Percutaneous Recanalization in Ischemic Stroke Management (PRIISM): A Feasibility Clinical Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Percutaneous Recanalization in Ischemic Stroke Management (PRIISM): A Feasibility Clinical Study (NCT00810095), a na phase 2 study. The primary outcome is Technical Device Success by as Assessed by the Percentage of Participants Which Established at Least TIMI 2 Flow Upon Deployment of the System Across the Occlusion and Within 30 Minutes of Placing the Guide Catheter..

2. Clinical Question

This is a feasibility question about technical performance in the treated participants, not a comparative estimate of the system’s effect against an alternative. The endpoint definition focuses on whether a specified level of blood flow was achieved under the stated procedural conditions. The registry also names the number of device-related serious adverse events as a secondary outcome, but it does not provide an analysis of that outcome. The listed serious adverse event terms should be read separately from the primary technical-success question: they describe safety information and do not supply a comparison or an estimate of technical success.

3. Trial Design

PRIISM is registered as a phase 2 feasibility clinical study of the MindFrame System in people experiencing an ischemic stroke. The registry lists ischemic stroke as the condition and describes the intended use as recanalization of occluded vessels. Enrollment is listed as 40. The record gives a start date of 2009-03 and a primary completion date of 2011-04, and its status is COMPLETED.

The study model is single-group. Allocation is listed as NA and masking as NONE. The record describes a Treatment Arm but does not provide a separate arm description. There is no like-for-like control arm specified, so outcomes within the treated group cannot by themselves establish how the same participants would have fared under another treatment or under no treatment.

The stated primary objective is to assess the feasibility of using the system to safely and effectively restore blood flow in a thrombotic neurovascular occlusion. The primary endpoint operationalizes the technical component of that objective as the percentage of treated participants who establish at least TIMI 2 flow under the specified procedural conditions. Its timeframe is immediately postprocedure. The registry names the number of device-related serious adverse events as a secondary outcome. It lists four outcome measures overall, but does not provide numerical results for the primary endpoint in the record summarized by these registry entries.

The registry does not report a detailed protocol, sample-size justification, statistical analysis plan, or reasons for choosing the enrollment target. It also does not report whether interim analyses were planned or conducted. These omissions matter when interpreting a feasibility study: its design and stated objective can be described, but the amount of evidence supporting the endpoint estimate, the precision sought in planning, and any prespecified decision criteria cannot be determined from 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: All participants treated with the Test System

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 Technical Device Success by as Assessed by the Percentage of Participants Which Established at Least TIMI 2 Flow Upon Deployment of the System Across the Occlusion and Within 30 Minutes of Placing the Guide Catheter., measured over Immediately postprocedure.

The primary endpoint is the percentage of participants treated with the Test System who establish at least TIMI 2 flow upon deployment of the system across the occlusion and within 30 minutes of placing the guide catheter. The assessment timeframe is immediately postprocedure. The registry describes TIMI flow as a perfusion scoring system: TIMI 0 means no perfusion, TIMI 1 means penetration without perfusion, TIMI 2 means partial reperfusion, and TIMI 3 means complete perfusion, described as normal flow.

This is a binary participant-level outcome for analysis: each treated participant either meets the threshold of at least TIMI 2 flow or does not. Reporting the percentage meeting that threshold can make a technical feasibility outcome understandable as a proportion of the treated group. The threshold combines partial and complete reperfusion, rather than requiring TIMI 3 flow alone.

As a general statistical point, a binary endpoint can be summarized by the number meeting the definition and the proportion of the analyzed group meeting it, with a confidence interval to convey uncertainty. The registry record defines the measure but does not report its observed percentage, event count, confidence interval, or analysis population beyond “All participants treated with the Test System.” Therefore, the frequency of technical success and its precision cannot be evaluated from the record information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods help distinguish the question a study asks from the evidence available to answer it. In PRIISM, the registry defines a technical endpoint and a single-group design. It does not report the numerical primary result, a confidence interval, or an analysis entry. General explanations of the relevant methods can clarify what such information would mean, but they cannot fill in the missing result.

What does a binary endpoint represent?

The primary measure classifies each treated participant according to whether the stated TIMI threshold was reached. This type of outcome is called binary because it has two possible classifications for analysis: meeting the endpoint or not meeting it. A group percentage describes the share of the analyzed participants in the first classification. It does not describe the severity or duration of flow for each participant, nor does it show the distribution across the TIMI categories unless those category results are also reported.

The endpoint definition sets a threshold at at least TIMI 2. The record defines TIMI 2 as partial reperfusion and TIMI 3 as complete perfusion. Combining these categories means a percentage for the primary endpoint would count participants who reached either category. It would not, on its own, indicate how many reached complete perfusion.

Why does a confidence interval matter?

As a general statistical concept, a confidence interval gives a range of values compatible with the observed data under the method’s assumptions. It conveys precision as well as the point estimate: a narrower interval indicates greater precision, while a wider interval indicates greater uncertainty. An interval does not remove limitations in study design, and it does not turn a single-group estimate into a comparison with an untreated or alternative-treatment group.

No primary-endpoint estimate or confidence interval is reported in the registry record. Precision therefore cannot be evaluated. A point estimate without an interval would also leave uncertainty difficult to assess; in this case, the record does not provide either. No particular interval method is reported, so it would be inappropriate to infer how one might have been calculated.

What does the single-group design allow?

A single-group analysis can describe outcomes among the participants who received the system. If a proportion were reported, it could characterize observed technical performance in that study group. It would not supply a randomized contrast, because the record describes no comparator arm and lists allocation as NA. General statistical adjustment cannot create a randomized comparison that is not part of the design.

The absence of masking is also relevant to interpretation, but the record does not describe which people knew the treatment assignment or how outcome assessment was conducted. The primary outcome has a defined perfusion threshold, yet the registry does not report details of assessment procedures or safeguards against measurement bias. Those details are not reported in the registry record.

How should planning calculations be understood?

General sample-size calculations use assumptions about the outcome, the effect to detect, the significance level, and the intended power. Such calculations are planning illustrations; they are not results observed in the trial and should not be described as observed power. The stated planning assumptions for the illustrations use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They describe the effect to detect as a stated fraction of the observed effect.

These assumptions do not describe PRIISM’s actual design: the registry identifies a single-group study, not equal allocation to two arms. The registry does not report a protocol-based sample-size justification or the assumptions used to set the enrollment target. The observed primary effect needed for an effect-based planning illustration is also not reported in the registry record for this analysis. No sample-size output should therefore be interpreted as the trial’s own design justification or as evidence about the trial’s actual power.

Why can event-count methods differ?

As a general statistical concept, some outcomes are modeled as counts rather than as binary participant outcomes. Counts may show over-dispersion when their variability exceeds what a basic count model expects. An analysis that accounts for over-dispersion can produce more appropriate uncertainty estimates than one that assumes less variability. This consideration does not establish that the PRIISM primary endpoint is a count outcome: the primary measure is a percentage of participants with a binary event, and no count-model analysis is reported.

The registry lists four outcome measures and no analysis entries. It does not report the statistical tests, models, confidence-interval procedures, or sensitivity analyses used for the primary endpoint. These methodological details are not reported in the registry record, so the endpoint’s inferential analysis cannot be reconstructed or independently assessed from the information described.

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("Treatment Group")
n      <- c(40)
events <- c(30)
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  Treatment Group  40  30  75.0  58.8  87.3  59.8  85.8  59.7  85.8

11. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures overall and names the number of device-related serious adverse events as a secondary outcome. It does not give a full outcome-by-outcome analysis, and it lists no analysis entries. The record does not state whether a multiplicity adjustment was planned, whether the primary endpoint was designated within a formal testing hierarchy, or how secondary outcomes were to be interpreted if several were tested. These details are not reported in the registry record.

Multiplicity is a general concern when multiple outcomes or statistical tests are considered: the more opportunities to find a nominally unusual result, the greater the chance of at least one such result under assumptions where no effects exist. A prespecified analysis plan can explain which outcomes are confirmatory and how uncertainty is handled. Without such information, no multiplicity strategy can be attributed to this study.

The primary endpoint population is described as all participants treated with the Test System. The registry does not report the number analyzed for this endpoint, whether any participants lacked an assessment, or how missing outcome data were handled. It also does not report an intention-to-treat population or another analysis-population definition. Therefore, the relationship between enrollment, treatment, and endpoint analysis cannot be evaluated.

Missing-data methods can affect a result when participants lack outcome assessments, particularly if missingness is related to outcome status. General options include describing the amount and pattern of missing data and assessing how assumptions about missing outcomes affect estimates. No such information or sensitivity analysis is reported in the registry record. The numerical primary result and its denominator are also not reported, preventing an assessment of completeness.

12. 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: death (20.0%), intracranial hemorrhage (15.0%), disorientation (2.5%), malignant infarction (2.5%).

The adverse-event record lists a Treatment Group with 40 participants at risk for other adverse events and 12 affected. For serious adverse events, it lists 40 at risk and 14 affected. These are separate event categories as recorded; the figures should not be combined into a total because the record does not establish whether participants overlap across categories.

The listed top serious adverse event terms are Death at 20.0%, Intracranial hemorrhage at 15.0%, Disorientation at 2.5%, and Malignant infarction at 2.5%. The record does not provide event counts for each term or explain how the percentages were calculated. It also does not report a death count in the adverse-event group information.

The secondary outcome is named as the number of device-related serious adverse events, but the listed serious-event entries do not by themselves identify which events were judged device-related. They should not be interpreted as proof of causation or as a comparative estimate of risk. No control group or comparative safety analysis is described. The adverse-event information is therefore descriptive, and the registry record does not provide enough detail to determine event attribution, timing, recurrence, or overlap among terms.

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

The registry record documents a phase 2 feasibility study of the MindFrame System in ischemic stroke and defines a primary technical endpoint based on achievement of at least TIMI 2 flow under specified procedural conditions. That definition makes the intended question clear: whether the threshold was reached among participants treated with the system immediately postprocedure.

However, the numerical result for that primary endpoint is not reported in the registry record. There is no reported percentage, event count, confidence interval, or analysis population beyond the endpoint’s stated definition. As a result, the posted information does not establish the observed frequency of technical success or how precise an estimate might be. The absence of that result is not evidence in either direction about the endpoint.

Even a reported within-group proportion would have a limited interpretation. A single-group study describes outcomes in the treated group, but it cannot provide a randomized comparison with another approach. It therefore cannot, by itself, estimate a causal difference between the system and an alternative or separate the system’s contribution from other factors. The registry lists allocation as NA, masking as NONE, and a single-group model.

The primary endpoint is technical rather than a complete assessment of clinical benefit. Its threshold includes partial and complete reperfusion, and it does not alone describe flow severity, durability, or patient-centered outcomes. The registry’s stated objective includes assessing safety and effectiveness, but the defined primary measure is technical success. The record does not report an analysis linking this endpoint to longer-term clinical outcomes.

The serious and other adverse-event entries add descriptive safety information, but do not establish causation or a comparative safety profile. The record does not specify which listed serious events were judged related to the device. Thus, the defensible interpretation is narrow: the registry describes the study’s design, endpoint definition, and adverse-event entries, while leaving the primary technical result and its precision unavailable in the registry record.

14. Why This Trial Matters Statistically

Feasibility studies are statistically important because they can define how a device is evaluated in practice and identify which outcomes are measurable in a clinical setting. PRIISM’s registry record makes the technical question explicit: whether participants achieved at least TIMI 2 flow after system deployment across an occlusion within the specified procedural window. The definition also makes clear that the endpoint counts partial as well as complete reperfusion.

The study is single-group, so its design answers a different statistical question from a randomized comparison. A group outcome can describe what was observed among treated participants, but it cannot establish how the same outcome would compare with another intervention. Recognizing this distinction helps prevent an observed proportion, if available, from being interpreted as a treatment effect relative to a control.

The record also illustrates the importance of complete reporting. An endpoint definition is necessary for understanding a study, but it is not a substitute for the observed estimate, denominator, and uncertainty. Without those elements, readers cannot judge the frequency or precision of technical success. Reporting the analysis population and missing-data handling would further clarify who contributed information to the endpoint.

Safety entries require similar care. Terms and event counts are useful for describing what was recorded, but attribution and comparison are needed for stronger conclusions about treatment-related risk. In this record, the device-related serious adverse event outcome is named, but its analysis is not reported. The statistical significance of the study therefore lies in clarifying the intended feasibility question and the limits of the available evidence, not in establishing an unreported efficacy or safety finding.

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 registry record does not report the numerical primary endpoint result, its denominator, or an interval estimate. This is the central limitation for interpreting technical performance: the outcome is defined, but its observed frequency and precision cannot be assessed. The record also lists no analysis entries, so the method used to estimate or test the endpoint is not described.

The single-group design provides no like-for-like control comparison. Allocation is listed as NA and masking as NONE. The record does not describe a comparator or explain how outcome assessment was conducted. Consequently, even a within-group outcome would not establish a comparative effect, and the possibility of measurement or selection influences cannot be evaluated from the information reported.

The enrollment entry is 40, but the number treated and the number with an evaluable primary endpoint are not reported separately. The registry does not state whether endpoint data were missing, how missing observations were handled, or which participants were included in an analysis. It also does not report protocol details, sample-size justification, interim analyses, a statistical analysis plan, or prespecified criteria for interpreting feasibility.

For safety, the record provides affected and at-risk entries and lists serious event terms, but does not provide event-level attribution, timing, recurrence, or overlap. It does not indicate which listed serious events were judged device-related. The absence of a comparator also limits comparative safety interpretation. These limitations constrain what can be concluded from the registry information without implying that unreported procedures or outcomes were absent from the actual study.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Percutaneous Recanalization in Ischemic Stroke Management (PRIISM): A Feasibility Clinical Study — NCT00810095.
• Registry record last updated 2012-07-26; status last verified 2012-06.
• Results first posted 2012-07-26.
• 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

NCT00810095 is the registry record for Percutaneous Recanalization in Ischemic Stroke Management (PRIISM): A Feasibility Clinical Study. It is listed as a phase 2, completed, single-group study of the MindFrame System in ischemic stroke. Enrollment is 40; allocation is listed as NA and masking as NONE. The record gives a start date of 2009-03 and a primary completion date of 2011-04.

The primary endpoint is the percentage of treated participants establishing at least TIMI 2 flow after system deployment across the occlusion and within 30 minutes of guide catheter placement, assessed immediately postprocedure. The registry record does not report the numerical primary-endpoint result or an analysis of it. It names the number of device-related serious adverse events as a secondary outcome and lists serious and other adverse-event entries, but does not report a comparative safety analysis or device attribution for the listed terms.