GORE PROPATEN Vascular Graft vs. Disadvantaged Autologous Vein Graft: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for GORE PROPATEN Vascular Graft vs. Disadvantaged Autologous Vein Graft (NCT00617279), a randomized phase 4 study. The primary outcome is Number of Patients With Primary Patency at 12 Months Post-procedure.

2. Clinical Question

Primary patency is defined in the record as hemodynamic evidence of blood flow through an open graft that has maintained uninterrupted patency and has not previously undergone revision to restore blood flow. This makes the question clinically focused on continued graft openness without a prior intervention to restore flow. The comparison is between a named vascular graft and a vein graft used for the same broad bypass application. Random allocation is recorded, but the method of sequence generation and the process used to conceal assignments are not reported in the registry record. Masking is listed as none. These features describe how the comparison was organized; they do not establish whether either approach had better patency. The registry record also notes that many enrolled participants did not have a 12-month follow-up visit before the study was terminated, making the missing outcome information important to interpretation.

3. Trial Design

PRODIGY is registered as a phase 4, randomized, parallel-group study with no masking. It compared GORE PROPATEN Vascular Graft with disadvantaged autologous vein graft for below-knee arterial bypass in peripheral arterial occlusive disease. The listed enrollment is 31. The sponsor is W.L.Gore & Associates. The recorded study start is 2007-12, and primary completion is recorded as 2010-02. The study status is terminated.

The parallel design means the two interventions were assigned in separate groups rather than compared sequentially within the same participant. Randomization is recorded, but details such as the randomization sequence, allocation concealment, stratification, and any restrictions on allocation are not reported in the registry record. The record lists no masking; it does not describe any separate masking of outcome assessors. Arm descriptions are blank, so further procedural detail is not reported in the registry record.

The primary outcome is the number of participants with primary patency at 12 months post-procedure. The registry also lists secondary outcomes for primary patency, assisted primary patency, and secondary patency at earlier and later follow-up times. There are 25 outcome measures listed, but the registry record does not report analysis results. The study status and the stated reason that many participants lacked a 12-month visit before termination are relevant when considering how much evidence is available for the primary comparison. The planned design alone cannot establish the size, direction, or precision of an intervention difference.

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: The number of patients analyzed at 12 months post-procedure does not equal the number of patients originally enrolled into the study. This is due to the fact that many enrolled patients did not have their 12 month follow-up visit prior to the termination of the 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 Number of Patients With Primary Patency at 12 Months Post-procedure, measured over 12 months.

The primary endpoint is the number of participants with primary patency at 12 months after the procedure. The registry defines primary patency as hemodynamic evidence of blood flow through an open graft, with uninterrupted patency and no prior revision to restore blood flow. Thus, the endpoint combines evidence that the graft remains open with the absence of an earlier procedure to restore flow.

Patency is used in bypass studies because it describes whether the conduit continues to provide blood flow through the treated pathway. The distinction between primary patency and assisted primary patency matters: the primary definition excludes a graft that required revision to restore flow, while the listed secondary outcomes separately include assisted primary patency. Secondary patency is also listed, but its definition is not reported in the registry record.

The endpoint is reported as a count of participants, not as a comparative effect estimate in the registry information available. A count needs its corresponding analyzed group denominator to be interpreted as a rate or proportion. The record explicitly says the number analyzed at 12 months did not equal the number originally enrolled, because many participants did not have that visit before termination. It does not provide the primary outcome counts, denominators by group, or an estimated between-group contrast. Consequently, the endpoint definition is clear, but the comparative result and its precision are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a randomized parallel-group study but does not report a statistical analysis plan or analysis results. The concepts below explain how such information is generally interpreted; they do not assert that a particular method was used in PRODIGY.

What does randomization contribute?

In general, random allocation aims to make assigned groups comparable with respect to both measured and unmeasured baseline factors. It supports a causal comparison when allocation is implemented as intended, outcomes are measured appropriately, and missing data and deviations are handled transparently. Randomization does not guarantee balance in a small study, and it does not remove uncertainty. The registry record does not describe sequence generation, allocation concealment, stratification, or the analysis population. It records no masking, so treatment assignment was not masked according to the registry entry.

How should a binary endpoint be read?

The primary outcome is a count of participants meeting a defined patency condition at 12 months. For a binary outcome, each participant’s status is classified into an outcome category, such as meeting or not meeting the endpoint, within the relevant follow-up and analysis definition. Counts should be read alongside the number assessed in each group. A count alone does not convey the chance of the outcome when group denominators differ or when outcome availability is incomplete. The registry record provides neither the primary counts nor the analyzed denominators by group.

A comparative analysis might express the group contrast using an absolute difference, a relative measure, or another prespecified estimand. These measures answer different questions and require a stated analysis approach. No such comparative estimate is reported in the registry record, so no effect measure can be interpreted for this trial. Any estimate would also need an uncertainty measure, commonly a confidence interval. In general, a confidence interval describes the range of effect values reasonably compatible with the data and the model assumptions; it is not a guarantee that the true effect lies within a particular interval.

What does an equivalence claim require?

As a general statistical principle, equivalence is not established merely because a conventional test fails to detect a difference. An equivalence analysis requires a justified margin defining differences considered acceptably small, together with a method for comparing the uncertainty interval with that margin. A noninferiority question similarly requires a prespecified margin and a suitable analysis. The registry summary uses the phrase “equivalent to or better than,” but a margin, formal hypothesis, and test are not reported in the registry record. The wording of the objective should therefore not be mistaken for an analysis conclusion.

Why does incomplete follow-up matter?

The record states that many participants did not have their 12-month follow-up visit before termination. In general, missing outcome data reduce the information available and can introduce bias if outcome availability is associated with the outcome or differs across assigned groups. A complete-case comparison uses participants with observed outcomes; its interpretation depends on assumptions about those without observed outcomes. Other approaches may make different assumptions and can be accompanied by sensitivity analyses. The registry record does not report group-specific missingness, reasons for missing visits, imputation, censoring rules, sensitivity analyses, or the primary analysis population. It is therefore not possible to assess how missing outcomes were addressed.

How should planning calculations be understood?

The record describes planning illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. The stated illustration varies the effect to detect as a fraction of the observed effect. These assumptions define a hypothetical planning exercise, not the trial’s original sample-size justification. The original design rationale is not reported in the registry record. Since no observed primary effect or primary comparison is reported, the illustrations cannot be used to infer observed power or to establish that the study was adequately sized. A sample-size calculation is a planning aid under specified assumptions; it does not replace an estimate and its uncertainty from the trial.

The record specifies that non-time-to-event planning figures would be participants per arm for 80% power, while time-to-event figures would give a total event count. Those conventions do not imply that a particular calculation is available for this primary comparison. No numerical planning result is reported in the registry record. General statistical interpretation therefore remains limited to the stated assumptions and the distinction between planning quantities and observed evidence.

Finally, analysis choices should align with the outcome definition and the randomized design. General considerations include defining the estimand, retaining participants in their assigned groups when appropriate, prespecifying handling of missing data, and reporting effect estimates with uncertainty. The registry record does not report whether these approaches were used. The listed outcome and design information alone cannot recover the missing analysis details.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 25 outcome measures, including primary patency at 12 months and secondary measures of patency at other follow-up times. It also lists assisted primary patency and secondary patency outcomes. Examining multiple outcomes and time points can increase the chance of finding at least one apparently noteworthy result by chance. General approaches to this issue include prespecifying a primary comparison, defining a hierarchy of outcomes, or adjusting inference across a family of tests. The statistical plan and any multiplicity procedure are not reported in the registry record. There are no analysis results listed, so it is not possible to determine which outcomes were tested or how multiplicity was addressed.

Missingness is specifically relevant to the primary endpoint: the registry states that many participants did not have a 12-month follow-up visit before termination, and that the number analyzed differed from the number enrolled. The number missing in each group, reasons for missingness, and any methods used to handle missing observations are not reported in the registry record. The record also does not describe an analysis population, such as whether analyses followed randomized assignment or included only participants with available follow-up.

In general, the interpretation of an analysis with incomplete outcome data depends on how missingness arose and on the assumptions behind the method used. Reporting participant flow, group-specific follow-up, and sensitivity analyses can help readers judge whether conclusions depend on those assumptions. These details are not reported in the registry record. Given the absent outcome results and analysis information, neither the impact of missing data nor the handling of multiple outcomes can be evaluated.

11. 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: below knee amputation (7.1%), cerebral infarction (7.1%), esophageal tear (7.1%), foot amputation (7.1%), graft infection (7.1%).

The registry reports serious adverse events for the two groups separately. For GORE PROPATEN Vascular Graft, 4 participants are reported as affected among 14 at risk. For disadvantaged autologous vein graft, 2 are reported as affected among 17 at risk. Other adverse events are reported for 4 participants among 14 at risk in the GORE PROPATEN group and 3 among 17 at risk in the vein-graft group.

The serious-event terms listed include below knee amputation, cerebral infarction, esophageal tear, foot amputation, graft infection, and myocardial infarction, each shown with 7.1%. The registry record does not provide enough detail to determine whether terms occurred in the same or different participants, or how these term-level percentages relate to group-specific denominators. They should not be added together or read as a group-level risk comparison.

These counts are descriptive safety information, not a randomized statistical comparison. The record does not report a safety analysis, event timing, severity grading beyond the serious-event classification, or attribution to the intervention. Death counts are not reported in the registry record. The figures do not establish that one intervention caused more or fewer adverse events.

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

The record establishes that PRODIGY was designed as a randomized comparison of GORE PROPATEN Vascular Graft and disadvantaged autologous vein graft in below-knee arterial bypass. It identifies a 12-month primary-patency outcome and provides a definition of that outcome. It also records that the study was terminated and that many enrolled participants did not have 12-month follow-up before termination. These registry entries describe the design and the limits of the available follow-up information.

The record does not report the primary outcome counts, group-specific denominators, a between-group estimate, a confidence interval, or a p-value. It therefore does not show whether primary patency was higher in either group, how large any difference was, or how precise an estimate might be. The objective’s wording about equivalence or better performance cannot substitute for those results or for a documented equivalence analysis.

Nor does the record establish that the interventions were equivalent, that one was superior, or that there was no meaningful difference. Such conclusions require outcome data and an analysis suited to the stated question. With incomplete 12-month follow-up and no reported handling of missing outcomes, even a result among participants who attended follow-up would need to be interpreted in light of the missing data.

The adverse-event counts offer a separate description of reported events. They do not answer the primary patency question, and the record does not provide enough detail to attribute events to treatment or compare safety formally. The study’s randomized design is relevant to how a complete analysis might be interpreted, but design labels alone do not constitute evidence of an intervention effect. The appropriate reading is that the registry record documents the question, design, endpoint definition, and some safety counts, while leaving the principal comparative result unreported.

13. Why This Trial Matters Statistically

This study is statistically notable because its stated objective is framed around equivalence or better performance, while the record does not provide the analysis needed to evaluate that claim. Equivalence is a demanding inference: readers need a prespecified margin and an estimate precise enough to rule out differences beyond that margin. Without the margin, endpoint results, and uncertainty interval, the objective cannot be converted into an evidential conclusion.

The record also makes follow-up completeness central to interpretation. The primary endpoint is assessed at 12 months, but many enrolled participants did not have that visit before termination. This means the enrollment figure cannot be treated as the primary analysis denominator. Group-specific follow-up and missing-outcome handling would be needed to understand the analysis population and possible bias; those details are not reported in the registry record.

There are multiple registered outcomes spanning patency definitions and follow-up times. In general, this makes prespecification and transparent reporting of the primary analysis important, because selective emphasis among multiple outcomes can complicate inference. The registry record does not report how multiplicity was handled or which analyses were performed.

More broadly, the record illustrates the difference between a trial’s scientific question and the evidence needed to answer it. Randomization and a clearly defined endpoint are important design features, but they do not replace outcome reporting, effect estimates, uncertainty, or information about missing data. The posted information permits a careful account of the intended comparison and its limitations, not a quantitative conclusion about comparative patency.

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 for interpretation is that the registry record does not report the primary-patency results or a comparative analysis. The analyzed numbers by group, outcome counts, effect estimate, and uncertainty are not reported in the registry record. Although the study enrolled 31 participants, the record says the number analyzed at 12 months differed from the number enrolled because many participants lacked that follow-up before termination.

The record does not describe why individual visits were missed, how many participants in each group lacked the primary outcome, or how missing outcomes were handled. It also does not report baseline characteristics, detailed eligibility criteria, the definition used to classify a vein graft as disadvantaged, or further descriptions of the assigned procedures. These absences limit assessment of the study population and the comparability of the groups in practice.

Randomization is recorded, but the sequence-generation and allocation-concealment methods are not reported in the registry record. Masking is listed as none. The statistical analysis plan, analysis population, equivalence margin, multiplicity approach, and sensitivity analyses are also not reported. The status is terminated, but the reason for termination is not reported in the registry record beyond the note that many participants lacked a 12-month visit before termination.

Safety information is limited to reported counts and listed serious-event terms. Timing, attribution, and a formal comparative safety analysis are not reported in the registry record. Together, these gaps prevent a full assessment of efficacy, precision, missing-data bias, and safety differences.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: GORE PROPATEN Vascular Graft vs. Disadvantaged Autologous Vein Graft — NCT00617279.
• Registry record last updated 2012-01-12; status last verified 2011-12.
• Results first posted 2012-01-12.
• 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

NCT00617279, the PRODIGY study, was a phase 4 randomized, parallel-group comparison with no masking. It studied GORE PROPATEN Vascular Graft versus disadvantaged autologous vein graft for below-knee arterial bypass in peripheral arterial occlusive disease. Listed enrollment was 31; the study is recorded as terminated. The recorded start was 2007-12, with primary completion at 2010-02.

The primary outcome was the number of participants with primary patency at 12 months. The registry record defines primary patency but does not report the primary outcome counts or comparative analysis. It notes that many participants lacked a 12-month visit before termination and that the number analyzed differed from the number enrolled. Serious and other adverse-event counts are listed by group, but a formal safety comparison is not reported in the registry record. Consequently, the record documents the study question and design but does not establish the comparative primary-patency result.