Post-market, Prospective Evaluation of PHOTO-oxidized Bovine Pericardium in Vascular Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Post-market, Prospective Evaluation of PHOTO-oxidized Bovine Pericardium in Vascular Surgery (NCT03669042), a na na study. The primary outcome is Incidence of Central Neurologic Events.

2. Clinical Question

This question is narrower than the overall study objective. The objective was to evaluate clinical outcomes among patients receiving PhotoFix in vascular repair or reconstruction; the primary endpoint concerns a particular group of procedures and a defined set of neurologic events. Other registry outcomes include survival, re-operation, explant, adverse events, restenosis, and secondary patency. The record does not report numerical results for those outcomes either.

3. Trial Design

This was a prospective, post-market clinical follow-up study of PhotoFix in vascular repair and reconstruction surgery. The registry marks the study as completed. The listed start date is 2018-11-20, and the primary completion date is 2020-07-10. The listed enrollment is 94.

The design is recorded as single-group, with allocation marked NA and masking recorded as none. Patients underwent a vascular repair or reconstruction procedure requiring a PhotoFix patch. The procedures and implant sites varied with the patient and underlying cause. As a result, this is a heterogeneous clinical setting rather than a study of one uniform operation or one fixed implant location.

The single-group structure is important for interpreting outcomes. Observed events can describe what was recorded among the treated group, but there is no concurrent control group to distinguish outcomes associated with the device from those related to the underlying vascular disease, the procedure, or other factors. The registry explicitly does not support treating any arms as a like-for-like control comparison.

The registry lists nine outcome measures and identifies secondary outcomes that include overall survival, all-cause re-operation, device-related re-operation, explant, adverse events, restenosis, and secondary patency. The analysis count is recorded as zero. The registry record does not report the statistical analysis plan, the sample-size justification, interim analyses, or detailed analysis populations. The study's completion status does not by itself establish that every planned outcome was analyzed or that results were posted.

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.

Population: Enrolled Patients

6. Primary Endpoint

The registry lists the primary outcome as Incidence of Central Neurologic Events, measured over Up to 6 months, post-op.

The primary endpoint is the incidence of central neurologic events among cases of carotid endarterectomy. It is defined as the percentage of patients who experienced at least one event from a specified set: transient ischemic attack, amaurosis fugax, stroke, or carotid occlusion. The follow-up timeframe is up to 6 months after surgery. The registry describes the measure in terms of participants, so the endpoint concerns whether a patient experienced an event, rather than the total number of separate event episodes.

This type of endpoint is used to capture clinically important neurologic outcomes after a carotid procedure. Combining the listed events into an “at least one” measure can describe how many patients experienced any event in the defined group, while avoiding the implication that repeated events in one patient represent multiple affected patients. The component events can differ in nature and severity, so a combined measure should not be read as showing that every event has the same clinical meaning.

The registry record does not report the primary endpoint result, the number of carotid endarterectomy cases contributing to it, or the event count for this endpoint. The 94 listed as enrollment should not be assumed to be the denominator for a procedure-specific endpoint. Without the relevant numerator, denominator, and uncertainty estimate, the endpoint's observed frequency and precision cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a single-group study estimate?

In general, a single-group study describes outcomes observed among participants receiving the intervention under the conditions of that study. For a binary endpoint such as experiencing at least one event, the basic descriptive quantity is the fraction of eligible participants who experienced the event. This describes the observed cohort; it is not automatically an estimate of the effect attributable to the intervention. A causal treatment effect requires a credible comparison that addresses what would have happened to comparable patients without the intervention or under an alternative.

Here, the registry records a single-group design and no comparator. Procedures and implant sites could vary by patient and underlying etiology. Those features make the clinical cohort relevant to a range of real-world uses, but they also mean that outcomes may reflect differences in patients and procedures as well as the implanted patch. The registry record does not report an adjusted comparison or a method for separating these influences.

What does an “at least one” event endpoint mean?

Generally, a participant-level binary endpoint classifies each eligible participant according to whether the participant experienced an event during the defined observation period. A participant with repeated episodes still contributes as a participant who experienced the endpoint, rather than as multiple affected participants. This is different from counting all event episodes. The primary endpoint is described in this participant-level way and includes a set of specified neurologic events. The record does not report whether each component was also analyzed separately or how events were adjudicated.

How should uncertainty be understood?

In general, a confidence interval expresses the uncertainty around an estimate under the assumptions of the statistical method. A narrower interval indicates greater precision, while a wider interval indicates less precision. Its interpretation depends on the design, the data, and the analysis; it does not correct for bias, confounding, or an unsuitable comparison. The primary endpoint estimate and confidence interval are not reported in the registry record, so neither the event frequency nor its precision can be evaluated from that record.

For event counts, the number of people eligible for the endpoint is essential context. A count without its relevant denominator cannot establish a rate, and the study's overall enrollment should not be substituted for the number eligible for a restricted endpoint. In this study the primary endpoint is limited to carotid endarterectomy cases, while the enrolled cohort includes varied vascular procedures. The number of eligible cases is not reported in the registry record.

Why do design and analysis choices matter?

In general, random allocation can help balance measured and unmeasured prognostic factors between treatment groups, while masking can reduce some forms of measurement or behavior bias. This study is recorded as single-group, with allocation NA and masking none. Those labels describe the registered design; they do not establish that a particular bias occurred. They do mean that a randomized, masked comparison should not be inferred.

Variation in clinical indication and procedure can also produce different baseline risks. A pooled outcome across a varied cohort may conceal differences between clinical subgroups. Subgroup estimates can help describe that variation, but they may be less precise, especially when the subgroup size is small. The registry record does not report subgroup results for the primary endpoint, nor does it report the count of carotid endarterectomy cases.

What do the planning assumptions mean?

In general, a sample-size calculation for a future two-arm study can illustrate how many participants per arm might be needed to detect a chosen effect under specified assumptions. The registry's planning assumptions refer to two-sided significance level 0.05, equal allocation, a normal approximation, and an effect set as a stated fraction of an observed effect. Such an illustration is not the observed power of the completed study, and it is not evidence that the study was designed around those assumptions. The registry record does not report the trial's own sample-size justification. Numerical planning results are not reported in the registry record.

Planning calculations also depend on the outcome type and analysis. A calculation based on an event proportion is not interchangeable with one based on time-to-event data. In general, an assumption about the size of an effect is especially consequential: a smaller target effect generally requires more information to detect with the same error and power criteria. These are general statistical principles, not findings from this study. No new sample-size estimate can be inferred from the available outcome information.

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("Carotid Artery Stenosis")
n      <- c(78)
events <- c(2)
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  Carotid Artery Stenosis  78  2  2.6  0.3  9.0  0.7  8.9  0.8  8.8

11. Multiplicity, Missing Data and Analysis Populations

The registry lists multiple outcome measures, including the primary neurologic endpoint and secondary outcomes covering survival, re-operation, explant, adverse events, restenosis, and secondary patency. When a study examines many outcomes or multiple versions of an outcome, the chance of at least one apparently notable result can increase. Statistical methods can address this issue through prespecified outcome hierarchies or multiplicity adjustments, but the choice depends on the study's aims and analysis plan.

The registry record does not report a multiplicity strategy, a hierarchy among the secondary outcomes, or an analysis plan. It also lists zero analyses. Therefore, it is not possible to tell from the record whether outcomes were tested inferentially, whether any tests were adjusted, or which results were designated confirmatory. An absence of reported analyses should not be interpreted as evidence that no analyses were performed outside the registry.

Missing-data handling is also not reported in the registry record. The record does not describe loss to follow-up, incomplete outcome assessments, censoring, or how missing values were handled. These details matter because participants with unknown event status may affect an endpoint estimate, particularly when follow-up duration varies. The endpoint timeframe is up to 6 months after surgery, but the record does not explain how that window was applied to participants with shorter or incomplete follow-up.

The record does not define detailed analysis populations, such as whether analyses included all enrolled participants, only those who received the device, or only those with complete endpoint data. For the primary outcome, the eligible population is restricted to carotid endarterectomy cases, but the size and analysis set are not reported. These omissions limit assessment of the denominator, missingness, and the robustness of any outcome estimate.

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: other (5.3%), infection (4.3%), bleeding event (2.1%), cardiac event (2.1%), stroke (2.1%).

The registry lists 12 participants affected by serious adverse events among 94 at risk in the treatment group. It separately lists 21 participants affected by other adverse events among 94 at risk, and deaths are listed as 0. These figures are descriptive participant counts. They do not compare risk with another treatment group, because the design is single-group.

The listed serious-event terms and percentages are Other, 5.3%; Infection, 4.3%; Bleeding event, 2.1%; cardiac event, 2.1%; Stroke, 2.1%; and Thrombosis, 1.1%. The registry record does not report the denominator used for each term, whether terms can overlap within a participant, or whether the term percentages represent participants or event episodes. They should not be added or treated as mutually exclusive categories.

These data do not establish that an event was caused by PhotoFix. The registry record does not provide a comparator, detailed event narratives, timing, severity grading beyond the serious-event classification, or an attribution method. Nor do the counts describe the primary neurologic endpoint specifically. They should be read as recorded safety information for the study group, with those interpretive limits.

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

The registry record establishes the study's purpose, design, intervention, and specified outcomes. It describes a completed prospective follow-up study in which PhotoFix was used as a patch during varied vascular repair or reconstruction procedures. It also defines a primary neurologic endpoint for carotid endarterectomy cases and records descriptive adverse-event counts for the treatment group.

It does not report the primary endpoint result. The number of carotid endarterectomy cases, the number who experienced the defined neurologic events, and any confidence interval are not reported in the registry record. The secondary outcome results are not reported in the registry record either. Therefore, the record does not support a conclusion about the frequency or precision of the primary neurologic outcome.

The adverse-event counts can describe what was recorded in the treated group, but they do not answer how those counts compare with another treatment or with the outcomes that would have occurred without PhotoFix. Because there is no comparator group, the study cannot isolate a device effect from differences in disease, procedure, implant location, or other factors. The record also does not provide enough information to determine how event categories overlap or how complete follow-up was.

In general, an observed outcome is not the same as a causal treatment effect. A causal interpretation relies on an appropriate comparison and assumptions about the groups and outcome measurement. A single-group post-market study can contribute descriptive follow-up information, but its design does not establish comparative efficacy or safety on its own.

Study completion means the registry marks the study as completed; it does not mean the primary result is available in the registry record. The appropriate interpretation is therefore limited: the record documents a clinical follow-up study and some safety counts, while leaving the primary endpoint estimate and several essential analysis details unreported.

14. Why This Trial Matters Statistically

This study raises a useful statistical distinction between evaluating a device in clinical practice and estimating its effect relative to an alternative. Prospective follow-up can define the intended observation period and collect outcomes as patients undergo treatment. In a post-market setting, such information can describe use across varied vascular procedures and underlying conditions. Yet a single-group design does not provide the counterfactual comparison needed to attribute observed outcomes to the device.

The primary endpoint also illustrates why the eligible population matters. The endpoint is restricted to carotid endarterectomy cases, whereas the study includes patients undergoing varying vascular procedures. The overall enrollment cannot stand in for the endpoint denominator without confirmation that all enrolled patients meet the endpoint definition. Because the number of eligible cases and the event result are not reported in the registry record, the primary estimate cannot be reconstructed or assessed for precision.

The record further shows why safety counts require context. Counts of affected participants and event-term percentages can be informative descriptively, but interpretation depends on definitions, follow-up, attribution, denominators, and whether categories overlap. Without those details and a comparator, the counts should not be treated as comparative risks or as proof of causation.

Finally, a completed study record with listed outcomes is not equivalent to a complete statistical report. Analysis methods, missing-data handling, multiplicity procedures, and endpoint results all affect how evidence should be weighed. Their absence from the registry record makes it important to separate what is documented—the design and selected counts—from what remains unreported. That distinction is central to responsible interpretation of post-market clinical evidence.

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 statistical interpretation is that the primary endpoint result is not reported in the registry record. The endpoint is limited to carotid endarterectomy cases, but the number of eligible participants, event count, and estimate of uncertainty are also not reported. The overall enrollment of 94 does not supply that missing endpoint denominator.

The study is registered as single-group, with no comparator. Consequently, outcome counts cannot establish how results would differ under another device or procedure, and they cannot isolate outcomes attributable to PhotoFix. The registry notes variation in procedures, underlying etiologies, and implant sites. It does not report adjusted analyses or subgroup estimates that could clarify variation across these clinical settings.

Important analysis details are absent from the registry record, including the statistical analysis plan, sample-size justification, interim analyses, missing-data approach, and detailed analysis populations. The registry also does not report how primary endpoint events were assessed or adjudicated, how the up-to-6-month timeframe was operationalized, or whether secondary outcomes were analyzed. These omissions prevent a full appraisal of potential bias, precision, and robustness.

The safety information is limited to participant counts and listed serious-event terms with percentages. The event-term denominators, overlap among terms, timing, and attribution are not reported in the registry record. The listed counts therefore support only a descriptive reading and should not be interpreted as comparative or causal estimates. Study completion and the presence of registered outcomes do not resolve these limitations.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Post-market, Prospective Evaluation of PHOTO-oxidized Bovine Pericardium in Vascular Surgery — NCT03669042.
• Registry record last updated 2024-10-08; status last verified 2024-09.
• Results first posted 2024-10-08.
• 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

NCT03669042 is a completed, prospective, post-market, single-group evaluation of PhotoFix as a patch in vascular repair or reconstruction surgery. The registry lists enrollment of 94, no masking, and procedures and implant sites that vary with the patient and underlying etiology.

The primary endpoint is the incidence of specified central neurologic events among carotid endarterectomy cases, up to 6 months after surgery. Its result and eligible denominator are not reported in the registry record. The treatment group lists 12 participants affected by serious adverse events among 94 at risk, 21 affected by other adverse events among 94 at risk, and deaths as 0. These are descriptive figures without a comparator.

The registry record does not report the analysis plan, missing-data approach, or detailed analysis populations. The design supports descriptive interpretation of the treated group, not a like-for-like comparison or a causal estimate of the device's effect.