Evaluate the Performance and Safety of Comet Pressure Guidewire in the Measurement of FFR: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluate the Performance and Safety of Comet Pressure Guidewire in the Measurement of FFR (NCT04098172), a na na study. The primary outcome is Fractional Flow Reserve (FFR).

2. Clinical Question

The study asked whether fractional flow reserve (FFR) measurements made with the Comet Pressure Guidewire agreed with measurements made with Pressure Wire Certus in Chinese patients undergoing diagnostic angiography and pressure wire assessment. The measurements were taken simultaneously, making the primary comparison paired within each participant rather than a comparison between separate treatment groups.

3. Trial Design

This was a prospective, multicenter study of the performance and safety of the Comet Pressure Guidewire in FFR measurement. It is listed as completed, with enrollment of 39. The registry lists the start date as 2019-09-03 and the primary completion date as 2020-03-11. The trial is classified as “other,” and its phase is listed as NA.

The design is single group and open label, with masking listed as none and allocation listed as NA. Participants did not enter separate randomized device groups. Instead, eligible participants received simultaneous FFR measurements using Comet and Pressure Wire Certus, so agreement could be assessed from paired readings within the same participant. This structure makes the two device readings a matched pair; it does not make the study a randomized comparison of clinical treatments.

The study population was described as stable patients with suspected or known coronary artery disease who were scheduled for diagnostic angiography and pressure wire assessment and signed informed consent. The registry identifies a Pressure Guidewire test subject group and a device intervention named Pressure Guidewire. It does not report how many sites participated, how participants were recruited at each site, or detailed eligibility criteria beyond the description above.

The registry’s design information does not give a protocol-based sample-size justification, a recruitment target beyond the reported enrollment, or a detailed statistical analysis plan. Those details are not reported in the registry record. The posted description of the agreement criterion is incomplete because it refers to both conditions being met but states only the paired-difference condition. The registry does not report the omitted condition.

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: Pressure guide wire

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 Fractional Flow Reserve (FFR), measured over during procedure, 1 hour.

The primary endpoint is fractional flow reserve, a ratio used to describe blood flow in a diseased coronary artery relative to the theoretical maximum flow in a normal coronary artery. The registry describes FFR measurement as determining the ratio between maximum achievable blood flow in a diseased artery and that theoretical maximum flow in a normal artery. It notes that an FFR of 1.0 is widely accepted as normal and that an FFR lower than 0.75-0.80 is generally considered associated with myocardial ischemia.

In this study, the purpose of the endpoint was to assess agreement between Comet and Pressure Wire Certus measurements, not to compare clinical outcomes between treatment groups. Because both readings were taken simultaneously in each participant, the paired difference is central to the stated criterion. The endpoint is described using a geometric mean and a 95% confidence interval, with the unit given as a ratio and the timeframe as during procedure, 1 hour.

The registry says agreement would be confirmed if both conditions were met and reports that the mean paired difference must be within +/- 0.005. The second condition is not reported in the registry record. Neither the observed geometric mean nor its confidence interval, nor the paired-difference result, is reported in the registry record. Therefore, the stated endpoint definition can be described, but the observed degree of agreement cannot be determined from the registry results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Several statistical ideas help explain the design, even though the registry record does not report the primary analysis results. The study compares two measurements made in the same participant at the same time. In general, paired measurements are analyzed as linked observations: the relevant comparison is the within-participant difference, rather than treating each device’s readings as if they came from independent groups. Pairing can account for stable participant-specific characteristics shared by both readings. It does not, by itself, resolve measurement error, systematic device bias, or all sources of variation.

What does a paired difference represent?

For each participant, a paired difference represents the difference between the Comet and Pressure Wire Certus readings. Across participants, the mean paired difference describes average directional separation between the methods. A value close to zero would indicate little average difference, but average agreement alone does not describe how widely individual pairs vary. Two devices could have a small average difference while still having substantial differences for some participants. A complete agreement assessment therefore depends on the prespecified criteria and the reported estimates and uncertainty, not solely on whether an average appears close to zero.

The registry states that the mean paired difference must be within +/- 0.005 as one condition for agreement. It also says that both conditions must be met, but the other condition is not reported in the registry record. The record does not provide the observed mean paired difference or show whether the stated condition was met. It therefore cannot support a conclusion about the primary agreement outcome.

What does the geometric mean describe?

The primary endpoint is listed with a geometric mean and a 95% confidence interval. In general, a geometric mean summarizes measurements on a multiplicative scale and is often used for positive, ratio-like quantities. A confidence interval expresses uncertainty around an estimate under the statistical model and sampling assumptions. It is not a range guaranteed to contain the value for every participant, nor does it directly show how much individual paired readings differ. Because the registry does not report the geometric mean or its confidence interval, the size and precision of that endpoint estimate cannot be assessed.

The endpoint is given as a ratio. The registry explains FFR as the ratio of maximum achievable blood flow in a diseased coronary artery to the theoretical maximum flow in a normal coronary artery. It states that an FFR of 1.0 is widely accepted as normal and describes values lower than 0.75-0.80 as generally considered associated with myocardial ischemia. These statements describe the endpoint’s clinical context; they do not provide the study’s observed measurements or establish how the two devices compared.

Why does study structure matter?

This is a prospective, multicenter, open-label, single-group study, with allocation listed as NA and masking listed as none. Since both devices were used in the same eligible participants, the design centers on paired measurement agreement, not between-group treatment effects. The absence of random allocation is not itself a defect for a paired measurement study, but it means the results should not be interpreted as a randomized device-versus-control clinical outcome comparison. Open-label measurement can also leave possible influences such as operator awareness; whether or how these were addressed is not reported in the registry record.

In general, measurement agreement and correlation are different concepts. Correlation describes how readings move together, whereas agreement concerns how close the readings are on the measurement scale. Two methods can have strong correlation while differing systematically or by clinically important amounts. The registry’s stated paired-difference criterion is therefore relevant to the agreement question. However, the full agreement method cannot be reconstructed because the second criterion and analysis details are not reported.

What can planning calculations say?

A planning illustration based on an observed effect is not the trial’s original design justification and is not observed power. The stated illustration assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect defined as a stated fraction of the observed effect. Its sample-size figures are not reported in the registry record presented for this study. More importantly, those assumptions describe a two-arm planning illustration, while the trial itself is a single-group paired measurement study. Such an illustration should not be treated as evidence that the original enrollment was sufficient for the paired agreement question.

In general, over-dispersion means that variability is greater than a model assumes. When present, it can make uncertainty estimates too small if the analysis does not account for it. The registry record does not report a model for variability, an over-dispersion assessment, or enough analysis information to determine whether these issues were relevant. No new estimate of precision or power can be derived from the posted information alone.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure and does not list any analyses. It does not report a multiplicity adjustment or a strategy for handling multiple hypotheses or endpoints. That does not establish that multiplicity was absent from the study protocol; the relevant plan is not reported in the registry record. There is also no reported analysis result from which to determine whether any adjustment was applied.

Missing-data handling is not reported in the registry record. The record does not state how incomplete or unusable FFR readings, withdrawals, or participants without paired measurements were handled. Enrollment of 39 is reported, but enrollment alone does not show that all enrolled participants contributed data to the primary endpoint. The number included in the primary analysis and any exclusions or missing measurements are not reported.

Analysis populations are also not described. The record does not identify a specific population used for the primary endpoint, such as all enrolled participants or those with complete paired measurements. It does not report whether any participants were excluded from the endpoint analysis or the reasons for exclusion. Consequently, the relationship between enrollment and the analyzed population cannot be assessed.

The endpoint description states that agreement would be confirmed if both conditions were met, but gives only the condition that the mean paired difference be within +/- 0.005. The second condition is not reported in the registry record. Without a complete decision rule, the analysis method, and the observed results, it is not possible to judge how the registry intended to handle the full primary hypothesis or its precision.

11. 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

Serious events with the highest arm-level rate: subclavian artery stenosis (2.6%).

For the Pressure Guidewire test subject group, the registry reports 39 participants at risk for serious adverse events and 1 participant affected. It reports 39 participants at risk for other adverse events and 0 affected. The record also lists 1 death. Subclavian artery stenosis is the leading serious adverse event term listed, at 2.6%.

These figures are descriptive counts in the registry record. The serious-event count and death count are not a comparison against another group: the study has a single-group design and does not report a separate randomized control group. The record does not say whether the death was considered related to the device or procedure, when events occurred, whether the serious event and death occurred in the same participant, or how event terms were coded. Those details are not reported in the registry record.

A zero count for other adverse events means that none were recorded in that category for the stated group; it does not establish that no other events could occur or that risk is absent. Likewise, the listed serious-event percentage should be read as the registry’s reported value, not as a comparative risk estimate. The safety information does not establish causation or provide a basis for treatment decisions.

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

The study addresses a specific measurement question: whether FFR readings from the Comet Pressure Guidewire agree with readings from Pressure Wire Certus when both are used simultaneously in eligible participants. Its prospective, paired design is relevant to that device-agreement question because each participant contributes readings from both methods. The registry also identifies the endpoint scale, its summary measure, and one stated agreement condition.

However, the posted results do not include the primary endpoint estimate, its 95% confidence interval, or the mean paired difference. The registry says agreement depends on both conditions being met, but only one condition is specified. As a result, the record does not establish whether the stated agreement criterion was satisfied. The study’s enrollment of 39 participants does not fill that gap: a participant count is not a substitute for observed estimates and their uncertainty.

The design also does not answer whether one device improves clinical outcomes relative to another. There is no randomized treatment comparison described; the comparator is another measurement device used in the same participants. FFR is a physiological measurement, and the registry’s endpoint concerns measurement agreement. It does not report outcomes such as changes in patient management, longer-term clinical events, or comparative clinical benefit.

The safety counts should likewise be interpreted narrowly. The registry records serious adverse events, other adverse events, and deaths in the study group, but gives no comparative group and does not report event attribution or timing. These counts describe what is recorded; they do not determine whether an event was caused by the device or establish comparative safety.

In general, a result can be informative only in relation to its estimand, analysis method, and uncertainty. For this study, those elements are incompletely reported. The record supports understanding of the intended paired measurement question and the study’s broad design, but the primary results needed to answer that question are not reported in the registry record.

13. Why This Trial Matters Statistically

Device studies that compare measurement methods raise a distinct statistical question from trials that compare treatments. For Comet and Pressure Wire Certus, the central issue is whether readings agree within participants, not whether participants assigned to one device have different clinical outcomes from participants assigned to another. Recognizing that distinction helps readers match the design to the claim being evaluated.

The paired structure is important because simultaneous measurements in the same participant create linked observations. A suitable agreement analysis must preserve that pairing and describe both average separation and uncertainty. General statistical reasoning also cautions that average agreement is not necessarily the same as close agreement for every individual measurement. The registry’s stated paired-difference condition is relevant, but the record does not report its result or the second condition needed under the stated decision rule.

Reporting completeness matters as much as design. A defined endpoint and sample size cannot show what the observed measurements were. Without the geometric mean, its confidence interval, the paired-difference estimate, and the complete agreement rule, readers cannot judge the direction, magnitude, or precision of the observed comparison. The absence of listed analyses also leaves the statistical implementation unclear.

The safety figures illustrate another important interpretive point: single-group event counts are descriptive, not comparative. They can show what the registry recorded among participants in the study, but cannot by themselves attribute events to the device or establish a difference in risk. Separating measurement performance from clinical outcomes, and descriptive safety reporting from causal comparison, keeps conclusions aligned with the information the record actually contains.

14. 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 principal limitation for interpretation is that the registry record does not report the primary FFR results. It identifies the endpoint as a geometric mean with a 95% confidence interval but gives neither estimate. The observed mean paired difference is also absent. Therefore, the record does not permit assessment of the stated paired-difference condition.

The agreement rule is incomplete in the registry description: it says both conditions must be met but states only that the mean paired difference must be within +/- 0.005. The other condition is not reported in the registry record. Without the complete rule, even a hypothetical estimate for the stated condition would not be enough to determine whether the registry’s full definition of agreement was met.

The record reports enrollment of 39 but does not report how many participants had complete paired measurements or contributed to the endpoint analysis. Missing-data methods, analysis populations, detailed statistical procedures, and a sample-size justification are not reported in the registry record. These omissions limit assessment of precision, potential exclusions, and the match between the analysis and the design.

The study is open label and single group, with no randomized comparison group. That structure fits a paired measurement question but does not support a randomized comparison of clinical outcomes or comparative safety. The registry does not report whether measurement procedures were standardized across centers, whether operator awareness was addressed, or how device-related and procedure-related events were attributed.

Finally, the posted adverse-event information is limited to counts and a listed serious-event term. Timing, attribution, overlap between events and death, and participant-level context are not reported. These limitations mean the safety figures should remain descriptive rather than being interpreted as evidence of causation or comparative risk.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Evaluate the Performance and Safety of Comet Pressure Guidewire in the Measurement of FFR — NCT04098172.
• Registry record last updated 2021-11-01; status last verified 2021-05.
• Results first posted 2021-06-07.
• 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.

18. Record Summary

NCT04098172 is a completed, prospective, open-label, multicenter, single-group study sponsored by Boston Scientific Corporation. It enrolled 39 participants and evaluated Comet Pressure Guidewire FFR measurements against simultaneous Pressure Wire Certus measurements in Chinese patients. The registry lists cardiovascular diseases as the condition, the intervention as a pressure guidewire device, and FFR as the primary endpoint, summarized by a geometric mean and 95% confidence interval.

The stated agreement rule requires both conditions to be met, but only the paired mean-difference condition of within +/- 0.005 is reported. The primary endpoint estimates, the second condition, and the analysis results are not reported in the registry record. Safety reporting lists 1 participant with a serious adverse event, 0 with other adverse events, and 1 death among the group of 39; subclavian artery stenosis is listed at 2.6%. The record does not report comparative safety analyses or event attribution.