Warming Blanket Comparison Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Warming Blanket Comparison Study (NCT04776954), a randomized na study. The primary outcome is AUC of Temperature vs Time.

2. Clinical Question

3. Trial Design

This was a randomized, parallel-group study with no masking reported. The registry lists 15 participants as enrolled and describes two device interventions: a forced air warming system and a resistive blanket warming system. The arm summaries include 7 participants in the forced air group and 8 in the resistive blanket group. These are the reported outcome group sizes; the record does not explain whether they represent every randomized participant or how participants were handled if outcome data were unavailable.

The study was conducted in the setting of renal transplant surgery. Its stated purpose was to compare the effectiveness of the two warming approaches in maintaining body temperature during the operation. The primary outcome timeframe is described as up to 5 hours. The study is listed as terminated, with a start date of 2021-09-27 and a primary completion date of 2022-11-17. The reason for termination is not reported in the registry record, so the status alone does not explain why the study ended.

The phase is listed as NA. The registry record does not report the randomization method, allocation concealment procedures, planned enrollment rationale, masking of outcome assessors, or a protocol for deviations from assigned warming. It also does not report whether enrollment stopped as planned or whether the termination affected outcome collection. Such details would help assess the conduct and completeness of a small randomized comparison, but cannot be inferred from the design labels.

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 AUC of Temperature vs Time, measured over up to 5 hours.

The primary endpoint is titled “AUC of Temperature vs Time.” It is described as the area under the curve of temperature versus time during hypothermia, defined in the record as core temperature below 36 degrees Celsius during surgery. Temperature comparison was based on a nasopharyngeal probe placed 10 to 20 cm into the nare. The stated timeframe is up to 5 hours, and the reported unit is celsius per minute.

An area-under-the-curve measure can combine the duration and extent of departures from a threshold into one continuous summary. In general, this can capture more of a temperature pattern over time than a single measurement at one moment. The record frames this endpoint as a measure of time spent under the threshold, although its description does not specify the exact calculation used to convert the temperature trajectory into the reported area or explain how the negative values should be interpreted.

The registry reports a mean and standard deviation for each group. It does not provide participant-level temperature trajectories, an endpoint calculation specification, or a between-group estimate with an uncertainty interval. A secondary outcome, body temperature upon arrival in PACU, is listed, but numerical results for it are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous, and the registry identifies the reported statistic as a mean with standard deviation. A mean describes the central value of a group’s observations, while a standard deviation describes how dispersed observations are around that mean. These summaries can characterize the observed groups, but they do not by themselves answer whether the groups differ beyond what could reasonably arise from sampling variation. For that, a comparison estimate and an uncertainty measure are generally needed.

What an uncertainty interval would add

In general, a confidence interval expresses uncertainty around an estimated quantity under the assumptions of the analysis. For a comparison between groups, an interval would show a range of values compatible with the observed data and the chosen statistical procedure. It can help readers judge both the direction and precision of an estimated difference. No confidence interval for the primary comparison is reported in the registry record, and the posted arm summaries do not allow that interval to be quoted as a registry result.

A p-value, when reported, addresses how compatible data are with a specified null model under the analysis assumptions; it does not measure the size or clinical importance of an effect. No primary-comparison p-value is reported. There are also no posted analyses in the record. Accordingly, no conclusion about statistical significance can be drawn from a sponsor-reported analysis, and no alternative test result should be imputed to the study.

Why the endpoint definition matters

The registry defines the endpoint as an area under a temperature-versus-time curve during periods below 36 degrees Celsius. In general, area-under-the-curve measures depend on the precise construction of the curve, how observations are timed, and how the area is accumulated or signed. The record gives the unit and the threshold-based description but does not report the calculation algorithm, handling of gaps in measurements, or a fuller explanation of the negative values. Those details matter for interpreting what a change in the endpoint represents. No reconstruction of the measure can be made from the group means and standard deviations alone.

The registry reports a mean and standard deviation, which suggests descriptive summaries of a continuous outcome. It does not report a model, covariate adjustment, test statistic, degrees of freedom, or assumptions used for an inferential analysis. No particular inferential procedure should therefore be attributed to the trial. General methods for comparing continuous outcomes may use a model for the mean difference, but the model and its assumptions must be specified and checked; a suitable choice cannot be selected retrospectively from these summaries alone.

Planning illustrations are not trial findings

The registry includes assumptions for planning illustrations based on the observed effect: a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. The illustration is described as targeting a stated fraction of the observed effect. Such calculations are planning exercises, not observed trial results and not observed power. They do not show that the trial had a particular probability of detecting an effect, nor do they replace an analysis of the enrolled participants. The registry record does not report the numerical planning outputs or a trial-specific sample-size justification.

In general, planning calculations depend on the effect one aims to detect, the variability assumed, the chosen error rate, and the design assumptions. If the effect is drawn from a small trial’s observed estimate, the resulting planning scenario can be especially sensitive to the uncertainty in that estimate. The record does not provide enough numerical planning details to evaluate the resulting target sample sizes. The published arm summaries should not be treated as evidence that the planning assumptions were met.

The primary endpoint is based on repeated temperature measurement over surgery, yet the posted results reduce it to one summary per group. Repeated measurements can be correlated within a participant; in general, an analysis of the trajectory must account for that dependence or define a participant-level summary before comparing groups. The registry does not report how repeated measurements were handled beyond describing the area-under-the-curve outcome. It is not possible to assess the measurement schedule, within-participant correlation, or model adequacy from the information recorded.

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("Forced Air Warming System", "Resistive Blanket Warming System")
n   <- c(7, 8)
m   <- c(-131, -147)
sp  <- c(93, 69)
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  Forced Air Warming System  7  -131.000  93.000  -217.011  -44.989
CARM  Resistive Blanket Warming System  8  -147.000  69.000  -204.685  -89.315

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary outcome and one secondary outcome, body temperature upon arrival in PACU. It reports two outcome measures in total, but numerical results are posted only for the primary outcome. Results for the secondary outcome are not reported in the registry record. No multiplicity strategy, such as a hierarchy among outcomes or adjustment for multiple comparisons, is reported. Without a posted analysis plan, it is not possible to determine how the investigators intended to interpret findings across outcomes.

Missing-data handling is not reported in the registry record. The record does not say whether every enrolled participant had an evaluable primary outcome, how incomplete temperature recordings were handled, or whether any measurements were excluded. It also does not report imputation, sensitivity analyses, or reasons for missing outcomes. The group sizes attached to the primary summaries do not establish whether participants without usable data were absent or whether all randomized participants were analyzed.

The analysis population is not reported in the registry record. In particular, it does not say whether the primary comparison was intended to include all randomized participants according to assigned group, only participants who received the assigned warming approach, or another defined population. There is no reported participant flow or account of crossovers and protocol deviations. These omissions limit assessment of how randomization was preserved in the analysis and whether exclusions could have affected the group comparison.

The registry reports zero analyses. Consequently, no analysis population, missing-data method, multiplicity adjustment, or inferential method can be attributed to a posted analysis. The listed event summaries also show zero at-risk participants in each group, so they cannot be read as complete evidence about adverse-event occurrence in the enrolled study population.

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

The registry result is a descriptive account of the primary endpoint in the two warming groups: a mean and standard deviation for each, with the number of participants contributing to each summary. It offers information about the observed values, but not a statistical estimate of the comparison between approaches. The absence of a confidence interval and p-value means that the precision and statistical compatibility of a between-group effect cannot be evaluated from posted inferential results.

These summaries do not establish that either warming approach is better, worse, or equivalent. Equivalence requires a defined margin and an appropriate analysis; neither is reported in the registry record. A difference between observed means, by itself, is not sufficient to establish a reliable or clinically meaningful difference. Likewise, the lack of an inferential result is not evidence that the groups are the same.

The endpoint description focuses on temperature below a threshold during surgery, but the record does not give enough detail about the calculation to translate the negative area values into a direct duration or severity statement. The mean summaries should therefore be interpreted in the reported unit and with caution about the endpoint’s sign and construction. A single summary also cannot show the timing or shape of individual temperature trajectories.

The secondary PACU temperature outcome has no numerical result posted. The adverse-event summary records zero at-risk participants, and the trial is listed as terminated without a reason. Those details do not support broad conclusions about safety, completeness, or why the study ended. The findings describe a small randomized comparison in renal transplant surgery, but the registry record does not establish how representative the participants were or how applicable the summaries may be outside this study setting.

13. Why This Trial Matters Statistically

This study raises a useful statistical issue: a trial can post arm-level summaries without posting the comparison needed to answer its randomized question. Means and standard deviations are informative descriptions, but a treatment contrast and its uncertainty are needed to assess how strongly the data distinguish the groups. The registry’s lack of a posted analysis makes that distinction especially important.

The outcome is based on temperature over time, rather than a single measurement. Summarizing a trajectory as an area under a curve can preserve information about both duration and magnitude of threshold excursions, but only when the calculation and interpretation are clear. Here the threshold and measurement approach are described, while the handling of the curve and the meaning of negative values are not fully specified. Statistical interpretation depends on those measurement details as well as on the chosen comparison method.

The study also illustrates why sample-size planning should be separated from trial results. The registry describes planning assumptions based on the observed effect, but such illustrations are not observed power and do not establish that a study was adequately sized. In a small trial, planning from an observed effect should be understood as a scenario rather than a precise forecast. The record does not report a trial-specific sample-size rationale or the numerical planning outputs.

Finally, randomized design labels do not replace reporting of the analysis population, missing-data procedures, outcome definitions, and inferential results. Those elements allow readers to assess how the design connects to the conclusions. Their absence limits what can be learned statistically from the posted record, even though group summaries are available.

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 primary endpoint is not described with enough computational detail to reproduce its value. The registry identifies the threshold, temperature measurement site, unit, and general area-under-the-curve concept, but it does not report the exact formula, how observations were timed, or how missing measurements and curve segments were treated. It also does not explain why the reported means are negative. This leaves uncertainty about the practical interpretation of the endpoint.

Only group-level means and standard deviations are posted for the primary outcome. Participant-level data, a between-group estimate, a confidence interval, and a p-value are not reported in the registry record. The record lists no analyses, so there is no reported inferential procedure to assess. The secondary outcome is named but has no numerical result posted.

The enrollment was 15, and the primary outcome summaries include 7 participants in one arm and 8 in the other. The record does not report participant flow, the analysis population, missing-data handling, adherence, crossovers, or protocol deviations. It also does not report the reason for termination, the trial’s sample-size justification, or whether stopping affected planned data collection. These gaps constrain assessment of selection and reporting processes.

Details of randomization, allocation concealment, outcome-assessor masking, and baseline characteristics are not reported in the registry record. The study is listed as unmasked, but the record does not specify who knew assignments or how temperature measurements were collected and reviewed. The event summaries list zero participants at risk, which prevents them from establishing that no adverse events occurred among participants. These limitations restrict interpretation of both the primary comparison and the broader completeness of the posted findings.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Warming Blanket Comparison Study — NCT04776954.
• Registry record last updated 2024-09-27; status last verified 2024-09.
• Results first posted 2024-09-27.
• 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

The University of Minnesota sponsored this randomized, parallel-group comparison of forced air warming and resistive blanket warming during renal transplant surgery. The study is listed as unmasked, with 15 enrolled participants, and its status is terminated. The registry gives a start date of 2021-09-27 and a primary completion date of 2022-11-17.

The primary outcome is the area under the temperature-versus-time curve during periods below 36 degrees Celsius, measured using nasopharyngeal temperature. The forced air group has a reported mean of -131 and standard deviation of 93 among 7 participants; the resistive blanket group has a mean of -147 and standard deviation of 69 among 8 participants. No primary inferential analysis is posted. Body temperature upon arrival in PACU is listed as a secondary outcome, but its results are not reported in the registry record.