Shared Decision Making in Dialysis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Shared Decision Making in Dialysis (NCT04392440), a randomized na study. The primary outcome is Mean Feasibility of Intervention Measure.

2. Clinical Question

3. Trial Design

DIAL-SDM (NCT04392440) is recorded as a completed, randomized, single-masked, parallel pilot cluster trial sponsored by the University of Rochester. The listed phase is NA. The trial began on 2022-02-28, and its primary completion date is 2024-05-14. Enrollment is recorded as 102.

The study targeted communication around dialysis decisions for older patients with chronic kidney disease. The brief summary describes the proposed study as involving nephrologists and their patients, with nephrologists assigned to an intervention or control group. Intervention nephrologists received 3 communication-training sessions led by a standardized patient instructor, who enacted clinical scenarios and offered feedback. Patients, and caregivers when available, received 2 coaching sessions. Control nephrologists provided usual care.

The brief summary describes the proposed participation as nephrologists (n=20) and patients (n=60). The registry's recorded enrollment is 102; the relationship between that total and the proposed counts is not reported in the registry record. The reported primary endpoint results include intervention patients, caregivers, and nephrologists, but no control participants with a score for that endpoint.

The registry identifies the trial as cluster randomized, but the allocation procedures, the number of clusters in each group, and the identity of the masked party are not reported in the registry record. The protocol's sample-size justification and details of any interim analyses are also 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.

Before assignment: This was a cluster randomized trial, with randomization performed at the nephrologist level. Each nephrologist's participating patients (and their caregivers, when applicable) were assigned to the same study arm as the nephrologist. A total of 17 nephrologists were randomized: 9 to the Intervention group and 8 to the Control group.). Enrollment included nephrologists, patients, and caregivers.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: This outcome was measured in the intervention group only.

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: Baseline measures include data from all participants who provided information at enrollment (patients, nephrologists, and caregivers). Separate rows show data for each group.

6. Primary Endpoint

The registry lists the primary outcome as Mean Feasibility of Intervention Measure, measured over Approximately 12-14 weeks.

The primary endpoint was the mean Feasibility of Intervention Measure score, reported approximately 12-14 weeks after baseline. The questionnaire asked whether the coaching, prepared question list, booklet, and videos seemed possible, doable, easy to use, and practical to carry out. Participants rated each item from 1, “completely disagree,” to 5, “completely agree.” Item scores were added for each participant, producing a total score from 4 to 20; higher scores indicate greater perceived feasibility.

Assessments occurred at 12 and 14 weeks after baseline. Data collected within that window were averaged to create one value per participant, and group means were reported. The endpoint was measured in the intervention group only. The registry reports a mean and standard deviation for intervention patients, caregivers, and nephrologists, but does not report control-group scores.

Feasibility is useful in a pilot because it describes participants’ assessments of whether intervention components can be used in practice. It is not itself a measure of whether communication changed, whether dialysis decisions aligned with patients’ preferences, or whether health outcomes changed. Those outcomes are not reported as primary results in this record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry reports means and standard deviations for a continuous score. It does not describe a statistical analysis plan, inferential model, or hypothesis test for the primary endpoint. The explanations below describe the general statistical meaning of the summaries and the issues relevant to interpreting a cluster trial; they should not be read as methods confirmed to have been used for the posted results.

What does a mean describe?

In general, a mean is a measure of the average value in a group. Here, the reported group means summarize the summed feasibility scores for intervention patients, caregivers, and nephrologists. The scale runs from 4 to 20, and a higher score represents greater perceived feasibility. The mean condenses the participant scores into a single group summary, but it does not show the full distribution, the most common score, or whether individual participants agreed with one another.

These scores are based on a questionnaire about whether intervention materials and activities seemed feasible to use. They represent reported perceptions, not an objective count of intervention use or a direct measure of decision quality. The measure's individual items and total score are described in the registry, but additional information about its validation or interpretation is not reported in the registry record.

What does a standard deviation describe?

In general, a standard deviation describes how dispersed observations are around their group mean. A smaller standard deviation indicates that observations are more clustered around the mean; a larger one indicates greater spread. The reported standard deviations are 3.4 for intervention patients, 2.4 for intervention caregivers, and 1.9 for intervention nephrologists. These values describe variation in the observed scores. They are not measures of uncertainty in the means and are not substitutes for confidence intervals.

A confidence interval, in general, gives a range of values compatible with a statistical estimate under a specified method and assumptions. It can communicate estimation uncertainty, which depends on factors such as the amount of observed variation and the number of independent observations. No confidence interval is reported for these feasibility means, and none can be reconstructed from the available endpoint results without adding assumptions.

Why does cluster randomization matter?

In general, a cluster-randomized trial assigns groups, rather than each individual participant independently, to study conditions. Participants within a cluster can share clinicians, settings, or practices, so their outcomes may be more alike than outcomes from participants in different clusters. This within-cluster similarity is often described using an intracluster correlation. If it is present, an analysis that treats every participant as fully independent can understate uncertainty.

The registry calls DIAL-SDM a randomized cluster trial and describes intervention and control groups of nephrologists and patients. It does not report the analysis method, how clustering was accounted for, or an intracluster correlation. Because the primary endpoint results are intervention-only descriptive summaries, the record does not present a cluster-adjusted intervention-versus-control estimate for that endpoint.

What can be inferred without a comparative analysis?

In general, an inferential comparison estimates how an outcome differs between groups while accounting for sampling variability and the study design. A p-value, when used, addresses compatibility of observed data with a specified null hypothesis under stated assumptions; it does not by itself measure the size or practical importance of an effect. An effect estimate with a confidence interval can convey both direction and precision. None of these comparative results is reported for the primary feasibility endpoint.

The primary endpoint has no control-group values, so a between-group effect cannot be obtained from the posted endpoint summaries. The registry reports zero analyses and no secondary outcomes. It therefore does not provide statistical tests or adjusted estimates to interpret. The descriptive scores should not be recast as evidence of a statistically tested difference.

How should planning calculations be read?

In general, sample-size calculations describe how many observations might be needed under specified assumptions to detect an effect using a chosen statistical approach. They are planning illustrations, not observed power and not evidence that a study did or did not detect an effect. The registry's planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect expressed as a fraction of an observed effect. However, the primary endpoint has no reported control-group value or two-arm effect estimate. Specific planning estimates are not reported in the registry record, and the posted endpoint summaries do not supply a comparative effect on which to base a direct interpretation.

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("Intervention Patients", "Intervention Caregivers", "Intervention Nephrologists")
n   <- c(25, 9, 8)
m   <- c(16.4, 16.1, 19)
sp  <- c(3.4, 2.4, 1.9)
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  Intervention Patients  25  16.400  3.400  14.997  17.803
CARM  Intervention Caregivers  9  16.100  2.400  14.255  17.945
CARM  Intervention Nephrologists  8  19.000  1.900  17.412  20.588

11. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when several outcomes, comparisons, or statistical tests are considered. In general, conducting multiple tests can increase the chance of at least one apparently positive result even when no true effect exists. Researchers may address this through prespecified outcome hierarchies, adjustment procedures, or cautious interpretation. The registry reports zero statistical analyses and zero posted secondary outcomes. A multiplicity strategy is not reported in the registry record, so it is not possible to determine whether any adjustment was planned or used.

The primary endpoint description says that assessments occurred at 12 and 14 weeks after baseline and that data collected within this window were averaged to yield one value per participant. The record does not explain how participants with missing assessments, incomplete questionnaires, or other unavailable data were handled. Missing-data assumptions, imputation procedures, and sensitivity analyses are not reported in the registry record.

The outcome population is described as the intervention group only. The record does not report whether the endpoint analysis followed an intention-to-treat, per-protocol, or other population definition. It also does not give a participant flow account linking overall enrollment to the endpoint counts. The reported numbers associated with the means are 25 intervention patients, 9 intervention caregivers, and 8 intervention nephrologists; corresponding control endpoint values are absent. Without additional details, the extent and possible consequences of missing endpoint data cannot be assessed.

These omissions limit assessment of how the endpoint results were selected and analyzed. They do not establish that data were missing in any particular way or that the reported means are biased; the relevant handling and analysis details are simply not reported in the registry record.

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 reports zero serious adverse events among the intervention patients at risk (30) and zero among control patients at risk (30). It also reports zero other adverse events for both patient groups. Among caregivers, zero serious adverse events and zero other adverse events are listed for intervention caregivers at risk (11) and control caregivers at risk (14). Among nephrologists, both event categories are zero for intervention nephrologists at risk (9) and control nephrologists at risk (8). No serious adverse event terms are listed.

Deaths are reported separately: 1 intervention patient and 2 control patients; 1 intervention caregiver and 2 control caregivers; and 0 nephrologists in each group. These are registry counts, not evidence that an event was caused by or prevented by the intervention. The record does not describe event timing, causes of death, attribution, or additional safety-monitoring procedures. Zero reported events should be read as the counts recorded for these groups, not as proof that no unreported events occurred.

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

The main result is a set of intervention-group feasibility summaries at approximately 12-14 weeks. The reported mean scores are 16.4 for intervention patients, 16.1 for intervention caregivers, and 19.0 for intervention nephrologists. The measure's range is 4 to 20, and higher scores indicate greater perceived feasibility. These means describe participants' responses to questions about whether intervention components seemed usable and practical.

The findings do not show whether DIAL-SDM improved shared decision making compared with usual care. Control-group feasibility scores are not reported, and there is no posted comparative estimate or inferential analysis for this outcome. The results also do not establish changes in patient preferences, treatment choices, communication, dialysis initiation, or health outcomes. Those conclusions would require outcomes and analyses not present in the registry record.

The findings are relevant as descriptive information from a pilot intervention involving patients, caregivers, and nephrologists. The reported score counts differ across these participant groups, and the registry does not explain the relationship between those counts and total enrollment. No confidence intervals or missing-data methods are reported, so the precision and representativeness of the means cannot be fully evaluated.

Accordingly, the record supports a narrow interpretation: intervention participants gave feasibility questionnaire responses that were summarized by group mean and standard deviation. It does not support claims about comparative effectiveness, statistical significance, or clinical benefit. Nor does the absence of control endpoint values demonstrate that the intervention and usual care had equal or different feasibility scores.

14. Why This Trial Matters Statistically

This trial is statistically informative in part because its primary endpoint is a feasibility measure rather than a comparative clinical outcome. Pilot studies can describe whether an intervention's components appear practical to participants and can help identify what should be measured or refined in later research. The DIAL-SDM score captures reported views of coaching, a prepared question list, a booklet, and videos, with higher scores indicating greater perceived feasibility.

The design also highlights an important issue for studies that train clinicians and enroll their patients. The registry identifies DIAL-SDM as cluster randomized, which is relevant because observations connected to the same nephrologist may not be statistically independent. General methods for cluster trials need to account for that structure when estimating uncertainty. The registry does not report the analysis method or how clustering was addressed, so the posted results cannot be used to assess that aspect of the design.

Another important distinction is between descriptive and comparative evidence. The registry reports means and standard deviations for intervention patients, caregivers, and nephrologists, but the primary endpoint was measured in the intervention group only. These summaries can describe responses among those with reported scores; they cannot estimate a contrast with usual care. The record also reports no statistical analyses and no secondary outcomes.

Reading the results with these distinctions in mind avoids treating a feasibility score as a test of clinical impact. The study record offers a focused description of intervention-group feasibility, while leaving comparative effect estimates, precision measures, and important analysis details unreported.

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 primary endpoint is available only for intervention participants. Although usual care is the control condition, the registry reports zero control patients, caregivers, and nephrologists with a primary feasibility value. This prevents a direct comparison for the endpoint and leaves no posted estimate of the intervention's relative effect on perceived feasibility.

The record reports group means and standard deviations but no confidence intervals, p-values, or other inferential results. It does not identify the statistical model or describe how the cluster-randomized design was accounted for. The number and structure of clusters, allocation procedures, and the identity of the masked party are not reported in the registry record.

Endpoint counts are 25 intervention patients, 9 intervention caregivers, and 8 intervention nephrologists. The registry records overall enrollment as 102, but does not explain how enrollment relates to these endpoint counts or describe participant flow for this measure. Missing-data handling, the analysis population, and sensitivity analyses are not reported in the registry record.

The outcome is a self-reported feasibility score, rather than a direct measure of whether communication changed or decisions aligned with patient preferences. The registry describes the score construction and interpretation but does not report additional validation information. Finally, the registry contains no posted secondary outcomes or statistical analyses, limiting assessment of outcomes beyond the descriptive primary results.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Shared Decision Making in Dialysis — NCT04392440.
• Registry record last updated 2026-09-22; status last verified 2026-08.
• Results first posted 2026-03-20.
• 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

NCT04392440, titled “Shared Decision Making in Dialysis,” is a completed randomized, single-masked, parallel pilot cluster trial sponsored by the University of Rochester. The listed phase is NA. The registry records enrollment of 102, a start date of 2022-02-28, and a primary completion date of 2024-05-14.

The primary endpoint was the mean Feasibility of Intervention Measure score, assessed approximately 12-14 weeks after baseline. Intervention patients, caregivers, and nephrologists had reported means of 16.4, 16.1, and 19.0, respectively. Control values for this endpoint are not reported. The registry lists zero statistical analyses and zero posted secondary outcomes. It also reports zero serious and other adverse events in the listed groups, with deaths recorded separately.