Simultaneous Assessment of FFR and SPECT: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Simultaneous Assessment of FFR and SPECT (NCT02749045), a na na study. The primary outcome is Concordance Between Gated SPECT Perfusion Data (QGS) and Fractional Flow Reserve (FFR).

2. Clinical Question

The study’s stated purpose was to identify disparities between ischemia measurement by FFR and myocardial perfusion stress SPECT, and to determine the correlation between measurements obtained simultaneously using regadenoson in the catheterization laboratory. The primary endpoint gives this question a classification-based form: it counts participants whose FFR and SPECT results were both abnormal, together with participants whose results were both normal, relative to the total number of participants.

In the endpoint definition, abnormal FFR is below 0.8, while normal FFR is at least 0.8. An abnormal SPECT result is described as a perfusion defect. The registry record does not report the number of participants in either agreement category, the total number with paired assessments, or the resulting concordance percentage. It therefore states the intended question and its operational definition, but does not report an answer to that question.

3. Trial Design

The registry describes NCT02749045, titled “Simultaneous Assessment of FFR and SPECT,” as a single-group study with no masking and no randomized allocation. Its listed phase and allocation are NA. The named arm is the Image Acquisition Arm; it is not a control arm. The registry reports enrollment of 27 and lists coronary artery disease as the condition under study.

Participants who had undergone a clinically indicated FFR measurement in the catheterization laboratory were to receive standard-dose Tc-99m sestamibi and undergo resting SPECT image acquisition within three hours from the end of the catheterization procedure. SPECT imaging is listed as the intervention, with type recorded as radiation. The study’s stated purpose also refers to simultaneous FFR and SPECT using regadenoson in the catheterization laboratory. The registry does not provide further procedural detail about the timing or conduct of that assessment.

The primary outcome is titled “Concordance Between Gated SPECT Perfusion Data (QGS) and Fractional Flow Reserve (FFR),” uses participants as its unit, and gives a timeframe of 24 hours. The record lists one outcome measure and zero analyses. It does not report a reason for the study’s terminated status, the number of participants with completed paired measurements, or an analysis result. Start and primary completion are recorded as 2016-07 and 2020-12, respectively. The sponsor is Prem Soman.

Because this is a single-group measurement study, the design does not support a treatment-versus-control interpretation. Its central comparison is between two diagnostic classifications recorded for participants in the same study group.

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

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 Concordance Between Gated SPECT Perfusion Data (QGS) and Fractional Flow Reserve (FFR), measured over 24 hours.

The primary endpoint is the concordance between gated SPECT perfusion data (QGS) and FFR, measured in participants over a stated timeframe of 24 hours. Concordance is defined as the proportion of participants whose two assessments agree: both FFR and SPECT are abnormal, or both are normal. Abnormal FFR is defined as below 0.8; normal FFR is at least 0.8. An abnormal SPECT finding is a perfusion defect.

This measure addresses whether the two assessments place participants in the same broad category. It is useful for describing agreement, but it is not identical to correlation. General statistical context: correlation describes how measurements vary together, whereas agreement asks how often their classifications or values coincide. A single overall concordance proportion also does not show whether disagreements mostly involve abnormal FFR with normal SPECT or the reverse. Those directions can matter when interpreting what agreement means.

The registry record does not report the concordance count or percentage, the number of paired observations used in the denominator, or an uncertainty interval. Although the endpoint definition explains how concordance was to be calculated, the posted record does not report the calculated result.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The methods that can be described from the registry are limited. The record identifies a single-group design, a binary classification-based primary endpoint, and a formula for concordance. It lists one outcome measure and zero analyses. It does not report an analysis method used to produce an endpoint estimate, a statistical model, or a precision estimate. The concepts below explain how the stated endpoint is generally interpreted; they are not a description of unreported procedures.

What does the concordance measure count?

The endpoint combines two kinds of agreement. One is a participant with an abnormal FFR and an abnormal SPECT result. The other is a participant with a normal FFR and a normal SPECT result. The sum of those agreeing classifications is divided by the total number of participants, according to the registry’s definition. FFR below 0.8 is classified as abnormal; FFR at least 0.8 is normal. SPECT is classified as abnormal when a perfusion defect is present.

This makes the endpoint a proportion based on paired classifications. A participant must have both assessments available to be classified as agreement or disagreement. The registry does not report how many participants had paired assessments or how the denominator was handled if one assessment was unavailable. It also does not report the resulting numerator or proportion.

How is concordance different from correlation?

General statistical context: correlation measures the extent to which two measurements vary together. Agreement asks whether the measurements or classifications are sufficiently alike under a defined criterion. Two measures may be associated without producing identical classifications, and a binary concordance measure does not describe the full relationship between underlying continuous measurements. Here, the primary endpoint operationalizes agreement through normal and abnormal categories; no numerical correlation analysis is reported.

General statistical context: an overall agreement proportion does not indicate the direction of disagreement. A participant may have abnormal FFR with normal SPECT, or normal FFR with abnormal SPECT, and those two patterns contribute equally to the overall count of non-matching pairs. Separate counts by pattern would give a more detailed account, but they are not reported in the registry record.

What would an uncertainty interval mean?

General statistical context: a confidence interval expresses uncertainty around an estimate under the assumptions of the statistical method used. For a concordance proportion, it would help readers judge how precisely the observed agreement was estimated. The registry does not report a concordance estimate or confidence interval, so neither the estimate nor its precision can be assessed. No p-value or hypothesis test result is reported either. The absence of these results does not establish that the agreement was high, low, or statistically distinguishable from any benchmark.

What can be said about sample-size planning?

The record includes planning assumptions for a sample-size illustration: a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and effects defined as stated fractions of an observed effect. These are planning assumptions, not a description of the enrolled study’s design: the trial is listed as single-group, with no randomized allocation or separate comparison arm. The registry does not report the resulting planning counts, the observed effect used for such an illustration, or a trial-specific sample-size justification. A planning calculation is not observed power and does not replace an analysis of the collected endpoint.

General statistical context: sample-size calculations depend on the outcome, assumptions about the effect to detect, the desired error rate, and the analysis method. They are prospective planning tools. They cannot establish the precision of an unreported result, and a calculation framed around two arms does not turn a single-group study into a comparative trial.

What does the absence of analyses imply?

The registry lists zero analyses. This means that no analysis result is posted in the registry record for interpretation. It does not reveal whether analyses were performed outside the record, what methods might have been used, or why no analysis is listed. Those details are not reported in the registry record. Without an analysis population, paired-data counts, an estimate, and a measure of uncertainty, the endpoint’s statistical result cannot be reconstructed from the information recorded.

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("Image Acquisition Arm")
n      <- c(27)
events <- c(19)
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  Image Acquisition Arm  27  19  70.4  49.8  86.2  51.5  84.1  51.3  84.1

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure and zero analyses. It does not report a multiplicity adjustment, a hierarchy among outcomes, or a prespecified strategy for handling multiple statistical tests. With no analyses reported, there is no posted set of test results from which to assess whether multiplicity affected interpretation. The record’s listing of one outcome measure alone does not establish what other analyses, if any, were planned or conducted.

Missing-data handling is not reported in the registry record. In particular, the record does not state how participants without a SPECT result, without an FFR result, or without a complete paired assessment would be handled in calculating concordance. It does not report the number with complete assessments, the number excluded from an endpoint analysis, or reasons for missing measurements. Enrollment of 27 should therefore not be assumed to equal the denominator for the primary endpoint.

Analysis populations are also not reported. The registry does not identify an intention-to-treat, per-protocol, complete-case, or other analysis population. General statistical context: the choice of population and the handling of missing paired measurements can affect a proportion based on agreement, because the denominator determines which participants contribute to the estimate. Without these details or an endpoint result, the robustness of any concordance estimate cannot be evaluated.

The record does not report interim analyses, stopping rules, or a statistical analysis plan. The terminated status does not explain whether any planned analyses were changed or why the study ended. These items are not reported in the registry record.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

The adverse-event record lists the Image Acquisition Arm with 27 participants at risk for serious events and 0 affected. It also lists 27 at risk for other events and 0 affected, with 0 deaths. No serious adverse-event terms are listed. These are the posted counts and should be read as registry entries, not as a complete account of every possible event or of how events were monitored.

The record does not provide further information about safety definitions, collection procedures, observation duration, completeness of reporting, or whether all 27 enrolled participants contributed to these counts. It also does not explain whether the risk groups correspond to the entire enrolled group or a particular analysis population. Consequently, the zero affected counts describe what is recorded, but the registry does not provide enough detail to assess the completeness or scope of adverse-event ascertainment.

These safety figures are separate from the primary concordance endpoint. They do not supply information about agreement between FFR and SPECT, and they do not resolve the absence of a reported primary endpoint analysis.

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

The posted record establishes the study’s intended statistical question and how its primary endpoint was defined. It describes a single-group assessment of whether FFR and SPECT classify participants in agreement, with abnormal FFR defined as below 0.8, normal FFR as at least 0.8, and abnormal SPECT as a perfusion defect. It also records enrollment of 27 and a terminated status.

It does not report the observed concordance count or percentage, the number of paired results included, an uncertainty interval, or an analysis. As a result, the statistical evidence needed to describe the observed agreement is absent from the registry record. The absence of a reported result does not show that the methods agreed or disagreed, and it does not establish that either method performed better.

Even if an overall concordance percentage were available, general statistical context is important: it would quantify matching classifications under the stated definitions, not demonstrate that the methods are interchangeable or that one is a definitive reference. It would not by itself describe the direction of disagreement, the relationship between continuous measurements, or the clinical significance of individual mismatches. Those questions require additional information and analyses, none of which are reported in the registry record.

The study’s stated aim includes assessing correlation, but the primary endpoint is defined as a classification-based concordance measure. No correlation estimate or other analysis is reported. The record therefore documents an intended comparison, not a posted statistical finding. The adverse-event entries list zero affected participants for serious and other events and zero deaths among the recorded groups, but do not provide further detail about collection or completeness.

14. Why This Trial Matters Statistically

This study raises a useful statistical distinction: two clinical measurements can be compared by asking whether they are associated, whether their values agree, or whether they place participants in the same category. The stated objective refers to correlation, while the primary endpoint defines agreement through normal and abnormal classifications. Keeping those questions separate helps prevent an overall concordance measure from being interpreted as a complete account of how two measurement methods relate.

The endpoint also illustrates why a clearly stated denominator and paired observations matter. Concordance requires both assessments for a participant, and an overall proportion depends on which participants are included. The registry reports enrollment of 27 but does not report the number with complete paired measurements or an endpoint result. That prevents a reader from judging either the observed agreement or its precision.

Another statistical issue is that a single agreement proportion can conceal different forms of disagreement. Counts for abnormal FFR with normal SPECT and normal FFR with abnormal SPECT would describe the mismatches more fully, but are not reported. General statistical context: this is one reason agreement summaries are best interpreted alongside the underlying classification pattern and a clear account of missing paired observations.

The study is also a reminder to distinguish a registry’s stated objective, endpoint definition, design, and analysis results. Here, the record specifies a single-group assessment and a concordance formula, but lists zero analyses. That gap is consequential: an endpoint definition is not evidence of an observed result, and enrollment alone cannot stand in for the endpoint denominator. The record supports discussion of the planned statistical question, but not a conclusion about the degree of agreement.

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 statistical interpretation is that the registry reports no primary endpoint result and lists zero analyses. It provides no concordance estimate, no agreement or disagreement counts, no paired-assessment denominator, and no confidence interval. The intended comparison therefore cannot be evaluated quantitatively from the posted results.

The study is listed as single-group, with allocation NA and no masking. There is no separate control group, and the design is not a randomized comparison. The primary question is about agreement between assessments within participants, so it should not be read as a treatment-effect comparison. The registry does not report why the study was terminated.

The record does not report how incomplete FFR or SPECT assessments were handled, what analysis population was used, or whether any participants were excluded from the endpoint calculation. Although enrollment is 27, the number contributing paired data is not reported. The primary outcome gives a timeframe of 24 hours, while the arm description specifies resting SPECT acquisition within three hours from the end of catheterization; the registry does not provide further detail connecting these timing descriptions.

The endpoint reduces each assessment to normal or abnormal status. That definition does not convey the underlying measurement values or, by itself, show the direction of discordance. The registry also does not report a correlation estimate despite the stated objective of determining correlation. Finally, the adverse-event counts are listed without information about ascertainment methods or completeness. These limitations are specific to what the registry record reports; they do not establish what was or was not done outside that record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Simultaneous Assessment of FFR and SPECT — NCT02749045.
• Registry record last updated 2022-02-02; status last verified 2022-01.
• Results first posted 2022-02-02.
• 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

NCT02749045 is a terminated, single-group study titled “Simultaneous Assessment of FFR and SPECT,” sponsored by Prem Soman. The registry lists coronary artery disease as the condition, enrollment of 27, no masking, and allocation NA. Start and primary completion are recorded as 2016-07 and 2020-12.

The study aimed to assess the relationship between invasive FFR and SPECT myocardial ischemia measurements. Its primary endpoint was concordance between gated SPECT perfusion data and FFR, defined by matching abnormal or normal classifications. The record lists one outcome measure and zero analyses, and reports no concordance result. The reason for termination, analysis population, missing-data approach, and statistical analysis plan are not reported in the registry record.

The adverse-event entries list 0 serious events, 0 other events, and 0 deaths, with 27 at risk in each listed risk group. No serious adverse-event terms are listed.