Focused Field of View Calcium Scoring Prior to Coronary CT Angiography: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Focused Field of View Calcium Scoring Prior to Coronary CT Angiography (NCT02972242), a randomized na study. The primary outcome is Qualitative Quality Comparison.

2. Clinical Question

The clinical and technical rationale is that calcium scoring may identify calcification that could influence subsequent CT image acquisition, while adding radiation exposure. The study asked whether a focused scan could provide information about coronary calcification relevant to the subsequent coronary CT angiogram, with image quality assessed as the primary outcome. The registry also lists outcomes concerning changes to CT parameters, high-definition scanning, radiation exposure, and scan termination events.

This question concerns the performance of imaging approaches and the resulting scan characteristics. It is not a comparison of treatments for coronary artery disease, nor does the primary score directly measure diagnosis, patient health, or long-term clinical outcomes. The registered endpoint describes readers’ qualitative assessment of the coronary CT images. Accordingly, the results speak to image quality as scored under the study’s assessment process, not to every possible consequence of choosing one scan approach over the other.

3. Trial Design

The study is registered as a randomized, single-masked, parallel-arm trial, with an enrollment of 175. Its status is completed. The registry lists the phase as not applicable. The sponsor is Walter Reed National Military Medical Center.

Participants were assigned to a modified field-of-view group or a standard field-of-view group. The modified approach used a focused non-contrast CT scan to assess coronary calcification before coronary CT angiography. The comparator was standard coronary artery calcium scoring. The brief summary describes the modified scan as having a significantly shorter scan length and lower radiation parameters, but the available arm descriptions are truncated and do not provide a complete technical protocol for either approach. Full acquisition settings should therefore not be inferred from the partial descriptions.

The study began in 2014-11, and primary completion is recorded as 2018-03. The registry states that outcome assessment followed completion of image acquisition for all patients, with the last patient scan on 2/26/18. It describes the outcome assessment process as spanning approximately 3 months from March to June 2018. This timing indicates that the image-quality assessments were conducted after scan acquisition; it does not establish whether the assessors were masked to allocation or how disagreements between assessors were handled. Those details are not reported in the registry record.

The group counts for the primary outcome are 79 in the modified field-of-view group and 93 in the standard field-of-view group. These are outcome-specific counts and should not be treated as a complete account of participant flow. The registry notes that, within the modified group, one patient had previously withdrawn consent and two additional scans were unavailable for review when outcomes were measured. A full account of randomization, follow-up, analysis-population definitions, and participant disposition is 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:

Analysis population for the primary outcome, as defined in the registry: Within the modified group: 1 patient had previously withdrawn consent and 2 additional scans were subsequently unavailable for review at the time of measurement of the outcomes.

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: 82 patients were enrolled to the Modified group. As previously mentioned, one withdrew consent immediately after randomization (i.e. prior to undergoing scan). Two additional scans within the modified group were unavailable to the PI at the time of data analysis (i.e. years after the scan, due to data migration failure)

6. Primary Endpoint

The registry lists the primary outcome as Qualitative Quality Comparison, measured over Following completion of data acquisition (i.e. CT scans) for all patients (last patient scan was 2/26/18), each outcome measure was then assessed (this process spanned approximately 3 months from March to June 2018)..

The primary endpoint is titled “Qualitative Quality Comparison.” It assesses coronary CT image quality using a four-point scale. A score of 1 is nondiagnostic: severe motion, blooming, noise, or insufficient contrast prevents appropriate coronary evaluation. A score of 2 is adequate: image quality is reduced by artifacts or low contrast, but remains sufficient to rule out significant stenosis. A score of 3 is good: artifacts may be present, but the ability to assess stenosis and calcified and non-calcified plaque is preserved. A score of 4 is excellent, describing the absence of motion artifacts, strong vessel-lumen attenuation, and clear vessel-wall delineation for assessing stenosis and plaque characteristics.

The registry lists the outcome parameter as a mean and its dispersion as an inter-quartile range. The posted group summaries are 4.0, with an inter-quartile range from 3.0 to 4.0, in each group. The outcome is useful for comparing how the images were judged under the study’s qualitative criteria. It is an imaging-quality measure rather than a direct measure of radiation exposure, diagnostic accuracy, or patient health.

As a general statistical consideration, this scale is ordinal: its categories have an order, but the distance between adjacent categories need not represent an equal change in image quality. A mean can be a compact summary, while the inter-quartile range conveys the spread of the middle portion of scores. Neither summary alone describes every score or establishes that the two groups are equivalent.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Randomization assigns participants to study groups by chance rather than by a clinician’s or participant’s choice. In general, this can reduce systematic differences between groups at the start of a trial. The registry identifies this study as randomized and parallel-arm, but details of sequence generation, allocation concealment, and the randomization process are not reported in the registry record. The designation “single-masked” is recorded, but the registry information available does not identify who was masked or how masking was maintained.

How to read the primary score

The registered primary measure is a qualitative score on an ordered scale. The outcome summary is listed as a mean, with an inter-quartile range. A mean gives a compact summary of the group scores; the inter-quartile range describes the span covering the middle half of the observed scores. These summaries answer different questions: a central summary describes location, while a measure of spread describes variation. They do not show the full distribution, and identical summaries can occur even when individual score patterns differ.

Because the score categories are ordered rather than necessarily equally spaced, a one-point change at one part of the scale need not represent the same amount of image-quality change as a one-point change elsewhere. This is a general property of ordinal measurements. The clinical descriptions attached to the score levels help explain what the categories mean, but do not make their distances numerically equal. The registry does not report a primary confidence interval or inferential test, so the precision of a group contrast cannot be assessed from the posted primary summaries alone.

Risk differences and uncertainty

For the secondary outcomes with group comparisons, the registry reports risk differences. A risk difference expresses the difference between the proportions of participants with an outcome in the two groups, with the comparison oriented to modified field of view relative to standard field of view. A negative value indicates a lower observed proportion in the modified group; a positive value indicates a higher observed proportion. The estimate is a point summary, not a guarantee that the underlying difference has that exact value.

A confidence interval describes a range of values compatible with the observed data under the statistical method used. In repeated use of a suitable method, intervals constructed at a stated confidence level would cover the underlying parameter at that rate. It is not a probability statement that the particular interval contains the true effect. When an interval includes zero for a risk difference, the data do not rule out no difference; the interval may also include effects in both directions. The reported intervals for the available secondary comparisons include zero, so they do not provide clear evidence of a direction or precise magnitude.

A p-value describes how unusual results at least as incompatible with a null hypothesis would be under the assumptions of the test, if that null hypothesis were true. It is not the probability that the null hypothesis is true, nor a measure of clinical importance. The posted secondary p-values are unadjusted. The registry does not report the underlying inferential analysis plan, and it reports no analyses for the primary outcome. Interpretation should therefore be anchored in the estimates and their uncertainty rather than treating a p-value as a stand-alone conclusion.

Unadjusted secondary comparisons

“Unadjusted” indicates that the reported comparisons do not account for a stated set of covariates or for the number of outcomes tested. The registry does not report adjusted analyses. An unadjusted comparison may be a straightforward description of the observed groups, but randomization does not guarantee that every measured or unmeasured characteristic is balanced in a particular study. The registry does not provide baseline characteristics or adjusted estimates that would allow further assessment of this issue.

Multiple comparisons are also relevant. When many outcomes are examined, chance alone can produce one or more apparently notable results even when there is no underlying difference. In general, a prespecified hierarchy, multiplicity adjustment, or cautious interpretation of exploratory outcomes can address this concern. No multiplicity procedure or outcome hierarchy is reported in the registry record. The secondary findings should thus be treated as exploratory evidence, especially because only some of the listed outcomes have numerical comparisons posted.

Planning illustrations are not observed power

The registry includes planning illustrations for the secondary risk-difference outcomes. These use the observed effect as a reference and show hypothetical participants per arm for 80% and 90% power under stated assumptions: a two-sided significance level of 0.05, equal allocation, and a normal approximation. The illustrations also consider planning for 75% and 50% of the observed effect. They are not the trial’s original sample-size justification, and the registry does not report that justification.

Such calculations ask how large a future study might need to be under particular assumptions if it were designed to detect a chosen effect. They do not measure the probability that this completed study detected an effect, and they should not be called observed power. Their values depend on the observed effect, which can be uncertain, particularly when estimated from limited data. The planning illustrations are not evidence that the trial was designed around those assumptions or that any one of the illustrated sample sizes is appropriate for a future study.

Missing observations and analysis populations

Outcome counts can differ from enrollment because of withdrawal, unavailable measurements, or other reasons. The registry specifically records one withdrawn consent and two scans unavailable for review in the modified group at the time outcomes were measured. It does not report whether any imputation was used, whether all randomized participants were analyzed as assigned, or whether the primary analysis followed an intention-to-treat principle. Those analysis-population details are not reported in the registry record. Without them, the reader cannot fully assess how missing image assessments affected the primary comparison.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary image-quality outcome and seven secondary outcomes. It does not report a statistical analysis plan, a hierarchy for testing outcomes, or any method for adjusting secondary analyses for multiple comparisons. When several outcomes are tested, the chance of at least one apparently unusual result can increase. This is a general statistical concern, not evidence that any particular finding in this trial is false. It means that isolated secondary results warrant caution, especially when they are unadjusted and not supported by a reported prespecified analysis strategy.

The registry reports no analyses for the primary endpoint. It therefore does not provide a primary group contrast with a confidence interval or p-value. For the secondary comparisons that are reported, the analyses are unadjusted. No interim analyses are reported in the registry record. Whether they were planned or conducted is not reported in the registry record.

Missing outcome information is specifically noted for the modified group: one patient had previously withdrawn consent, and two additional scans were unavailable for outcome review. The registry does not state whether these missing observations were excluded from all analyses, imputed, or addressed through a sensitivity analysis. Nor does it define the analysis population in terms of all randomized participants, participants who completed scanning, or participants with outcome data. These analysis-population details are not reported in the registry record.

Consequently, the posted group summaries should be understood as summaries of the available recorded outcomes, with the limits of missingness and analysis-population reporting in mind. The registry does not establish whether the missing assessments would have changed the summary or the comparison. A transparent account of participant flow, missing-data handling, and prespecified analyses would be needed for a fuller assessment of these issues.

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.

The registry records zero serious adverse events and zero other adverse events in the modified field-of-view group, among 82 participants at risk. It records zero serious adverse events and zero other adverse events in the standard field-of-view group, among 93 participants at risk. Deaths are recorded as zero in both groups. These are the event counts reported for the study’s safety categories.

A zero count does not prove that the underlying risk is zero. It means that no events in that category were recorded in the relevant group during the period and under the reporting procedures represented in the registry. The record does not provide confidence intervals or further details about safety-event definitions, collection, or follow-up for these results. Thus, the counts are descriptive and cannot precisely rule out uncommon events.

The safety counts should also be kept distinct from the primary image-quality outcome and the technical secondary outcomes. They do not measure radiation dose, image quality, or diagnostic performance. The absence of recorded events in these categories is reassuring as a description of the registry entries, but is not a comprehensive estimate of safety.

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

The primary endpoint describes how coronary CT images were qualitatively rated after the modified or standard field-of-view approach. The posted group summaries are alike: each has a reported value of 4.0 and an inter-quartile range of 3.0 to 4.0. This is a descriptive similarity in the recorded summaries. Because the registry does not report a primary inferential comparison or confidence interval, it does not show how precisely a difference between approaches has been estimated.

Equal summaries are not the same as proof of equivalence. An equivalence conclusion ordinarily depends on a prespecified margin defining what size of difference would be considered acceptably small, together with an analysis that evaluates uncertainty against that margin. An equivalence margin and such an analysis are not reported in the registry record. The results therefore cannot establish that the approaches produce identical image quality or that any possible difference is negligible.

The primary endpoint is an image-quality score, not a direct measure of coronary artery disease diagnosis, patient outcomes, or the full radiation burden of the imaging pathway. The study rationale concerns a shorter scan length and lower radiation parameters for the modified non-contrast scan, but the registry does not report numerical results for all listed radiation-exposure outcomes. The posted primary score alone cannot establish a reduction in radiation exposure or a change in diagnostic accuracy.

The available secondary comparisons describe selected CT parameter outcomes, but they are unadjusted and have intervals that include zero. The remaining listed secondary outcomes lack numerical results in the registry record. Those limits constrain conclusions about technical differences and radiation exposure. Likewise, the zero safety-event counts are descriptive and do not demonstrate an absence of risk.

In short, the registry shows similar primary image-quality summaries and reports no inferential primary comparison. It does not establish superiority, equivalence, diagnostic benefit, or a complete radiation or safety profile. The result is best understood as a limited account of qualitative image ratings and selected technical outcomes in this randomized imaging study.

13. Why This Trial Matters Statistically

This trial raises a practical statistical question about how to evaluate an imaging modification when the outcome is an ordered quality score and the motivation includes radiation exposure. The primary summary communicates the central image ratings and their spread, but without a reported group contrast and uncertainty interval it is difficult to distinguish a genuinely small difference from an estimate that is simply imprecise. The same caution applies when two group summaries happen to match.

The endpoint also illustrates how measurement scale matters. The four categories have clinically described meanings, yet they are ordinal rather than assuredly equal steps on a quantitative scale. A mean and inter-quartile range are compact summaries, but they do not show the full distribution or resolve whether differences in category frequencies matter. Clear reporting of the scoring process, assessor masking, and analysis approach would help readers judge the strength of the comparison. These details are not reported in the registry record.

Statistical interpretation also depends on connecting the primary quality result with the secondary technical and radiation outcomes. Here, the registry provides numerical comparisons for selected technical outcomes, but not all listed secondary outcomes. The incomplete secondary reporting limits the ability to assess the study’s broader rationale from the posted results. Multiplicity matters as well: unadjusted comparisons across multiple outcomes are not independent confirmatory tests.

The record is therefore useful as an example of why outcome estimates, uncertainty, missing-data accounting, and analysis plans all matter. The reported summaries describe what was recorded, but do not by themselves answer whether the imaging approaches are equivalent, whether one is diagnostically preferable, or whether radiation exposure differs. Those are distinct questions requiring appropriately reported outcome data and statistical analyses.

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 registry gives incomplete technical detail for the scan protocols. The arm descriptions end mid-description, so the full acquisition settings for the modified and standard approaches are not available in the record. The rationale refers to shorter scan length and lower radiation parameters for the modified scan, but the posted primary quality summaries do not quantify radiation exposure.

The main limitation for interpreting the primary endpoint is the absence of a reported inferential comparison. The registry provides group summaries but no confidence interval, p-value, or other estimate of uncertainty for the primary contrast. It also does not report a prespecified equivalence margin or a statistical plan, so similarity in the summaries cannot establish equivalence.

Outcome assessment involved qualitative scoring, but the registry does not report who performed the ratings, whether they were masked to assignment, how many readers contributed, or how disagreement was resolved. The assessment scale is ordered, and the reported mean and inter-quartile range do not convey all details of the score distributions.

The record notes missing image review in the modified group, including a prior consent withdrawal and scans unavailable at measurement. It does not report the missing-data method, sensitivity analyses, or analysis-population definition. Detailed numerical results are also absent for some listed secondary outcomes, including radiation exposure measures and scan termination. Finally, the available secondary comparisons are unadjusted, and no multiplicity approach is reported. These gaps limit conclusions about technical effects, radiation, missingness, and the overall pattern across outcomes.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Focused Field of View Calcium Scoring Prior to Coronary CT Angiography — NCT02972242.
• 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.

18. Record Summary

NCT02972242 is a completed randomized, single-masked, parallel-arm study titled “Focused Field of View Calcium Scoring Prior to Coronary CT Angiography.” The registry lists an enrollment of 175 and Walter Reed National Military Medical Center as the sponsor. The study began in 2014-11, with primary completion recorded as 2018-03.

The study compared modified and standard field-of-view approaches to coronary calcium scoring before coronary CT angiography. Its primary outcome was qualitative image quality on a four-point scale. Both groups had a reported primary value of 4.0 and an inter-quartile range of 3.0 to 4.0. The registry does not report an inferential primary comparison. It lists seven secondary outcomes, with numerical comparisons posted for selected outcomes; detailed numerical results for all listed secondary outcomes are not reported in the registry record.

The registry records zero serious adverse events, zero other adverse events, and zero deaths in each group. Missing image review is noted for the modified group. The analysis plan, multiplicity approach, and handling of missing outcome data are not reported in the registry record.