Real-time Location System Feasibility Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Real-time Location System Feasibility Study (NCT03988751), a randomized na study. The primary outcome is Characterize Number of Participants Who Tolerate Continuous vs Interval 40m Walk..

2. Clinical Question

3. Trial Design

The registry describes a completed, randomized, single-masked, parallel study of continuous and interval ambulation. Its title identifies it as a feasibility study, and the brief description calls it a small pilot study. The phase is listed as NA. Wake Forest University Health Sciences is named as sponsor. The registry lists a start date of 2019-06-06 and a primary completion date of 2019-06-19.

The intended setting was postoperative recovery among patients who had undergone surgery requiring inpatient admission to a surgical ward. The broader study aim was to investigate whether a real-time location system could monitor patient movement in hospital and to compare those records with actual movement. The description also says that a subgroup would be randomized to continuous or interval walking to assess tolerability of different walking intensities. The registry does not explain how the subgroup relates to the overall enrollment or provide a participant flow account.

The continuous group was to walk 40 meters at a pace chosen by the participant, with team members walking alongside, supporting, and coaching. The interval group was to cover 40 meters in four 10-meter intervals, with two minutes of rest between intervals. The interval-group description says participants would be supported and coached to walk as fast as the; the remaining wording is not reported in the registry record. Posted outcome data list 10 participants in each group.

The study is marked completed, but details that would clarify the conduct of the trial are not reported in the registry record. These include the randomization method, allocation concealment, the identity of the masked party, adherence to the assigned walking approach, and how participants were selected for the randomized subgroup. The record also does not give a sample-size justification or explain how the overall enrollment of 22 corresponds to the posted outcome groups. Such omissions limit what can be concluded about conduct and applicability, even when the posted outcome counts are straightforward to describe.

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:

Analysis population for the primary outcome, as defined in the registry: Number of participants who completed 40 meter ambulation without adverse event or significant change in vital signs

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 Characterize Number of Participants Who Tolerate Continuous vs Interval 40m Walk., measured over 1 day.

The primary endpoint counts participants who completed a 40-meter walk without an adverse event or significant change in vital signs. The registry says this was evaluated over one day. It is a binary, participant-level outcome: each participant either meets the stated completion-and-tolerability definition or does not. The posted values are counts, rather than a continuous measure of walking speed, distance beyond the target, or change in vital signs.

This endpoint is relevant to the study’s stated pilot focus on tolerability of continuous versus interval walking. Comparing the counts gives a direct description of how many participants in each group met the endpoint definition. It does not, by itself, capture all aspects of feasibility. In particular, it does not report how closely the location system recorded patient movement, how complete the movement records were, or how the system’s records compared with actual movement. Although those questions appear in the broader study description, no location-system accuracy result is posted as the primary outcome.

The definition includes both completion and the absence of an adverse event or significant vital-sign change. The record does not define what counted as a significant change, how vital signs were measured, or how adverse events were assessed during the walk. Those details matter for interpreting how consistently the endpoint could be applied. The endpoint therefore provides a compact description of the stated tolerability criterion, while leaving its operational details unclear.

7. Results Posted in the Registry

• Interval Ambulation: 100.0% (10/10) versus 100.0% (10/10) on control; risk difference 0.0 percentage points (95% CI 0.0 to 0.0), risk ratio 1.00 (1.00–1.00); unadjusted two-proportion z-test p = n/a.

8. Statistical Interpretation

9. Statistical Methods Explained

What does a count endpoint represent?

The primary outcome is a count of participants meeting a defined condition: completing the 40-meter walk without an adverse event or significant change in vital signs. The registry labels the outcome as a participant count. In general, a count endpoint records how many people satisfy a criterion, whereas a continuous endpoint records a measured quantity such as distance or time. For this trial, the posted count can be understood only in relation to the stated endpoint definition. The record does not provide a separate count of participants who did not meet the criterion or describe how incomplete walks were classified.

A count can be presented alongside the number of participants assessed in each group. The record lists 10 participants for the continuous group and 10 for the interval group, and it reports that each group’s count meeting the endpoint was 10. These are group-level summaries. They do not show which participants experienced particular changes, how the assessment was made, or whether observations were missing. The registry does not report participant-level data.

What do the risk difference and risk ratio describe?

In general, a risk difference compares the proportions meeting an outcome in two groups by subtracting one group’s proportion from the other. A risk ratio compares those proportions as a ratio. These measures express different views of a group comparison: the difference is on an absolute scale, while the ratio is relative. The posted comparison reports a risk difference of 0.0 and a risk ratio of 1.0. Both are consistent with the equal observed counts recorded for the two groups.

These effect measures are descriptive estimates based on the observed participants. They do not determine whether the groups are equivalent, and they do not make the endpoint more precise than the underlying data allow. A risk difference of 0.0 means the posted group proportions are the same in this dataset; a risk ratio of 1.0 likewise indicates equal observed proportions. Neither result rules out a difference in a larger population.

Why can an all-success result be difficult to interpret?

In general, when every observed participant meets a binary endpoint, the observed proportion is at its upper boundary. There are no observed failures in the posted outcome groups to help characterize how often the endpoint might not be met in a wider population. Standard methods can behave differently at boundaries, and interval estimates can depend strongly on the method selected. The registry does not state which method was used for its comparison interval or whether the interval accounts for the small group sizes.

The posted interval for the risk difference runs from 0.0 to 0.0, and the posted interval for the risk ratio runs from 1.0 to 1.0. Because the method is not reported, these intervals cannot be independently interpreted as a particular conventional confidence-interval procedure. Their zero width should not be taken to mean there is no sampling uncertainty. A statistical interval is intended to communicate uncertainty about an estimate under stated assumptions; its meaning depends on the method and assumptions. Those details are absent from the registry record.

What does randomization contribute?

In general, random allocation aims to make treatment groups comparable with respect to factors that might affect outcomes, including factors that are not measured. This can support a fairer comparison than assigning groups based on participant preference or clinical judgment. The record labels the study randomized, but does not report how the random sequence was generated, how assignments were concealed, or how the randomized subgroup was selected. The label alone does not establish that these procedures were implemented in a particular way.

The study is also described as single-masked, but the registry does not identify who was masked or what information was concealed. Participants and staff may be aware of the walking format, but the record does not specify masking arrangements. It is therefore not possible to assess the role masking may have played in outcome assessment.

What do the sample-size assumptions mean?

The registry describes planning illustrations based on the observed effect, equal allocation, a two-sided significance level of 0.05, and a normal approximation. The illustrations are described as targeting stated fractions of the observed effect; for time-to-event outcomes, the planned quantity would be total events, while other outcomes would be expressed as participants per arm. These are planning assumptions, not observed trial outcomes and not evidence of achieved power. The registry record does not report the trial’s own sample-size justification. The calculated planning values are not reported in the record summarized by these results.

In general, a planning calculation estimates the amount of information that might be needed to detect a chosen effect under specified assumptions. Its answer depends on the assumed effect, variability or event rate, design, and statistical method. Using an effect observed in a small pilot as the basis for planning can be especially uncertain. No sample-size rationale, target power, or prespecified effect of interest is reported in the registry record, so the planning assumptions should not be treated as the original design basis.

Why does over-dispersion matter in other settings?

Over-dispersion is a general issue for count outcomes when the observed variation exceeds what a chosen statistical model expects. It can make standard errors too small if the extra variation is ignored. The primary endpoint in this study is a count of participants meeting a binary criterion, not a count of repeated events per participant; the registry does not report an over-dispersion analysis. This concept is therefore not a reported feature of the posted analysis, but it illustrates why statistical methods should match the outcome structure.

10. Confidence Intervals and Precision

The comparison reports a risk difference of 0.0, with interval endpoints of 0.0 and 0.0. It also reports a risk ratio of 1.0, with interval endpoints of 1.0 and 1.0. These are the posted estimates for the primary comparison. They align with the equal observed counts: 10 participants meeting the endpoint in each group, with 10 participants listed in each group.

A confidence interval is generally used to describe the uncertainty around an estimated effect under a particular statistical method and its assumptions. A narrow interval can indicate that the data are compatible with a relatively limited range of effects under that method. The posted intervals have no width, but the registry does not report how they were calculated. They should not be treated as proof of no uncertainty, especially because all participants recorded in each group met the endpoint and the study is described as a small pilot.

With a binary outcome at the boundary of all observed participants meeting the criterion, interval estimates may depend on the statistical procedure. The record does not identify whether the intervals are confidence intervals, give their confidence level, or explain whether they use an exact, approximate, or other method. Those omissions prevent a full assessment of the interval’s coverage properties or the uncertainty it was intended to express. The comparison also reports no p-value or named hypothesis test.

Precision and equality are distinct. The observed difference is 0.0, but that does not mean the true difference must be 0.0. A study can record identical outcomes in its groups while still leaving meaningful uncertainty about what would be seen in a broader population. The posted interval endpoints do not resolve that uncertainty without a stated calculation method and its assumptions. The registry record also does not report an alternative analysis that would allow the estimate’s robustness to be assessed.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure and no posted secondary outcomes. It also lists no analyses. There is therefore no reported set of multiple outcome comparisons or multiple analysis results from which to assess how multiplicity was handled. The registry record does not describe a multiplicity adjustment, a testing hierarchy, or a plan for choosing among outcomes or analyses. This absence should be read as missing reporting, not as evidence that a particular adjustment was or was not used.

The record does not report how missing outcome data were handled. It does not state whether all participants assigned to a group completed the walk, whether all vital-sign assessments were available, or how an uncompleted or unevaluable walk would be classified. The posted group counts list 10 participants in each group and 10 meeting the endpoint in each group, but the record does not provide a participant flow account or describe exclusions from the outcome analysis. The overall enrollment of 22 is not reconciled with the posted outcome groups.

Analysis populations are also not described. The registry does not say whether the primary comparison was based on all randomized participants, those who completed the assigned walking approach, or another population. In general, the choice of analysis population can affect how a randomized comparison is interpreted, particularly when outcomes are missing or participants do not follow the assigned approach. No such details are reported for this study.

The registry does not report an analysis plan, imputation method, sensitivity analysis, or prespecified handling of protocol deviations. It is therefore not possible to determine whether the posted counts reflect the intended primary analysis or a subset defined after study conduct. These reporting gaps do not change the arithmetic description of the posted counts, but they limit assessment of the analysis process and the possibility of bias from missing or excluded observations.

12. 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 serious adverse events for the continuous-ambulation group among 10 participants at risk, with 0 affected, and for the interval-ambulation group among 10 participants at risk, also with 0 affected. It reports 0 deaths in each group. For other adverse events, the record likewise lists 10 participants at risk and 0 affected in each group. No serious adverse-event terms are listed.

These safety figures are counts from the registry record. They describe what was reported for the groups and do not establish that no adverse events could occur in a broader population. The follow-up period and the methods used to collect or classify adverse events are not described in the safety results presented. The primary endpoint’s definition includes absence of an adverse event and absence of significant change in vital signs, but the registry does not provide the threshold or assessment procedures for the vital-sign component.

The serious adverse-event counts should not be confused with a complete account of all postoperative complications or with the primary tolerability endpoint. The record separately reports zero affected for other adverse events, but does not provide event-level descriptions. These data are best read as no serious or other adverse events recorded in the posted group summaries, rather than as proof of no risk.

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

The posted result shows that all participants counted in each outcome group met the registry’s stated criterion for tolerating the 40-meter walk. The recorded counts are equal, and the comparison reports a risk difference of 0.0 and a risk ratio of 1.0. This is a clear description of the recorded outcome, but the small pilot context and limited reporting constrain what can be inferred beyond those observations.

The result does not demonstrate that continuous and interval ambulation are equivalent. Equivalence is a specific statistical claim that requires an appropriate design, a prespecified margin defining acceptable differences, and an analysis suited to that question. The registry does not report an equivalence margin or an equivalence analysis. Nor does the result establish that either approach is superior. Equal observed counts do not, on their own, distinguish between genuinely similar population outcomes and uncertainty from limited information.

The result also does not establish the performance of the real-time location system. The study description says that actual patient movement would be monitored and compared with location-system data, but the posted primary endpoint concerns completion and tolerability of walking. No location-system accuracy, completeness, or agreement result is reported in the registry record. The two aims should not be treated as interchangeable.

Generalization is limited by absent information about participant characteristics, surgical procedures, the selection of the randomized subgroup, and outcome assessment. The record does not define a significant vital-sign change or detail how adverse events were assessed. It also does not report the randomization procedure, analysis population, or missing-data handling. Those gaps make it difficult to assess whether the posted group counts capture the full randomized comparison.

The safety summaries report no serious or other adverse events in either group, and no deaths. This is a statement about events recorded in this trial, not a guarantee about risks in other settings. Overall, the result is useful as a descriptive pilot observation: the recorded participants met the specified walking criterion in both groups. It does not answer all questions about tolerability, comparative effectiveness, or location-system feasibility.

14. Why This Trial Matters Statistically

This trial matters statistically because it illustrates the distinction between a simple observed comparison and a strong conclusion about a population. The two groups have equal posted counts for the primary endpoint, yielding an observed risk difference of 0.0 and a risk ratio of 1.0. Those values are easy to describe, but they do not remove uncertainty about what might occur beyond the participants represented in the record.

The endpoint is binary and all recorded participants meet its criterion. Such boundary results can make statistical intervals sensitive to the method used. Here, the posted intervals have identical endpoints, while the method and confidence level are not reported. This makes the example a useful reminder that an interval’s label or appearance is not enough: interpretation depends on the procedure that produced it and the assumptions it requires.

The study also illustrates the importance of distinguishing outcomes from broader study aims. The registry describes a real-time location system intended to monitor postoperative movement, yet the posted primary result addresses walking tolerability. The available outcome counts cannot answer whether the location system accurately recorded movement. Clear separation of aims helps prevent a tolerability result from being read as evidence about a measurement system.

Finally, reporting details affect how well a randomized pilot can inform later research. Information about the allocation process, analysis population, missing data, endpoint definition, and sample-size rationale would help readers assess reliability and plan follow-up work. The registry does not report those details. The statistical value of the result is therefore primarily descriptive and hypothesis-generating, rather than a definitive comparison of walking approaches or a validation of the location system.

15. 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 outcome groups and enrollment are not reconciled. The registry lists enrollment of 22, while the posted primary outcome lists 10 participants in each group. It does not explain the relationship between overall enrollment and the outcome counts, describe participant flow, or say whether anyone was excluded from the outcome assessment. This limits assessment of how complete the reported comparison is.

The primary endpoint includes completion of the walk without an adverse event or significant vital-sign change, but the registry does not define significant change, specify measurement procedures, or describe adverse-event ascertainment. It also does not report how participants who did not complete the walk or lacked an assessment would be classified. The resulting endpoint count is therefore clear as posted, while its operational application is not fully described.

Details of study conduct and analysis are limited. The record labels the study randomized and single-masked but does not identify the randomization method, the masked party, or how the randomized subgroup was selected. The analysis population, missing-data handling, and statistical method for the comparison intervals are not reported. No analyses are listed, and no p-value or named test is given.

The record does not provide participant characteristics or detail the surgeries represented, making it difficult to judge applicability to other postoperative populations. The broader location-system objective is not addressed by a posted accuracy or agreement result. The registry also does not report a sample-size justification. These are limitations in the available record and should not be taken as proof that the corresponding procedures or analyses were absent in the study itself.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Real-time Location System Feasibility Study — NCT03988751.
• Registry record last updated 2024-02-22; status last verified 2023-07.
• Results first posted 2024-02-22.
• 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.

19. Record Summary

The registry describes a completed randomized, single-masked, parallel feasibility study of continuous versus interval ambulation among patients recovering after surgery requiring inpatient admission to a surgical ward. Wake Forest University Health Sciences is listed as sponsor. The record gives a start date of 2019-06-06, a primary completion date of 2019-06-19, and enrollment of 22.

The primary outcome counts participants who completed a 40-meter walk without an adverse event or significant change in vital signs, assessed over one day. The posted counts are 10 of 10 in each group. The comparison reports a risk difference of 0.0 and a risk ratio of 1.0; the posted interval endpoints are identical within each measure. No analyses or secondary outcomes are listed.

The broader aim concerned monitoring postoperative movement with the Wake Forest Real-time Location System, but the registry record does not report a result on system performance. It also does not report the interval-estimation method, analysis population, missing-data handling, or sample-size justification.