A Study of the Gore VIABAHN BX for Treatment of Occlusive Disease in the Iliac Arteries.: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of the Gore VIABAHN BX for Treatment of Occlusive Disease in the Iliac Arteries. (NCT02080871), a na na study. The primary outcome is Composite of Major Adverse Events (MAEs).

2. Clinical Question

This question is descriptive for the treated study group. Without a concurrent comparison group, the registry cannot establish how the observed event experience compares with another strategy under the same study conditions. The results can describe recorded outcomes in the study population, but they cannot by themselves isolate the effect of the device from other influences on those outcomes.

3. Trial Design

The registry identifies this as a completed, single-group study of stenting for occlusive disease in the common and/or external iliac arteries. The device was the Gore VIABAHN BX, described as a balloon-expandable endoprosthesis. The sponsor was W.L.Gore & Associates. Enrollment was 134. The recorded start was 2014-07 and primary completion was 2016-05.

Allocation is listed as NA, masking as none, and phase as NA. These entries do not describe a randomized assignment process or a blinded comparison. The record does not report a control arm. As a result, comparisons with an untreated group or another device are not part of the trial design described in the registry. The study can characterize outcomes after the intervention, but a change over time or an outcome after treatment cannot, on its own, show what would have happened to comparable participants under an alternative strategy.

The primary outcome is a composite of major adverse events assessed over 9 months, using component-specific windows of 30 days or 9 months. The registry also lists secondary outcomes including acute procedural success, 30-day clinical success, and primary, primary assisted, and secondary patency. There are 78 outcome measures recorded and 1 analysis. Those counts do not reveal how outcomes were prioritized in the analysis or whether multiplicity was addressed.

The registry record does not report the protocol’s sample-size justification, detailed eligibility criteria, recruitment procedures, treatment-delivery details, or a statistical analysis plan. The available planning assumptions are explicitly illustrations based on the observed effect, not evidence of the trial’s original design. They should not be read as a description of how participants were assigned or how the study was planned.

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: Population includes enrolled subjects who either experienced the defined event or were followed for at least 240 days.

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 Composite of Major Adverse Events (MAEs), measured over 9 months.

The primary endpoint is the percentage of study subjects experiencing a composite of major adverse events. A subject qualifies through device- or procedure-related death within 30 days, myocardial infarction within 30 days, target lesion revascularization within 9 months, or major amputation of the target limb within 9 months. The registry defines the relevant population as enrolled subjects who either experienced a defined event or were followed for at least 240 days.

A composite endpoint combines clinically different outcomes into a single summary. In general, this can capture a broader range of important events than any component alone and can make an overall event measure useful when individual events are uncommon. But the components can differ in seriousness, frequency, and relationship to treatment. A combined percentage therefore does not show which component accounts for the result. Component-specific counts and estimates are important for understanding what the composite represents.

The registry gives the endpoint’s unit as a percentage and identifies a 95% confidence interval as its dispersion measure. The primary-endpoint percentage and confidence-interval limits are not reported in the registry record. Without those estimates, the magnitude and precision of the endpoint cannot be assessed from the information recorded.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry labels the primary endpoint as a percentage and identifies a 95% confidence interval as the measure of dispersion. The endpoint estimate and interval limits are not reported in the registry record. The statistical ideas below explain how such summaries are generally interpreted; they do not supply missing study results.

What does a percentage endpoint represent?

For a binary outcome such as whether a participant experienced a defined event, a percentage summarizes the share of the analysis population meeting that definition. Its interpretation depends on both the numerator and denominator: what counts as an event, and which participants are included in the analysis population. The registry defines the composite events and gives a population rule based on event occurrence or follow-up of at least 240 days. It does not report the endpoint’s observed numerator, percentage, or interval limits.

Percentages for event outcomes are sometimes described as risks or proportions, but such language should match the analysis method and follow-up definition. A participant with adequate follow-up may have an opportunity to experience an event throughout the stated period, whereas shorter follow-up can leave event status less complete. The record does not report the detailed handling of incomplete follow-up, censoring, or other missing outcome information. Those choices can affect what a reported percentage means.

Why report a confidence interval?

A point estimate alone does not communicate how much uncertainty is associated with it. In general, a confidence interval gives a range of values compatible with the data and the method’s assumptions. Its width reflects statistical precision, which is influenced by the amount of information in the data and by the outcome’s variability. It does not measure every source of uncertainty: selection, measurement, outcome classification, loss to follow-up, and design limitations may remain.

The registry’s reference to a 95% confidence interval identifies the intended type of summary, but the lower and upper limits are not reported in the registry record. The interval cannot be reconstructed from the enrollment count alone. That would require the relevant endpoint result and the analysis details, which are not reported.

What does a composite endpoint do?

A composite combines multiple event types into a shared endpoint. In general, this may increase the number of participants who meet an endpoint definition and can provide a concise summary of several outcomes. Its meaning depends on the component definitions, the assessment period for each component, and whether all components are clinically and statistically informative in a similar way.

This study’s composite includes device- or procedure-related death and myocardial infarction within 30 days, plus target lesion revascularization and major amputation of the target limb within 9 months. The components do not share the same time window. If the composite estimate were available, it would still not identify which component contributed to it. Component-specific results and clear event-adjudication rules would help interpret a composite; those numerical results and adjudication details are not reported in the registry record.

How does the design affect statistical interpretation?

A single-group design estimates outcomes in the group studied, subject to the outcome definition and analysis methods. A randomized comparison, by contrast, can support a treatment contrast when allocation and analysis are appropriately conducted. This registry lists a single group, allocation as NA, and masking as none; it does not describe a control group. Therefore, the primary endpoint is not a comparative treatment effect. Differences from an external benchmark, if considered elsewhere, would be vulnerable to differences in participant selection, care, outcome measurement, and follow-up.

The record lists 134 enrolled participants. Enrollment alone does not establish how many contributed to the primary analysis, because the endpoint population has its own follow-up rule. The record does not report the number included in the primary-endpoint analysis, the number with incomplete follow-up, or how missing data were handled. These details matter because an analysis population can differ from the enrolled group.

What do the planning assumptions mean?

The planning illustration is described as a calculation based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It is not described as the trial’s original design and should not be interpreted as observed power. The registry does not report the protocol’s sample-size justification or show a planned two-arm comparison in the study design.

In general, a sample-size calculation asks how much information a hypothetical study might need to detect a specified effect under stated assumptions. Its answer depends on the effect chosen, outcome variability, analysis method, allocation, and error-rate target. An illustration that scales a stated fraction of an observed effect is conditional on that observed estimate and those assumptions; it does not establish that the original study was adequately powered, nor does it prove that an effect is present or absent. No planning-illustration values are reported in the registry record details.

Why can over-dispersion matter?

For count outcomes, a simple model may assume that variability is determined by the average count. In general, over-dispersion means the observed variation is greater than that model expects. Ignoring it can make standard errors too small and intervals too narrow, producing an impression of greater precision than the data warrant. Methods designed for over-dispersed counts can accommodate extra variability. The primary endpoint in this study is described as a percentage, not a count endpoint, and the registry does not report a count-model analysis or a test for over-dispersion.

More broadly, the statistical plan, analysis-population details, missing-data methods, interval calculation method, and any multiplicity procedure are not reported in the registry record. These omissions limit reproducibility and prevent a complete assessment of the assumptions behind the endpoint estimate, even if a numerical result were available.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 78 outcome measures, including the primary composite and several secondary outcomes concerning procedural success, clinical success, and patency. It records 1 analysis. These registry entries do not show whether all outcomes were tested inferentially, which analyses were prespecified, or whether adjustments were made for multiple comparisons. A multiplicity plan is not reported in the registry record.

In general, testing many outcomes or making repeated statistical comparisons increases the chance that at least one result will appear notable by chance. Prespecified outcome hierarchies, adjusted significance thresholds, or other strategies can address this concern, but no such approach should be assumed without a report. The number of listed outcomes alone does not establish that every outcome was tested or that a particular adjustment was required.

The primary population includes enrolled subjects who experienced a defined event or were followed for at least 240 days. The registry does not report the count analyzed, the follow-up distribution, missing outcome status, or how participants with shorter follow-up and no recorded event were treated. It also does not report whether analysis followed an intention-to-treat principle or another population definition. These details affect the denominator and can affect interpretation if follow-up or missingness is related to outcomes.

In general, complete-case analysis can be biased when the chance of missingness is related to outcome status or participant characteristics. Other methods may address incomplete data under explicit assumptions, but no missing-data method is reported in the registry record. The reported population rule should therefore be distinguished from a complete account of analysis-population construction.

11. 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

Serious events with the highest arm-level rate: wound dehiscence (1.5%), claudication (1.5%), hemorrhagic anemia (0.7%), acute myocardial infarction (0.7%), chest pain - cardiac (0.7%).

The registry’s safety group is titled “Iliac Stenting.” It lists 30 participants affected by serious adverse events among 134 at risk, 0 participants affected by other adverse events among 134 at risk, and 1 death. These are the recorded group counts; the registry information does not state that the serious events were caused by the device or procedure. The serious-event percentage and the count of deaths should not be treated as interchangeable outcomes.

The registry lists wound dehiscence and claudication at 1.5% each. Hemorrhagic anemia, acute myocardial infarction, chest pain - cardiac, and congestive cardiac failure aggravated are each listed at 0.7%. These are listed serious-event terms and percentages. They do not, by themselves, show the number of episodes, whether a participant had multiple events, the timing of each event, or the investigator’s attribution. Those details are not reported in the registry record.

Safety counts in a single-group study describe events recorded in the treated group; they do not provide a comparative estimate of excess harm or benefit. Interpretation also depends on event definitions, ascertainment, follow-up, and attribution procedures. Those details are not fully reported in the registry record. The listed counts should therefore be read as descriptive registry safety information, not as evidence establishing causation or comparative risk.

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

The registry record describes a completed evaluation of the Gore VIABAHN BX for iliac occlusive disease and defines a primary composite endpoint of major adverse events. It also lists safety counts and adverse-event terms. These details help identify the study question and the outcomes being tracked, but they do not include the numerical primary-endpoint percentage or its 95% confidence-interval limits.

As a result, the primary endpoint’s observed level and precision cannot be assessed from the record details available. A confidence interval, when reported, would help show the uncertainty around an estimate under the analysis assumptions. Without its bounds and the estimate itself, there is no basis for describing the endpoint as high, low, precise, or imprecise.

The single-group design also sets a limit on what the study can establish. It can describe outcomes recorded among the participants studied, but it does not compare them with outcomes in a concurrent control group. A causal treatment effect or comparative safety conclusion cannot be drawn from the listed group alone. Differences from other studies or benchmarks would not substitute for a direct comparison unless the differences in populations and methods were addressed.

The safety listing reports 30 serious-adverse-event affected participants among 134 at risk, 0 other-adverse-event affected participants among 134 at risk, and 1 death. The record does not establish that every listed event was treatment-related. Event counts and named event terms are not, by themselves, proof of causation, and absence of a listed event in one category does not establish absence of all possible harms.

The appropriate reading is therefore limited and descriptive: the registry identifies the intervention, design, endpoint definition, follow-up windows, and recorded safety information. The clinical importance of the results, the comparative performance of the device, and the precision of the primary endpoint remain uncertain because the relevant comparative and endpoint estimates are not reported in the registry record.

13. Why This Trial Matters Statistically

This study illustrates why the design of a trial matters as much as the endpoint name. A single-group study can provide structured information about outcomes after an intervention, but it does not create a direct comparison with an alternative. That distinction prevents a descriptive event percentage from being mistaken for a treatment effect. The registry’s single-group design and allocation listed as NA make this limitation explicit.

The primary endpoint also demonstrates the interpretive trade-off involved in composite outcomes. Combining death, myocardial infarction, revascularization, and major amputation can provide a broad summary, but these events differ in nature and are assessed over different time windows. A composite result needs component-level context to show what drives it. The registry record defines the components but does not report the primary estimate or its component results in the information available for this analysis.

Statistical precision is another important issue. The registry identifies a 95% confidence interval, but its bounds are not reported. Without an estimate and interval, readers cannot judge how uncertain the primary result is. Enrollment is reported as 134, but enrollment alone does not indicate the number contributing to the endpoint analysis or the information available for each outcome.

Finally, the record lists many outcome measures, while details of multiplicity, missing-data handling, and the analysis plan are not reported. Those omissions matter because readers need to know which outcomes were primary, how incomplete follow-up was treated, and how inference across outcomes was handled. The study is statistically instructive precisely because it separates what a registry description can establish from what requires complete estimates, methods, and a comparison design.

14. 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 is the absence of a reported numerical result for the major-adverse-event endpoint. Although the registry identifies the endpoint as a percentage and specifies a 95% confidence interval, neither the estimate nor the interval limits are reported in the registry record. The primary result’s magnitude and precision therefore cannot be evaluated.

The study is recorded as a single-group evaluation, with allocation listed as NA and masking as none. No concurrent control group is described. The outcomes cannot be interpreted as a comparative estimate of the device’s effect, and the design does not separate treatment-related changes from other influences on participants’ outcomes.

The composite endpoint includes different events with different assessment windows. It combines device- or procedure-related death and myocardial infarction within 30 days with target lesion revascularization and major amputation within 9 months. Component-specific results, event adjudication procedures, and details of how attribution was determined are not reported in the registry record.

The endpoint population includes enrolled subjects with a defined event or follow-up of at least 240 days. The number analyzed, participant follow-up distribution, handling of incomplete follow-up, and missing-data methods are not reported. The available enrollment count does not resolve those questions.

The registry lists 78 outcome measures and 1 analysis, but it does not report a detailed statistical analysis plan, multiplicity procedures, or the original sample-size justification. The planning assumptions are described as illustrations based on the observed effect, not the study’s own design. These gaps limit reproducibility and make it difficult to assess how the recorded outcome definitions and analysis choices relate to the protocol.

The safety listing is descriptive and does not, by itself, establish event causation or comparative risk. More detailed event-level information and safety-ascertainment procedures are not reported in the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Study of the Gore VIABAHN BX for Treatment of Occlusive Disease in the Iliac Arteries. — NCT02080871.
• Registry record last updated 2019-01-16; status last verified 2018-12.
• Results first posted 2018-07-17.
• 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.

18. Record Summary

NCT02080871 is a completed, single-group study of the Gore VIABAHN BX for occlusive disease in the common and/or external iliac arteries. Enrollment was 134; the recorded start was 2014-07 and primary completion was 2016-05. Allocation is listed as NA and masking as none.

The primary endpoint is the percentage of subjects experiencing a composite of major adverse events, with components assessed within 30 days or 9 months. Its percentage and 95% confidence-interval limits are not reported in the registry record. The primary population includes enrolled subjects with a defined event or follow-up of at least 240 days.

The safety listing records 30 serious-adverse-event affected participants among 134 at risk, 0 other-adverse-event affected participants among 134 at risk, and 1 death. The record lists 78 outcome measures and 1 analysis, but detailed analysis, missing-data, and multiplicity methods are not reported in the registry record.