Evaluation of a New 6 Minute Walk Test Smartphone App in Patients With Pulmonary Hypertension: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of a New 6 Minute Walk Test Smartphone App in Patients With Pulmonary Hypertension (NCT04633538), a registered phase not stated study. The primary outcome is Percentage of Participants Who Perform App-based Home 6MWT.

2. Clinical Question

These details define a question about use of a measurement tool, rather than a comparison of treatments for pulmonary hypertension. The central issue is whether participants performed home tests with the app; related outcomes address how app measurements compare with clinic measurements and whether community testing is repeatable and followed as intended.

3. Trial Design

The registry record describes the 6-APP Study as an evaluation of a new 6 Minute Walk Test smartphone app in patients with pulmonary hypertension. Its brief summary says the study compares the standard 6 minute walk test with an app. The listed intervention is a device, the 6MWT smartphone app, and the arm description refers to patients using it for tests at the clinic and in the community.

Enrollment is listed as 30. The study status is completed, with a start date of 2018-01-15 and a primary completion date of 2019-08-28. Oxford University Hospitals NHS Trust is listed as sponsor. These registry entries describe the study record, but do not establish how many participants completed each test or contributed data to each outcome.

The primary outcome is the percentage of participants who perform app-based home 6MWT, with a 6 months timeframe. Secondary outcomes concern walked-distance differences between physiologist-measured clinic tests and app measurements in indoor and outdoor settings, test-retest reliability of community-based testing, and compliance with the community monitoring regime.

The record does not state an allocation method. It does not describe a randomized comparison, and the listed arm information does not provide a like-for-like control comparison. Therefore, the standard-test and app measurements should be understood as measurement comparisons, not as evidence from randomized treatment groups. The record does not report further details of the study design, visit schedule, or planned statistical analysis.

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.

Population: We approached 33 patients; of these, 30 were eligible and consented to participate. Five patients withdrew from the study (3 were lost to follow-up, 1 died, and 1 considered the study not to be relevant any longer).

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants Who Perform App-based Home 6MWT, measured over 6 months.

The primary endpoint is described as the percentage of participants who perform an app-based home 6MWT during a timeframe of 6 months. It focuses on whether home testing was undertaken, rather than on the distance walked or a change in health. The registry record labels the unit as participants and the parameter as a participant count, so it does not fully specify how the percentage is calculated or what denominator is used.

A measure of test completion can describe whether a monitoring approach was used in the study setting. It is distinct from a measure of measurement accuracy: completing a test does not by itself show that its distance agrees with a clinic measurement. The listed secondary outcomes address other questions, including distance differences, test-retest reliability, and compliance with community monitoring.

The registry record does not report the primary endpoint result, the number of participants who performed a home test, or the analysis denominator. It also does not explain how incomplete, repeated, or unusable tests were handled. Without these details, the outcome definition can be described, but the extent of home-test completion cannot be quantified from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods describe how observations are converted into estimates and how uncertainty is assessed. The registry record identifies outcomes but does not report the analysis methods or results. The explanations below are general statistical context, not claims about procedures used in this study.

What kind of outcome is the primary endpoint?

The primary endpoint concerns whether a participant performs an app-based home 6MWT, a binary outcome: each participant either meets the stated completion definition or does not. For a binary outcome, an analysis may report a count and a proportion. A proportion needs a clearly defined denominator, such as participants eligible for the outcome or participants with an observed status. The registry record calls the endpoint a percentage, lists the unit as participants, and identifies a participant count as the parameter. It does not report the denominator or operational definition used to decide that a home test was performed.

These details matter because different denominators or completion rules can lead to different interpretations. For example, an analysis of all enrolled participants answers a different question from an analysis restricted to participants with recorded follow-up. This is a general distinction; the registry record does not say which approach was used.

How should estimates and uncertainty be read?

An estimate is a summary of the observed data, such as a proportion for a binary endpoint or a difference in walked distance for a measurement comparison. A confidence interval communicates uncertainty around an estimate under the chosen statistical method and its assumptions. It is not a guarantee that the true value lies within the interval. A p-value, when reported, describes how compatible the data are with a specified null hypothesis under the analysis assumptions; it does not measure clinical importance or the probability that the null hypothesis is true.

The registry record does not report estimates, confidence intervals, or p-values for the outcomes. Therefore, readers cannot assess the magnitude or precision of the results from the registry entry. Statistical significance, if it had been assessed, would not substitute for examining the estimate, its uncertainty, and the design that produced it.

What do the measurement outcomes ask?

A comparison of walked distances asks whether measurements made under different conditions tend to differ. The listed comparisons involve physiologist measurements at the clinic and app measurements in indoor or outdoor settings. A mean difference can describe average disagreement, but it may not show how well measurements agree for individual participants. Methods for agreement can examine both the average difference and the spread of individual differences. These are general concepts; the registry record does not state which summaries or methods were used.

Test-retest reliability concerns the consistency of repeated measurements under the conditions being studied. Reliability is not the same as agreement with a reference measurement: repeated app tests might be consistent while still differing from clinic measurements. The registry record names a community-based test-retest outcome but gives no repeat-testing schedule, reliability statistic, or result.

Compliance with a monitoring regime concerns whether the requested monitoring was carried out. A useful interpretation depends on what counted as compliance, the period over which it was assessed, and how missing monitoring records were treated. Those definitions and results are not reported in the registry record.

What do planning calculations mean?

Sample-size planning estimates are design illustrations, not observed results. The stated planning approach uses a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; it describes the target effect as a stated fraction of the observed effect. It also distinguishes participants per arm for non-time-to-event outcomes from total events for time-to-event outcomes. These assumptions describe an illustration and do not establish that the study itself used that design or analysis.

The record does not describe a randomized two-arm comparison, and its listed arm information is not a like-for-like control comparison. Thus, an illustration based on equal allocation between two arms should not be read as a description of the enrolled study or as a justification for its enrollment. A planning calculation is also not observed power: it does not show how likely the completed study was to detect an effect after data collection. The registry record does not report its sample-size justification or a prespecified statistical analysis plan.

Why do design and analysis details matter?

Measurements collected from the same participant are related, rather than independent. General statistical methods for paired or repeated measurements account for that relationship. Treating related observations as independent can misstate uncertainty. The registry record does not describe the data structure or the method used for the clinic and community comparisons. Similarly, over-dispersion is a general concern when count data vary more than a simple statistical model expects; it is not a reason to assume a particular model for this binary completion endpoint. The registry entry does not report a model choice or diagnostic assessment.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("6MWT App Group")
n      <- c(30)
events <- c(30)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  6MWT App Group  30  30  100.0  88.4  100.0  88.6  100.0  88.8  99.9

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists a primary outcome and secondary outcomes covering distance comparisons, test-retest reliability, and compliance. Examining multiple outcomes can raise a multiplicity issue: the chance of at least one apparently unusual result can increase when many hypotheses are tested. Statistical approaches may adjust for multiple testing or define selected outcomes as exploratory. The registry record does not report a multiplicity strategy, identify which secondary analyses were confirmatory, or provide results for the listed outcomes. It is therefore not possible to assess how multiple comparisons were handled.

Missing-data methods also affect interpretation. For the primary outcome, a participant without a recorded home test could represent a test not performed, an unrecorded test, or an unavailable outcome; the registry record does not explain how such cases were classified. It also does not report missing-data counts, reasons for missingness, or an imputation or sensitivity-analysis plan. These distinctions matter because excluding participants with missing data can change the population represented by an estimate.

The record lists enrollment of 30 but does not report analysis populations for individual outcomes. It does not say whether analyses used all enrolled participants, only participants with recorded measurements, or another defined group. Although the study status is completed, that status does not supply the missing analysis details. No statistical analyses are listed in the registry record.

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 record lists the 6MWT App Group with 30 participants at risk for serious events and 0 participants affected. It also lists 30 at risk for other events and 0 affected, alongside 1 death. These are the posted safety figures; they should be read as registry counts, not as a complete description of the circumstances or causes of events.

The record does not provide serious-event terms, and it does not report the event definitions, assessment period, relationship of events to app use, or further details about the death. A listed count of 0 affected for serious or other events does not establish that no unrecorded events occurred, nor does it demonstrate that the device is safe. Interpretation depends on how events were sought, classified, and reported, details that are not reported in the registry record.

These figures are safety reporting information and do not answer the primary question about completion of home tests or the secondary questions about measurement performance. They should not be used to infer a causal relationship between the app and any event.

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

The registry record establishes that the 6-APP Study evaluated a 6MWT smartphone app in patients with pulmonary hypertension. The primary outcome concerns performance of app-based home testing during a 6 months timeframe. Other listed outcomes address walked-distance comparisons, repeatability of community testing, and compliance with monitoring. This information describes what the study set out to assess.

The registry record does not report the primary outcome value, measurement-comparison results, reliability estimates, or compliance results. It therefore does not show whether participants performed home tests at any particular level, whether app and clinic distances agreed, or whether community measurements were repeatable. Without estimates and uncertainty measures, the magnitude and precision of any findings cannot be evaluated.

The study is not described as a randomized comparison, and the registry record does not state allocation. The listed information is therefore not a basis for interpreting the app and standard test as randomized groups. Measurement comparisons can answer questions about differences between methods, but their interpretation depends on how and when tests were conducted and how participant-level pairing was handled. Those details are not reported.

Enrollment of 30 and completed status are administrative details, not outcome findings. They do not show how many participants completed home testing or contributed data to each analysis. The safety counts likewise do not establish a causal link to app use or provide a full account of safety monitoring.

In short, the record conveys the study question and its outcome domains but does not report findings that answer them. It cannot support a conclusion about the app's measurement performance, uptake, or safety. Those conclusions would require reported results and sufficient information about outcome definitions, participants analyzed, missing data, and methods.

14. Why This Trial Matters Statistically

This study raises several statistical questions that are important when evaluating a measurement tool. First, uptake and measurement performance are different outcomes. Whether a participant performs a home test describes use of the monitoring approach; it does not establish whether the resulting distance is accurate or agrees with a clinic measurement. The registry record separates these topics across its primary and secondary outcomes.

Second, comparisons between measurement settings require attention to paired observations. Clinic and app measurements may come from the same participant, so the analysis should reflect that relationship. Differences in setting or measurement procedure may also affect how results should be interpreted. The record lists indoor and outdoor app comparisons but does not describe the analysis methods or report results.

Third, community monitoring combines measurement questions with implementation questions. Test-retest reliability asks about consistency; compliance asks whether monitoring was carried out. Clear definitions and transparent reporting are needed to distinguish an unperformed test from a missing record and to understand the denominator for each outcome. The registry record does not provide these details.

Finally, a completed status does not guarantee that results are available in the registry record. Here, the listed outcomes give a useful outline of the questions, but the absence of reported estimates prevents assessment of magnitude and precision. This illustrates why outcome definitions, analysis populations, uncertainty measures, and results all matter alongside a study's stated aims.

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 registry record leaves important details about this study unreported. It does not state allocation, give further eligibility criteria, or describe how the app tests and clinic tests were scheduled. The arm description identifies app use at the clinic and in the community, while the brief summary refers to comparison with the standard test; the record does not explain the precise design of those comparisons.

The primary outcome is described as a percentage, but its unit and parameter are listed as participants and a participant count. The record does not specify the denominator, the operational definition of a performed home test, or how incomplete and unusable tests were classified. It also does not report outcome values or the number analyzed for each measure.

For the distance, reliability, and compliance outcomes, the registry record gives titles but not methods, results, or uncertainty estimates. It does not describe how repeated observations were handled, how missing data were addressed, or whether multiple testing was considered. The statistical analysis plan and sample-size justification are not reported in the registry record.

Finally, the safety information lacks event terms and context. The record does not report assessment procedures, event timing, or relationship to app use. These reporting gaps limit interpretation of the study's outcomes and safety counts; they do not, by themselves, indicate what the unreported results would have been.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Evaluation of a New 6 Minute Walk Test Smartphone App in Patients With Pulmonary Hypertension — NCT04633538.
• Registry record last updated 2025-03-07; status last verified 2025-02.
• Results first posted 2025-03-07.
• 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 6-APP Study evaluated a smartphone app for the 6 Minute Walk Test in patients with pulmonary hypertension. The registry lists enrollment of 30, a completed status, and Oxford University Hospitals NHS Trust as sponsor. The recorded study dates are 2018-01-15 and 2019-08-28 for start and primary completion.

The primary outcome concerns participants performing app-based home testing during a timeframe of 6 months. Secondary outcomes address clinic-versus-app walked-distance differences, community test-retest reliability, and compliance with community monitoring. The registry record does not report results or statistical analyses for these outcomes.

Safety figures list 0 participants affected by serious events, 0 affected by other events, and 1 death in the 6MWT App Group. Event definitions and further context are not reported in the registry record. Allocation and the statistical analysis plan are also not reported.