Low Cost QTc Meter for Long QT Syndrome Screening in Primary Care: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Low Cost QTc Meter for Long QT Syndrome Screening in Primary Care (NCT04441892), a non-randomized na study. The primary outcome is Low Cost QTc Meter for Long QT Syndrome Screening.

2. Clinical Question

3. Trial Design

The registry describes a parallel, non-randomized study with no masking. Its official title calls it Phase II, while the registry phase classification is NA. The sponsor is Mayo Clinic. The study began on 2019-02-07, had a primary completion date of 2020-03-26, and is listed as terminated. The reason for termination is not reported in the registry record.

The listed intervention is the QTc Meter, classified as a device. One arm is named QTc Meter and the other QTc Meter - Healthy Controls. Both descriptions refer to infants and children from Day 0 to age 5 and say that participants record 30 seconds of data using the QTc screening device. The primary outcome description refers to participants with or without Long QT Syndrome. The record does not explain how participants were assigned to the two arms or give the number in each arm for the primary outcome.

Enrollment is listed as 33. The safety information lists 28 participants at risk in the QTc Meter group and 5 in the healthy-controls group. Those group counts describe the safety record; the registry does not give further details about enrollment, withdrawal, or which participants contributed to the primary endpoint.

Because allocation was not randomized and the registry cautions that the arms are not a like-for-like control comparison, differences between the groups would not automatically be attributable to the device or to health status. The record does not report a prespecified statistical plan, the method used to define a successful tracing, or details of any comparison between groups. It also does not report a statistical analysis of the primary endpoint.

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 Low Cost QTc Meter for Long QT Syndrome Screening, measured over Baseline.

The primary endpoint is the number of participants with a successful tracing recorded by the QTc Meter at baseline. It applies to participants with or without Long QT Syndrome between Day 0 and age 5. This is a count of participants meeting a defined recording outcome, rather than a measure of how much QTc changed or how accurately the device classified Long QT Syndrome.

A successful tracing can serve as a basic measure of whether a device obtains usable data in the population and setting for which it is being considered. For a proposed screening instrument, the ability to record a tracing is a necessary practical question: diagnostic interpretation depends on having data to interpret. However, a successful recording by itself does not establish that a tracing is accurate, that the device identifies Long QT Syndrome correctly, or that it is suitable for screening in primary care.

The endpoint is listed with a baseline timeframe. The registry record does not define success, report how tracing quality was assessed, or describe how unsuccessful or absent recordings were handled. Most importantly, it does not report the endpoint count or any statistical analysis. The available record therefore identifies the intended measure but does not establish how often recording succeeded in this study.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The methods that can be described from the registry record are limited. It identifies a binary endpoint expressed as a count of participants with a successful tracing, a baseline timeframe, and a parallel non-randomized design with no masking. The record lists one outcome measure and no analyses. It does not report a detailed statistical analysis plan, an endpoint result, or an uncertainty estimate.

What does a participant count represent?

A participant-count endpoint records how many people meet a specified condition. In this study, the condition is having a successful tracing recorded with the QTc Meter. The count is not a measurement of the size of a biological change. To interpret a count fully, readers would also need to know the number of participants assessed, the operational definition of success, and how missing or unusable recordings were handled. These details are not reported in the registry record for the primary endpoint.

In general, a count can describe the observed experience in the participants evaluated, but a count alone does not show how precisely that experience estimates what might occur in a broader population. Statistical uncertainty depends on the observed result and the denominator, among other aspects of the analysis. Since the endpoint result and its uncertainty are not reported, no confidence interval or other measure of precision can be interpreted for the primary outcome.

What would a confidence interval add?

In general, a confidence interval expresses the uncertainty around an estimate under a specified statistical method. It can help distinguish a relatively precise estimate from one that remains compatible with a broad range of underlying values. It does not remove limitations in study design, measurement, or participant selection, and it does not establish that an endpoint is clinically meaningful. No confidence interval for the primary endpoint is reported in the registry record.

Why does non-randomized allocation matter?

Randomization is a method for assigning participants that can, on average, reduce systematic differences between groups. This study is explicitly listed as non-randomized. In a non-randomized study, group membership may be related to participant characteristics or other factors that also affect the outcome. A difference between groups could therefore reflect differences in who entered each group, how measurements were obtained, or other unreported factors, rather than a device effect. Here, the registry specifically says the arms are not a like-for-like control comparison. The record does not describe a method to adjust for group differences.

No masking is listed. In general, masking can reduce the influence of expectations on certain study procedures or assessments. Its relevance depends on the measurement and how success is judged. The record does not say whether endpoint assessment could be influenced by knowledge of group assignment, or describe safeguards for that assessment. No assumption about the effect of the absence of masking can be made from the registry entry alone.

What do the planning assumptions mean?

General planning illustrations based on a stated effect are not observed power and do not demonstrate that a study was adequately powered. The planning assumptions associated with this record specify a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation, with the effect to detect expressed as a fraction of an observed effect. These are described as planning illustrations rather than as the trial's own design justification. The registry record does not report the protocol's sample-size rationale or the planning values needed to interpret a particular illustration. The non-randomized arms are also explicitly not a like-for-like control comparison, so an equal-allocation comparison assumption should not be mistaken for evidence that the study used randomized, balanced groups.

In general, a significance level is a convention used in some hypothesis-testing procedures to define how unusual data must be under a null model before that model is rejected. A two-sided procedure considers departures in either direction. Such a threshold does not measure the probability that a hypothesis is true, the size or importance of an effect, or the likelihood that a result will replicate. No hypothesis test or p-value for the primary endpoint is reported in the registry record.

Why might over-dispersion matter?

In general, over-dispersion means that observed variability is greater than a statistical model expects. It can affect methods for count data by making standard errors too small if the extra variability is ignored. This endpoint is described as a count of participants with an event, but the registry does not report a count-data model, a dispersion estimate, or an analysis that assesses over-dispersion. There is therefore no basis for saying that such a model was used or that over-dispersion was observed in this study.

Overall, the registry record permits a plain description of the intended endpoint and broad design, not a reconstruction of the statistical analysis. The primary outcome result, analysis method, precision estimate, and any adjusted or subgroup analyses are not reported in the registry record.

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("QTc Meter", "QTc Meter - Healthy Controls")
n      <- c(28, 5)
events <- c(20, 4)
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  QTc Meter  28  20  71.4  51.3  86.8  52.9  84.7  52.8  84.7
ARM  QTc Meter - Healthy Controls  5  4  80.0  28.4  99.5  37.6  96.4  35.9  95.7

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure, the count of participants with a successful tracing, and no analyses. That does not establish that the study protocol included only one planned outcome or that no additional analyses were conducted outside the registry. The full statistical plan and any analysis plan amendments are not reported in the registry record.

Multiplicity arises when several outcomes, time points, subgroups, or statistical comparisons are assessed. In general, examining many results can increase the chance of finding an apparently notable result by chance, depending on the methods used. The available record does not describe a multiplicity adjustment or explain how multiple comparisons would have been handled. With no posted analyses, it is not possible to evaluate whether multiplicity was relevant or how it was addressed.

Missing data handling is also not reported. The registry does not specify how an unsuccessful tracing, a missing recording, an incomplete assessment, or a participant who did not contribute endpoint data was classified. It does not report the number assessed for the endpoint or whether all enrolled participants were included in the analysis. These omissions matter for a feasibility outcome because an absent or unusable recording could affect the count, depending on the prespecified endpoint definition.

The analysis population is not described in the registry record. There is no reported intention-to-treat, per-protocol, or other defined population for the primary outcome. Those terms refer generally to different rules for deciding which participants are included in an analysis; the appropriate interpretation depends on the design and prespecified methods. No such rules can be inferred from the arm descriptions or safety counts.

The record therefore does not allow assessment of how missingness, exclusions, multiple outcomes, or analysis populations may have affected the primary result. Since the primary result itself is not reported, robustness to alternative analysis choices cannot be evaluated.

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.

The registry safety listing records 28 participants at risk in the QTc Meter group and 5 in the QTc Meter - Healthy Controls group. For serious adverse events, the recorded affected count is 0 in each group. For other adverse events, the recorded affected count is also 0 in each group. The recorded death count is 0 in both groups.

These are descriptive counts in the registry record, not estimates of comparative risk. The groups are non-randomized and are not described as a like-for-like control comparison. The different group sizes also mean the counts should not be read as a controlled comparison of safety. The registry does not report event terms, and no serious adverse event terms are listed.

A recorded count of 0 means that no affected participants are listed for that category in the posted safety information. It does not, by itself, prove that an event is impossible, rule out events that were not captured or reported, or establish safety in other populations or settings. The registry does not provide additional detail about the method or duration of safety monitoring. These figures should be read as the safety information recorded for this study, not as a broader claim about the device.

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

The record establishes that a study of a QTc Meter for Long QT Syndrome screening was conducted in infants and children aged 0 to 5 and is now listed as terminated. Its primary question concerned whether participants with or without Long QT Syndrome had a successful tracing recorded at baseline. The registry record does not report the count of successful tracings, so the result of that feasibility question cannot be determined from the posted information.

Even if a successful-tracing count were available, that endpoint would address the ability to obtain a recording, not the ability to identify Long QT Syndrome correctly. Diagnostic performance generally requires information about how test results correspond to an appropriate reference classification. The record does not report such a comparison or diagnostic accuracy measures. It also does not establish whether the device was used in routine primary care; screening in that environment is part of the study's stated purpose, not a reported finding.

The study's non-randomized allocation and the registry's warning that the arms are not a like-for-like control comparison limit interpretation of any potential contrast between the groups. The record does not give enough information to determine whether group characteristics or recording circumstances differed. The study's termination status likewise does not explain why it stopped or what effect, if any, that had on data collection.

The safety listing reports zero serious adverse events, zero other adverse events, and zero deaths in each group. These are the posted counts, not proof of an absence of risk. No statistical analysis is listed, and the endpoint result and its precision are not reported. The evidence in the registry is therefore insufficient to judge the frequency of successful recordings, diagnostic performance, comparative performance, or broader clinical utility.

Statistically, the most defensible reading is a distinction between an intended question and an observed result. The record identifies the former but does not report the latter. No conclusion that the device succeeds or fails at screening follows from the missing primary result.

14. Why This Trial Matters Statistically

This study is statistically notable because it separates a practical measurement question from a diagnostic question. For a screening device, obtaining a tracing is an important part of the measurement process. Yet the number of successful recordings alone would not establish whether the device distinguishes participants with Long QT Syndrome from those without it. The registry identifies the recording endpoint, making clear that feasibility and diagnostic accuracy are distinct claims.

The non-randomized design also illustrates why a group label does not make two groups interchangeable. One arm is labelled healthy controls, but the registry warns that the arms are not a like-for-like control comparison. Without randomized allocation or reported adjustment for differences, group contrasts could be confounded. This design context matters even before any numerical comparison is considered.

The registry also illustrates the difference between a planning illustration and evidence from an analysis. General sample-size calculations can describe what a design might require under stated assumptions, but they do not show that the study had a particular probability of detecting an effect, nor do they replace a reported endpoint estimate. The record does not report an endpoint result or analysis from which precision or statistical evidence could be assessed.

Finally, status and safety counts need narrow interpretation. Termination does not disclose the reason a study ended, and zero event counts do not prove zero risk. A clear statistical reading therefore depends on separating the study's stated aim, design limitations, posted counts, and unreported results. That distinction prevents the intended evaluation of a device from being mistaken for evidence of its diagnostic performance.

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 primary endpoint is not reported as an observed result. The record gives the endpoint description but not the number of participants with successful tracings, its denominator, or an uncertainty estimate. As a result, the central feasibility question cannot be answered from the registry entry.

The registry does not define what counted as a successful tracing, how tracing quality was assessed, or how incomplete and unusable recordings were treated. It also does not describe the reference standard, if any, used to establish Long QT Syndrome status. These omissions prevent assessment of measurement validity and of whether the endpoint was applied consistently.

Participants were not randomly allocated, and the registry explicitly says the arms are not a like-for-like control comparison. Characteristics of participants in each group, the allocation process, and any statistical adjustment are not reported. The group labels alone cannot establish comparability. The registry does not report whether recordings took place in primary care, even though primary care is part of the study's stated screening aim.

The study is listed as terminated, but the reason is not reported in the registry record. It is also not reported whether the enrolled sample represents all participants who entered the study, whether all were assessed for the endpoint, or whether recruitment and data collection were completed as intended. No protocol, detailed statistical plan, missing-data rules, or analysis population is reported. The registry phase classification is NA despite the Phase II wording in the official title, so the record does not supply a phase category beyond that title wording.

Finally, no diagnostic accuracy result or broader clinical performance measure is reported. The posted safety counts are limited to the recorded categories and group totals, without event terms. Together, these limitations mean the registry supports a description of the study's intent and design, but not a substantive estimate of tracing success or screening performance.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Low Cost QTc Meter for Long QT Syndrome Screening in Primary Care — NCT04441892.
• Registry record last updated 2023-07-25; status last verified 2023-07.
• Results first posted 2023-07-25.
• 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

NCT04441892 is a Mayo Clinic study titled Low Cost QTc Meter for Long QT Syndrome Screening in Primary Care. Its official title includes Phase II, while the registry phase classification is NA. The study is listed as non-randomized, parallel, and unmasked, with enrollment of 33. It began on 2019-02-07, reached its listed primary completion date on 2020-03-26, and has terminated status.

The primary outcome is the number of participants aged 0 to 5, with or without Long QT Syndrome, who had a successful baseline tracing recorded with the QTc Meter. The outcome result and any statistical analysis are not reported in the registry record. The record cautions that the two arms are not a like-for-like control comparison.

Safety listings show 28 participants at risk in the QTc Meter group and 5 in the healthy-controls group, with zero serious adverse events, zero other adverse events, and zero deaths recorded in each group. The reason for termination, the detailed statistical plan, and the handling of missing endpoint data are not reported in the registry record.