Validation of the Mercy TAPE: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Validation of the Mercy TAPE (NCT01507090), a registered phase not stated study. The primary outcome is Predictive Performance of the Mercy TAPE (Percent of Participants Predicted Within 20% of Their Actual Weight).

2. Clinical Question

3. Trial Design

The registry identifies this study as “Validation of the Mercy TAPE,” with the official title “Taking the Guesswork Out of Pediatric Weight Estimation (TAPE): Validation of the Mercy TAPE.” It is marked completed. The listed enrollment is 642. The recorded start is 2012-02, and primary completion is 2012-03. The sponsor is Susan Abdel-Rahman.

The study concerns a device intended to estimate children’s weight. The intervention is listed as the Mercy TAPE, and the described group is Normal Children: otherwise healthy children aged 2 months to 16 years. The study summary frames the problem as situations in which a child’s weight is desirable or necessary but unavailable, and describes the study as intended to validate the device in children in this age range. This describes the motivation and intended evaluation; it does not establish the performance result.

The primary outcome compares weights generated by the 2D and 3D Mercy TAPE with actual weight. The stated timeframe is study day 1, and the outcome is the percentage of participants whose estimate falls within 20% of actual weight. The registry also lists secondary outcomes concerning inter-rater reliability, print batch variability, and several aspects of predictive performance, including intercept, slope, mean error, and mean percentage error.

Allocation is not stated, and the registry record does not describe a randomized comparison. The listed group is not a like-for-like control arm. Accordingly, the design should be read as a device-validation assessment against actual measured weight, rather than as a trial establishing a comparative treatment effect. More detail about measurement procedures, eligibility decisions, and analysis conduct 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: Final population for data analysis.

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 Predictive Performance of the Mercy TAPE (Percent of Participants Predicted Within 20% of Their Actual Weight), measured over study day 1.

The primary endpoint is the percentage of participants whose 2D or 3D Mercy TAPE weight estimate was within 20% of that participant’s actual weight. The registry identifies the timeframe as study day 1 and describes actual weight as the reference. The endpoint therefore turns the difference between an estimate and its reference into a pass-or-not-within-tolerance classification, then expresses performance as a percentage of participants meeting the criterion.

This type of measure is useful for communicating how often estimates fall inside a prespecified range of the reference value. It is more directly interpretable as a proportion meeting a tolerance than an average error alone, since an average can conceal how widely individual estimates vary. The endpoint does not, by itself, describe the direction of errors, the size of errors among estimates outside the tolerance, or how performance differs across ages or weights.

The registry identifies the measure as a percentage and specifies a 95% confidence interval, but the observed percentage and interval are not reported in the registry record. Without those estimates, readers cannot determine the observed proportion meeting the criterion or how precisely it was estimated. The endpoint is a measure of predictive performance; it is not a clinical outcome or a randomized comparison.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is a proportion: participants are classified according to whether an estimate is within 20% of actual weight, and the result is expressed as a percentage of participants meeting the criterion. In general, this kind of endpoint is sometimes called a binary or categorical outcome because each assessment is classified as meeting or not meeting a defined condition. The registry’s description makes clear that the condition is an estimation tolerance, not an adverse event. The reported result would ordinarily need both an estimate and a confidence interval to convey magnitude and uncertainty; neither numerical result is reported in the registry record.

What does the confidence interval describe?

In general, a confidence interval expresses uncertainty about an estimated quantity under a specified statistical procedure. For a percentage, it indicates a range of values compatible with the observed data under that procedure. It does not show the range of individual participants’ estimates, and it does not guarantee that the true value lies in the interval. The registry specifies a 95% confidence interval for the primary outcome, but the interval and the procedure used to calculate it are not reported in the registry record. The level alone is not enough to assess how narrow or wide the interval is.

The analysis denominator is important for interpreting a proportion. The listed enrollment is 642, while the primary outcome identifies the final population for data analysis. These descriptions do not establish that every enrolled participant had usable actual and estimated weights or was included in the endpoint calculation. The number analyzed, the number meeting the tolerance, and the handling of missing or excluded observations are not reported in the registry record. It would be a mistake to use enrollment as the denominator without that information.

Why does the within-tolerance definition matter?

A threshold-based endpoint is easy to interpret as the fraction meeting a specified accuracy criterion, but it compresses information. Estimates just inside and comfortably inside the tolerance are treated alike, while estimates just outside and far outside it are also grouped together. The percentage does not reveal whether errors tend to be overestimates or underestimates. Other listed predictive-performance outcomes, such as mean error and mean percentage error, could describe additional features, but their numerical results are not reported in the registry record.

In general, continuous error measures and threshold-based proportions answer different questions. An average error can be near zero when positive and negative errors offset one another, even if individual estimates vary. Conversely, a threshold percentage indicates how many observations met the chosen criterion but not the magnitude or direction of errors beyond it. A fuller assessment of predictive performance may therefore consider multiple complementary measures. The registry lists several such outcomes, but does not provide their estimates or analysis details.

What can be said about 2D and 3D measurements?

The primary outcome description names both 2D and 3D Mercy TAPE estimates and compares them with actual weight. The registry also lists inter-rater reliability for the 2D and 3D devices and device print batch variability as secondary outcomes. These topics concern distinct sources of measurement performance: agreement between raters and variation associated with print batches are not the same as the proportion within the weight tolerance. The specific procedures, estimates, and uncertainty measures for these outcomes are not reported in the registry record. No ranking or comparison between the device formats can be drawn from outcome titles alone.

In general, measurement reliability and predictive accuracy should not be treated as interchangeable. Reliability concerns the consistency of measurements under specified conditions; predictive accuracy concerns how closely estimates correspond to a reference. A device could be consistent without being accurate, or accurate on average while showing inconsistency across raters or batches. The registry’s secondary-outcome list indicates that these different questions were of interest, but does not document their results.

What is known about the statistical plan?

The registry records 0 analyses and does not report a statistical analysis plan, the confidence-interval method, missing-data procedures, subgroup methods, or adjustment for multiple outcomes. These details should not be reconstructed from general conventions. A confidence interval can be calculated in different ways, and methods can behave differently depending on data and assumptions. The method actually used for the primary endpoint is not reported in the registry record.

The record also includes planning assumptions for illustrative sample-size calculations: a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and effects defined as fractions of the observed effect. These are described as planning illustrations based on the observed effect, not as the trial’s own design. They are not observed power, and they do not show that the study was designed or conducted as a randomized comparison. The record states that time-to-event planning displays use total events and other displays use participants per arm; the primary endpoint is not a time-to-event outcome. No planning estimate or sample-size value needs to be treated as an observed trial result.

Over-dispersion is a general concern when variation in binary outcomes exceeds what a simple probability model assumes. If present, a model that understates variability can make uncertainty appear too small. Whether over-dispersion was assessed or relevant to the primary analysis is not reported in the registry record. Given the absence of the numerical result, analysis denominator, and method, there is no basis for evaluating model fit or recalculating the primary confidence interval.

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("2D-TAPE", "3D-TAPE")
n      <- c(624, 624)
events <- c(612, 582)
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  2D-TAPE  624  612  98.1  96.7  99.0  96.7  98.9  96.7  98.9
ARM  3D-TAPE  624  582  93.3  91.0  95.1  91.0  95.0  91.0  95.0

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 19 outcome measures, including the primary percentage within the 20% tolerance and secondary outcomes related to inter-rater reliability, print batch variability, and predictive performance. It records 0 analyses. The numerical results, analysis-specific denominators, and any ordering or prioritization among secondary outcomes are not reported in the registry record.

When a study evaluates multiple outcomes or makes multiple statistical comparisons, the chance of obtaining at least one seemingly notable result can increase. General approaches to multiplicity include prespecifying a hierarchy, adjusting significance thresholds, or treating secondary results as exploratory. Which approach, if any, was used is not reported in the registry record. No adjustment should be assumed, and no conclusion about statistical significance across outcomes can be drawn from the outcome list.

The primary outcome specifies the final population for data analysis, but the criteria defining that population are not reported in the registry record. The number included in the primary analysis, the number with missing actual weights or device estimates, the reasons for missingness, and the handling of incomplete measurements are also not reported. Without these details, the impact of missing information on the percentage cannot be evaluated. In general, excluding participants with unavailable measurements can affect a proportion if their likelihood of meeting the criterion differs from that of participants with complete measurements.

Subgroup definitions, prespecified analyses, sensitivity analyses, and the use of any adjusted models are not reported in the registry record. The listed outcomes alone do not establish that those analyses occurred. The absence of these details limits assessment of the analysis population, multiplicity, and robustness.

12. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0.01% reporting threshold.

The registry’s adverse-event figures list 642 at risk and 0 affected for serious events in the Normal Children group. For other events, it also lists 642 at risk and 0 affected. No serious event terms are listed. These entries describe the counts recorded in the registry; they do not provide event narratives, observation time, or additional detail about how adverse events were collected.

The death entry is not populated with a numerical value, so deaths are not reported in the registry record. A blank or null entry should not be read as a confirmed count of zero. Likewise, the recorded zero affected counts describe what is entered in the registry, not proof that no event could have occurred outside the reporting process. The record does not describe the event definitions, surveillance procedures, or completeness of safety reporting.

These figures should be read separately from the primary accuracy endpoint. They do not indicate how closely weight estimates matched actual weight, and the predictive-performance results do not establish safety. The adverse-event entries are registry counts, with limited accompanying detail.

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

The registry record identifies a pediatric device-validation question and defines a measurable accuracy criterion: the percentage of participants whose Mercy TAPE estimate was within 20% of actual weight on study day 1. It names 2D and 3D Mercy TAPE estimates and lists additional outcomes concerning reliability and predictive performance. These details clarify what the study set out to evaluate.

The numerical primary result and its 95% confidence interval are not reported in the registry record. As a result, the record does not establish the observed percentage meeting the criterion or how precisely that percentage was estimated. It also does not report the numerator or analysis denominator. The enrollment figure cannot fill those gaps, because the endpoint refers to a final analysis population and the inclusion of participants in that population is not described.

The endpoint itself has a specific interpretation: it counts estimates within a chosen tolerance. It does not indicate the direction or size of errors outside the tolerance, and it does not show how performance varies across the stated age range. Results for separate device formats, raters, batches, or subgroups are not reported in the registry record. The study’s completion status and outcome titles do not replace those missing estimates.

This is not a randomized treatment comparison. Actual weight is the reference against which estimates are assessed. The record does not support causal claims about a treatment or comparative claims about the device formats. Nor do the safety entries answer the predictive-accuracy question. They are separate registry counts, and the death value is not reported.

The appropriate conclusion is therefore about what can be assessed from the record: the intended population, device, reference, and tolerance-based endpoint are described, but the performance result is unavailable. Any claim about the degree of accuracy, precision, consistency, or comparative performance would require results and analysis details not reported in the registry record.

14. Why This Trial Matters Statistically

Weight estimation is an important measurement problem in the setting described by the registry: a child’s weight may be desirable or necessary when it is unavailable. A device-validation study asks whether a proposed estimate corresponds sufficiently closely to a measured reference. Statistically, that is different from testing whether a treatment changes a health outcome. Making this distinction helps readers identify what an endpoint can and cannot answer.

The within-20% measure is useful because it expresses performance as a proportion meeting a defined tolerance. It is also a reminder that a single summary can simplify a more complex pattern of errors. Error direction, the magnitude of estimates outside the tolerance, and variation across participants or measurement conditions matter for a complete statistical account. The registry lists other predictive-performance and reliability outcomes that address some distinct questions, but their numerical results are not reported in the registry record.

The record also illustrates why precision and analysis-population details matter. Enrollment is listed as 642, but the primary endpoint refers to a final population for analysis. Without the number analyzed, the observed percentage, and its confidence interval, readers cannot judge either the estimate or its uncertainty. A completed study with a clearly defined endpoint is not, by itself, enough to quantify performance.

Finally, distinguishing validation from randomized comparison prevents overinterpretation. The registry describes actual weight as the reference and does not state allocation. The evidence question is about correspondence between estimates and a reference, not a causal treatment effect. The record’s design description and its missing numerical results should both shape how the study is interpreted.

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 principal limitation for interpreting this registry record is that it does not report the primary outcome value or the specified 95% confidence interval. The number meeting the within-20% criterion and the number included in the primary analysis are also not reported. The listed enrollment of 642 therefore does not establish the denominator used for the endpoint or the completeness of the measurements.

The primary outcome refers to the final population for data analysis, but the criteria defining that population are not reported in the registry record. There is no description of exclusions, missing actual weights, unavailable device estimates, or the handling of incomplete records. These omissions prevent assessment of whether the analyzed participants represent the population enrolled.

The registry names 2D and 3D estimates, but their separate results and any direct comparison are not reported. Although secondary outcomes include inter-rater reliability, print batch variability, intercept, slope, mean error, and mean percentage error, estimates and methods for these outcomes are not reported in the registry record. Outcome names alone cannot establish their results or whether they were analyzed.

Allocation is not stated, and the record does not describe a randomized comparison. The Normal Children group is not a like-for-like control comparison. Details about measurement procedures, actual-weight measurement, blinding, subgroup analyses, and statistical methods are not reported in the registry record. The confidence-interval method and any multiplicity handling are also unspecified. These limits preclude a detailed appraisal of bias, precision, or robustness, and they do not permit conclusions about performance beyond the registered endpoint description.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Validation of the Mercy TAPE — NCT01507090.
• Registry record last updated 2015-02-10; status last verified 2015-02.
• Results first posted 2015-02-10.
• 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

The registry record identifies a completed device-validation study of the Mercy TAPE in otherwise healthy children aged 2 months to 16 years. Enrollment is listed as 642, with start recorded as 2012-02 and primary completion as 2012-03. The device intervention is the Mercy TAPE; the described group is Normal Children.

The primary outcome is the percentage of participants whose 2D or 3D estimate was within 20% of actual weight on study day 1, with a 95% confidence interval specified. The primary numerical result, interval, analysis denominator, and analysis methods are not reported in the registry record. Secondary outcomes address reliability, print batch variability, and other predictive-performance measures, but their numerical results are not reported. The record lists 19 outcome measures and 0 analyses.

Safety entries record 0 affected for serious events and 0 affected for other events; deaths are not reported in the registry record. The available record describes the validation question but does not quantify the observed accuracy or its precision.