Shared Decision Making Aid for Prosthetic Design: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Shared Decision Making Aid for Prosthetic Design (NCT04536025), a registered phase not stated study. The primary outcome is Number of Participants Who Participated in and Completed 1 Hour Qualitative Interview Data Collection Via a Semi Structured Interview Guides.

2. Clinical Question

In statistical terms, the central question is about feasibility of collecting interview data and the qualitative information needed to describe decision needs. That differs from a question about whether one clinical intervention improves a health outcome relative to another. The registry lists enrollment of 66, but does not report the number completing the primary interview outcome or the resulting qualitative themes. As a result, the record describes the study question and intended approach more clearly than it documents an answer to that question.

3. Trial Design

NCT04536025, titled “Shared Decision Making Aid for Prosthetic Design,” is listed as a completed study sponsored by the University of Colorado, Denver. The registry lists a start date of 2020-06-06, a primary completion date of 2022-06-01, and enrollment of 66. The conditions are amputation and prosthesis user. The overall purpose was to learn more about decision making for prosthetic design, with the goal of producing a decision-making aid.

The registry describes qualitative focus group interviews with prosthetists and semi-structured individual interviews with people with lower limb amputation. The prosthetist group was described as up to 24 people actively providing prosthetic care. The patient interview group was described as an estimated 14 people within 1 year of lower limb amputation who were receiving their first prosthesis. An expert working group was also described, with participants drawn from people receiving prosthetic care and experienced prosthetic care providers. The registry record does not provide a complete description of that group’s recruitment process.

This is not a randomized comparison. The registry does not state an allocation method, and the participant groups have distinct roles in gathering perspectives rather than functioning as like-for-like control groups. The focus groups and interviews are classified as other interventions, not as assigned clinical treatments.

The primary outcome is the number of participants who participated in and completed the semi-structured interview data collection. The registry says that interviews occurred at baseline only and lasted an average of 1 hour during 1 day. It also lists secondary outcomes concerning preferences for control in health decisions and perceived ability to find and use health information, measured by the Control Preferences Scale Survey and eHealth Literacy Scale Survey. Outcome results and a detailed statistical analysis plan are 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.

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 Number of Participants Who Participated in and Completed 1 Hour Qualitative Interview Data Collection Via a Semi Structured Interview Guides, measured over Data collection of the semi structured qualitative interview occurred at the baseline time point only, lasting an average of 1 hour during 1 day..

The primary endpoint is a count of participants who participated in and completed the 1 hour semi-structured interview data collection. The registry identifies this as the numerical outcome that could be recorded for the interview process. The interview questions addressed decisional needs of patients and prosthetists concerning prosthetic design decisions.

The count serves a descriptive and operational purpose: it records whether the intended interview data collection was completed by participants. It does not quantify the content of the interviews, the importance of particular decision needs, or whether a decision aid changes choices or health outcomes. The registry explains that qualitative information is not numerical. Instead, interview transcripts were analyzed using directed content analysis, drawing on the Ottawa Decision Support Framework and the Elwyn Shared Decision Making Model. The resulting themes were intended to guide the content of a prosthetic design decision aid.

That distinction matters when interpreting the endpoint. A completion count can describe participation in the interview activity, but it cannot stand in for the qualitative analysis or its conclusions. Nor does the count directly assess the secondary survey concepts of preference for control in a health decision or perceived ability to find and use health information. The registry record does not report the number of participants completing the interviews, the themes identified, or results for the secondary outcomes. The endpoint’s stated purpose is therefore clear, but its observed result is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a completion count capture?

The primary endpoint counts participants who participated in and completed the semi-structured interview data collection. A count is a direct summary of how many people met the stated completion criterion. It does not encode the substance of interview responses. The registry explicitly distinguishes numerical recording of completion from qualitative analysis of transcripts. Because the registry does not report the observed count, the endpoint’s definition is available but its result cannot be assessed from the registry record.

How does qualitative content analysis differ from a numerical comparison?

The registry states that interview transcripts were analyzed using directed content analysis, guided by the Ottawa Decision Support Framework and the Elwyn Shared Decision Making Model. In general, directed content analysis uses an established conceptual structure to guide interpretation of text, while still examining the material for relevant content and themes. The aim described in the record was to use final qualitative themes to guide the content of a decision aid for prosthetic design. The registry does not report the coding details, who conducted the analysis, how differences in interpretation were handled, or the themes that resulted. Those details are not reported in the registry record and should not be inferred from the named frameworks alone.

Why is a randomized comparison not the right reading?

The registry does not describe random assignment, and it explicitly identifies the study as not a randomized comparison. Its participant groups serve different functions: prosthetists were to describe their decisional needs in focus groups, people with lower limb amputation were to describe their needs in individual semi-structured interviews, and an expert working group was described as part of the project. These roles do not make the groups comparable treatment arms. In general, a treatment-effect comparison requires a clearly defined contrast between groups and outcome measurements appropriate to that contrast. Neither is described for testing the effect of the decision aid in this record.

The study’s qualitative purpose also calls for a different kind of interpretation. General statistical measures such as a confidence interval describe uncertainty around a numerical estimate. They do not substitute for the account of how qualitative themes were developed or for evidence that a theme reflects participants’ experiences. The registry record supplies no numerical estimate of an intervention effect and no confidence interval for one.

What do the planning assumptions mean?

The registry metadata describes sample-size illustrations based on an observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the target effect expressed as a fraction of the observed effect. The stated convention is participants per arm for non-time-to-event outcomes. In general, such calculations explore the sample size that might be needed under specified assumptions for a hypothetical comparison. They are not the actual study’s design justification unless the record says so, and they are never a measure of observed power.

Those assumptions do not align with the described qualitative design as a randomized two-arm effectiveness trial. No observed effect or analysis is reported in the registry record, and the record does not identify an actual two-arm allocation. Any planning illustration therefore cannot be read as evidence that the study had a particular probability of detecting a clinical benefit, or as a result from this study. A formal sample-size justification for the qualitative work is not reported in the registry record.

What can be concluded from the recorded analysis information?

The registry lists six outcome measures and zero analyses. It identifies two secondary survey measures: participant preference for control in a health decision, measured with the Control Preferences Scale Survey, and perceived ability to find and use health information, measured with the eHealth Literacy Scale Survey. The record does not report survey scores, summaries, comparisons, missingness, or model results. It also does not report p-values or uncertainty intervals.

In general, inferential analyses depend on a defined outcome, a target comparison, and a statistical model or method matched to the design and data. A p-value, when used, addresses compatibility of data with a specified statistical null model; it is not a measure of clinical importance or proof that a hypothesis is true. A confidence interval, when reported, conveys uncertainty in an estimate under the chosen analysis. Neither can be interpreted for this study from the registry record because no such results are listed.

Over-dispersion is a general concern for count data when observed variation exceeds what a simple count model expects; it can make uncertainty estimates too narrow if ignored. That issue is not assessable from the registry record: the primary outcome is a participant completion count, but no count data or statistical model is reported. There is no basis to claim that a count model, adjustment, or over-dispersion correction was used.

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("Prosthetists", "People With Lower Limb Amputation", "Expert Working Group")
n      <- c(38, 17, 11)
events <- c(38, 17, 11)
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  Prosthetists  38  38  100.0  90.7  100.0  90.8  100.0  91.0  99.9
ARM  People With Lower Limb Amputation  17  17  100.0  80.5  100.0  81.6  100.0  81.5  99.9
ARM  Expert Working Group  11  11  100.0  71.5  100.0  74.1  100.0  73.5  99.8

11. Multiplicity, Missing Data and Analysis Populations

The registry lists six outcome measures, including the primary interview-completion count and secondary measures of preference for control in a health decision and perceived ability to find and use health information. It lists zero analyses. The record does not state a hierarchy for testing outcomes, a multiplicity adjustment, or whether any outcomes were treated as exploratory. A statistical plan for handling multiple outcomes is not reported in the registry record.

In general, testing or interpreting many outcomes can increase the chance of highlighting an apparently notable result by chance, especially when analyses are selected after results are known. A prespecified hierarchy or adjustment can clarify how multiple comparisons are handled. That general concern cannot be evaluated for this study because the registry record provides no analysis results and no multiplicity strategy.

Missing-data procedures and analysis populations are also not reported in the registry record. The completion outcome’s wording identifies participants who completed interviews, but it does not state how people who did not complete an interview were handled in any analysis, or whether incomplete interviews contributed qualitative material. The registry record does not report the number of participants with data for each outcome, missing survey responses, exclusions, or a population definition for analysis.

The enrollment listing of 66 should not be treated as proof that every participant contributed to every outcome. Nor does the completed study status establish completeness of the interview or survey data. Without outcome-specific denominators and missing-data information, the extent to which the reported population, if any, differs from the enrolled population cannot be assessed. No imputation method, sensitivity analysis, or other missing-data procedure is reported in the registry record.

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

The record describes a study designed to learn about prosthetic design decision making and to use qualitative themes in developing a decision aid. It identifies the participant groups and interview methods, and it defines an interview-completion count as the primary numerical outcome. These features explain the study’s intent and the kind of evidence it sought to collect.

The registry does not report the primary completion count, qualitative themes, secondary survey results, or analyses. It therefore does not establish what decisional needs participants identified, how frequently particular needs arose, or whether the decision aid was ultimately developed or evaluated. The listed completed status and enrollment of 66 do not fill those outcome-reporting gaps.

The study is not described as a randomized test of the aid. The record does not compare participants using an aid with a control group, and it does not report outcomes that would estimate the aid’s effect on decisions, health, or other consequences. It cannot be used to conclude that the aid improves decision making or that it fails to do so. It also cannot support a numerical estimate of benefit, harm, or precision.

In general, qualitative findings can help describe how people understand a decision, what information they need, and where support might be useful. Their interpretation depends on the collected accounts and analysis process. Here, the planned use of directed content analysis is described, but the resulting themes are not reported in the registry record. Thus the registry record conveys the rationale and methods, not the substantive qualitative answer.

The adverse-event entries show zero recorded events in the listed categories for each group and no serious-event terms. This is a statement about the registry entries, not proof of an absence of all harms or a comprehensive safety evaluation. The record does not describe event ascertainment methods or provide broader safety conclusions. The appropriate reading is therefore limited: the registry documents a completed qualitative study with a stated aim and outcome framework, but it does not report the results needed to judge what the study found.

13. Why This Trial Matters Statistically

Clinical decisions about prosthetic design involve choices made by people receiving prosthetic care and by clinicians involved in providing it. A study that seeks to characterize the needs of both groups can contribute a foundation for decision-support tools. Statistically, the important point is that the evidence target is qualitative understanding and documentation of data collection, rather than a comparison of assigned treatments.

That distinction affects what counts as an informative result. For the primary outcome, the registry defines a completion count. For the substantive goal, it describes analysis of interview transcripts and development of themes. These are related but different evidence streams: a completion count indicates participation in data collection, while themes convey the content identified in participants’ accounts. A reader needs both the reported count and the qualitative findings to assess how the project’s aims were addressed. Neither result is reported in the registry record.

The study also illustrates why labels such as “completed” or an enrollment total cannot substitute for outcome reporting. A completed study can have a clear design and still leave readers without numerical outcome results, qualitative findings, or detail about missing data and analysis populations. Here, the registry lists enrollment of 66 and completed status, but does not state the number completing interviews or report the themes.

For biostatisticians and clinical researchers, the record reinforces the need to match analytic expectations to study purpose. A sample-size illustration framed around equal allocation and an observed effect is a planning device for a comparison, not a measure of success in a qualitative needs-assessment study. Likewise, the absence of reported analyses means that conventional inferential claims cannot be reconstructed from the record. Clear reporting of the qualitative process, participant contributions, and outcome completeness would be needed to judge the evidence’s scope and transferability.

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 main limitation of interpretation is the lack of reported outcome results. The registry defines the primary completion count but does not report its value. It describes a qualitative analysis approach but does not report the resulting themes. The secondary survey outcomes are named, but their results are not reported in the registry record. This limits assessment of both the descriptive study process and its substantive findings.

Recruitment descriptions should not be confused with achieved participant counts. The registry describes up to 24 prosthetists, an estimated 14 people with lower limb amputation, and an expert working group with specified membership ranges. It does not report how many people were recruited into each group or how many contributed data. The enrollment listing of 66 does not supply those group-specific details.

The record does not report the qualitative coding procedures beyond naming directed content analysis and the conceptual frameworks used. It does not state how coding was conducted, how analytic disagreements were resolved, or how the final themes were selected. Those omissions make it difficult to assess analytic transparency from the registry record alone.

Statistical limitations include the absence of reported analyses, outcome-specific denominators, missing-data procedures, and a stated analysis population. The registry record does not report a sample-size justification for the qualitative study, an inferential statistical plan, interim analyses, or multiplicity handling. The planning assumptions described in the metadata do not establish the study’s actual design or analysis.

Finally, the record does not describe a randomized evaluation of the decision aid or a direct comparison of its use with an alternative. It therefore cannot answer whether the aid changes decisions or improves outcomes. The adverse-event entries are limited to the listed registry categories and do not establish the completeness of safety ascertainment.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Shared Decision Making Aid for Prosthetic Design — NCT04536025.
• Registry record last updated 2024-09-26; status last verified 2024-06.
• Results first posted 2024-09-26.
• 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

NCT04536025, “Shared Decision Making Aid for Prosthetic Design,” is listed as completed, with enrollment of 66 and sponsorship by the University of Colorado, Denver. The registry lists a start date of 2020-06-06 and a primary completion date of 2022-06-01. The study aimed to understand prosthetic design decision making and develop a decision aid.

Its activities included qualitative focus groups with prosthetists and semi-structured interviews with people with lower limb amputation, alongside an expert working group. The primary outcome is a count of participants completing the semi-structured interview data collection. Transcript analysis was described as directed content analysis using the Ottawa Decision Support Framework and the Elwyn Shared Decision Making Model. Two secondary survey outcomes concern control preferences and eHealth literacy.

The registry record does not report the primary outcome result, qualitative themes, secondary outcome results, or analyses. It does not describe a randomized comparison or an evaluation of the decision aid’s effects. The record therefore documents the study purpose and planned evidence sources, but not the findings needed to assess its substantive conclusions.