Pressure Guidewire System Multi-center, Prospective, Self-Control, Clinical Trial: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pressure Guidewire System Multi-center, Prospective, Self-Control, Clinical Trial (NCT04582877), a na na study. The primary outcome is Number of Participants With Diagnostic Consistency When Comparing FFR Measurement Between Control Device and Investigational Device.

2. Clinical Question

The clinical question is one of agreement in classification at the stated FFR threshold, rather than a comparison between separately assigned groups. The registry also lists secondary outcomes concerning sensitivity, specificity, predictive values, a receiver operating characteristic curve, and several analyses of measurement relationships. These describe additional ways to assess diagnostic classification or agreement, but their results are not reported in the registry record.

The record describes a within-participant device comparison in which the control device supplies the reference classification. This setup makes the paired nature of the measurements central to interpreting the question: each participant undergoes measurement with both devices, rather than receiving one device or the other. The registry record does not report the observed consistency count or rate, so it does not establish from the posted results how often the classifications matched.

3. Trial Design

This is a prospective, multicenter, single-group clinical trial of FFR measurements using a test device and a predicate device. The listed enrollment is 300, the trial status is completed, and the study is described as beginning on 2020-09-23 with primary completion on 2023-11-15. The phase and allocation are listed as NA, and masking is listed as none. The sponsor is Zurich Medical Inc.

The study does not assign participants to separate device arms for the primary comparison. Instead, participants with intermediate-grade coronary stenosis undergo measurement using both the Zurich Pressure Guidewire System and the Abbott PressureWire System. Measurements are taken sequentially during the same visit, and each participant is described as completing the procedure in one visit. The timeframe for the primary outcome is acute; a procedure may take up to 30 minutes.

The primary description treats each subject as a research unit and identifies the control-device FFR measurement as the reference. For participants with multiple lesions, the method of converting lesion-level results to the patient level is said to be defined in the statistical analysis plan. That conversion method is not reported in the registry record.

Because the comparison is paired within participants, the device results should not be interpreted as outcomes from independently allocated groups. The registry does not describe random assignment, and the listed allocation is NA. It also does not report a masking procedure. The available record therefore supports describing the intended comparison and measurement setting, but not assumptions about sequence randomization, blinding, or other procedural safeguards.

The registry lists ten outcome measures and zero analyses. The outcome descriptions include the primary diagnostic-consistency measure and secondary diagnostic or measurement-agreement outcomes. Their definitions appear in the record, but results for the primary and secondary outcomes 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

Reasons for not completing this period:

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: The study started with 300 participants, however, 7 patients never completed the study. Additionally, 1 participant violated protocol, however, their baseline characteristics were still recorded.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Diagnostic Consistency When Comparing FFR Measurement Between Control Device and Investigational Device, measured over Acute - all measurements are taken and assessed during each procedure. Each participant completes their procedure in one visit, with each procedure taking up to 30 minutes..

The primary endpoint is titled as the number of participants with diagnostic consistency when comparing FFR measurements from the control and investigational devices. Its description also calls the measure a diagnostic consistency rate. Consistency is defined by whether the investigational device gives the same positive or negative classification as the control device at the stated threshold.

The control-device reference is positive at FFRPW ≤ 0.80 and negative at FFRPW > 0.80. The corresponding investigational-device classification is positive at FFRWS ≤ 0.80 and negative at FFRWS > 0.80. Each participant is treated as a research unit, and the control-device measurement is the reference for the comparison. The registry notes that participants may have multiple lesions, while the patient-level conversion method is assigned to the statistical analysis plan; that method is not reported in the registry record.

As a general statistical concept, a classification-consistency endpoint asks how often two measurement systems place the same unit in the same category. It is useful when a decision depends on a threshold, because a close numerical relationship between measurements does not necessarily guarantee identical classifications near that threshold. The count or rate would describe agreement in this study, not by itself the clinical consequences of any disagreement.

The observed primary count, rate, and any measure of uncertainty are not reported in the registry record. The endpoint definition can therefore be described, but its observed magnitude and precision cannot be assessed from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes several distinct statistical questions. The primary measure compares threshold-based classifications from two devices, while the secondary outcomes include both diagnostic-performance measures and methods for comparing numerical measurements. These methods answer different questions and should not be treated as interchangeable. The registry record does not report the numerical results or the detailed analysis procedures used.

What does diagnostic consistency measure?

In general, diagnostic consistency counts whether two classifications agree for the same research unit. Here, the control-device measurement is the reference, and the investigational-device result is assessed against it. The stated positive category is FFRPW ≤ 0.80 for the control and FFRWS ≤ 0.80 for the investigational device; the negative category is FFRPW > 0.80 and FFRWS > 0.80, respectively. This describes classification agreement, not necessarily equality of the underlying numerical readings.

A threshold can make small numerical differences important for classification when readings lie near the cutoff. Conversely, two devices can produce different numerical readings while retaining the same positive or negative category. General interpretation therefore distinguishes categorical agreement from numerical agreement. The registry record does not report the observed number or rate of matching classifications, nor uncertainty around that result.

How do sensitivity and specificity differ?

In general, sensitivity describes the proportion of reference-positive units identified as positive by the device under evaluation. Specificity describes the proportion of reference-negative units identified as negative. These quantities use different parts of the reference classification, so they can reveal patterns that a single overall consistency measure might conceal. The registry lists sensitivity and specificity as secondary outcomes, but their observed values are not reported in the registry record.

Positive predictive value and negative predictive value answer related but different questions. In general, positive predictive value is the proportion of device-positive classifications that are reference-positive; negative predictive value is the proportion of device-negative classifications that are reference-negative. These predictive values depend on the mix of positive and negative reference results in the studied population. Their interpretation is tied to the participants and measurement context in which they are estimated. The registry lists both outcomes, but does not report their results.

What does an ROC curve add?

In general, a receiver operating characteristic curve describes diagnostic classification across possible thresholds by relating sensitivity and the false-positive rate. It can show how classification changes as the threshold varies, rather than focusing only on one cutoff. The registry lists an ROC curve outcome for the trial device. It does not report the curve, a summary measure from it, or the analysis details in the registry record.

How do the measurement-comparison methods differ?

Passing-Bablok regression is generally used to examine the relationship between two measurement methods and assess whether their values show a systematic relationship or departure from equality. Bland-Altman analysis generally examines the differences between paired measurements in relation to their average, to characterize bias and the spread of differences. Pearson correlation generally quantifies the strength of a linear association between paired numerical values. These approaches address numerical relationships; correlation alone does not establish that two methods agree closely, because a strong association can coexist with systematic differences.

The registry lists Passing-Bablok regression, Bland-Altman bias analysis, and Pearson linear correlation as secondary outcomes. Their results, assumptions, and implementation details are not reported in the registry record. The record likewise does not state how repeated or multiple lesions contributed to these calculations.

Why does pairing matter?

As a general statistical principle, paired measurements from the same participant are related. Analyses should account for this relationship rather than treating the two device readings as observations from independent groups. The trial description states that both devices are used in each participant during the same visit, sequentially. It does not report the exact estimator or test used for the primary endpoint.

For participants with multiple lesions, the registry says that the method for converting lesion-level findings to patient-level results is defined in the statistical analysis plan. The selected method could affect how each participant contributes to the analysis, but the method itself is not reported in the registry record. The record also does not report confidence intervals, missing-data procedures, multiplicity adjustments, or a detailed statistical analysis plan. Accordingly, the listed outcome names indicate the statistical questions considered, not the numerical findings or the complete methods used to answer them.

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("FFR Measurement in Intermediate-Grade Coronary Ste")
n      <- c(292)
events <- c(274)
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  FFR Measurement in Intermediate-Grade Coronary Ste  292  274  93.8  90.4  96.3  90.5  96.1  90.5  96.1

11. Multiplicity, Missing Data and Analysis Populations

The registry lists ten outcome measures, including the primary diagnostic-consistency endpoint and secondary outcomes for sensitivity, specificity, predictive values, ROC analysis, and measurement-comparison methods. The record does not report a multiplicity strategy, such as a hierarchy of outcomes or an adjustment for testing multiple questions. It is therefore not possible to determine from the registry how the interpretation of multiple outcome analyses was controlled. No outcome-specific results or p-values are reported in the registry record.

The registry lists zero analyses. It does not report a statistical analysis plan or explain how the primary analysis was carried out. In particular, the patient-level conversion for participants with multiple lesions is assigned to the statistical analysis plan, but the conversion method is not reported in the registry record. The number of participants with evaluable primary measurements is also not reported.

Missing-data handling is not reported in the registry record. There is no description of how incomplete, unavailable, or technically unsuccessful measurements would be treated, or whether any participants were excluded from particular outcome analyses. The listed enrollment of 300 and the 295 participants at risk in each safety group do not establish the primary analysis population or explain any difference between these figures.

The record does not report whether analyses were planned for subgroups or whether there were interim analyses. These details should not be inferred from the study’s status or outcome list. Without analysis populations, missing-data procedures, and a multiplicity plan, the registry’s outcome definitions alone are insufficient to reconstruct the full inferential approach.

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 non-serious adverse event terms

The adverse-event record lists two device groups, each with 295 participants at risk. For the subject device, it reports zero serious adverse events, one other adverse event, and zero deaths. For the control device, it reports zero serious adverse events, zero other adverse events, and zero deaths. No serious adverse-event terms are listed.

These are the posted counts, not a comparative estimate of device safety. The registry does not report the nature, timing, severity, or relatedness of the one other adverse event, so those details cannot be characterized. It also does not report an analysis comparing the groups or uncertainty around these counts. The entries should not be interpreted as evidence that the devices have identical safety profiles.

The study uses both devices in the same participants, while the adverse-event record organizes counts by device group. The registry does not explain the event-attribution procedure or how participant overlap is handled for these safety entries. The 295 participants at risk in each group should not be assumed to represent the primary endpoint analysis population. As a general principle, small event counts can provide limited information about the range of possible event rates, but no additional rate or estimate is calculated.

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

The registry record establishes that the trial was designed to compare FFR measurements from the Zurich Pressure Guidewire System with those from the Abbott PressureWire System in the same participants. It specifies a threshold-based primary question: whether the investigational device gives the same positive or negative classification as the control device, with the control measurement serving as the reference. It also lists secondary diagnostic and numerical-comparison outcomes.

The record does not report the primary consistency count or rate, estimates of sensitivity or specificity, predictive values, ROC results, or results from the listed measurement-comparison analyses. It also does not report uncertainty intervals for those outcomes. Consequently, the posted information does not establish the observed level of diagnostic consistency or the precision of any estimate. A completed trial status and a defined endpoint do not substitute for outcome results.

Even if a consistency estimate were available, general interpretation would distinguish agreement at the stated threshold from agreement in numerical FFR readings. The secondary methods listed address different aspects of the comparison. Sensitivity and specificity assess classification relative to the reference; predictive values describe the composition of device classifications; regression, bias, and correlation analyses address relationships between numerical measurements. No one of these concepts should be treated as a replacement for the others.

The trial’s design also matters. Both devices are used in each participant, so the comparison is paired, not a randomized comparison between separate groups. The registry does not report masking, and the method for converting multiple lesion readings to patient-level results is not included. These gaps limit reconstruction of the analysis and its potential sources of uncertainty.

The appropriate reading is therefore descriptive: the registry defines a prospective, within-participant device-comparison question and reports limited adverse-event counts, but does not report the primary or secondary outcome results. No conclusion about comparative diagnostic performance follows from the design description alone.

14. Why This Trial Matters Statistically

This trial raises a statistical issue common to diagnostic-device comparisons: a device can be evaluated both as a classifier at a chosen threshold and as a measurement method producing numerical readings. The primary endpoint focuses on agreement in positive or negative classification at FFR 0.80. The listed secondary outcomes extend the question to diagnostic performance and to relationships between the numerical values. Keeping those questions distinct is important because agreement on a category does not mean that readings are numerically interchangeable, and correlation is not itself proof of agreement.

The within-participant design is also statistically meaningful. Each participant is measured with both devices during the same visit, so the observations are paired. The comparison therefore concerns within-person measurement differences or classification matches, rather than a contrast between independent participant groups. The control measurement is named as the reference, which defines how the primary classification question is framed.

The record illustrates why endpoint definitions and analysis details matter. It says that participants with multiple lesions are reduced to a patient-level research unit according to a method in the statistical analysis plan, but that method is not reported in the registry record. Without it, readers cannot fully reconstruct how lesion-level information contributes to the participant-level outcome. The record also does not report the primary result, uncertainty, missing-data approach, or multiplicity strategy.

The statistical significance of the study’s question is not the same as an available statistical finding. The study’s completed status and list of ten outcome measures describe the record, but do not show whether or how well the devices agreed. The posted safety counts likewise do not establish comparative safety. The main statistical value of the record is its description of a paired, threshold-based design and the range of diagnostic and agreement questions it set out to address.

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 most direct limitation for interpretation is that the registry record does not report results for the primary endpoint or the listed secondary outcomes. There is no reported consistency count or rate, no estimate of uncertainty, and no reported numerical results for the diagnostic or measurement-comparison analyses. The completed status does not fill this gap.

Although enrollment is listed as 300, the record does not state the number of participants with usable data for each outcome. The safety entries list 295 participants at risk in each device group, but the record does not explain how those figures relate to the primary or secondary analysis populations. No missing-data approach or reasons for unavailable measurements are reported.

The device measurements are paired within participants and collected sequentially during the same visit. The registry does not report whether measurement order was randomized or otherwise managed, nor does it describe masking beyond listing masking as none. The statistical analysis plan’s method for converting results from multiple lesions to a participant-level result is not reported in the registry record.

The available information also does not specify the exact statistical procedures, confidence-interval methods, multiplicity handling, or planned subgroup analyses. The registry lists diagnostic and numerical-comparison outcomes but does not provide enough detail to assess how each was implemented. Because the control device is used as the reference, the described diagnostic outcomes measure comparison against that reference, not against an independently described standard. No further reference-standard details are reported in the registry record.

The safety information is limited to counts of serious events, other events, and deaths. The one other event listed for the subject device is not described, and event attribution is not explained. These limitations mean that conclusions should be restricted to the design and counts recorded, without extrapolating to unreported diagnostic results or event details.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Pressure Guidewire System Multi-center, Prospective, Self-Control, Clinical Trial — NCT04582877.
• Registry record last updated 2024-12-02; status last verified 2024-11.
• Results first posted 2024-12-02.
• 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

NCT04582877 is a completed, prospective, multicenter, single-group trial sponsored by Zurich Medical Inc. It lists enrollment of 300 and evaluates FFR measurement with the Zurich Pressure Guidewire System and Abbott PressureWire System in participants with intermediate-grade coronary stenosis. Both devices are used sequentially in the same participant during one visit, with the control-device result serving as the reference for the primary classification comparison.

The primary outcome concerns the number of participants with diagnostic consistency at the stated FFR threshold. Listed secondary outcomes include sensitivity, specificity, predictive values, ROC analysis, Passing-Bablok regression, Bland-Altman bias analysis, and Pearson correlation. The registry record does not report results for these outcomes or the method for handling multiple lesions at the participant level.

The safety entries list zero serious adverse events and zero deaths in both device groups, with one other adverse event in the subject-device group and none in the control-device group. Details of that other event are not reported in the registry record.