Capillary Refill Time Measurement Utilizing Mobile Application in Children: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Capillary Refill Time Measurement Utilizing Mobile Application in Children (NCT05472116), a registered phase not stated study. The primary outcome is Accuracy and Precision of a Mobile Health Application (Cap App).

2. Clinical Question

The question is about measurement performance, rather than a comparison of assigned treatments. Accuracy concerns how closely app measurements correspond to the manual measurements used for comparison. Precision concerns the consistency or spread of measurements. These concepts are related but are not interchangeable: a method could produce closely grouped readings that are not close to a comparator, or readings that vary while their average is near a comparator. General statistical interpretation depends on the particular summaries and comparison methods used.

The study is described as cross-sectional and as measuring capillary refill time with the app and two manual methods. The registry does not describe whether each child received all three measurements, how measurements were paired, or whether measurements were repeated. Those details matter for understanding which observations are compared and whether the analysis accounts for measurements from the same child.

The record identifies healthy children as the study population. It does not report a clinical population with a specified condition, nor does it state that the study evaluated clinical decisions or patient outcomes. The question is therefore bounded to measurement performance in the recorded population and setting. It cannot, on the available record, establish how the application would perform in other populations or circumstances.

3. Trial Design

The registry describes a completed cross-sectional study titled “Capillary Refill Time Measurement Utilizing Mobile Application in Children,” sponsored by the University of Minnesota. The listed start date is 2022-08-26, the primary completion date is 2023-01-01, and enrollment is 193. The listed condition is healthy children from 1 month to 17 years old. The study summary states that capillary refill time was measured using Cap App and two additional manual methods for comparison.

This is not described as a randomized comparison. The registry does not state an allocation scheme, and its record cautions that the listed arms are not a like-for-like control comparison. The only listed intervention is the Mobile Health application (CapApp), classified as a device. The record does not provide a detailed design description of the manual measurements, participant flow, or the way the three methods were scheduled. It therefore does not support assumptions about randomization, masking, order of measurement, or a particular within-child measurement protocol.

The cross-sectional description indicates a measurement study rather than a follow-up study of changes over time. In general, measurement studies examine how readings from a method relate to readings from another method or to a defined reference. The study’s stated aim is to determine accuracy and precision. However, the registry does not define a reference standard or state which statistical quantities were to represent accuracy and precision.

The registry status is COMPLETED, but completion status does not itself provide outcome results. Although one primary outcome measure is listed, the record does not report an analysis for it. The numerical measurements, estimates of agreement or difference, uncertainty intervals, and statistical tests are not reported in the registry record. A sample-size justification, protocol details, and a full statistical analysis plan are also not reported in the registry record. The available design description supports identifying the study’s population, measurement methods, and broad objective, but not reconstructing unreported procedures.

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 Accuracy and Precision of a Mobile Health Application (Cap App), measured over Time it takes for blood to return to issue on the fingertip after pressure application for 5 seconds.

The primary endpoint is described as the accuracy and precision of Cap App capillary refill time measurement, compared with two manual methods. Capillary refill time is recorded in seconds. The timeframe description defines the measurement as the time it takes for blood to return to the fingertip after pressure application for 5 seconds. The outcome is continuous and is characterized in the registry as a mean with standard deviation.

The endpoint is relevant to the stated research question because the study is evaluating a measurement method, not a treatment effect. Comparing app measurements with manual measurements can provide information about whether readings correspond across methods. The mean describes the average value in a group of measurements, while the standard deviation describes the spread of individual values around that mean. General interpretation of measurement agreement requires more than comparing group means: the relationship between paired readings, any systematic differences, and the variation in those differences can all be important.

The registry does not report the endpoint values, the corresponding standard deviations, or the statistical method used to operationalize accuracy and precision. It does not state whether the app was compared separately with each manual method or how results from the two manual methods were combined. The endpoint’s name and description establish the intended measurement question, but the reported record does not give the numerical evidence needed to quantify performance.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry classifies the primary outcome as a continuous measure, reported using a mean and standard deviation. It describes capillary refill time in seconds and gives the measurement timeframe as the time for blood to return to the fingertip after pressure application for 5 seconds. Those details define the kind of outcome being collected. They do not identify the statistical method used to compare the app with the manual methods, and no analysis is reported in the registry record.

What does a mean describe?

In general, the mean is the arithmetic average of a set of measurements. It provides a summary of the central location of those measurements. For a measurement study, separate means could describe results from different methods, but the means alone do not show whether individual readings from the methods correspond. Similar group averages can coexist with substantial disagreement for individual pairs. Conversely, a difference between group averages does not, on its own, describe the full pattern of paired differences.

The registry names the mean as the outcome parameter but does not give a mean value for Cap App or either manual method. It does not report whether the primary comparison was based on paired readings, a difference in group means, or another quantity. As a result, there is no numerical estimate to interpret and no basis for identifying the specific comparison procedure.

What does a standard deviation describe?

In general, a standard deviation summarizes the spread of observations around their mean. A larger standard deviation indicates more variation among the measurements in the analyzed group; it is not itself a measure of bias or agreement between methods. The registry identifies standard deviation as the dispersion measure but reports no standard deviation values. It also does not say whether the analysis considered within-child variation, variation between children, or both.

For repeated or paired measurements, the structure of the data matters. General statistical methods for paired data account for the fact that two readings from the same person may be related. Treating related measurements as if they came from unrelated people can misrepresent uncertainty. The study summary says that the app and two manual methods were used, but it does not report whether every child received each method, whether measurements were paired in the analysis, or whether repetitions were taken. The appropriate covariance structure therefore cannot be identified from the record.

How should accuracy and precision be distinguished?

In general, accuracy concerns closeness to a reference value or method. Precision concerns repeatability or variability. Assessing agreement often requires examining the differences between corresponding measurements, including their average and spread. Correlation alone, if used, would describe association rather than guarantee agreement: two methods can move together while giving systematically different values. This is a general statistical distinction, not a report of a method used in this study.

The registry’s broad endpoint description does not specify a reference standard, an acceptable difference, an agreement statistic, or the rule used to decide whether performance would be considered adequate. It also does not specify whether each manual method was analyzed independently. These are key methodological details for interpreting an accuracy-and-precision objective. They are not reported in the registry record.

Why does uncertainty matter?

In general, a point estimate is an estimate from the observed data, while a confidence interval communicates uncertainty about that estimate under a specified model and sampling procedure. A narrow interval can indicate greater precision in estimating a quantity, whereas a wide interval indicates more uncertainty. An interval is meaningful only when the underlying quantity and method are clear. No point estimates, confidence intervals, or other uncertainty measures for the primary endpoint are reported in the registry record.

A p-value, in general, measures how compatible data are with a specified null hypothesis under the assumptions of a statistical test. It does not measure the magnitude or practical importance of an effect, and it cannot establish agreement between methods by itself. No primary analysis or p-value is reported in the registry record. There is therefore no basis to discuss statistical significance for the stated measurement question.

What can sample-size planning show?

General sample-size planning calculations depend on assumptions such as the target effect, variability, significance level, allocation, and desired power. The registry’s planning note describes an illustration based on a stated fraction of an observed effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation. It specifies that the calculation is a planning illustration rather than the trial’s own design, and that sample-size interpretations differ for time-to-event outcomes and other outcome types. This primary endpoint is described as continuous, not time-to-event.

Such planning calculations are conditional on their assumptions. They do not establish that a study was designed using those assumptions, nor do they turn an observed result into evidence of adequate precision. Sample sizes in a planning illustration are not observed power. The study’s own sample-size justification is not reported in the registry record. Moreover, the registry record contains no numerical observed effect for this endpoint, so the measurement result underlying any illustration cannot be assessed from the information reported.

More broadly, a complete analysis description would identify the comparison estimand, the handling of paired or repeated measurements, missing-data procedures, analysis population, and uncertainty measure. These details are not reported in the registry record. The statistical concepts above are general explanations of what such methods can address; they should not be read as a description of methods actually used in this study.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Mobile Health Application")
n   <- c(152)
m   <- c(0.01)
sp  <- c(1.31)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Mobile Health Application  152  0.010  1.310  -0.200  0.220

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure and no analyses. It does not report a statistical analysis plan, so it is not possible to determine whether additional outcomes or comparisons were planned, whether any multiplicity adjustment was considered, or how the primary comparison was selected. The number of listed outcome measures alone does not establish how many statistical tests were performed.

In general, multiplicity arises when several hypotheses are tested or several estimates are examined. Considering many tests can increase the chance of finding an apparently notable result by chance if no adjustment or prespecified hierarchy is used. Whether that issue applies depends on the full analysis plan, including the number of comparisons between Cap App and the two manual methods. The registry does not report those details. No conclusion about multiplicity control can be drawn.

Missing-data information is also absent. The record does not state whether all enrolled children contributed a capillary refill time measurement for each method, how many observations were missing, why any observations were unavailable, or how missing measurements were handled. In general, missingness can affect both the population represented in an analysis and the validity or precision of its estimates, depending on its extent and pattern. Without participant flow and analysis counts, the impact cannot be assessed.

The analysis population is not reported in the registry record. It is not stated whether analyses used every enrolled child, only children with complete measurements, or another defined set. The record lists enrollment of 193, but does not provide a count of participants included in an outcome analysis. It also does not describe protocol deviations, exclusions, or sensitivity analyses. Accordingly, the enrolled population and the population contributing to any numerical result cannot be confirmed from the registry record.

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

The study’s stated aim is to evaluate the accuracy and precision of Cap App capillary refill time measurement in healthy children, using two manual methods for comparison. This is a useful distinction from a treatment trial: the central question concerns measurements and their correspondence, not whether a clinical intervention changes health outcomes. The registry describes the measurement and population, but does not report numerical analyses that answer the question.

The record therefore does not establish that the app agrees with either manual method, that it differs from either method, or that its measurements are consistent. It also does not quantify the uncertainty around any such conclusion. A completed status and a listed primary outcome are not substitutes for the reported estimates and methods needed to assess the results. The absence of posted results should not be interpreted as a positive or negative finding.

Even if numerical agreement results were available, general interpretation would remain bounded by the study population and measurement procedures. Findings from healthy children would not automatically describe performance in other groups. Likewise, an observed relationship with manual methods would not alone establish that app measurements improve clinical decisions or patient outcomes. The registry does not report clinical utility outcomes or a clinical decision threshold.

The record also does not supply enough information to judge whether the manual methods represent an agreed reference standard, how readings were paired, or how repeatability was assessed. Those design choices affect what an accuracy or precision estimate means. Without them, the endpoint label cannot be translated into a specific performance claim.

The adverse-event record lists zero participants at risk in its recorded categories. That entry cannot be used to estimate event rates or to infer that no events occurred among a defined exposed population. The study’s focus, as described, is measurement performance, and the available registry information does not support a broader safety conclusion.

In short, the registry establishes what the study set out to compare, the population named, and the general endpoint definition. It does not provide the observed outcome evidence necessary to determine the degree of correspondence, variability, or uncertainty. The meaning of the record is consequently descriptive of the research question and design, not a conclusion about the app’s measurement performance.

13. Why This Trial Matters Statistically

Measurement studies address a different statistical problem from conventional intervention comparisons. Their central concern is whether one method yields readings that can be used consistently in relation to another method. This study’s stated comparison of a mobile application with two manual methods makes those questions explicit: accuracy and precision of capillary refill time measurement in healthy children.

Such questions require careful definitions. In general, the choice of comparator, pairing structure, and agreement statistic determines what a result can say. Mean values summarize central tendency and standard deviations summarize dispersion, but neither alone describes the full agreement between two methods. Clear reporting of individual-level relationships and uncertainty is important when a method-comparison claim is being considered. The registry record does not report those analyses, so it also illustrates why a stated objective and endpoint are not enough to evaluate performance.

The record distinguishes the study from a randomized treatment comparison and cautions against treating its arms as like-for-like controls. That distinction matters because the study is described as cross-sectional measurement using an app and two manual approaches, rather than allocation to competing therapies. Statistical interpretation should follow the measurement design rather than impose an unrelated treatment-trial framework.

For biostatisticians and clinical researchers, the record highlights the value of reporting the intended reference method, how readings are paired or repeated, which agreement measures are used, and how missing observations are handled. Those details support reproducibility and allow readers to judge whether uncertainty is adequately represented. Their absence in the registry record means that the performance question remains unanswered by the posted information, even though the study is marked completed.

The statistical importance is therefore methodological rather than a claim about the result: the study poses a practical measurement question, while the registry record does not report the analysis needed to resolve it. This reinforces the distinction between a study’s purpose, its design description, and its evidential findings.

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 main limitation for interpretation is that the registry record does not report numerical results for the primary outcome. Without those results, the accuracy and precision question cannot be quantified. The record also lists no analyses, so there are no reported estimates, uncertainty intervals, or tests to interpret.

The study description is brief. The two manual methods are not named or described in detail, and the record does not identify a reference standard. It does not explain whether each participant was measured by all methods, whether readings were repeated, how measurement order was handled, or whether assessors were aware of other readings. These details are not reported in the registry record and should not be inferred.

Enrollment is listed as 193, but the record does not give participant characteristics beyond the healthy pediatric population aged 1 month to 17 years. It does not report the number contributing to each measurement or analysis, missing observations, exclusions, or reasons for nonparticipation. The applicability of any potential result to populations beyond the named healthy children cannot be established from the information recorded.

The record does not report the sample-size justification, a complete statistical analysis plan, the planned agreement criteria, or how comparisons with the two manual methods were to be handled. It also does not report whether multiplicity, repeated measurements, or missing data were addressed. The study status is COMPLETED, but completion does not resolve these reporting gaps.

Finally, adverse-event entries list zero participants at risk, leaving no usable denominator for interpreting those entries. The registry record does not support an adverse-event rate or a safety conclusion. These limitations concern the interpretability and completeness of the recorded information; they are not evidence for or against the app’s measurement performance.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Capillary Refill Time Measurement Utilizing Mobile Application in Children — NCT05472116.
• Registry record last updated 2024-05-22; status last verified 2024-05.
• Results first posted 2024-05-22.
• 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

NCT05472116 is a completed cross-sectional study sponsored by the University of Minnesota. Its title is “Capillary Refill Time Measurement Utilizing Mobile Application in Children.” The registry lists enrollment of 193 and a population of healthy children from 1 month to 17 years old. The listed start date is 2022-08-26, and the primary completion date is 2023-01-01.

The study aimed to assess the accuracy and precision of capillary refill time measurements made with Cap App compared with two manual methods. The primary measure is continuous, expressed in seconds, and described using a mean and standard deviation. The timeframe definition refers to the return of blood to the fingertip after pressure application for 5 seconds.

One primary outcome measure is listed, but no analyses are listed and numerical outcome results are not reported in the registry record. Details of the statistical plan, missing data, analysis population, and the manual comparison methods are also not reported. The registry’s adverse-event entries list zero participants at risk, so they do not support an event-rate interpretation.