Zenith® Low Profile AAA Endovascular Graft: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Zenith® Low Profile AAA Endovascular Graft (NCT02535065), a na na study. The primary outcome is Number of Patients Without Major Adverse Events Within 30 Days.

2. Clinical Question

3. Trial Design

This was a single-group clinical study of the Zenith Low Profile AAA Endovascular Graft and ancillary components. The registry describes the device as being used in conjunction with the Zenith Spiral-Z AAA Iliac Leg Graft for abdominal aortic, aortoiliac, and iliac aneurysms. The study is identified as a device study, with 62 participants enrolled.

The listed design has no comparator arm: the model is single group, allocation is recorded as NA, and masking is listed as none. These features matter when interpreting results. Without a concurrent comparison group, observed events can be described for the enrolled group, but cannot by themselves show how those events compare with another treatment or with what would have happened without the device. The registry itself cautions that the arms are not a like-for-like control comparison; no comparison arm is described in the record.

The study is marked completed. Its recorded start is 2014-08 and its primary completion date is 2017-01-23. The sponsor is Cook Research Incorporated. The phase is listed as NA. The registry identifies 2 outcome measures, but lists 0 analyses. The primary outcome measure concerns the number of participants without major adverse events within 30 days; the result for that measure is not reported in the registry record.

Other design details that could clarify how participants were assessed or how the study was conducted are not reported in the registry record. In particular, the record does not describe a comparator, masking procedures beyond the listed value, or the analysis population used for the primary outcome. The design should therefore be read as a registry-listed single-group evaluation, rather than as a randomized trial establishing a comparative treatment effect.

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:

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 Number of Patients Without Major Adverse Events Within 30 Days, measured over 30 days.

The primary endpoint is the number of participants without major adverse events within 30 days. It is a participant count, not a measure of how severe an event was or how long participants remained event-free. The registry’s definition of major adverse events includes all-cause death, Q-wave MI, renal failure requiring dialysis, paralysis, stroke, bowel ischemia, and re-intubation.

A composite endpoint combines several kinds of events into one outcome. In general, this can capture a range of clinically important events in a single summary, but it also means that the overall count does not reveal which event types account for the result. Separate component results are needed to understand the contribution of each event type. The registry record does not report the primary endpoint count or component counts, so the number of participants meeting the endpoint definition cannot be described from the record.

The stated 30-day timeframe defines the period relevant to this endpoint. A result for this endpoint would need to be interpreted with its analysis denominator and handling of missing assessments in mind. Those details are not reported in the registry record. The enrollment of 62 participants does not, on its own, establish that all enrolled participants contributed evaluable endpoint data.

This endpoint is a safety-oriented summary as defined in the record. It is not a direct measure of comparative effectiveness: the study has no comparator group, and the endpoint result is not reported. The endpoint definition can be explained, but a conclusion about the observed frequency of participants without major adverse events cannot be drawn from the registry information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical interpretation begins with the question the endpoint is designed to answer and the kind of data it records. Here the primary endpoint is a count of participants without major adverse events within 30 days. It is a binary participant-level outcome in the sense that each assessed participant either meets the stated endpoint definition or does not. The registry labels the outcome as a participant count. It does not report an endpoint result, an analysis denominator, or a statistical estimate for this outcome.

What does a participant count convey?

A count conveys how many assessed participants fall into a defined category. For a count to be understood in context, readers also need to know how many participants were assessed and how missing outcome information was handled. The overall enrollment is 62, but the registry record does not state how many participants contributed data to the primary endpoint analysis. It is therefore not appropriate to treat enrollment alone as the endpoint denominator or to derive an endpoint proportion.

The endpoint is defined by the absence of any of the listed major adverse events: all-cause death, Q-wave MI, renal failure requiring dialysis, paralysis, stroke, bowel ischemia, and re-intubation. Composite outcomes can summarize multiple event types, which may be useful when the study question concerns a broad category of events. At the same time, the composite count cannot show which component occurred, how often each component occurred, or whether one component accounts for most of the overall result. The registry does not report component results for this primary endpoint.

What would an estimate and confidence interval add?

In general, an estimate describes the observed outcome in the analyzed participants, while a confidence interval gives a range of values compatible with the data under the chosen method and assumptions. A narrower interval generally indicates greater precision, whereas a wider interval indicates more uncertainty. Neither an estimate nor an interval can correct limitations of the study design, such as the absence of a comparator. For this study, the registry record does not report an endpoint estimate or confidence interval, so the precision of the primary outcome cannot be evaluated.

For a single-group study, an analysis may describe the outcome frequency within the group. This is not the same as estimating a treatment contrast. A comparison requires data from groups that answer a clearly defined comparative question and a method appropriate to that design. Here, the registry lists a single group and no comparator. Thus, any within-group descriptive result would not by itself show what the outcome would have been under another approach.

How should the listed sample-size assumptions be understood?

The registry record describes planning illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Those are assumptions for an illustrative calculation, not evidence that the actual study used a two-arm design. The registered study is single group and has no comparator described. The record does not report the trial’s own sample-size justification, so the illustration should not be read as its design rationale or as a description of the study’s actual allocation.

A planning calculation asks what sample size might be needed under specified assumptions to detect a chosen effect. Its result depends on the effect used and the calculation method. Such a calculation is not observed power, and it does not establish whether a study found an effect. The record’s sample-size description is explicitly an illustration using a stated fraction of the observed effect; the particular calculated sample sizes and the effect values are not reported in the registry record. No numerical sample-size interpretation can be made from that description alone.

What can be inferred from the analysis listing?

The registry lists 0 analyses. This means that the record does not present analysis results for the endpoint in its analysis listing. It does not establish what analyses may have been performed outside the registry or whether the study had a prespecified statistical analysis plan. Those details are not reported in the registry record. In particular, the record does not state how covariates, incomplete assessments, or deviations from a planned analysis were handled.

Statistical methods should be matched to the endpoint, study design, and data available. General methods for binary outcomes can estimate a proportion and its uncertainty when the numerator and relevant denominator are known. Methods for comparative binary outcomes require comparable groups and a defined contrast. Neither an endpoint numerator and denominator nor a comparative group is reported for the primary outcome. It would therefore be inappropriate to supply a recalculated estimate or comparative test. The available information supports explaining the endpoint and design constraints, not reconstructing an unreported analysis.

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 Graft")
n      <- c(62)
events <- c(62)
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 Graft  62  62  100.0  94.2  100.0  94.2  100.0  94.3  100.0

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 2 outcome measures and 0 analyses. It does not state how many of the outcome measures were treated as primary for statistical testing beyond identifying the primary endpoint described in the record, nor does it report a plan for controlling multiplicity. When several outcomes are examined, the chance of a chance-positive finding can increase if each is tested separately. In general, a prespecified testing hierarchy or an adjustment can address that issue, but whether either approach was used is not reported in the registry record. No multiplicity-adjusted results are listed.

The record does not describe how missing outcome data were handled. It does not state the number of participants with complete assessment of the 30-day endpoint, how participants lost to follow-up were treated, or whether any imputation or sensitivity analysis was used. These details matter because the analyzed group may differ from the enrolled group if outcome data are incomplete. Enrollment of 62 participants does not establish the number included in an endpoint analysis.

The registry does not specify the analysis population, such as whether the primary endpoint was assessed in all enrolled participants or in a defined subset. It also does not report whether participants were excluded from analysis or how protocol deviations were handled. The study is listed as single group, and no comparator is described, so there is no randomized allocation population to interpret as an intention-to-treat comparison. Further detail on the prespecified analysis plan, analysis populations, missing-data procedures, and multiplicity handling is not reported in the registry record.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: pneumonia (14.5%), chronic obstructive pulmonary disease (11.3%), arrhythmia (9.7%), myocardial ischaemia (8.1%), stent-graft endoleak (8.1%).

For the Endovascular Graft group, the registry reports 49 participants affected by serious adverse events among 62 at risk, and 7 affected by other adverse events among 62 at risk. It also reports 13 deaths. These figures describe the safety entries in the record; they are not the reported result for the primary endpoint of participants without major adverse events within 30 days. The registry record does not specify the timeframe for these safety summaries or explain how the death count relates to the primary endpoint.

The listed serious adverse-event terms and percentages are Pneumonia, 14.5%; Chronic obstructive pulmonary disease, 11.3%; Arrhythmia, 9.7%; Myocardial ischaemia, 8.1%; Stent-graft endoleak, 8.1%; and Vascular stent occlusion, 8.1%. The figures are term-specific. The record does not give the underlying counts or term-specific denominators in the information, so percentages should not be translated into counts. Nor should they be added to produce an overall total: adverse-event categories can overlap unless the record explicitly says they are mutually exclusive. These descriptive entries alone do not establish a cause or a comparison with another group.

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

The posted information establishes that the study was registered as a completed, single-group evaluation of the Zenith Low Profile AAA Endovascular Graft and ancillary components. It identifies a 30-day primary endpoint based on whether participants were without a defined set of major adverse events. It also records adverse-event summaries for the Endovascular Graft group. Those are useful descriptions of what the registry lists, but they do not provide the missing primary endpoint result.

The record does not show how many participants met the primary endpoint, how many had each component event, or how many participants were included in the endpoint analysis. Without those details, the primary outcome cannot be quantified, and its statistical precision cannot be assessed. The adverse-event summaries are distinct from that endpoint and have no timeframe specified in the record. They should not be used as substitutes for an unreported primary outcome.

The single-group design also defines the reach of any interpretation. A description of outcomes in one group is not a direct comparison with another device, usual care, or no intervention. It cannot determine what would have happened to the same participants under an alternative. The registry does not provide a like-for-like control group or a comparative analysis. As a result, the record does not support a comparative estimate of benefit or harm.

These limitations do not mean the study has no descriptive information. The enrollment, endpoint definition, study design, and listed adverse-event figures can be reported as recorded. But those details should not be stretched into conclusions about a treatment effect, the frequency of the primary endpoint, or the relative safety of the device. Additional endpoint results, analysis methods, follow-up details, and an appropriate comparison would be needed to answer questions beyond the descriptive content of the registry record.

14. Why This Trial Matters Statistically

This study illustrates why a clearly defined endpoint and a reported endpoint result are both necessary for statistical interpretation. The primary outcome specifies a 30-day period and a set of major adverse events, making the intended measure understandable. But without the observed number of participants meeting the definition, the endpoint cannot be summarized quantitatively. Enrollment alone does not fill that gap because the number assessed for the endpoint is not reported.

The single-group design is also statistically important. It permits description of outcomes in the study group, but it does not produce a concurrent contrast with another intervention. That distinction separates a within-group account from a comparative treatment estimate. Readers should not interpret an observed safety count as proof of a device effect, in either direction, when the record does not include a control group or comparative analysis.

The registry’s safety entries additionally show why counts, percentages, endpoints, and analysis populations need to be distinguished. Serious and other adverse-event summaries are not the same measure as the defined primary endpoint, and the record does not supply the safety time window or all term-specific denominators. Their interpretation depends on details that are not reported. Preserving these distinctions avoids treating separate summaries as if they were one outcome.

Finally, a completed status and a stated enrollment do not guarantee that an analysis is available in the registry. The record lists 0 analyses, and it does not describe missing-data handling, the analysis population, or multiplicity procedures. These are central considerations for judging the completeness and precision of reported results. The trial is therefore statistically informative as an example of the limits of registry-based interpretation when endpoint results and analysis details are absent, while its recorded design and safety entries remain descriptively reportable.

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.

Several trial-specific details needed to interpret the results are not reported in the registry record. Although the primary endpoint is defined, its participant count is absent, as are component-level results. The record also does not report the analysis denominator for that endpoint. The enrollment of 62 participants should not be treated as proof that all enrolled participants had a complete 30-day assessment.

The study is listed as single group, with no comparator described and allocation recorded as NA. It therefore cannot provide a like-for-like control comparison in the registry record. The information also does not report a statistical analysis plan or the trial’s own sample-size justification. The planning assumptions described for illustrative sample-size calculations do not establish the actual design rationale or analytical choices used in the study.

The safety summaries have their own interpretive gaps. The registry reports 49 participants affected by serious adverse events among 62 at risk, 7 affected by other adverse events among 62 at risk, and 13 deaths, but does not specify the timeframe for these summaries. The underlying counts and denominators for the listed serious-event terms are not reported alongside their percentages in the record. The relationship between the death count and the primary endpoint is also not described.

Finally, the registry lists 0 analyses and does not describe missing-data handling, analysis populations, multiplicity adjustments, or sensitivity analyses. These omissions prevent assessment of how complete the outcome data were and how the reported safety entries were analyzed. Details about participant characteristics and other aspects of trial conduct are not reported in the registry record. These limitations restrict interpretation to the design and descriptive figures recorded, and preclude a fuller appraisal of the primary endpoint or comparative effects.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Zenith® Low Profile AAA Endovascular Graft — NCT02535065.
• Registry record last updated 2022-04-19; status last verified 2022-03.
• Results first posted 2018-06-06.
• 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

The registry record identifies NCT02535065 as a completed, single-group device study of the Zenith® Low Profile AAA Endovascular Graft. It lists 62 participants enrolled and describes use of the device with ancillary components, in conjunction with the Zenith® Spiral-Z® AAA Iliac Leg Graft, for abdominal aortic, aortoiliac, and iliac aneurysms. The recorded start is 2014-08 and the primary completion date is 2017-01-23. Cook Research Incorporated is listed as sponsor.

The primary outcome is the number of participants without major adverse events within 30 days. Its result is not reported in the registry record. The safety entries list 49 participants affected by serious adverse events, 7 affected by other adverse events, both among 62 at risk, and 13 deaths. The registry lists 2 outcome measures and 0 analyses. No comparator, endpoint analysis denominator, missing-data method, or statistical analysis plan is reported, limiting interpretation to the recorded design and descriptive safety information.