interpretation of the registry entries; they do not establish what occurred beyond what the record states.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Endovascular Exclusion of Abdominal Aortic Aneurysms in High Risk Patients — NCT00583414.
• Registry record last updated 2019-01-25; status last verified 2019-01.
• Results first posted 2019-01-25.
• 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 identifies NCT00583414, Endovascular Exclusion of Abdominal Aortic Aneurysms in High Risk Patients, as a completed, single-group device study sponsored by The Cleveland Clinic. Enrollment is recorded as 401. The intervention is Endovascular Aneurysm Repair using an investigational stent-graft implant to exclude an aneurysm. The listed conditions are abdominal aortic aneurysm, iliac aneurysm, and internal iliac aneurysm.

The primary outcome is Freedom From Aneurysm Rupture at 2 years, defined as absence of blood extravasation outside the aneurysm sac demonstrated by CT scan. The registry lists one outcome measure and zero analyses, and does not report the primary outcome result. It records 9 serious adverse events, 9 other adverse events, 292 deaths, and Aneurysm Growth at 2.2% among the top serious adverse-event terms. Follow-up and attribution details for these entries are not reported in the registry record.