Auto Control of Volume Management for Limb Loss: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Auto Control of Volume Management for Limb Loss (NCT03550118), a non-randomized na study. The primary outcome is Change in Limb Volume.

2. Clinical Question

3. Trial Design

The record identifies NCT03550118, titled Auto Control of Volume Management for Limb Loss. The sponsor is the University of Washington. The study is marked completed, with a start date of 2015-08-07 and primary completion listed as 2021-09. Enrollment is listed as 104. The phase is recorded as NA. These registry entries describe the study’s status and scope; they do not establish how many participants contributed to each analysis.

The design is classified as non-randomized, with no masking and a single-group model. The listed study arms correspond to different aims and device activities, including researcher-, participant-, and automatically controlled adjustments; release and recovery testing; panel pull during rest or ambulation; and out-of-lab testing. This range of activities makes the overall record broader than a single two-arm treatment comparison. The record’s own caution is important: the arms are not a like-for-like control comparison.

The primary outcome is Change in Limb Volume, described as a within-session comparison between a period without socket adjustment and a period with adjustment. It was monitored only for Arms 2, 6A, 6B, 8 and 9. The outcome description says the periods were commonly each one hour long and separated by a seated period of approximately 30 minutes; this wording does not establish that every participant followed an identical schedule.

The registry record lists one secondary outcome, Adjustable Socket Mode Preference, and seven outcome measures overall. It reports zero analyses. It does not report the allocation of participants to the different aims, the number contributing to each outcome, or a statistical analysis plan. Consequently, enrollment should not be treated as the analysis sample size for any particular endpoint, and the various aims should not be interpreted as randomized comparisons.

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.

Only the first 6 of 8 groups are shown.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Change in Limb Volume was monitored only for Arms 2, 6A, 6B, 8 and 9.

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.

Only the first 6 of 9 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Change in Limb Volume, measured over Change from baseline period (non-adjustment) to test period (adjustment), commonly each 1 hour long and separated by a seated period of approximately 30 minutes..

The primary outcome is titled Change in Limb Volume, with the unit recorded as participants and the measure type described as a count of participants. Its narrative description focuses on changes in residual-limb volume while socket adjustment strategies are tested. The planned assessment compares a baseline period without socket adjustment with a test period in which adjustments are made during the same test session. The registry describes real-time monitoring using a portable bioimpedance device with thin sticky electrodes placed on the residual limb.

This kind of measurement is relevant to the stated study aim because the record describes volume fluctuation as a concern for people using a prosthesis. In general, a repeated measurement within a participant can characterize change across two conditions while reducing the influence of stable differences between people. That general rationale does not establish that the registry’s analysis used a particular paired statistical method: the analysis method is not reported in the registry record.

The endpoint description does not state the scale, direction, or threshold used to classify participants as having a change. Although the outcome is presented as a participant count, no count of participants with a particular result, no continuous volume-change estimate, and no uncertainty measure is reported. The outcome was monitored only for Arms 2, 6A, 6B, 8 and 9, not for every listed aim. These details limit what can be inferred from the endpoint title alone. The record identifies what was intended to be measured, but does not provide the observed result needed to quantify the amount or consistency of change.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the design classification imply?

The record classifies the study as non-randomized, unmasked, and single-group. In general, random allocation helps make comparison groups similar, on average, with respect to measured and unmeasured characteristics. When allocation is not randomized, that protection is not assured. Differences observed between groups or study aims may reflect participant characteristics, study procedures, or other factors as well as the device approach under study. Here, the registry explicitly cautions that the arms are not a like-for-like control comparison, so comparisons among them should be interpreted descriptively rather than as randomized treatment effects.

The single-group label does not mean that every activity or measurement was identical across participants. The arm descriptions cover several aims and approaches. Some involve adjustments controlled by researchers, some by participants, and one uses automatic control. Other aims address release and recovery, panel pull, or use outside the laboratory. The registry does not report a unified allocation scheme across those activities. It is therefore important to distinguish the overall study classification from the detailed activities associated with each aim.

What would a within-session change represent?

The primary outcome description contrasts a baseline period without socket adjustment with a test period when adjustments are made, within the same test session. In general, repeated measurements from the same participant can be analyzed as paired observations. A paired analysis focuses on within-person differences and accounts for the fact that two measurements from one participant are related. The registry record does not identify the statistical method used, so it is not possible to say whether this or another approach was applied.

The outcome is described as a participant count, while its narrative describes real-time limb-volume fluctuation. These descriptions do not give the numerical scale, a definition of what qualifies as a change, or the observed measurement values. The record also does not say whether the outcome was summarized as a continuous change, categorized into groups, or analyzed in another way. Those details are not reported in the registry record.

How should estimates and uncertainty be read?

In general, an effect estimate summarizes the size and direction of an observed difference or change. A confidence interval describes uncertainty around an estimate under the assumptions of the statistical method. A narrow interval indicates greater statistical precision than a wide interval, but neither an estimate nor its interval establishes clinical importance on its own. The registry record does not report an effect estimate or confidence interval for limb-volume change, so the precision of the primary result cannot be assessed.

A p-value, in general, describes how compatible the observed data are with a specified statistical model and null hypothesis. It does not measure the size or importance of an effect, and it is not the probability that a hypothesis is true. No p-value or primary-outcome analysis is reported in the registry record. It would therefore be inappropriate to infer statistical significance or its absence.

What do the planning illustrations mean?

Any sample-size figures associated with the posted results are planning illustrations based on an observed effect, not evidence of the study’s original design assumptions. The stated illustration method uses a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the target effect is a stated fraction of the observed effect. In general, such calculations ask what sample size might be needed under specified assumptions to detect a target effect. They do not describe the number of participants actually analyzed, and they are not observed power.

The record does not report the study’s original sample-size justification or statistical analysis plan. Without the primary effect estimate and its uncertainty, a planning illustration cannot establish how reliably the study could detect a clinically meaningful difference. In addition, the stated equal-allocation, two-arm framework does not convert the non-randomized aims into a valid like-for-like comparison. Sample-size calculations depend on the design and assumptions to which they are applied.

Why are the outcome and analysis populations important?

In general, an analysis result is interpretable only when its population is clear. The number enrolled, the number assessed for a particular outcome, and the number included in a specific analysis can differ. The record gives overall enrollment, but does not report the primary-outcome analysis population or aim-specific primary-outcome denominators. It also does not report missing-data methods, exclusions, or an intention-to-treat analysis. These omissions prevent assessment of how representative the analyzed observations were of enrolled participants.

Finally, multiple aims and outcomes can raise questions about multiplicity: if many comparisons are examined, the chance of at least one apparently unusual result can increase. In general, investigators may prespecify a primary comparison, adjust for multiple testing, or treat secondary analyses as exploratory. The registry record does not report which approach, if any, was used. With no posted primary analysis, there is no basis for determining whether multiplicity affected reported conclusions.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists seven outcome measures overall, including the primary outcome Change in Limb Volume and the secondary outcome Adjustable Socket Mode Preference. It also reports zero analyses. The record does not describe a prespecified hierarchy of outcomes, a multiplicity adjustment, or a plan for interpreting several comparisons across the different aims. These details are not reported in the registry record.

In general, multiplicity matters when multiple outcomes, time points, groups, or comparisons are tested. Without an approach specified in advance, selective emphasis on results can make apparently notable findings harder to interpret. That is a general concern, not evidence that selective reporting occurred in this study. Since the registry does not post outcome analyses, the effect of multiplicity on conclusions cannot be assessed.

The record lists enrollment as 104, but does not state the number included in each primary-outcome analysis. It also does not describe withdrawals, missing bioimpedance readings, exclusions, or the handling of incomplete observations. Missing-data assumptions and methods are not reported in the registry record. It is therefore not possible to determine whether the posted results, if any, represent all enrolled participants or only those with usable measurements.

Analysis populations are likewise not described. The record does not report whether analyses followed an intention-to-treat principle, used only participants with complete observations, or applied another definition. The primary outcome was monitored only for Arms 2, 6A, 6B, 8 and 9; group-specific denominators are not given. These gaps matter because an outcome estimate depends on who contributed data and how missingness was handled. The record supports no further conclusion about those analysis choices.

11. 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 adverse-event information for the listed groups. For each group, the number at risk is given separately for serious and other adverse events, and the number affected is zero in every entry. Deaths are also recorded as zero for each group. The listed group sizes at risk vary; these are group-specific safety figures and should not be treated as the primary-outcome denominators.

A zero recorded event count means that no affected participants are recorded in that registry entry. It does not establish that an event is impossible, that no symptoms occurred outside the categories reported, or that the device has no risks. In general, the interpretation of safety counts depends on the scope of event collection, the time under observation, and how completely events were reported. Those details are not reported in the registry record.

The record lists no top serious-event terms. It does not provide an event narrative, an assessment of relatedness to the device, or a comparison against a control group. Because the design is non-randomized and the arms are not described as like-for-like controls, the safety entries should be read as recorded counts, not as comparative evidence. They describe the registry’s reported safety information, but do not establish comparative safety or rule out uncommon harms.

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

The record is useful for understanding the scope of a study of adjustable sockets and the types of control strategies examined. It describes a primary outcome based on limb-volume change from a period without adjustment to a period with adjustment, and identifies the aims in which that outcome was monitored. It also records enrollment, study status, and adverse-event counts.

However, the registry does not report the observed primary-outcome results or any analyses. No effect estimate, uncertainty interval, or test result is available for interpreting limb-volume change. The record therefore does not establish the size or direction of any measured change, whether results were consistent across participants, or whether results differed across aims. The fact that a study is marked completed does not supply those missing outcome findings.

The design also limits causal interpretation. The study is non-randomized and single-group, and the registry cautions that its arms are not like-for-like control comparisons. Descriptive differences among aims cannot be treated as evidence that one approach caused a better or worse result than another. Participant characteristics, study procedures, and other unreported factors could differ across aims.

The safety entries record zero affected participants for serious and other adverse events and zero deaths in the listed groups. These counts should be understood as registry-recorded events, not proof that no risk exists. The record does not describe the full safety-surveillance process or the length of observation for every group.

Accordingly, the available information supports a description of what the study set out to examine, not a conclusion about whether an adjustable socket changes limb volume or how one control mode compares with another. Outcome values, analysis populations, methods, and uncertainty estimates would be needed to make those statistical judgments.

13. Why This Trial Matters Statistically

This study is statistically interesting because it combines a focused physiological measurement with multiple device-development aims. The primary outcome description uses real-time bioimpedance monitoring to examine limb-volume fluctuation across periods with and without socket adjustment. The registry also describes different ways of controlling adjustments and additional activities involving release and recovery, panel pull, and out-of-lab testing. Such breadth makes clarity about the specific aim, population, and outcome especially important when interpreting results.

The design classification is central to that interpretation. This is a non-randomized, single-group study, and the registry cautions that the arms are not like-for-like control comparisons. Statistical summaries can describe observed measurements, but a difference between aims would not by itself isolate the effect of the control strategy. Recognizing that distinction helps prevent descriptive comparisons from being overstated as causal evidence.

The record also illustrates why outcome definitions and analysis populations matter. The outcome is titled Change in Limb Volume and is designated as a participant count, while its description concerns measured volume fluctuation. The record does not report the outcome values, how a participant-level result was defined, or how many participants contributed to each aim. Those omissions prevent an assessment of effect magnitude and precision, regardless of the study’s overall enrollment.

Finally, the study is marked completed, yet the registry reports zero analyses and no primary-outcome results. Completion status and enrollment do not substitute for posted estimates. The contrast underscores a basic principle of clinical biostatistics: a design can describe a meaningful question, but conclusions depend on transparent outcome data, analysis methods, and uncertainty. The recorded safety counts are informative as registry entries, but they too require context about observation and ascertainment.

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 principal limitation for statistical interpretation is that the registry record does not report primary-outcome values or analyses. It is therefore not possible to estimate limb-volume change, assess precision, or determine how results varied across study aims. The record also does not state the analysis method, report confidence intervals or p-values, or provide aim-specific primary-outcome denominators.

The study includes several distinct aims and device activities, rather than a single clearly defined randomized comparison. Its non-randomized, single-group classification and the registry’s warning that arms are not like-for-like controls limit causal comparisons across arms. The record does not describe how participants entered each aim or whether their characteristics were comparable.

The primary outcome description leaves some measurement details unresolved. It describes volume fluctuation assessed with bioimpedance and a baseline-to-test comparison, but does not report the scale, a threshold for defining a participant-level change, or the observed measurements. The outcome is recorded as a count of participants, while the description centers on change in volume. The registry does not explain how those elements were reconciled in analysis.

Overall enrollment is listed, but aim-specific enrollment for the primary endpoint is not. Missing-data handling, withdrawals, exclusions, analysis populations, and the statistical analysis plan are not reported in the registry record. The registry also does not report a sample-size justification or multiplicity strategy. These omissions make it difficult to evaluate potential selection, measurement, and analytic limitations beyond those inherent in the non-randomized design.

Safety information is limited to recorded affected-participant counts and deaths. The registry does not describe event ascertainment, follow-up duration for each group, or event relatedness. These limitations concern interpretation of the registry record and do not establish that unreported methods or observations were absent from the broader study documentation.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Auto Control of Volume Management for Limb Loss — NCT03550118.
• Registry record last updated 2023-05-03; status last verified 2023-04.
• Results first posted 2023-05-03.
• 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

NCT03550118, Auto Control of Volume Management for Limb Loss, is a completed, non-randomized, unmasked, single-group study sponsored by the University of Washington. The record lists enrollment of 104, a start date of 2015-08-07, and primary completion in 2021-09. The listed activities examine adjustable socket strategies, including researcher, participant, and automatic controls, alongside other device aims.

The primary outcome is Change in Limb Volume, described as a comparison of periods without and with socket adjustment using real-time bioimpedance monitoring. It was monitored only for Arms 2, 6A, 6B, 8 and 9. The record lists Adjustable Socket Mode Preference as a secondary outcome and seven outcome measures overall, but reports zero analyses and no primary-outcome results.

Adverse-event entries record zero affected participants for serious and other events, and zero deaths, in each listed group. The registry does not report analysis populations, missing-data methods, a statistical analysis plan, or primary-outcome estimates and uncertainty. The record therefore describes the study’s scope but does not support a statistical conclusion about limb-volume change.