Healthcare Utilization in Obese Caregiver Living Donors: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Healthcare Utilization in Obese Caregiver Living Donors (NCT04341896), a registered phase not stated study. The primary outcome is Emergency Department Utilization.

2. Clinical Question

The study's stated goal was to estimate healthcare use after donation attributable to informal caregiving among obese living donors. The primary outcome named in the registry record is emergency department utilization. It is described as the proportion reporting at least one emergency department visit since donation or the previous questionnaire, with a timeframe of 44 months.

The word “attributable” expresses the study's objective, not a causal conclusion established by the group definitions. Caregiver status was not assigned at random, and the record does not describe adjustment for differences between the groups. The comparison therefore raises a question about an association between caregiving status and reported healthcare use; it cannot, from the record alone, isolate caregiving as the cause of any group difference. The registry record does not report the group-specific outcome proportions or an estimated contrast.

3. Trial Design

The study is titled “Healthcare Utilization in Obese Caregiver Living Donors,” with the official title “The Role of Caregiving in Healthcare Utilization Among Obese Living Kidney Donors.” The sponsor is the University of Alabama at Birmingham. The registry lists an enrollment of 784 and a status of COMPLETED. The recorded study start is 2020-07-01, and the primary completion date is 2024-03-07.

The two groups are defined by whether prior obese living kidney donors served as the primary caregiver for their recipient. Caregivers are compared with non-caregivers. The registry explicitly identifies this as a non-randomized comparison and says the arms are not a like-for-like control comparison. Allocation is not stated. Thus, the group labels describe participants' caregiving status rather than an assigned experimental treatment.

The primary outcome is emergency department utilization, measured as a participant count and described as the proportion self-reporting at least one visit since donation or the previous questionnaire. Its stated timeframe is 44 months. The denominator is based on responses to the corresponding survey item. The registry record does not report the number of item respondents, the group-specific outcome counts, or the proportions.

The record lists 2 outcome measures and 0 analyses. It does not describe a statistical analysis plan, a sample-size justification, adjustment variables, or a method for handling repeated questionnaires. The posted information therefore supports describing the study question, group definitions, and registered endpoint, but not reconstructing how the investigators analyzed the data. The caregiver and non-caregiver groups should not be interpreted as randomized treatment and control arms.

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

Analysis population for the primary outcome, as defined in the registry: The denominator for this outcome is based on participants who responded to the survey item asking about emergency department utilization since donation

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: These numbers correspond to the individuals who completed survey measures during the study period and indicated whether or not they were the primary caregiver for their transplant recipient.

6. Primary Endpoint

The registry lists the primary outcome as Emergency Department Utilization, measured over 44 months.

The primary endpoint is emergency department utilization. The registry describes it as a participant-level measure: whether a respondent self-reported at least one emergency department visit since donation or the previous questionnaire. It is expressed as a proportion, with the unit listed as participants, and has a stated timeframe of 44 months.

This outcome is useful for addressing the study's question because it captures reported healthcare use after donation rather than a clinical outcome unrelated to service use. A binary endpoint classifies each eligible respondent according to whether the event was reported. Comparing the proportions in the caregiver and non-caregiver groups can describe whether reported utilization differs between those groups. That comparison alone does not establish that caregiving caused a difference.

The denominator is limited to participants who responded to the survey item about emergency department utilization. The registry record does not report the number of respondents, the group-specific counts or proportions, or how unanswered items were handled. The description also does not clarify how responses across questionnaires were combined when a participant had more than one survey. Those details matter for understanding exactly which reports contribute to the endpoint and how precisely the observed proportions represent the intended donor groups.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical interpretation begins by separating the registered question from the information needed to estimate an answer. The registry names emergency department utilization as the primary outcome and describes it as a proportion based on survey responses. It identifies caregiver and non-caregiver groups, but it does not report their endpoint results or an analysis. The general concepts below explain how such a comparison may be understood; they are not claims about methods used in this study.

What does a proportion describe?

For a binary outcome, each eligible respondent is classified according to whether the event was reported. A group proportion represents the fraction of respondents in that group who reported the event. The endpoint description refers to at least one emergency department visit, so it concerns whether a participant reported a visit, not the total number of visits. A proportion needs both an event count and a denominator. Because the denominator is based on survey-item respondents, the enrolled population and the endpoint population need not be identical. The registry record does not report the item-response counts or the group-specific proportions.

A difference in proportions would express the absolute gap between the groups, while a ratio would express their relative comparison. These are distinct ways of presenting a contrast, and each answers a different interpretive question. Neither can be derived from the registry description alone. The record reports no endpoint counts, group proportions, or contrast estimate, so no numerical comparison can be made.

What would uncertainty add?

A confidence interval is a general statistical device for describing uncertainty around an estimated effect. It indicates the range of effect values reasonably compatible with the data and the assumptions of the analysis. A narrow interval generally indicates greater precision than a wide interval, but an interval does not eliminate bias in the underlying data or design. No confidence interval for emergency department utilization is reported in the registry record.

A p-value, in general, measures how incompatible the observed data are with a specified null hypothesis under a statistical model. It does not measure the probability that the null hypothesis is true, nor does it tell whether a difference is important in practice. The registry lists 0 analyses and does not report a p-value or the model used to test a comparison. Statistical significance therefore cannot be assessed from the posted record.

Why does non-randomized grouping matter?

Random assignment can, on average, balance measured and unmeasured characteristics between groups. Here, the groups are defined by primary caregiving status, and the record explicitly characterizes the comparison as non-randomized, with allocation not stated. A difference between groups could therefore reflect caregiving status or other differences associated with being a caregiver. Statistical adjustment can address measured differences when appropriate variables and a suitable model are available, but it cannot automatically remove unmeasured confounding. The registry record does not report an adjustment strategy or covariates.

For a binary endpoint, general analysis options can include models for proportions or methods that directly compare group risks. The choice depends on the design, data structure, and analysis objective. If participants contribute repeated survey responses or are clustered in meaningful groups, dependence among observations may need consideration; the registry record does not describe whether responses were repeated in the analysis or how such dependence was handled. It would not be appropriate to assume a particular model based only on the endpoint's binary form.

How should the planning assumptions be read?

The record includes general planning assumptions for sample-size illustrations: a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the effect to detect defined as a stated fraction of the observed effect. These are described as planning illustrations computed from an observed effect, not as the trial's own design. The record also distinguishes planning quantities by outcome type. No resulting sample-size values or observed effect are included in the registry record for this analysis. Such planning illustrations are not observed power, do not replace the endpoint results, and do not demonstrate that a comparison was adequately powered.

More broadly, the methods needed to interpret an estimate include a clearly defined analysis population, an explicit treatment of missing item responses, a prespecified comparison, and an account of uncertainty. These details help readers understand which people contributed information, what effect was estimated, and what assumptions support the inference. The registry record does not report those analysis details for the emergency department endpoint, so the appropriate conclusion is descriptive: the question and endpoint are registered, but the statistical result is not reported.

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("Caregivers", "Non-caregivers")
n      <- c(144, 618)
events <- c(77, 305)
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  Caregivers  144  77  53.5  45.0  61.8  45.3  61.4  45.3  61.4
ARM  Non-caregivers  618  305  49.4  45.3  53.4  45.4  53.3  45.4  53.3

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists 2 outcome measures and 0 analyses. Emergency department utilization is identified as the primary outcome. The other outcome measure is not described in the available record information. No multiplicity procedure or hierarchy for interpreting multiple outcomes is reported in the registry record.

In general, evaluating multiple outcomes can increase the chance of obtaining an apparently notable finding by chance if each is tested separately. A prespecified primary outcome and an explicit strategy for secondary outcomes help clarify how evidence should be interpreted. Because the record does not report analyses or a multiplicity plan, it is not possible to determine whether or how the investigators accounted for multiple outcomes. This does not establish that a particular adjustment was required or omitted from the actual study; it indicates that the registry record does not report the approach.

Missing data are also important because the primary endpoint denominator is based on participants who responded to the survey item asking about emergency department use. The number of respondents and the amount or pattern of nonresponse are not reported in the registry record. Nor is a method for handling unanswered items described. If people who do not answer differ in utilization or caregiver status from those who answer, a respondent-based proportion may not represent the broader group in the same way. That is a general concern, not evidence that such a difference occurred in this study.

The analysis population, handling of incomplete questionnaires, and any sensitivity analyses are not reported in the registry record. Consequently, the full relationship between enrolled participants, survey respondents, and the outcome analysis cannot be assessed. The adverse-event group counts do not resolve this issue because they are not reported as the emergency department endpoint denominators.

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 lists serious adverse event entries for caregivers and non-caregivers. The caregiver entry reports 148 at risk, 0 serious adverse events, 0 other adverse events, and 0 deaths. The non-caregiver entry reports 636 at risk, 0 serious adverse events, 0 other adverse events, and 0 deaths. These are the safety figures recorded for the listed groups.

These entries should be read as event counts in the registry's adverse-event fields. They are not the primary endpoint results. The primary endpoint concerns self-reported emergency department utilization among respondents to a survey item; the safety entries do not report how many respondents reported a visit. A zero in an adverse-event field therefore cannot be interpreted as zero emergency department utilization.

Zero recorded events in these fields does not, by itself, demonstrate that no adverse experiences occurred outside the scope or reporting process represented by the registry entry. The record does not provide further information about adverse-event definitions, collection procedures, or completeness. The safety figures also do not establish a comparative safety effect between the groups. They are counts, not adjusted comparisons, and the registry describes the group comparison as non-randomized. The figures should therefore be kept separate from the healthcare-utilization question and interpreted only as the adverse-event counts recorded for each group.

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

The study addresses a meaningful statistical question: whether self-reported emergency department use after donation differs between obese living kidney donors who served as primary caregivers and those who did not. Its registered endpoint is understandable, participant-based, and linked to a stated 44-month timeframe. The comparison also draws attention to an important design feature: the groups arise from caregiving status, rather than randomized assignment.

What the record does not establish is the actual outcome comparison. It reports no group-specific emergency department counts or proportions, no estimated difference, and no uncertainty interval or test result. It is therefore not possible to say from the registry record whether reported utilization was more common in one group, how large a difference might have been, or whether the data were precise enough to distinguish a difference from chance variation. Missing results should not be read as a null result.

Even if an unadjusted difference were reported, it would describe an association between group membership and the outcome in the analyzed respondents. It would not by itself show that caregiving caused the difference. Caregiver status was not randomized, and the record does not report an adjustment plan or measured characteristics used to account for differences between groups. A causal interpretation would require assumptions and analysis details that are not reported in the registry record.

The response-based denominator further limits what can be inferred about all enrolled donors. The record does not report item response counts or the handling of missing answers. The adverse-event entries report zeros for serious events and deaths in both groups, but those are not the emergency department outcome and cannot stand in for its missing results. The most defensible interpretation is that the registry defines a relevant utilization question and group comparison, while the posted information is insufficient to determine the result or its precision.

14. Why This Trial Matters Statistically

This study matters statistically because it illustrates the difference between a clearly stated research objective and an interpretable estimate. The registry identifies a target population, a caregiving-based comparison, and a participant-level utilization endpoint. Those elements tell readers what was intended to be compared. To judge the evidence, however, readers also need the outcome counts, denominators, estimated contrast, and uncertainty. These results are not reported in the registry record.

The study also highlights the challenges of non-randomized comparisons. Caregiving status can define groups that differ in other ways, so a crude comparison may combine the association of interest with differences in participant characteristics. A thoughtful analysis can describe and, where possible, adjust for measured differences, but the registry does not report whether such adjustment was performed. Without that information, a reader cannot distinguish an unadjusted descriptive comparison from an adjusted estimate or assess the assumptions behind a causal interpretation.

Survey-based outcome definitions add another statistical consideration. The endpoint denominator consists of respondents to the relevant item, rather than automatically including everyone enrolled. Reporting response counts and missing-data handling would help readers assess how well the respondent results represent the intended donor groups. The record does not report those details.

Finally, the record lists 2 outcome measures but 0 analyses. This makes it especially important not to infer findings from the study aim, completion status, or adverse-event entries. A completed registry record is not equivalent to a posted statistical result. Clear reporting of the endpoint estimates, denominators, analysis methods, and uncertainty would be necessary to evaluate the strength and scope of the evidence.

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.

Several limitations specific to this record affect interpretation. First, the emergency department endpoint is described, but its group-specific counts and proportions are not reported. The number of respondents contributing to the endpoint denominator is also not reported, so the precision and coverage of the measure cannot be assessed. There is no reported estimate of the group contrast or its uncertainty.

Second, the comparison is non-randomized and the record says the arms are not a like-for-like control comparison. The record does not report adjustment variables or an analysis strategy that might address differences between the groups. Any causal interpretation would therefore require information and assumptions beyond what is recorded.

Third, the endpoint relies on self-report. The registry description does not explain how responses were verified, how multiple questionnaires were combined, or how the reference period was handled for each respondent. It describes visits since donation or the previous questionnaire and states a 44-month timeframe, but the response-level implementation is not reported. The item-response denominator also raises the possibility that missingness could affect representativeness; the extent and handling of missing responses are not reported.

Finally, the record lists 2 outcome measures and 0 analyses, without reporting the analysis population, multiplicity approach, or detailed statistical methods. The serious adverse-event counts are separate from the primary endpoint and do not fill these gaps. These limitations concern what can be established from the registry record; they do not determine what analyses may have been conducted outside the information recorded there.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Healthcare Utilization in Obese Caregiver Living Donors — NCT04341896.
• Registry record last updated 2025-02-10; status last verified 2025-02.
• Results first posted 2025-02-10.
• 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 describes a completed, non-randomized comparison of prior obese living kidney donors classified as primary caregivers or non-caregivers for their recipients. Enrollment is listed as 784. The study start date is 2020-07-01, and the primary completion date is 2024-03-07. The sponsor is the University of Alabama at Birmingham.

The primary outcome is self-reported emergency department utilization since donation or the previous questionnaire, with a timeframe of 44 months. Its denominator is based on responses to the relevant survey item. The record lists 2 outcome measures and 0 analyses, but does not report group-specific primary outcome values, estimates, or uncertainty.

The adverse-event entries report zero serious adverse events, zero other adverse events, and zero deaths in each listed group. Those entries are not the emergency department utilization results. Overall, the registry defines the study question and endpoint but does not report the statistical outcome needed to assess the comparison.