Mild Compression Sock for Control of Lower Extremity Edema in Individuals With Diabetes: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Mild Compression Sock for Control of Lower Extremity Edema in Individuals With Diabetes (NCT01529385), a randomized na study. The primary outcome is Cutaneous Water Content.

2. Clinical Question

The study summary describes broader aims: reducing leg swelling, improving blood flow to the legs, and improving physical activity patterns. These aims should be distinguished from the registered primary outcome, cutaneous water content measured as percentage change in dielectric constant. Physical Activity Level is listed as a secondary outcome. Although blood flow appears among the stated aims, the available record does not identify a corresponding outcome measure or its result.

The comparison is randomized, so the intended contrast is between assignment to the two sock types. The registry does not report enough detail to establish how the primary analysis handled adherence, missing measurements, or participants who did not complete follow-up. Nor does it report a numerical estimate, confidence interval, or test result for the primary comparison. Consequently, the clinical question can be described from the study design and outcome definition, but the posted record does not support a conclusion about the direction or precision of the observed primary effect.

3. Trial Design

The registry describes a randomized, triple-masked, parallel trial of a mild-compression diabetic sock against a standard diabetic sock. The study is listed as completed, with enrollment of 80. Its phase is listed as NA. The sponsor is Rosalind Franklin University of Medicine and Science. The recorded start is 2012-02, and primary completion is recorded as 2014-09.

The intervention is a device: a diabetic sock described as applying 18-25mm Hg pressure to the lower extremities. The comparator is also a device, described as a standard diabetic sock designed to limit foot ulcer formation but not to provide leg compression. The record identifies the arms, but does not report further details about how participants were assigned, how the masking was implemented, or whether masking was maintained throughout follow-up. The designation “triple” is recorded; the identities of the masked parties are not reported in the registry record.

The primary outcome is cutaneous water content, expressed as percentage change in dielectric constant, with change from baseline assessed after 4 weeks of sock usage. The measurement description specifies non-invasive tissue dielectric constant measurement using a MoistureMeter at a location 2 inches distal and 2 inches lateral to the fibular head. Physical Activity Level is listed as a secondary outcome. The registry lists 10 outcome measures and 9 analyses, but does not supply a primary numerical comparison in the available record.

The enrollment figure describes the study record, not necessarily the number included in every analysis. Arm-specific numbers enrolled, followed, and analyzed for the primary endpoint are not reported in the registry record. The protocol's sample-size justification, planned interim analyses, detailed statistical plan, and analysis-population definitions are also not reported. The design labels establish the broad randomized, parallel comparison, but do not answer those further questions.

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

Reasons for not completing this period:

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 Cutaneous Water Content, measured over change from baseline after 4 weeks of sock usage.

The registered primary endpoint is cutaneous water content, expressed as percentage change in dielectric constant. The record describes measurement of tissue dielectric constant with a MoistureMeter, a non-invasive method, at a specified location near the fibular head. The assessment is framed as change from baseline after 4 weeks of sock usage. This endpoint therefore represents a measured change in a local tissue-water indicator over the stated follow-up, rather than a direct report of a participant's overall swelling or physical activity.

As a general measurement principle, a continuous endpoint can retain information about the size of changes across participants, rather than reducing observations to categories such as improved or not improved. A baseline-to-follow-up change can express how the measured value shifted during the specified period. The measure's interpretation depends on the measurement procedure, the variability of the observations, and the precision of the comparison between groups. The registry does not provide the primary outcome estimate or its 95% confidence interval, so the size and precision of the observed difference cannot be assessed from the posted record.

The endpoint is relevant to the study's stated focus on lower-extremity edema, but a local dielectric-constant measurement is not interchangeable with every possible assessment of swelling, blood flow, symptoms, or function. The record's description identifies where and how the primary measurement was taken; it does not establish how well this measure corresponds to those other outcomes in this trial. Physical Activity Level is listed separately as a secondary outcome, and a result for it is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Understanding a trial result requires separating the design, the outcome measurement, the estimate of the group contrast, and the uncertainty around that estimate. The registry records the design and measurement details for this study, but does not report the primary numerical comparison. General statistical explanations below clarify what those elements would mean without implying that a particular analysis was conducted.

What does randomization contribute?

In general, random assignment is intended to make treatment groups comparable, on average, with respect to factors present before assignment. It supports interpreting a between-group contrast as an effect of assignment when the trial is conducted and analyzed appropriately. Randomization does not guarantee that every characteristic is balanced in a particular trial, and it does not remove concerns about missing outcomes, deviations from assigned treatment, or selective reporting. The registry identifies allocation as randomized, but details of the sequence generation, concealment, adherence, and primary analysis population are not reported in the registry record.

A parallel design means that participants are assigned to a group that receives its assigned intervention during the trial, rather than switching between the study interventions as part of a crossover design. The record identifies the model as parallel. It does not give further operational details about the duration or use of each sock beyond the stated assessment after 4 weeks of sock usage.

What does masking tell readers?

The registry labels the study triple-masked. In general, masking is intended to reduce the influence of knowledge about assignment on study conduct, measurement, or assessment. The designation alone does not identify which parties were masked or how masking was maintained. Those implementation details are not reported in the registry record, so the label should not be expanded into assumptions about participants, clinicians, assessors, or analysts.

How should a continuous endpoint be understood?

The primary measure is continuous: percentage change in dielectric constant. In general, a mean describes the average value in a group, while a between-group mean contrast describes the difference in group averages under a specified analysis. The registry identifies the reported parameter as a mean and the dispersion as a 95% confidence interval. A confidence interval conveys uncertainty about an estimated quantity under the method used to calculate it; it is not a range that contains every participant's value. Without the estimate and interval, neither the size of the group contrast nor its precision can be assessed.

The measurement description specifies change from baseline after 4 weeks of sock usage and a non-invasive tissue dielectric constant measurement at a defined location. A baseline-change analysis can be presented in different statistical ways, and the appropriate interpretation depends on the actual model and estimand. The detailed model, covariate adjustment, handling of baseline values, and method used to obtain the confidence interval are not reported in the registry record. No particular approach should be inferred from the endpoint description alone.

Why does variation matter?

General statistical interpretation considers both the estimated contrast and the variability in the data. Greater variability can make an estimate less precise, while a confidence interval communicates uncertainty in the estimated contrast. For continuous outcomes, the shape of the outcome distribution and the analysis assumptions can matter. The posted record does not report the outcome distributions or the primary estimate, so it is not possible to assess those features for this trial.

Over-dispersion is a general concern in some models for count data: observed variation can exceed what a model assumes, which may make standard errors too small if the model does not account for it. That concept does not establish a problem in this trial's continuous primary endpoint. The registry identifies the primary parameter as a mean and does not report a count-model analysis for that endpoint. No model details are available to evaluate assumptions for the analyses listed.

What do the planning assumptions mean?

The record describes sample-size illustrations as planning calculations based on the observed effect, not as the trial's own design justification. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. Such calculations are planning illustrations. They do not show the probability that the completed trial detected an effect, and they are not observed power. The numerical outputs of those illustrations and the trial's own sample-size justification are not reported in the registry record.

In general, planning calculations depend on assumptions about the target effect, variability, allocation, and statistical procedure. If an observed effect is used as a reference, calculations based on fractions of it describe hypothetical design targets, not additional outcomes from the trial. The stated assumptions do not reveal whether those calculations were part of the original protocol or how the trial's enrollment was chosen; that information is not reported.

What can a significance test establish?

In general, a p-value measures how incompatible data are with a specified null model, under the assumptions of the test. It does not measure the probability that the null hypothesis is true, the probability that a finding will replicate, or the clinical importance of an effect. A p-value should be considered alongside an effect estimate and its confidence interval. The primary p-value and numerical estimate are not reported in the registry record, so no test-based conclusion can be drawn about the primary outcome.

Multiplicity arises when multiple outcomes, comparisons, or analyses are considered. Repeated testing can increase the chance of at least one apparently notable result under a collection of null hypotheses. General approaches include prespecifying a primary outcome and adjusting for multiple testing when appropriate. The registry lists multiple measures and analyses, but does not report a multiplicity procedure or enough detail to determine which analyses were confirmatory. It is therefore not possible to assess how multiplicity was handled.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 10 outcome measures and 9 analyses. These counts indicate that the record includes multiple outcomes and analyses, but do not by themselves establish which results were prespecified, which analyses were primary, or whether every planned outcome was reported. The primary endpoint is identified as cutaneous water content. A multiplicity strategy, such as a stated adjustment or hierarchy for testing outcomes, is not reported in the registry record.

In general, when several outcomes or comparisons are examined, the chance of a statistically notable finding somewhere among them can be greater than for a single prespecified test. Interpretation depends on the analysis plan, which outcomes were designated primary or secondary, and whether any correction or other strategy was used. The available record does not supply enough detail to judge those choices. The existence of multiple listed analyses is not evidence, by itself, that the results are invalid or that a particular correction was required.

Information about missing measurements is also not reported in the registry record. The enrollment figure is 80, but the numbers with baseline and follow-up primary measurements, withdrawals, and missing observations are not given. The record does not describe imputation, complete-case analysis, sensitivity analyses, or reasons for missingness. These omissions limit assessment of whether the observed analysis, if reported elsewhere, would represent all randomized participants.

The analysis population is not reported in the registry record. The information does not state whether the primary comparison used all randomized participants, participants who received their assigned sock, or another defined group. It also does not describe adherence or protocol deviations. These points matter because the analysis population and missing-data methods affect the population to which an estimate applies and the assumptions required for interpretation. They cannot be resolved from the registry entries available.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: spine infection c2-c5 (2.6%), excessive fluid retention (2.6%), fluid retention and hypertension (2.6%).

The registry reports serious adverse events and other adverse events separately for the two sock groups. For the mild-compression sock, 2 of 38 participants at risk were recorded as affected by serious adverse events, and 4 of 38 were affected by other adverse events. For the standard sock, 1 of 39 participants at risk was recorded as affected by serious adverse events, and 6 of 39 were affected by other adverse events. These are the posted group figures; they should not be combined into a new overall count or treated as evidence of causation.

The listed serious-event terms are spine infection C2-C5, excessive fluid retention, and fluid retention and hypertension, each reported as 2.6%. The record does not provide enough detail in these entries to establish the relationship of each event to sock assignment, its timing, or whether the terms refer to separate episodes or participants. Death counts are not reported in the registry record.

In general, adverse-event counts describe reported events or affected participants according to the registry's definitions; they do not by themselves show that an intervention caused an event. Comparisons also depend on how events were collected, the observation period, and the number of participants with safety follow-up. Those details are not reported. The group counts should therefore be read as descriptive registry entries, not as a stand-alone estimate of comparative safety.

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

The registry establishes the basic question and design: a randomized, parallel comparison of a mild-compression diabetic sock with a standard diabetic sock in people with diabetes and lower-extremity edema. It identifies cutaneous water content as the primary endpoint, measured as percentage change in dielectric constant from baseline after 4 weeks of sock usage. These details tell readers what the trial set out to compare and how the primary measure was defined.

The record does not report the numerical primary comparison. It therefore does not show whether the measured cutaneous water content changed more in either group, how large any group contrast was, or how precisely it was estimated. The trial's completed status and enrollment of 80 cannot fill that gap. Without an effect estimate and its uncertainty, no conclusion about the statistical evidence for the primary outcome can be drawn from the registry record.

The broader stated aims include reducing swelling, improving blood flow, and improving physical activity patterns. A stated aim is not an observed result. Physical Activity Level is listed as a secondary outcome, but its result is not reported in the registry record. The record also does not provide a blood-flow result. The primary measure is a local tissue dielectric-constant assessment; it should not be treated as a direct report of every clinical outcome named in the study summary.

The safety entries describe serious and other adverse events in the two groups. They are useful as recorded counts, but do not establish that the sock caused an event or provide a complete comparative safety assessment. Details such as event attribution and the safety observation period are not reported in the registry record.

In general, a trial's result is interpreted through its estimate, uncertainty, design, outcome definition, analysis population, and completeness of reporting. Here, several design and measurement details are available, but the primary result and important analysis details are not. The defensible conclusion is about what the registry documents, rather than a claim about whether either sock achieved the study's aims.

13. Why This Trial Matters Statistically

This trial illustrates why a clear endpoint definition is only part of statistical interpretation. The registry identifies a continuous primary measure, describes the instrument and measurement location, and specifies a baseline-to-follow-up assessment after 4 weeks of sock usage. Those details help readers understand what was measured. They do not reveal the observed group contrast or its precision, which are essential for assessing the primary result.

The distinction between an intervention's stated purpose and its registered primary endpoint is also important. The study summary discusses swelling, blood flow, and physical activity, while the primary endpoint is cutaneous water content measured through tissue dielectric constant. Physical Activity Level is listed as secondary. Keeping these outcomes distinct prevents a measurement of local tissue water from being mistaken for a direct assessment of every stated aim.

The record also demonstrates the limits of reading design labels in isolation. Randomized, triple-masked, and parallel describe important aspects of study design, but do not supply details about allocation procedures, masking implementation, analysis populations, missing data, or multiplicity. Those details help determine how confidently an estimate can be interpreted and how broadly it applies.

Finally, adverse-event entries need context. Group-specific counts and listed event terms are descriptive, but do not establish causality or replace information about event definitions and observation. Taken together, the record offers a useful outline of the trial's question, design, endpoint, and some safety reporting. Its missing primary numerical result sharply limits statistical interpretation. Recognizing that boundary is part of evaluating clinical trial evidence, rather than a reason to infer a result from the study's aims or completion status.

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 outcome comparison is not reported in the registry record. In particular, the numerical estimate, group-specific primary outcome summaries, 95% confidence interval, and test result are not available. This prevents assessment of the observed effect's direction, magnitude, and precision. The record's note that the primary outcome has several categories or time points and was not reduced to one comparison further means that a single primary contrast cannot be recovered from the listed information.

The registry does not report the primary analysis population, arm-specific primary endpoint counts, or participant flow through follow-up. It also does not describe missing-data methods, adherence, protocol deviations, or sensitivity analyses. As a result, readers cannot determine how the analyzed participants relate to the randomized groups or evaluate the possible influence of missing measurements.

The study summary names aims involving swelling, blood flow, and physical activity, but the reported primary measure is a local tissue dielectric-constant assessment. Physical Activity Level is listed as a secondary outcome; its result is not reported in the registry record. A corresponding blood-flow outcome and its result are not reported. The record therefore does not support interpreting the primary endpoint as a complete assessment of all stated aims.

Further limitations include the absence of a reported multiplicity strategy despite the listing of 10 outcome measures and 9 analyses. The statistical model, adjustment choices, and rationale for enrollment are not reported in the registry record. The identities of those masked and implementation details for masking are also not reported. These gaps constrain evaluation of analysis choices and potential sources of bias. They do not establish that the trial was improperly conducted; they mark what cannot be assessed from the registry entries.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Mild Compression Sock for Control of Lower Extremity Edema in Individuals With Diabetes — NCT01529385.
• Registry record last updated 2016-06-22; status last verified 2016-05.
• Results first posted 2016-06-22.
• 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 describes NCT01529385, a completed randomized, triple-masked, parallel trial comparing a mild-compression diabetic sock with a standard diabetic sock. Enrollment is listed as 80. The mild-compression sock is described as providing 18-25mm Hg of pressure to the lower extremities; the standard sock is described as not providing leg compression.

The primary endpoint is cutaneous water content, measured as percentage change in dielectric constant from baseline after 4 weeks of sock usage. The measurement description specifies non-invasive tissue dielectric constant measurement at a location 2 inches distal and 2 inches lateral to the fibular head. Physical Activity Level is listed as a secondary outcome.

The registry does not report the numerical primary outcome comparison or its confidence interval. The primary analysis population, missing-data methods, and multiplicity strategy are not reported in the registry record. Safety entries list serious and other adverse events by group, while event attribution and death counts are not reported. The record supports description of the trial's design and registered measures, but not a numerical interpretation of the primary result.