Trial to Evaluate the Safety & Efficacy of the Absolute Pro™ Peripheral Self-Expanding Stent System in Subjects With Atherosclerotic de Novo or Restenotic Lesions in the Native Common Iliac Artery and/or Native External Iliac Artery.: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Trial to Evaluate the Safety & Efficacy of the Absolute Pro™ Peripheral Self-Expanding Stent System in Subjects With Atherosclerotic de Novo or Restenotic Lesions in the Native Common Iliac Artery and/or Native External Iliac Artery. (NCT00844532), a non-randomized phase 3 study. The primary outcome is Major Adverse Event (MAE) Rate.

2. Clinical Question

3. Trial Design

NCT00844532 is a phase 3, prospective, multi-center clinical trial with a non-randomized, parallel design and no masking. The registry lists an enrollment of 151 for the Absolute Pro record. The study is marked completed; its recorded start and primary completion dates are 2009-03 and 2011-03.

The official title describes two arms: an Absolute Pro arm and an Omnilink Elite arm. The Omnilink Elite arm is separately posted as NCT01396525, and the record identifies that system as investigational. The Absolute Pro arm includes both the Absolute Pro and Absolute Pro Long Lesion systems. Because allocation was non-randomized, differences between arms, if considered across the separate records, cannot be interpreted as if assignment had been randomized. The record itself cautions that the arms are not a like-for-like control comparison.

The study’s stated purpose was to evaluate safety and efficacy in people with atherosclerotic de novo or restenotic lesions in the native common iliac artery and/or native external iliac artery. The registry lists Peripheral Vascular Disease as a condition. It does not report the allocation process, masking procedures beyond the designation of none, or a detailed protocol for treatment selection. A sample-size justification and any planned interim analyses are not reported in the registry record.

The record lists 81 outcome measures and 0 analyses. Those fields do not supply an observed treatment effect or a statistical comparison. In particular, the enrollment entry is not a substitute for the number analyzed at a given endpoint time point: the primary outcome description says that the analysis includes participants with available follow-up data at that time point.

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: Intent to treat (ITT) population. The number of participants analyzed includes the subjects with available follow-up data at that time-point.

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 Major Adverse Event (MAE) Rate, measured over 9 months.

The primary endpoint is the major adverse event rate at 9 months, expressed as a percentage of participants. Its definition combines death, myocardial infarction, clinically-driven target lesion revascularization, and major amputation on the treated side or sides. It is therefore a composite endpoint: a participant meeting any one of the specified event criteria contributes to the endpoint.

In general, a composite can summarize several clinically important types of events in a single outcome. Its interpretation depends on knowing which events are included and how often each occurs; a composite percentage alone would not show whether one component accounted for most events. The registry record provides the definition but does not report the observed percentage, component-specific results, or a confidence interval.

The endpoint is specified for the intent-to-treat population, while the description also states that the number analyzed includes subjects with available follow-up data at that time point. This makes the actual number contributing to the 9-month result important for understanding the precision and completeness of the estimate. That number is not reported in the registry record. Without the observed estimate and its uncertainty, the endpoint definition alone cannot establish the size or precision of the result.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a binary participant-level measure: a participant either meets the major adverse event definition during the stated 9-month timeframe or does not. The registry identifies its unit as a percentage of participants and its parameter as a number. In general, a percentage expresses the number meeting an outcome relative to the participants assessed for that outcome. The record does not report the observed percentage or the number assessed at 9 months, so neither can be reconstructed from the enrollment entry.

What does the confidence interval describe?

The endpoint’s stated dispersion measure is a 95% confidence interval. In general, a confidence interval describes uncertainty around an estimate under the assumptions of the statistical method used. It is not a guarantee that the true value lies inside a particular calculated interval, and its width is relevant to precision. The registry record does not give the interval limits, the calculation method, or the endpoint estimate. It is therefore not possible to assess the precision of the primary result from the listed endpoint definition alone.

What can the design establish?

The trial is prospective and parallel, but allocation is non-randomized and masking is listed as none. In general, random allocation helps balance measured and unmeasured characteristics between comparison groups, while masking can limit some forms of assessment or treatment bias. Those protections cannot be assumed for this record. The official title describes a separate Omnilink Elite arm, but the Absolute Pro record is not a randomized comparison and explicitly cautions that the arms are not a like-for-like control comparison. Any between-arm contrast would therefore require careful attention to how participants entered each arm and to potential differences between them. Details of adjustment or other methods for handling such differences are not reported in the registry record.

How should the planning assumptions be read?

The record describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says that the effect to detect is a stated fraction of the observed effect. For time-to-event tables, the stated quantity is the total number of events; for other tables, it is participants per arm. These are planning assumptions, not a description of the trial’s own design rationale. The actual illustration values and the trial’s sample-size justification are not reported in the registry record. Such planning quantities are not observed power and do not demonstrate that a trial had a particular probability of detecting an effect.

Why does over-dispersion matter in general?

For count outcomes, over-dispersion means that observed variability is greater than a model assumes. If that feature is present but ignored, standard errors and confidence intervals may be too small, making results appear more precise than they are. This is a general statistical consideration; the primary endpoint is described as a percentage of participants, and the record does not identify an over-dispersion assessment or a count-model analysis. No such method should be inferred from the listed outcome information.

What analysis details are absent?

The registry lists 81 outcome measures and 0 analyses, but does not provide the primary endpoint estimate, its confidence interval, or a p-value. The detailed statistical analysis plan, covariate adjustments, handling of repeated or multiple outcomes, and methods for missing data are not reported in the registry record. The outcome description specifies an intent-to-treat population and available follow-up at the time point, but does not state how participants without available follow-up were treated analytically. These omissions limit assessment of how the endpoint was calculated and how robust any estimate would be.

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("Absolute Pro™ Peripheral Self-Expanding Stent Syst")
n      <- c(147)
events <- c(9)
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  Absolute Pro™ Peripheral Self-Expanding Stent Syst  147  9  6.1  2.8  11.3  3.3  11.2  3.3  11.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 81 outcome measures and 0 analyses. The secondary outcomes include device success, technical success, procedure success, and repeated listings of Thigh Brachial Index for the treated limb or limbs. The record does not provide enough detail to determine the timing or analytical role of each repeated listing. It also does not report a multiplicity strategy, such as whether a particular outcome was designated as the sole confirmatory test or whether adjustment was planned for testing multiple outcomes.

In general, when many outcomes or statistical tests are considered, the chance of at least one apparently notable result can increase. Methods for controlling that risk depend on the study’s objectives and analysis plan. No such plan is reported in the registry record, and no analysis results are listed. Therefore, no conclusion about multiplicity-adjusted inference can be drawn.

The primary outcome description names the intent-to-treat population but says the number analyzed includes participants with available follow-up data at the time point. It does not give the number with available 9-month follow-up, explain why data might be unavailable, or describe imputation, censoring, or sensitivity analyses. In general, missing outcome data can affect both the estimate and its precision, especially if missingness is related to outcomes or participant characteristics. The record does not report how this issue was addressed. The enrollment entry should not be treated as the number analyzed for the primary endpoint.

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.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: stenosis (13.9%), other: peripheral vascular disease (9.3%), cancer (6.0%), musculoskeletal (6.0%), pneumonia (6.0%).

The registry record lists 151 participants at risk for serious adverse events and 91 affected. For other adverse events, it lists 151 at risk and 88 affected. These are posted counts; the record does not give a definition for the “other” category in the registry record. The figures should not be converted into percentages or treated as mutually exclusive groups. A participant may potentially appear in more than one event category, and the record does not specify overlap.

The serious adverse-event terms with listed percentages are stenosis at 13.9%, other: peripheral vascular disease at 9.3%, cancer at 6.0%, musculoskeletal at 6.0%, pneumonia at 6.0%, and occlusion at 6.0%. The record does not provide counts for those terms in the registry record, nor does it clarify whether an individual could contribute to more than one term. These percentages should therefore be read as registry-listed term figures, not as a sum or as a complete accounting of all serious events.

The death entry is null, so a death count is not reported in the registry record. These safety entries do not establish a causal relationship between the device and any event. They also do not replace the primary endpoint result, which is not reported.

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

The record is useful for identifying the clinical question, study design, primary endpoint definition, and selected adverse-event entries. It describes evaluation of the Absolute Pro peripheral stent system in people with atherosclerotic de novo or restenotic lesions in native common and/or external iliac arteries. It also identifies a 9-month major adverse event endpoint combining death, myocardial infarction, clinically-driven target lesion revascularization, and major amputation on the treated side or sides.

However, the registry information does not include the observed primary endpoint percentage, its 95% confidence interval, or a component breakdown. It therefore does not establish the frequency of the composite endpoint in the analyzed population or the precision of an estimate. It also does not show whether any observed result differed from a comparator, because a primary comparison result is not reported.

The record’s design details matter for interpretation. Allocation was non-randomized, masking was none, and the Omnilink Elite arm was separately posted. The registry cautions that the arms are not a like-for-like control comparison. These registry entries mean that a direct comparative causal conclusion cannot be inferred from the record. No medical conclusion about the device should be drawn from the design description or adverse-event counts alone.

The posted safety information describes affected-participant counts and selected serious-event term percentages, but it does not provide the context needed to attribute events to the device or compare risk across randomized groups. The death count is not reported in the registry record. Missing follow-up handling, endpoint analysis details, and multiplicity methods are also not reported. Accordingly, the record supports a careful account of what was defined and listed, while leaving the central question about the observed primary outcome unanswered.

14. Why This Trial Matters Statistically

This trial is statistically notable because its stated clinical question concerns a defined composite outcome, while the available record does not include the estimate needed to assess that outcome. A clear endpoint definition is essential: it identifies which events count and the time window in which they are assessed. Yet definition and result are distinct. Without the observed percentage and its confidence interval, readers cannot assess either the endpoint frequency or the precision of an estimate.

The non-randomized allocation is also central to interpretation. A parallel study can describe outcomes in its arms, but non-random assignment does not ensure that the groups are comparable at baseline. The separate posting of the Omnilink Elite arm and the registry’s caution against a like-for-like comparison make it especially important not to read the study title as evidence of a randomized device comparison.

The record also illustrates why analysis populations and follow-up availability matter. The primary outcome is identified with the intent-to-treat population, but the description says the analyzed number includes participants with available follow-up at the time point. Without the number assessed or a missing-data approach, readers cannot determine how complete the endpoint information was.

Finally, the registry lists many outcome measures but no analyses. That distinction matters: a list of outcomes does not reveal which tests were performed, how multiple outcomes were handled, or what the results were. The record is therefore informative about trial structure and outcome definitions, but not sufficient for a statistical assessment of the primary result.

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 interpretation is that the registry record does not report the primary endpoint result. It gives the endpoint definition and timeframe, but not the observed 9-month percentage, the corresponding confidence interval, the number analyzed, or component-specific outcomes. The primary statistical finding and its precision therefore cannot be assessed from this record.

The study is non-randomized and has no masking. The official title describes an Omnilink Elite arm that is separately posted, while the registry cautions that the arms are not a like-for-like control comparison. The record does not report how treatment or arm selection occurred, how groups differed at baseline, or whether any statistical adjustment was used. These omissions restrict interpretation of any potential comparison.

The outcome description refers to the intent-to-treat population while qualifying the analyzed number by available follow-up. The number with outcome data at the relevant time point and the handling of missing data are not reported in the registry record. The record also does not report a detailed statistical analysis plan, multiplicity methods, interim analyses, or a sample-size justification.

Safety information is limited to the posted affected and at-risk counts, selected serious-event terms and percentages, and a null death entry. The registry entries do not establish event attribution, overlap among terms, or comparative safety. The secondary outcome list repeats Thigh Brachial Index, but does not give sufficient detail to identify the timing or role of each listing. These are limitations of what the registry record reports, rather than evidence that the underlying study did not collect further information.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Trial to Evaluate the Safety & Efficacy of the Absolute Pro™ Peripheral Self-Expanding Stent System in Subjects With Atherosclerotic de Novo or Restenotic Lesions in the Native Common Iliac Artery and/or Native External Iliac Artery. — NCT00844532.
• Registry record last updated 2015-06-09; status last verified 2015-05.
• Results first posted 2012-09-07.
• 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

NCT00844532 is a completed phase 3, prospective, multi-center, non-randomized parallel trial with no masking. It evaluated the Absolute Pro Peripheral Self-Expanding Stent System in people with atherosclerotic de novo or restenotic lesions in native common and/or external iliac arteries. The Absolute Pro arm includes the Absolute Pro and Absolute Pro Long Lesion systems.

The primary outcome is the percentage of participants with a major adverse event at 9 months, defined as death, myocardial infarction, clinically-driven target lesion revascularization, or major amputation on the treated side or sides. The record identifies the intent-to-treat population and available follow-up at each time point, but does not report the primary result or its confidence interval. It lists 81 outcome measures and 0 analyses.

The official title describes a separate Omnilink Elite arm, and the record cautions against treating it as a like-for-like control comparison. Safety entries include affected-participant counts and selected serious-event terms; the death count is not reported in the registry record.