Reverse Medical Barrel™ Device for Adjunctive Treatment for Wide-Neck, Intracranial, Bifurcating/Branching Aneurysms: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Reverse Medical Barrel™ Device for Adjunctive Treatment for Wide-Neck, Intracranial, Bifurcating/Branching Aneurysms (NCT02179190), a na na study. The primary outcome is Number of Participants With Neurologic Death or Major Ipsilateral Stroke Within 12 Month Follow-up Period..

2. Clinical Question

3. Trial Design

The registry describes a prospective, multicenter, single-arm study of the Barrel VRD as an adjunct to embolic coils. The target aneurysms were wide-neck, intracranial, bifurcating aneurysms of the middle cerebral and basilar arteries. The listed intervention was the Barrel VRD, implanted alongside embolic coils. The study is marked as completed, with enrollment of 138 participants.

There was no randomized allocation and no masking. Because the study had a single group, it was not designed as a like-for-like comparison between the device-assisted treatment and an alternative. Its results can describe outcomes observed among participants who received the device, but the design does not by itself separate treatment effects from differences in patient characteristics, clinical care, or other influences.

The primary endpoint concerned neurological death or major ipsilateral stroke during follow-up for 12 months after device implantation. The registry also lists secondary outcomes relating to successful device deployment, aneurysm occlusion, modified Rankin score, in-stent stenosis, and death. However, the record does not report results for these outcomes. It lists 8 outcome measures and no analyses.

The registry record does not report a sample-size justification, a detailed statistical analysis plan, interim analyses, or the methods used to handle missing endpoint data. The recorded enrollment and study status therefore describe the study’s registry design and conduct, but do not establish how many participants were included in each endpoint analysis or how the primary safety result was estimated.

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.

Enrollment

Reasons for not completing this period:

Index Procedure With Barrel VRD Attempt

Reasons for not completing this period:

Follow-Up Post Barrel VRD Implanted

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Participants implanted with the Barrel VRD

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: Participants with enrolled (consented ) with an attempted Barrel VRD Implant

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Neurologic Death or Major Ipsilateral Stroke Within 12 Month Follow-up Period., measured over 12 months, after device implant.

The primary endpoint counts participants reported to have neurological death or major ipsilateral stroke during the 12 months after device implantation. It combines two serious neurological outcomes into one safety measure. A participant meeting either component would meet the composite endpoint as described. Major ipsilateral stroke was defined as an NIHSS increase of at least 4 lasting more than 24 hours.

The NIHSS is a scale used to quantify neurological impairment caused by stroke. The registry description gives interpretations ranging from no stroke symptoms to severe stroke. A threshold based on a change in this scale provides a specified criterion for classifying a major stroke event, while the time condition distinguishes a sustained change from a shorter-lasting one. The endpoint also includes neurological death, which is a distinct event type from stroke.

In general, a composite endpoint can capture more than one clinically important event type within a single outcome definition. Its interpretation depends on which events qualify and how frequently each component occurs. A combined count does not reveal the contribution of each component unless component-specific results are also reported. Here, the registry record states the endpoint definition and timeframe but does not report the number of participants meeting it, the separate component counts, or an estimate of precision.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a single-arm design tell readers?

The registry classifies this study as a single-group study, with no randomized allocation and no masking. In general, a single-arm study can describe what happened to participants receiving a treatment under the study’s conditions. It does not provide a concurrent control group for estimating what would have happened to similar participants under a different treatment. This limits causal interpretation: an observed event count cannot, by itself, show whether the treatment caused, prevented, or changed the frequency of an outcome.

The lack of masking is also part of the recorded design. In general, masking can reduce the risk that knowledge of treatment assignment influences assessment or care. Its relevance depends on the outcome and how it is measured. The registry record does not describe specific procedures for outcome adjudication or blinded assessment, so those details are not reported in the registry record.

How should a participant count be interpreted?

The primary endpoint is a count of participants meeting a defined event criterion during follow-up. A count is not an event rate unless its denominator and the relevant follow-up are also specified. In general, the denominator should represent participants who could be evaluated for that endpoint, and the analysis should explain how participants without complete follow-up are handled. The registry gives enrollment of 138 and describes the primary population as implanted participants, but does not report the primary endpoint count or its analysis denominator.

The adverse-event fields separately list participants at risk and participants affected. These counts describe the registry’s adverse-event reporting, but they should not be confused with the primary endpoint analysis population. The record does not explain how the adverse-event observation period relates to the primary endpoint follow-up or whether every event was considered related to the device.

What does an endpoint definition contribute?

A prespecified endpoint definition tells readers which events count toward the outcome. Here, the primary endpoint combines neurological death and major ipsilateral stroke, with stroke characterized by an NIHSS increase of at least 4 lasting more than 24 hours. Clear definitions support consistent classification across participants. However, a definition alone does not provide the observed result, the adjudication process, or evidence about how consistently events were classified. Those details are not reported in the registry record.

In general, composite outcomes are most informative when their components are reported as well as the combined result. Different components may have different clinical meanings and different frequencies. A single combined count can obscure that variation. The registry record does not report primary endpoint component counts.

What does statistical precision mean?

In general, an estimate is more informative when readers can assess its uncertainty. A confidence interval expresses uncertainty around an estimated quantity under the assumptions of the method used. For an event count or proportion, precision depends in part on the number of participants with evaluable follow-up and on how many events occurred. A confidence interval cannot be interpreted without knowing what was estimated and how it was calculated. The registry record does not report a primary endpoint estimate or confidence interval.

In general, sparse events can make estimates imprecise, while incomplete or unequal follow-up can complicate simple comparisons of counts. For time-to-event outcomes, methods that account for time under observation may be appropriate. The registry record does not report a time-to-event analysis for the primary endpoint or provide information needed to determine whether such an analysis was used. No statistical method should be inferred from the endpoint timeframe alone.

What can planning calculations establish?

In general, sample-size calculations are planning tools. They describe the number of participants needed under stated assumptions about an effect, variability, significance level, power, and analysis method. They are not evidence that a study had a particular chance of detecting its observed result after the fact. Planning illustrations based on an observed effect are not the trial’s own design justification and should not be interpreted as observed power. The registry record does not report the study’s sample-size justification or its original planning assumptions.

A statistical plan would ordinarily clarify the primary analysis population, handling of missing outcomes, adjustment for covariates, and treatment of multiple outcomes. Those elements are not reported in the registry record. The listed count of 8 outcome measures and absence of listed analyses do not establish whether analyses were conducted outside the registry or what methods they used. The record also does not report interim analyses or multiplicity procedures. Accordingly, the design and outcome definitions can be described, but the analysis methods and precision of the primary endpoint cannot be reconstructed from the registry record.

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("BARREL VRD")
n      <- c(127)
events <- c(5)
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  BARREL VRD  127  5  3.9  1.3  8.9  1.7  8.9  1.7  8.9

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 8 outcome measures, including the primary safety endpoint and several secondary outcomes. It does not report a multiplicity strategy, such as whether one endpoint was designated as the sole basis for formal inference or whether adjustment was planned across multiple outcomes. The record also lists no analyses. These omissions mean that the registry record does not establish how multiple statistical tests, if any, were handled.

In general, testing many outcomes can increase the chance of obtaining at least one apparently notable result by chance. Methods for addressing multiplicity depend on the purpose and hierarchy of the outcomes. Descriptive reporting of each outcome is different from confirmatory testing with a controlled error rate. Without a reported analysis plan and results, the inferential status of any outcome cannot be assessed.

The record does not report missing-data methods, endpoint-specific analysis populations, or the number of participants with complete follow-up for the primary endpoint. Enrollment of 138 does not establish that all enrolled participants were implanted, followed for the full 12 months, or included in a particular analysis. The record also does not explain how withdrawal, death from other causes, or incomplete assessments were handled.

In general, missing outcome data can affect both the denominator and the interpretation of an estimate. The impact depends on why data are missing and how missingness relates to participant outcomes. Without the number and reasons for missing assessments and the analysis approach, readers cannot evaluate that risk for the primary endpoint. These details are 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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: ischaemic stroke (6.3%), anaemia (3.1%), urinary tract infection (2.4%), acute respiratory failure (2.4%), acute myocardial infarction (1.6%).

For the BARREL VRD group, the registry lists 127 participants at risk for serious adverse events and 44 affected participants. For other adverse events, it lists 127 at risk and 73 affected participants. It also lists 3 deaths. These are reported counts, not estimates of comparative risk, and no causal interpretation should be attached to them without further information.

The most frequently listed serious adverse-event terms are ischaemic stroke at 6.3%, anaemia at 3.1%, urinary tract infection at 2.4%, acute respiratory failure at 2.4%, acute myocardial infarction at 1.6%, and cardiac failure congestive at 1.6%. The registry record does not provide further context in these fields about event onset, duration, severity criteria, relatedness to the device, or whether participants could have experienced more than one event. These percentages should therefore be read as the record’s reported event-term figures, not as evidence that the device caused the events.

The 3 deaths listed in the adverse-event information are not identified there as neurological deaths. The primary endpoint count is not reported in the registry record, so the death count cannot be used to determine the primary endpoint result.

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

This registry record describes a prospective, multicenter, single-arm evaluation of the Barrel VRD used with embolic coils for specified wide-neck, bifurcating aneurysms. It reports the study’s enrollment, design, outcome definitions, and adverse-event counts. It does not report the primary endpoint result or results for the listed secondary outcomes. As a result, the record alone does not show how often the primary safety endpoint occurred or how precisely it was estimated.

The study’s design also sets limits on what outcomes could establish. Without a concurrent comparator, descriptive outcomes among treated participants do not quantify how outcomes would differ under another treatment strategy. This does not make the observations irrelevant, but it means they should not be interpreted as a comparative treatment effect. The record does not establish causality for the adverse events or deaths listed.

In general, absence of a result in a registry record is not evidence that no event occurred. It means the result is not reported in the registry record. Likewise, the presence of an endpoint definition is not a result. Readers need the observed event count, analysis population, follow-up completeness, and an uncertainty estimate to judge the primary endpoint’s frequency and precision.

The adverse-event information provides some descriptive safety context, but its interpretation is limited by the lack of detail about event attribution and observation periods in the record. The listed deaths cannot be assumed to meet the primary endpoint, which specifically includes neurological death or major ipsilateral stroke. The record does not say whether any listed death was neurological.

Accordingly, this record supports a description of the study design and reported adverse-event counts, but not a conclusion that the device improves outcomes, worsens outcomes, or is equivalent to another approach. Those comparative conclusions would require evidence and analyses not reported in the registry record.

14. Why This Trial Matters Statistically

This study illustrates the distinction between an endpoint’s definition and its result. A registry can specify a clinically relevant safety outcome, its timeframe, and the threshold used to classify a stroke, yet still not report the observed endpoint count. Statistical interpretation requires both the definition and the result, along with the denominator and information about follow-up.

The single-arm design is also important to statistical reading. Counts from a treated group can describe experience during a study, but they do not provide a direct randomized comparison. The design therefore frames the kinds of conclusions that can be drawn, regardless of how clearly the endpoint is defined. Readers should distinguish descriptive safety information from evidence about relative effects.

The record also highlights why participant flow and analysis populations matter. Enrollment is not necessarily the same as the number implanted or the number with evaluable follow-up. When those numbers and missing-data methods are not reported, the relationship between the enrolled population and an endpoint estimate remains unclear.

Finally, the listed adverse-event counts show why contextual information matters alongside counts. A count does not identify cause, timing, or whether multiple events occurred in the same participant. Statistical summaries are most useful when their definitions, denominators, follow-up, and analysis methods are clear. These details are not all reported in the registry record, limiting the conclusions available from it.

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 central limitation for interpreting the primary safety outcome is that its observed result is not reported in the registry record. The record gives the endpoint definition and 12-month timeframe, but not the number meeting the endpoint, component-specific counts, analysis denominator, or precision estimate.

The study is single-arm, with no randomized comparator. Outcomes among participants treated with the Barrel VRD and coils therefore cannot be interpreted as a direct comparison with another approach. The record also identifies no masking. It does not report whether outcome assessment or event adjudication used procedures intended to reduce assessment bias.

Although enrollment is listed as 138, the record does not report endpoint-specific participant flow or the number with complete follow-up. It does not describe missing-data handling or the analysis population. Readers therefore cannot determine how enrollment relates to the primary endpoint analysis. A detailed sample-size justification, statistical analysis plan, and interim-analysis information are not reported in the registry record.

The registry lists secondary outcomes but does not report their results. It also does not report how multiplicity was handled. The adverse-event entries give counts and selected event-term percentages, but the record does not provide enough context to assess attribution, timing, overlap between events, or the relationship of those events to the primary endpoint. These limitations constrain interpretation of both efficacy-related outcomes and safety findings.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Reverse Medical Barrel™ Device for Adjunctive Treatment for Wide-Neck, Intracranial, Bifurcating/Branching Aneurysms — NCT02179190.
• Registry record last updated 2018-12-26; status last verified 2018-12.
• Results first posted 2018-12-05.
• 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 describes a completed, prospective, multicenter, single-arm study of the Barrel VRD as an adjunct to embolic coils for wide-neck, bifurcating aneurysms of the middle cerebral and basilar arteries. Enrollment is listed as 138. The primary endpoint was neurological death or major ipsilateral stroke during the 12 months after device implantation, with major stroke defined by an NIHSS increase of at least 4 lasting more than 24 hours.

The record lists 8 outcome measures and no analyses. It does not report the primary endpoint result or results for the listed secondary outcomes. For the BARREL VRD group, it reports 44 participants with serious adverse events and 73 with other adverse events, with 127 at risk in each category, and lists 3 deaths. The design has no randomized comparator, and the registry record does not report a detailed analysis plan, missing-data methods, or the primary endpoint’s precision.