Case Review of the Penumbra and Indigo Systems for Mechanical Thrombectomy in the Periphery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Case Review of the Penumbra and Indigo Systems for Mechanical Thrombectomy in the Periphery (NCT02085551), a na na study. The primary outcome is Angiographic Assessment of Vessel Patency at Immediate Post-procedure as Measured by TIMI Scores.

2. Clinical Question

In plain terms, the study was intended to describe immediate angiographic findings and procedural safety in a treated cohort. It was not designed as a like-for-like comparison of Indigo thrombectomy with a control intervention. The record gives an enrollment total and safety counts, but does not report the primary outcome count or an estimate of its uncertainty.

3. Trial Design

The Prism Trial is described in the registry as a retrospective, single-arm, multicenter case review. Its official title identifies it as a retrospective review of technical success using the Penumbra and Indigo Systems for mechanical thrombectomy in the periphery. The listed intervention, however, is mechanical thrombectomy by the Indigo System. No separate intervention arm or control group is listed.

The registry reports enrollment of 85 participants. The study summary says that up to 100 patients at up to 10 centers would be enrolled. These are descriptions of the study and its intended scale, not evidence that the maximum enrollment or center count was reached. The record identifies the study as completed, with a start date of 2014-03 and primary completion date of 2015-09.

Allocation is listed as NA, and masking as NONE. In a retrospective single-group review, these entries do not define a randomized comparison; the record explicitly describes a single arm. The registry lists the phase as NA. It does not report a prospective enrollment process, a control treatment, or a method for assigning participants to devices.

The stated study objective was to assess safety and effectiveness in patients with confirmed peripheral or visceral arterial occlusion or embolus. The primary endpoint concerns angiographic vessel patency immediately after the procedure, classified using TIMI scores. The study summary also mentions procedural serious adverse events. The registry record does not report a detailed protocol, the methods for collecting retrospective records, or a statistical analysis plan. It lists no analysis records. Thus, the design can be described as a retrospective treated-cohort assessment, but its operational details and analytic procedures are not reported in the registry record.

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

Analysis population for the primary outcome, as defined in the registry: TIMI score at immediate post-procedure was unavailable for one patient.

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 Angiographic Assessment of Vessel Patency at Immediate Post-procedure as Measured by TIMI Scores, measured over Immediate post-procedure.

The primary endpoint is the proportion of patients with a post-procedure TIMI score of 2 to 3, assessed immediately after the procedure. It is described as an angiographic assessment of vessel patency. The registry identifies the unit as participants and the parameter as a count of participants, so the intended result is a participant count or proportion rather than a continuous measurement.

Angiographic vessel patency is used as a procedural measure because it characterizes the appearance of blood flow through the treated vessel at the time of imaging. TIMI scoring supplies a classification framework for interpreting that angiographic assessment. The endpoint's stated threshold groups scores of 2 to 3 together. The registry record does not provide the detailed scoring rules, the imaging review process, or information about who adjudicated the images.

The timing matters to interpretation: this is an immediate post-procedure endpoint, not a measure of durability over later follow-up. It describes a technical finding at a specified point, and by itself does not establish longer-term vessel status or patient-centered outcomes. The registry notes that the immediate post-procedure TIMI score was unavailable for one patient. It does not report the number of participants who met the endpoint, the resulting proportion, or an interval estimating its precision. Therefore, the endpoint's definition is available, but its observed primary result is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a retrospective, single-group case review. This design gathers information from cases that have already occurred rather than assigning participants prospectively to treatment groups. A descriptive analysis can report what was observed in the reviewed cohort, but a single-group study does not create a direct counterfactual comparison. Without a control group, differences attributable to the intervention cannot be distinguished from other differences in patients, care, or clinical circumstances.

What does the primary endpoint estimate?

The primary endpoint is a participant count for those with a post-procedure TIMI score of 2 to 3, expressed in the endpoint description as a proportion. For a binary endpoint, each participant is classified according to whether the specified condition was met. The estimated proportion would describe the share of assessed participants meeting that criterion. The registry record defines the criterion but does not report the count or proportion, so the estimate itself is unavailable.

A confidence interval, if reported, would describe the statistical uncertainty around an estimated proportion under the assumptions of the method used. A narrower interval generally indicates greater precision, while a wider interval indicates more uncertainty. No confidence interval for the primary endpoint is reported in the registry record. Without both an outcome estimate and its uncertainty, readers cannot judge the precision of the intended endpoint from the posted results.

Why does the design matter?

In a randomized comparison, allocation can support interpretation of differences between groups, subject to the trial's conduct and analysis. Here, allocation is listed as NA, masking as NONE, and the model as SINGLE GROUP. The registry also explicitly describes a retrospective single-arm study. There is consequently no between-group treatment contrast to estimate. Counts within the treated cohort can still be informative as descriptive observations, but they are not equivalent to evidence from a controlled comparison.

Retrospective reviews may depend on records created for clinical rather than research purposes. The registry record does not describe how cases were identified, whether data were abstracted using common rules, or whether angiographic results were reviewed independently. These details matter because differences in documentation and measurement can affect who is included and how outcomes are classified. Such procedures are not reported in the registry record and cannot be assumed.

How should the safety counts be read?

The registry reports serious adverse events affecting 15 of 85 participants and other adverse events affecting 27 of 85 participants. A count of participants with an event is distinct from a total count of event episodes: one participant may experience more than one event. The registry's summarized figures should therefore be read as participant-level counts, not as a complete event-frequency distribution. It also reports 0 deaths. No comparison group is available to put these counts in a comparative context.

The listed serious-event terms are accompanied by percentages, including Anaemia at 8.2% and Leg Amputation at 2.4%. These are registry entries, but the record does not provide the event-level detail needed to assess timing, recurrence, attribution, or overlap among terms. The percentages should not be interpreted as proof that the device caused the events. The relationship between an event and treatment, as well as the definition used to classify an event as serious, is not detailed in the registry record.

What can planning calculations say?

Sample-size calculations are planning tools, not observed results. The planning illustration described for this record uses a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; its target effect is a stated fraction of the observed effect. Such assumptions do not describe the actual design, which is single group and retrospective. A hypothetical calculation based on a treatment contrast cannot create a control group or transform the cohort into a randomized comparison. It also should not be read as observed power or as evidence that the study was adequately or inadequately sized. The registry record does not report the trial's own sample-size justification.

More generally, a statistical analysis plan would specify the endpoint analysis, missing-data approach, and any adjustments or subgroup analyses before results are interpreted. Those methods are not reported in the registry record, which lists no analyses. As a result, the posted information supports a description of the study design, endpoint definition, and safety counts, but not a reconstruction of inferential analyses that are absent from the 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("Mechanical Thrombectomy by the Indigo System")
n      <- c(84)
events <- c(74)
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  Mechanical Thrombectomy by the Indigo System  84  74  88.1  79.2  94.1  79.5  93.4  79.4  93.4

11. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures and does not list any analyses. It does not report a multiplicity strategy, such as a hierarchy for testing endpoints or an adjustment for multiple statistical tests. Because no analysis results are listed, there are no reported p-values to interpret in light of multiplicity. Whether the study protocol specified any approach to multiple outcomes is not reported in the registry record.

The primary endpoint description notes that an immediate post-procedure TIMI score was unavailable for one patient. The record does not say why it was unavailable, whether the participant was excluded from the endpoint denominator, or how missing endpoint data were handled. It also does not provide the number of participants with a recorded score or the observed endpoint count. No imputation or sensitivity analysis is reported in the registry record.

The adverse-event entries use 85 participants as the number at risk for both serious and other adverse events. The registry does not provide further detail about missing safety information, follow-up completeness, or the period over which events were collected. It also does not describe the analysis population for the primary endpoint, safety outcomes, or any other outcome measure. These details are important to understanding which participants contributed to each result, but are not reported in the registry record.

Without an analysis population definition and a documented missing-data method, readers cannot determine whether the endpoint estimate—if reported elsewhere—would represent all enrolled participants or only those with an available assessment. The absence of a posted primary result further prevents evaluation of the effect of the unavailable score. No assumptions about missingness or handling should be made from the registry description alone.

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: anaemia (8.2%), leg amputation (2.4%), acute respiratory failure (1.2%), abdominal compartment syndrome (1.2%), intestinal ischaemia (1.2%).

The registry reports serious adverse events for 15 of 85 participants and other adverse events for 27 of 85 participants in the mechanical thrombectomy by the Indigo System group. It reports 0 deaths. These are participant counts in a single treated cohort, not rates compared with a control group. The record does not provide a comparative safety estimate.

The serious-event terms listed include Anaemia at 8.2%, Leg Amputation at 2.4%, Acute Respiratory Failure at 1.2%, Abdominal Compartment Syndrome at 1.2%, Intestinal Ischaemia at 1.2%, and Myocardial Infarction at 1.2%. The percentages are reported as registry entries. The record does not explain whether participants could appear under multiple event terms, or provide event-level counts, onset times, duration, or attribution details.

These figures should be read as safety reporting within the reviewed cohort. They do not establish that the device caused a particular event, nor do they show how event frequencies compare with another treatment. The registry does not report the safety follow-up window or further definitions for the listed categories. The entries describe what is recorded, while the missing context limits conclusions about event patterns and comparative risk.

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

The registry record establishes that the Prism Trial was a completed retrospective, single-arm review with enrollment of 85 participants. It identifies immediate post-procedure TIMI score of 2 to 3 as the primary endpoint and describes procedural serious adverse events as a safety assessment. It also reports participant counts for serious and other adverse events and reports 0 deaths.

The record does not report the number of participants who met the primary endpoint or the associated proportion. Consequently, it does not provide a posted numerical result for the central angiographic question. It also does not report a confidence interval, p-value, or analysis result for that endpoint. The single missing immediate post-procedure TIMI score is noted, but its handling is not described.

Even a complete endpoint count from a single treated group would answer a descriptive question about that cohort, not a controlled question about what would happen under an alternative intervention. This design has no comparator group and no randomized allocation. The registry therefore cannot support a direct estimate of relative effectiveness or comparative safety. It also does not establish whether observed outcomes were caused by treatment rather than patient characteristics, clinical circumstances, or other factors.

The safety counts are meaningful as reported observations, but they do not indicate comparative risk or event causation. The absence of reported deaths in this record does not establish that risk is absent, particularly without details of safety follow-up and ascertainment. Similarly, the listed serious-event terms do not by themselves describe the complete clinical course or the relationship of those events to treatment.

In short, the available registry information defines the study and its intended endpoint, and offers limited descriptive safety information. It does not provide the primary outcome result or the comparative and analytic details needed for broader conclusions. Claims beyond those reported observations are not supported by the registry record.

14. Why This Trial Matters Statistically

This study illustrates how a clear endpoint definition and a posted endpoint result are different things. The registry specifies that immediate post-procedure vessel patency is assessed through TIMI scores, with scores of 2 to 3 defining the primary outcome. Yet it does not report how many participants met that criterion. Statistical interpretation depends on both the endpoint's definition and the observed data; a definition alone cannot establish an estimate or its precision.

The design is also central to interpretation. A retrospective single-group review can describe findings in a treated cohort, while a controlled comparison is needed to estimate differences between treatment strategies. The record lists no comparator and no randomized allocation. This makes it important to distinguish descriptive safety counts from comparative safety claims, and intended effectiveness questions from estimates that the posted results actually support.

The missing TIMI score is a practical reminder that endpoint availability and analysis population definitions affect interpretation. The record notes the missing assessment but does not say how it was handled. Without that information, the denominator and missing-data approach for the endpoint cannot be evaluated. More broadly, the registry lists no analysis records and does not report an analysis plan.

Finally, the safety figures show why counts require context. Participant counts, event terms, follow-up periods, and attribution are not interchangeable. The record offers reported counts and terms but limited detail on event timing, overlap, and ascertainment. Statistical reading therefore involves identifying what the data directly describe as well as what remains unreported, rather than treating a registry entry as a complete comparative analysis.

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 interpreting the primary endpoint is the absence of its observed result. The registry defines the endpoint and notes one unavailable TIMI score, but does not report the number meeting the criterion, the resulting proportion, or an interval. A statistical summary of the primary outcome cannot be reconstructed from the registry record.

The design is retrospective and single arm, with no control group. It is therefore not a like-for-like comparison and cannot provide a randomized estimate of comparative effects. The record does not describe how cases were selected, how complete case identification was assessed, or whether imaging assessments were standardized or independently reviewed. It does not give detailed eligibility criteria beyond confirmed peripheral or visceral arterial occlusion or embolus.

The study title refers to the Penumbra and Indigo Systems, while the listed intervention is mechanical thrombectomy by the Indigo System. The record does not explain whether or how both systems were used, or how device choice was made. That limits interpretation of which intervention or device exposure is represented by the cohort.

For safety, the registry reports counts and selected serious-event terms but not a follow-up window, detailed event-level data, attribution, or the extent of missing safety information. For the primary endpoint, the handling of the unavailable score and the analysis population are not reported. The statistical analysis plan, sample-size justification, and multiplicity procedures are also not reported in the registry record. These gaps restrict assessment of precision, completeness, and analytic choices.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Case Review of the Penumbra and Indigo Systems for Mechanical Thrombectomy in the Periphery — NCT02085551.
• Registry record last updated 2020-06-22; status last verified 2020-06.
• Results first posted 2020-06-22.
• 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 Prism Trial, NCT02085551, is listed as a completed retrospective, single-group, multicenter case review of mechanical thrombectomy for peripheral or visceral arterial occlusion or embolus. Enrollment was 85. The listed intervention is mechanical thrombectomy by the Indigo System; allocation is NA and masking is NONE.

The primary endpoint is the proportion of participants with an immediate post-procedure TIMI score of 2 to 3. A score was unavailable for one patient, but the primary outcome count and proportion are not reported in the registry record. Safety reporting lists serious adverse events for 15 of 85 participants, other adverse events for 27 of 85, and 0 deaths. The registry lists two outcome measures and no analyses. No control group or comparative result is reported.