Diuretic/Cool Dialysate Trial: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Diuretic/Cool Dialysate Trial (NCT02593526), a randomized na study. The primary outcome is Slow the Rate of Residual Renal Function (RRF).

2. Clinical Question

The clinical question concerns preservation of residual kidney function during chronic dialysis, rather than a single measurement at one time point. The study description identifies RRF as a standard-of-care assessment for dialysis patients and gives quality of life and survival as reasons it is assessed. Those statements describe the rationale for tracking RRF; they do not establish that this trial measured an effect on either quality of life or survival.

The factorial structure was intended to examine two treatment dimensions: use of bumetanide and dialysate temperature. The posted record does not give an estimable comparison between any pair of arms. It therefore cannot answer whether either dimension, or their combination, changed the rate of RRF decline. The registry record also does not report a threshold defining what degree of slowing would be clinically important.

3. Trial Design

The registry describes a randomized, unmasked, factorial pilot study. Its four assigned groups crossed two diuretic conditions with two dialysate temperatures. The no-diuretic groups used either 37°C or 35.5°C dialysate; the bumetanide groups used those same respective temperatures. The record identifies the 37°C, no-diuretic condition as standard of care and describes the intervention combination of bumetanide and cool dialysate.

Enrollment is listed as 11, but the study description says only one participant met criteria for randomization. The arm entries record a participant only in the bumetanide plus 35.5°C dialysate group. The other three arms have zero participants listed. These entries describe the registry’s posted outcome data; they should not be taken to show that the planned comparisons were completed.

The primary outcome was intended to assess the rate of RRF change over 6 months. Eligibility for randomization depended on adequate RRF being determined from the first 24-hour collection. For a randomized participant, the description specifies a pre-dose, day 0 collection and further collections at Month 4 and Month 6. The record does not report additional operational detail about the study procedures or how RRF values were translated into the posted outcome count.

The trial is listed as terminated. Its start is recorded as 2017-01 and its primary completion date as 2022-05-27. The registry does not report why it was terminated. The stated phase is NA. No analysis is listed, and the record does not report a statistical analysis plan, allocation concealment procedures, or a masking procedure beyond identifying the trial as unmasked.

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.

Before assignment: Of the 11 enrolled participants only 1 met randomization criteria and was randomized to treatment.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Only one participant met criteria for randomization.

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: Of the 11 enrolled participants only 1 met randomization criteria and was randomized to treatment.

6. Primary Endpoint

The registry lists the primary outcome as Slow the Rate of Residual Renal Function (RRF), measured over 6 months.

The primary endpoint is titled “Slow the Rate of Residual Renal Function (RRF)” and is recorded as a count of participants. The description indicates that RRF was to be measured using 24-hour collections: an initial collection to determine eligibility, followed for a randomized participant by a day 0 pre-dose collection and collections at Month 4 and Month 6. The intended endpoint therefore concerns change over time, not simply the presence of RRF at one visit.

Tracking RRF is relevant in this setting because the registry describes it as a standard-of-care assessment for people on dialysis and cites quality of life and survival as reasons for assessment. That rationale does not mean this trial directly evaluated either of those outcomes. The registry does not report the actual RRF measurements, a rule for classifying an individual participant as having slowed decline, or an estimated rate of change.

The posted outcome is expressed as a participant count. One participant and a count of 1 are recorded in the bumetanide plus 35.5°C dialysate arm; the other arms list zero participants and zero outcome counts. The record does not clarify what event or threshold the count represents. With no reported comparison estimate, the endpoint entries cannot establish the size or direction of a difference in RRF trajectory.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies a randomized factorial design, but it does not report an analysis for the primary outcome. The explanations below describe statistical concepts relevant to this design in general; they are not a description of analyses carried out in this trial.

What does a factorial design separate?

In general, a factorial design varies more than one intervention dimension within the same study. Here the dimensions were diuretic use and dialysate temperature, with groups representing each combination. A factorial analysis can estimate the average contrast associated with one dimension while accounting for the other, if the data and prespecified analysis support that approach. It can also assess whether the effect of one dimension depends on the level of the other. Such dependence is called an interaction.

These are distinct questions. A comparison of bumetanide with no diuretic could average across dialysate temperatures, while a temperature comparison could average across diuretic conditions. An interaction asks whether those contrasts vary across combinations. In general, estimation of these effects requires outcome information across the relevant groups. With only one participant listed in one arm and none in the other arms, the registry does not provide the data needed to estimate these contrasts. It reports no factorial effect or interaction analysis.

Why does randomization matter, and what can it not fix?

In general, random assignment aims to make treatment groups comparable, on average, with respect to measured and unmeasured characteristics. That purpose depends on having groups with participants and outcome data. Randomization does not itself create information when outcome data are absent from most assigned conditions. It also does not guarantee that a small realized set of groups will be balanced. The registry record does not report details of the randomization sequence or allocation concealment, so those procedures cannot be assessed from the record.

The trial is described as unmasked. In general, masking can reduce the risk that knowledge of assignment influences participant behavior, clinical management, outcome assessment, or reporting. Its relevance depends on the interventions and outcome measurements. The record does not describe whether outcome assessment was conducted by personnel unaware of assignment. No conclusion about the impact of masking can be drawn from the information recorded.

What would a confidence interval communicate?

In general, a confidence interval describes the statistical uncertainty around an estimated effect under the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval; an interval that includes values on both sides of no difference can be compatible with multiple possible effects. It does not resolve problems in outcome definition, missing observations, or design execution. No comparative effect estimate or confidence interval is reported for this trial, so precision cannot be assessed from an interval.

A p-value, in general, measures how unusual data at least as incompatible with a specified null hypothesis would be under the assumptions of a statistical test. It does not measure the probability that the null hypothesis is true, the size of an effect, or its clinical importance. The registry lists no analyses, and there is no reported p-value for the primary outcome. The available counts do not support substituting a new significance test for the sponsor’s analysis.

How should a binary count be understood?

The endpoint is categorized as binary and expressed as participants with an event, recorded as counts. In general, a binary endpoint requires a clearly defined event and an appropriate denominator of participants with outcome status known. A count without an event definition or usable denominators is difficult to interpret as a risk or probability. The record lists one participant and a count of 1 in one arm, while the remaining arms list no participants. It does not report enough information to calculate or interpret a comparative risk, and no such recalculation is warranted.

With very sparse information, estimates can be unstable or impossible to calculate. Conventional approximations may also be unsuitable when group counts are empty or very small. Specialized methods can sometimes address sparse binary data, but they cannot recover missing outcome information or create a meaningful between-arm contrast when comparison arms have no listed participants. The registry does not report a chosen statistical method, and the comparison is designated as not estimable.

What do the planning assumptions mean?

In general, a sample-size calculation uses assumptions about the effect to detect, the significance level, allocation, and statistical method. The registry describes planning illustrations based on fractions of an observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It specifies that illustrations for non-time-to-event outcomes are expressed as participants per arm. These are planning assumptions, not evidence that the study achieved a particular power or that a planned comparison was conducted.

The record does not report a usable comparative effect estimate for the primary outcome, nor does it list analysis results or numerical planning estimates. A sample-size illustration should not be interpreted as observed power. In general, observed power calculated from an observed effect does not replace an effect estimate with its uncertainty. Here, the sparse arm entries and the absence of an estimable comparison mean that the planning assumptions do not establish what the trial could detect or what effect the interventions had.

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("Diuretic and 35.5°C Dialysate")
n      <- c(1)
events <- c(1)
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  Diuretic and 35.5°C Dialysate  1  1  100.0  2.5  100.0  20.7  100.0  15.8  98.7

11. Multiplicity, Missing Data and Analysis Populations

The study had a factorial structure, with two intervention dimensions and four combinations, but the registry record does not report a statistical plan for handling multiple comparisons. It does not say whether any primary contrasts were prioritized, whether an interaction was planned for testing, or whether multiplicity adjustments were intended. The absence of posted analyses means there are no reported inferential results to assess for selective testing or adjustment. These details are not reported in the registry record.

The registry lists one primary outcome measure and zero secondary outcomes. The primary outcome description specifies several planned collection times, but the record does not state how repeated measurements were to be modeled or how a participant’s rate of RRF change was to be summarized. It also does not report a prespecified definition of the outcome count or a primary contrast among the factorial arms. Those analytical choices are not reported in the registry record.

Missing-data handling and analysis populations are not reported in the registry record. There is no stated intention-to-treat, per-protocol, or other analysis population, and no account of incomplete collections or withdrawals. The arm entries show no participants in three groups, but the record does not explain why those groups have no posted outcome data. That absence should not be recast as ordinary missing follow-up or as evidence that outcomes were observed and were zero.

Without definitions of the analysis population, outcome, missing-data procedures, and planned contrasts, the posted counts cannot support a reproducible statistical interpretation. These gaps also prevent assessment of whether the intended longitudinal endpoint was analyzed as planned.

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 counts by arm. The bumetanide plus 35.5°C dialysate arm lists one participant at risk and zero affected by serious adverse events. Each of the other arms lists zero participants at risk and zero serious adverse events. The record lists no serious adverse event terms. It also records zero deaths in every arm.

The non-serious adverse event entries follow the same pattern: one participant at risk and zero affected in the bumetanide plus 35.5°C dialysate arm, and zero at risk and zero affected in the other arms. These entries describe what the registry reports; they do not provide a meaningful comparison of safety between interventions. In arms with no participants listed at risk, a zero event count is not evidence that no event would occur among participants receiving that condition.

The at-risk count is important because event counts need a population exposed or otherwise assessed for context. Even in the arm with one participant at risk, a zero count is a sparse observation and cannot precisely characterize the frequency of adverse events. The registry does not report further details about adverse event ascertainment, follow-up duration, or event definitions. The safety entries therefore offer limited descriptive information and do not establish comparative safety.

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

The registry record documents a randomized factorial pilot study intended to examine bumetanide and dialysate temperature in relation to RRF over 6 months. It also documents that only one participant met the stated criteria for randomization, that the trial is listed as terminated, and that no statistical analyses are posted. The arm-level outcome entries place one participant in the bumetanide plus 35.5°C dialysate group and none in the other groups.

These registry entries describe the extent of the available record; they do not show that the combined intervention slowed RRF decline. The outcome is described as a rate over time, but the registry does not post the underlying collections or a rate estimate. The posted count is not accompanied by a clear event definition. There is no comparative effect estimate, confidence interval, or inferential test to quantify an effect or its precision.

The entries also do not show that the interventions had no effect. In general, absence of an estimable comparison is different from an estimate near no difference. Here, most arms have no participant listed, so the record lacks the cross-group information needed to distinguish possible treatment effects. The counts cannot establish whether bumetanide, cool dialysate, or their combination changed RRF relative to the listed standard-of-care condition.

Nor can the record support conclusions about effects on quality of life or survival. Those outcomes appear in the rationale for assessing RRF, not as reported trial results. The safety counts are similarly too limited to establish comparative adverse event rates. The appropriate interpretation is therefore descriptive: the registry records a planned clinical question and sparse posted outcome and safety data, without evidence sufficient for an efficacy or comparative safety conclusion.

14. Why This Trial Matters Statistically

This trial illustrates a basic statistical distinction between a study question and information capable of answering it. A randomized factorial design can, in principle, distinguish the contributions of two treatment dimensions and assess whether they interact. That strength depends on outcome information across the combinations. When the registry lists a participant in only one arm, the planned contrasts cannot be estimated from the posted data.

The record also shows why enrollment figures and analysis populations should not be treated as interchangeable. Enrollment is listed as 11, while the description says only one participant met randomization criteria. Those statements refer to different aspects of study conduct. The arm-level entries and the statement about eligibility help clarify why the primary comparison is not reported as analyzable, without explaining why the remaining potential participants did not meet criteria.

A further statistical lesson concerns the endpoint definition. The stated aim is to assess a rate of change in RRF using repeated collections, while the posted outcome is a count of participants. Without the underlying measurements and a definition of the count, the path from collected RRF values to the reported binary outcome cannot be evaluated. Clear specification of outcome construction is essential for interpreting a result.

Finally, this record underscores that a zero in an empty arm is not a treatment result. Counts need denominators, and comparative estimates need usable information in the groups being compared. Sparse data can prevent estimation altogether rather than merely produce a wide interval. Recognizing that distinction prevents unsupported claims of either benefit or no effect and keeps the interpretation aligned with what the registry actually records.

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 is the lack of an estimable comparison for the primary outcome. Only one participant met criteria for randomization according to the study description, and the arm entries place a participant in one of the four groups only. The other groups have no participants listed. The registry explicitly indicates that a two-arm comparison of the binary endpoint is not estimable and lists no analyses.

The outcome information is also incomplete for understanding the intended endpoint. The primary question concerns the rate of RRF change across planned collections, but the registry does not provide measured RRF values, an estimated rate, or a definition of the participant count. This prevents assessment of the outcome’s magnitude and direction, as well as the relationship between the stated longitudinal aim and the posted count.

Additional design and analysis details are not reported in the registry record. These include the reason for termination, the statistical analysis plan, the planned contrasts, multiplicity handling, missing-data procedures, analysis populations, and the handling of repeated measurements. The registry also does not give details that would allow assessment of allocation concealment or outcome-assessment masking.

The sparse adverse-event entries offer little basis for safety comparisons. Only one arm lists a participant at risk, and no events are recorded there; the other arms have no participants listed at risk. The record does not report further ascertainment details. These limitations mean that neither efficacy nor comparative safety can be characterized from the posted information. They also limit any attempt to generalize the observed entries beyond the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Diuretic/Cool Dialysate Trial — NCT02593526.
• Registry record last updated 2024-01-11; status last verified 2023-12.
• Results first posted 2024-01-11.
• 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 describes a randomized, unmasked factorial pilot study of bumetanide and dialysate temperature in people with chronic kidney insufficiency. The four combinations used no diuretic or bumetanide and dialysate at 37°C or 35.5°C. The primary outcome concerned slowing the rate of RRF change over 6 months, using planned 24-hour collections.

Enrollment is listed as 11, while the description says only one participant met criteria for randomization. The outcome entries list one participant and a count of 1 in the bumetanide plus 35.5°C dialysate arm, with zero participants in each other arm. The record lists zero analyses and indicates that a binary two-arm comparison is not estimable. The trial is listed as terminated; the reason is not reported in the registry record.

The available entries do not include a comparative effect estimate, confidence interval, or analysis of RRF trajectory. They therefore do not establish whether any intervention changed RRF or provide a comparative safety assessment.