A Multicenter Trial of a Shared DECision Support Intervention for Patients Offered Implantable Cardioverter-DEfibrillators: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Multicenter Trial of a Shared DECision Support Intervention for Patients Offered Implantable Cardioverter-DEfibrillators (NCT03374891), a randomized na study. The primary outcome is Knowledge About Defibrillation at Baseline.

2. Clinical Question

The trial’s stated goal was to assess the real-world effectiveness of patient decision aids for high-risk decisions, using the implantable cardioverter-defibrillator as a model. The primary endpoint’s baseline timeframe is important: a baseline measure describes knowledge at the specified starting point, whereas an intervention effect generally requires an outcome comparison that reflects the intervention period. The endpoint description also refers to knowledge changes over time, but the primary measure is titled and timed as baseline. The registry record does not clarify how that wording relates to any later assessment or analysis.

3. Trial Design

The registry record lists a randomized, parallel trial with no masking. It records 790 participants enrolled and identifies the University of Colorado, Denver as sponsor. The study is marked completed. Its stated objective was to assess real-world effectiveness of patient decision aids for high-risk decisions, using decisions about implantable cardioverter-defibrillators as a model.

The two arm descriptions distinguish surveys only from an educational video and/or handout followed by surveys. Both arms were asked about experiences, opinions, and knowledge of the defibrillator process. The record does not say how allocation was generated, whether allocation was concealed, or which staff or participants knew the assigned arm beyond the fact that masking is listed as none. The registry record does not report the planned sample-size justification, detailed protocol, or statistical analysis plan.

There is a design-description tension relevant to interpretation. The design fields list randomized parallel allocation, while an analysis note identifies the trial as cluster-randomized and cautions that a simple individual-level re-analysis would be misleading. The record says only the sponsor’s own analysis is shown, yet it lists no analyses and reports no numerical primary-outcome analysis. The basis for the cluster-randomized designation and the relationship between that designation and the design fields are not reported in the registry record. Without those details, the analysis note supports caution, but it does not permit reconstruction of the intended analysis.

The listed primary measure is baseline knowledge about defibrillation, and reach of eligible patients is listed as a secondary outcome. Seven outcome measures are recorded. The registry record does not provide enough information to determine which outcomes were measured at which additional time points, how the analysis handled the trial’s design, or whether all enrolled participants were included in each outcome analysis.

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: Data was not able to be collected for all participants.

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 characteristics were only collected for participants who completed the study.

6. Primary Endpoint

The registry lists the primary outcome as Knowledge About Defibrillation at Baseline, measured over Baseline.

The primary endpoint is titled “Knowledge About Defibrillation at Baseline.” It is a continuous score, summarized as a mean with standard deviation, and is measured at baseline. The measure is described as the Decision Quality Knowledge Survey. Its stated range is 0 to 100, and higher scores indicate more knowledge and better outcomes. The survey is intended to assess what participants know about defibrillators.

Knowledge is relevant to a decision-support intervention because such an intervention is intended to inform people considering a high-risk decision. A knowledge score can describe participants’ understanding of the subject addressed by the educational material. General statistical context: a continuous score retains gradations across its scale, rather than reducing each participant’s response to a simple category. A group mean describes the average score, while the standard deviation describes how dispersed individual scores are around that mean.

The endpoint’s timing limits what it can establish. A baseline score describes knowledge at the baseline assessment; on its own, it does not show change after exposure to the educational material. Although the endpoint description says multiple survey responses will indicate knowledge changes over time, the primary measure is specifically titled and timed as baseline. The registry record does not clarify this distinction or report a later knowledge score. It also says data could not be collected for all participants, without giving the number or characteristics of those missing from the endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

General statistical context: the endpoint is described as continuous and summarized by a mean and standard deviation. A mean provides a measure of the group’s average score. A standard deviation describes how much scores vary among participants. These summaries answer different questions: the mean locates the group’s average on the score scale, while the standard deviation characterizes spread among individual scores. Neither summary alone establishes whether groups differ beyond what could arise from sampling variability.

What would a confidence interval convey?

General statistical context: a confidence interval gives a range of values compatible with the data and the statistical model used to calculate it. Its width conveys precision: a narrower interval indicates greater precision under that model, and a wider interval indicates greater uncertainty. For a comparison between groups, an interval around the estimated difference can show both the direction and the range of effect sizes consistent with the analysis. The registry record does not report a confidence interval for the primary endpoint, so the precision of a primary comparison cannot be assessed.

What does a p-value address?

General statistical context: a p-value quantifies how unusual data at least as inconsistent with a specified null hypothesis would be, assuming that hypothesis and the analysis model. It is not the probability that the null hypothesis is true, and it does not describe the size or practical importance of a difference. A p-value is most informative alongside an effect estimate and an interval describing uncertainty. No primary-outcome p-value is reported in the registry record.

Why does the allocation structure matter?

General statistical context: analyses of randomized studies need to respect how randomization occurred. If allocation is by clusters, participants within a cluster may share characteristics or experiences, so their outcomes may be correlated. An individual-level analysis that assumes each participant contributes independent information can understate uncertainty. Methods that account for clustering adjust the analysis to reflect dependence within clusters. The registry record’s analysis note says the trial is cluster-randomized and that a simple individual-level re-analysis would be misleading. It does not report the cluster definition, number of clusters, or the sponsor’s numerical analysis, so those details cannot be examined.

The design fields separately list randomized allocation and a parallel model. Those descriptions do not, on their own, explain the cluster-randomized note. General statistical context: a parallel structure describes participants being assigned to different arms, while the unit of randomization determines what is randomized. Clear reporting of both the intervention arms and the allocation unit is important because the allocation unit informs the standard errors and the analysis population. The registry record does not resolve the apparent difference in emphasis between its design fields and analysis note.

What does the planning illustration represent?

The registry record describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. It states that the effect to detect is a specified fraction of the observed effect. General statistical context: sample-size calculations estimate how many observations would be needed to detect an assumed effect under stated design and analysis assumptions. Their values depend on the assumed effect and variability as well as the planned error rate and allocation. If the assumed effect is smaller, planning generally requires more information to distinguish it from random variation; this is a general principle, not a reported result for this trial. The record does not state the observed effect or the numerical planning outputs.

Those calculations are not “observed power.” General statistical context: power is a design probability defined under a particular assumed effect and analysis model. After a study, a sample-size calculation based on the observed effect does not replace the effect estimate, its uncertainty interval, or the actual analysis. Since no numerical primary result or planning outputs are reported in the registry record, neither can be interpreted quantitatively.

How should missing outcome data be considered?

The endpoint population note says data could not be collected for all participants. General statistical context: missing outcome data can reduce precision and can also bias a comparison if the chance of missingness is related to outcomes or differs across groups. The consequences depend on how much data are missing, why they are missing, and how missingness relates to observed and unobserved scores. The registry record does not report the amount of missing primary-outcome data by arm, reasons for missingness, or the method used to address it. Those omissions prevent assessment of how missingness may affect the endpoint estimate.

For a complete statistical interpretation, reporting would ordinarily connect the outcome definition and timing to the analysis population, arm-specific data, effect estimate, and uncertainty. In this record, the scale and baseline timeframe are stated, but the numerical primary analysis and key analysis details are not reported. No inference about a treatment effect should be filled in from the design description or the planning assumptions alone.

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("Surveys Only", "Educational Video and/or Handout + Surveys")
n   <- c(312, 412)
m   <- c(53.4, 55.4)
sp  <- c(17.6, 17)
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  Surveys Only  312  53.400  17.600  51.439  55.361
CARM  Educational Video and/or Handout + Surveys  412  55.400  17.000  53.754  57.046

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists seven outcome measures and identifies reach of eligible patients as a secondary outcome. It does not report which measures were treated as confirmatory, how many comparisons were planned, or whether any adjustment for multiple testing was intended or used. The multiplicity strategy is not reported in the registry record. General statistical context: examining several outcomes or comparisons can increase the chance that at least one appears notable by chance. A prespecified testing hierarchy or multiplicity adjustment can help make the interpretation of multiple tests more controlled, but no such approach can be attributed to this trial from the registry information.

Missingness is a stated concern for the primary measure: the record says data could not be collected for all participants. It does not report the number with missing baseline scores, the reasons for missing data, the amount missing in each arm, or any method used to handle missing values. The analysis populations are not reported in the registry record. It is therefore unclear how many participants contributed to each outcome measure or whether the reported enrollment corresponds to the population used for any analysis.

The record lists 0 analyses. It also includes a note that only the sponsor’s own analysis is shown and warns that a simple individual-level re-analysis would be misleading because the study is cluster-randomized. No numerical sponsor analysis is reported in the registry record. The analysis plan, interim analyses, and sample-size justification are not reported in the registry record. These gaps mean that neither multiplicity control nor the handling of missing data and analysis populations can be evaluated from the entry.

General statistical context: these details matter because statistical results depend not only on the outcome measure but also on which participants are analyzed, how missing observations are treated, and how multiple outcomes are interpreted. Without those details and a numerical result, uncertainty and risk of selective interpretation cannot be assessed.

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

The registry record establishes that the study compared surveys alone with an educational video and/or handout followed by surveys, in a trial addressing decisions about implantable cardioverter-defibrillators. It identifies baseline knowledge about defibrillation as the primary measure, describes the scale’s range and direction, and records that data were not collected for all participants. Those are descriptions of the study question and measurement, not evidence of an intervention effect.

No numerical primary-outcome analysis is reported in the registry record. There is no reported estimate of a difference in knowledge, no measure of its precision, and no follow-up result from which to assess change over time. The baseline endpoint cannot by itself show that knowledge changed after the educational material. The record’s statement that survey responses will indicate knowledge changes over time does not substitute for reported follow-up data.

The adverse-event entries report 3 other events among 346 at risk in the Surveys Only arm and 0 among 444 at risk in the educational video and/or handout arm. Serious events and deaths are recorded as 0 in both arms. These counts describe the registry entries; they do not establish the absence of all possible harms or provide evidence about knowledge. The types of the other adverse events are not reported in the registry record.

General statistical context: a null or unreported result is not evidence of equivalence. Demonstrating that two approaches are sufficiently similar would require an appropriate design, a prespecified equivalence margin, and an analysis with adequate precision. Those details and a primary-outcome result are not reported in the registry record. Likewise, the record cannot establish that the intervention increased knowledge, improved decision quality, or changed decisions. The trial’s stated goal and the selected endpoint do not prove those outcomes.

13. Why This Trial Matters Statistically

Statistically, this trial raises questions about how decision-support interventions should be evaluated and how outcome measurement connects to the intended claim. The stated goal concerns real-world effectiveness of patient decision aids, while the listed primary measure is baseline knowledge about defibrillation. A baseline measure can describe participants’ starting knowledge, but assessing an intervention-related change requires a clearly reported post-intervention measure or an analysis that compares outcomes over time. The registry record does not provide that numerical analysis.

The study also illustrates why reporting the unit of randomization matters. The design fields describe randomized parallel allocation, while the analysis note identifies a cluster-randomized design and cautions against simple individual-level re-analysis. General statistical context: respecting the allocation unit is necessary for valid uncertainty estimates. When people are assigned through groups, their outcomes may be statistically related, and the analysis must account for that structure. The record does not explain the relationship between these design descriptions or provide the sponsor’s numerical analysis for review.

Reporting on missing data is consequential as well. The registry record acknowledges that primary-measure data were not collected for all participants, but gives no amount, arm-specific detail, or missing-data method. Those details would help readers judge how representative the analyzed scores are and how robust the comparison may be.

The trial is therefore statistically informative as an example of the importance of aligned endpoint timing, explicit allocation-unit reporting, transparent missing-data handling, and an interpretable analysis. Its registry entry states the question and design elements, but does not report the primary numerical findings needed to estimate the intervention comparison.

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 limitation for interpreting this trial is that the registry record does not report a numerical result for its primary endpoint. Without arm-specific scores or an effect estimate and its uncertainty, the size, direction, and precision of a knowledge comparison cannot be assessed. The primary endpoint is timed at baseline, while its description refers to knowledge changes over time; the record does not clarify whether or how a later measurement was analyzed.

The primary measure was not collected for all participants, but the extent and distribution of missing data are not reported. There is no description of reasons for missingness or of any analysis method for addressing it. The analysis populations are also not reported. These omissions limit assessment of whether the available scores represent the enrolled participants and whether the comparison could be biased by incomplete data.

The record’s design information needs clarification because the design fields list randomized parallel allocation, whereas an analysis note says the trial is cluster-randomized. The record does not identify the clusters or explain the relationship between these descriptions. It warns against a simple individual-level re-analysis, but provides no numerical sponsor analysis to evaluate. The record lists 0 analyses.

Other trial-specific information that is not reported in the registry record includes a detailed statistical analysis plan, interim analyses, the sample-size justification, and the multiplicity strategy for the seven outcome measures. The adverse-event entries provide counts for other events but do not report their terms. Taken together, these limitations mean that the registry entry is useful for describing the trial’s aims and endpoint, but is insufficient for a quantitative assessment of the primary result.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Multicenter Trial of a Shared DECision Support Intervention for Patients Offered Implantable Cardioverter-DEfibrillators — NCT03374891.
• Registry record last updated 2022-07-08; status last verified 2022-06.
• Results first posted 2022-07-08.
• 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 registry record describes a completed randomized parallel trial with no masking and 790 enrolled participants. It compares surveys only with an educational video and/or handout about the defibrillator process followed by surveys. The stated goal is to assess real-world effectiveness of patient decision aids, using implantable cardioverter-defibrillators as a model.

The primary measure is baseline knowledge about defibrillation, assessed using a score ranging from 0 to 100, with higher scores indicating more knowledge and better outcomes. Reach of eligible patients is listed as a secondary outcome. The record says data were not collected for all participants and lists 0 analyses; no numerical primary-outcome analysis is reported in the registry record.

The record’s design fields and its cluster-randomized analysis note require clarification for interpreting any analysis. It does not report the detailed statistical plan, missing-data methods, analysis populations, or sample-size justification. Adverse-event entries record 3 other events in the Surveys Only arm and 0 in the educational video and/or handout arm; serious events and deaths are recorded as 0 in both arms.