SCANREP: Reliability of 3D Lower Limb Scanning: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for SCANREP: Reliability of 3D Lower Limb Scanning (NCT04032041), a registered phase not stated study. The primary outcome is Width of the Metatarsal Heads (Minimal Detectable Change [MDC]).

2. Clinical Question

The clinical motivation in the registry is that lower-cost three-dimensional scanning systems have been adopted for fitting prosthetic and orthotic devices, while evidence about repeatability and validity is limited. The stated research question is therefore about measurement performance, not a comparison of treatment effects. The record does not report a separate primary question about clinical outcomes, device use, or patient benefit.

3. Trial Design

SCANREP is registered as a study of the reliability of three-dimensional lower-limb scanning. The sponsor is the University of Iowa. The record lists 30 participants enrolled, with a start date of 2019-09-27 and a primary completion date of 2021-07-31. Its status is TERMINATED.

The registry describes two participant groups. Group 1 consisted of healthy, able-bodied individuals with no history of lower-extremity trauma. Group 2 was intended for people with unilateral, below-knee functional deficits requiring an AFO for daily activities; examples listed include fracture, muscle or nerve injury, ankle arthritis, and peripheral neurologic disease. The record says no participants were enrolled for group 2. Study activities for that group were delayed due to the COVID pandemic and then terminated to focus on higher-priority efforts.

The listed devices are the Structure Sensor and a caliper. The primary outcome description identifies repeated measurements by rater and session, including caliper and scan conditions. It states that data are presented only for group 1 because group 2 activities were terminated. The record does not establish that the devices were assigned randomly, nor does it state a randomized allocation sequence. The two participant groups are not described as a like-for-like control comparison.

The record lists 35 outcome measures, but no analysis records. This does not establish whether analyses were conducted outside the registry. The registry record does not report a sample-size justification, a detailed schedule of measurement visits, or a complete statistical analysis plan. In particular, the title and design description identify a reliability study, but the available record does not give the numerical results needed to assess reliability estimates or precision.

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: No participants were enrolled for group 2 (individuals requiring AFO use). Study related activities were delayed due to the COVID pandemic and then terminated to focus on higher priority efforts.

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: No participants were enrolled for group 2 (individuals requiring AFO use). Study related activities were delayed due to the COVID pandemic and then terminated to focus on higher priority efforts.

6. Primary Endpoint

The registry lists the primary outcome as Width of the Metatarsal Heads (Minimal Detectable Change [MDC]), measured over Less than 2 days.

The primary endpoint is the minimal detectable change (MDC), in millimeters, for width of the metatarsal heads. The measurement is defined as the distance from the medial aspect of the first metatarsal head to the lateral aspect of the fifth metatarsal head. MDC is intended to describe how large a difference between repeated measurements must be before it can be distinguished from measurement error under the specified method. In general, a smaller MDC indicates that less change is needed to exceed the estimated measurement error.

The registry describes MDC estimates for four conditions: caliper intrarater-intersession, scan intrarater-intersession, scan interrater-intrasession, and scan interrater-intersession. These distinctions matter because repeatability can depend on whether the same or different raters perform measurements, and whether measurements occur in the same or separate sessions. This endpoint is a measurement-property outcome; it is not a direct measure of treatment efficacy or patient improvement.

The record describes the calculation using the standard error of measurement (SEM), a multiplier of 1.96, and a square-root term. It says SEM was calculated using the standard deviation and intraclass correlation coefficient (ICC), with the standard deviation described as pooled variance. The square-root expression following the MDC formula is incomplete in the posted description. Numerical MDC values, SEM values, ICC estimates, and standard deviations are not reported in the registry record, so the endpoint's magnitude and precision cannot be assessed from the record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The endpoint is a minimal detectable change (MDC), a way to express the amount of change needed to distinguish a measured difference from measurement error. In general, measurement error is the variation that arises when a measurement is repeated under conditions intended to be comparable. MDC is expressed in the same units as the underlying measure. In this study, the unit is millimeters and the measure is width across the metatarsal heads. The registry says smaller MDC values are better, because a smaller value corresponds to a smaller amount of change needed to exceed estimated measurement error.

The record describes the standard error of measurement (SEM) as the basis for MDC. In general, SEM expresses measurement variability on the scale of the measurement itself. The registry says SEM was calculated from the standard deviation multiplied by the square root of one minus the ICC. It identifies the standard deviation as pooled variance. The posted MDC formula includes SEM multiplied by 1.96 and a square-root term, but the expression after “SQRT” is not completed in the description. The registry record does not report the component estimates or numerical MDC values, so the calculation cannot be independently evaluated from the description alone.

The intraclass correlation coefficient (ICC) is a reliability statistic used to characterize how strongly repeated measurements resemble one another relative to their variability. In general, ICC estimates depend on the study design and the way raters, sessions, and measurement targets are treated in the model. A high ICC does not by itself guarantee small error in the original measurement units: an ICC is relative to variation in the observed sample, whereas SEM and MDC express measurement error on the measure's scale. The record says ICC values were calculated using SPSS v.25 with model (2,k). Numerical ICC values are not reported in the registry record.

The listed measurement conditions separate two sources of repeatability. “Intrarater” means that the same rater repeats the measurement; “interrater” means that measurements are compared across raters. “Intrasession” refers to measurement within a session, while “intersession” refers to measurement across sessions. These conditions address different practical sources of variability, so a scan-based estimate for one condition should not automatically be treated as equivalent to an estimate from another condition. The endpoint description lists caliper intrarater-intersession and three scan conditions: intrarater-intersession, interrater-intrasession, and interrater-intersession.

In general, measurement reliability can be affected by variation between people as well as variation in repeated measurements. The composition of the study group therefore matters when interpreting an ICC. The registry distinguishes healthy, able-bodied participants from people with functional deficits requiring an AFO, but states that no participants were enrolled in the latter group and that outcome data are presented only for the healthy group. The record does not support extending any unreported estimates to the AFO population.

The record also refers to validity as an aim in its study summary, but the registered primary endpoint is an MDC reliability measure. It does not report a numerical validity result in the record described. Reliability and validity answer different questions in general: reliability concerns consistency of measurements, while validity concerns whether the measurement represents the intended construct or quantity. Evidence about one does not, by itself, establish the other.

For sample-size planning, the registry describes an illustration based on an observed effect rather than the trial's own design. The assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. Such calculations are planning illustrations, not observed power and not evidence that the study had a particular probability of detecting an effect. The record does not report a sample-size justification for the original study. The numerical outputs of the planning illustrations are not reported in the registry record.

Finally, the registry lists 35 outcome measures and no analysis records. That absence means the registry record does not show the analysis results; it does not establish that no analysis took place. The statistical plan, handling of missing measurements, and any multiplicity adjustment are not reported in the registry record. Without these details and the numerical endpoint results, readers cannot assess the full analysis workflow or quantify uncertainty around the reliability findings.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 35 outcome measures, while the primary endpoint description focuses on metatarsal-head width MDC. A study with multiple outcomes can raise multiplicity concerns because examining many outcomes may increase the chance of finding apparently notable results by chance. In general, multiplicity procedures can control or describe that issue, but the registry record does not report whether an adjustment was planned or used. No analysis records are listed, and the record does not provide a complete statistical analysis plan.

The handling of missing measurement data is not reported in the registry record. The record also does not describe whether all planned measurements were collected, how incomplete measurement sessions were treated, or whether any participants were excluded from particular analyses. These details are important in a repeatability study because estimates may depend on which repeated observations are available and how those observations are paired or grouped.

The record says no participants were enrolled in the AFO group, and that group’s study activities were terminated after delays related to the COVID pandemic. This is a lack of enrollment in that intended group, rather than a reported pattern of missing outcome measurements among enrolled AFO participants. The endpoint description says data are presented only for the healthy group.

Analysis populations are not reported in detail. The safety information identifies 30 participants at risk in the healthy group and none in the AFO group, but it does not establish the number contributing to each primary endpoint analysis. The registry record does not report a participant flow for the measurement analyses, analysis-specific denominators, or rules for handling absent data. These limitations prevent a complete assessment of selection into each analysis.

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 safety record lists the healthy group as having 30 participants at risk, with 0 serious adverse events, 0 other adverse events, and 0 deaths. The AFO group has 0 participants at risk and 0 reported serious adverse events, other adverse events, and deaths. The latter figures do not represent observed safety experience among enrolled AFO participants, because no participants were enrolled in that group.

These registry figures describe what is recorded for the listed groups; they do not establish that the study could rule out adverse events or quantify safety precisely. In particular, counts of zero should be read alongside the number at risk and the scope of study participation. The record does not provide further detail about adverse-event collection methods, observation duration for safety, or event definitions beyond the serious and other adverse-event categories. No serious adverse-event terms are listed.

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

The registry record identifies a practical measurement question: whether repeated lower-limb measurements made with a low-cost three-dimensional scanner have acceptable repeatability, and how scan-based repeatability compares with caliper measurement. The primary endpoint is an MDC for metatarsal-head width. In general, MDC translates measurement error into the original unit and can help readers understand how much observed change may be needed to exceed that error. However, the registry record does not report numerical MDC estimates, so it does not show the magnitude of error for any listed measurement condition.

The record also distinguishes among repeated measurements by the same or different raters and within or across sessions. These are meaningful design distinctions because repeatability in one setting does not automatically represent repeatability in another. Without the estimates, uncertainty, and analysis details, the record cannot establish which condition is more consistent or whether any differences between conditions are important.

The scope is limited to the group for which the primary outcome description says data are presented: healthy, able-bodied individuals. The AFO group had no enrolled participants, after activities were delayed due to the COVID pandemic and then terminated to focus on higher-priority efforts. The record therefore does not report an evaluation of measurement repeatability in people requiring an AFO.

The study is marked TERMINATED, and the registry lists 35 outcome measures but no analysis records. These registry entries describe the status and content of the registry, not whether analyses were performed elsewhere. The intended study summary mentions validity as well as repeatability, but the quantitative primary endpoint is an MDC reliability measure, and numerical validity findings are not reported in the registry record.

Accordingly, the record documents an important measurement aim and its intended comparisons, but does not permit a quantitative judgment about scanner repeatability, validity, or performance relative to calipers. It also does not support claims about clinical benefit or treatment efficacy: the listed devices are measurement tools, and the registered question concerns measurement properties.

13. Why This Trial Matters Statistically

Measurement error matters when clinical or research decisions rely on repeated measurements. A difference between two readings can reflect a genuine change, variation in the person being measured, or inconsistency in the measurement process. In general, a reliability study helps characterize the measurement process so that later users can interpret repeated values with appropriate caution. An MDC is useful because it expresses this issue in the same units as the measurement rather than only as a relative reliability statistic.

The study's focus is also practically relevant to prosthetic and orthotic settings. The registry notes that lower-cost three-dimensional limb-scanning systems have been implemented for clinical fitting as costs have decreased, while data on repeatability and validity were limited. Evaluating scanner measurements against repeated measurements and a caliper can address whether the measurement process is sufficiently consistent for its intended use. That question is distinct from whether a treatment or device improves health outcomes.

Separating intrarater from interrater repeatability, and intrasession from intersession repeatability, is statistically valuable in general because different sources of variation can affect use in practice. A measurement procedure that is consistent when one rater repeats it may not have the same consistency across raters or sessions. The registered endpoint description recognizes these separate conditions.

The record's limitations are especially important to the scope of interpretation. No participants were enrolled in the intended AFO group, and numerical MDC estimates are not reported in the registry record. Thus, the stated question is relevant, but the registry information does not provide the quantitative evidence needed to judge repeatability in either the healthy group or the AFO population. The record illustrates why study registration and numerical results are both needed for a full statistical assessment.

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 central limitation is that the registry record does not report numerical primary-outcome estimates. It identifies the MDC outcome and its measurement conditions, but gives no MDC, SEM, ICC, or standard-deviation results. Without those estimates, readers cannot judge the size or precision of the measurement error, compare the listed conditions, or assess the direction and magnitude of any differences.

The record states that the AFO group had no enrolled participants and that its activities were terminated after delay due to the COVID pandemic. Therefore, no result for that intended population can be inferred. The reported primary outcome description says data are presented only for group 1, the healthy, able-bodied group. Applicability beyond that group is not established by the record.

The posted formula description for MDC includes a square-root term without a completed expression. Although the record gives an SEM formula and identifies the ICC model, it does not report component estimates or enough detail to reproduce the calculation. The statistical analysis plan, measurement-level data structure, missing-data procedures, analysis populations, and multiplicity approach are not reported in the registry record.

The record lists 35 outcome measures but no analysis records. This limits what can be learned from the registry, but does not establish that analyses were never conducted. The status is TERMINATED, and the registry does not provide enough information to determine how termination affected the planned measurement work in the enrolled group. Allocation is not stated, so the devices should not be interpreted as randomized treatment arms or as a randomized comparison.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: SCANREP: Reliability of 3D Lower Limb Scanning — NCT04032041.
• Registry record last updated 2025-01-10; status last verified 2024-11.
• Results first posted 2025-01-10.
• 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

SCANREP (NCT04032041), sponsored by the University of Iowa, is registered as a study of the reliability of three-dimensional lower-limb scanning. It lists 30 participants enrolled, a start date of 2019-09-27, a primary completion date of 2021-07-31, and status TERMINATED. The listed devices are the Structure Sensor and a caliper.

The primary outcome is the MDC, in millimeters, for width between the first and fifth metatarsal heads. The record describes four caliper or scan measurement conditions and says data are presented only for the healthy group. It states that no participants were enrolled in the AFO group, whose activities were delayed due to the COVID pandemic and then terminated. Numerical MDC estimates and analysis results are not reported in the registry record.