Diagnostic Yield of an Ambulatory Patch Monitor in Unexplained Emergency Department Syncope: A Pilot Study (PATCH-ED): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Diagnostic Yield of an Ambulatory Patch Monitor in Unexplained Emergency Department Syncope: A Pilot Study (PATCH-ED) (NCT02683174), a na na study. The primary outcome is Number of Ambulatory Patch Monitor Participants Having Significant Symptomatic Arrhythmia.

2. Clinical Question

3. Trial Design

PATCH-ED is registered as a pilot study of ambulatory patch monitoring among patients with syncope that remained unexplained after emergency department assessment. The registry lists a single study arm and a single-group model. Allocation is recorded as NA, and masking is listed as none. This is not a randomized comparison: the study design does not assign participants to patch monitoring versus a concurrent control intervention.

The registry describes the intervention as a novel ambulatory patch, identified as the ZIO® XT Patch. Its arm description says the patch continuously records heartbeats for up to 14 days. The study arm also includes BNP and hs-troponin I measurements at 0 and 3 hours after emergency department attendance. The description records the intended procedures but does not establish the extent to which every participant completed each procedure or wore the device for a particular duration.

The registry reports enrollment of 86 and a completed status. The recorded study start is 2015-11-01, and primary completion is 2017-06-13. The sponsor is NHS Lothian. These administrative details locate the study record but do not substitute for a report of outcome estimates or an account of how participants were selected and followed.

The design is suited to describing what was detected and reported during the study, including arrhythmia findings, participant experience, device wear time and serious outcomes. Without a control group, it cannot isolate the effect of the patch from other care, participant characteristics or the natural course of events. Additional protocol details, including further eligibility criteria and the statistical analysis plan, are not reported in the registry record.

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

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 Number of Ambulatory Patch Monitor Participants Having Significant Symptomatic Arrhythmia, measured over 90 days.

The primary endpoint is the count of participants with significant symptomatic arrhythmia, with a 90-day timeframe. It is a participant-level outcome: the question is whether a participant meets the stated definition, rather than how many separate rhythm episodes occur. The record lists a range of qualifying findings, including ventricular tachycardia, bradycardia, sick sinus syndrome, sinus pause, atrioventricular block, junctional or idioventricular rhythm, supraventricular tachycardia, and atrial flutter or fibrillation at specified rates. Some listed findings have symptomatic criteria; the record also says arrhythmias will be classified as symptomatic or asymptomatic according to concurrent symptoms.

As a general statistical point, a prespecified endpoint gives a study a consistent outcome to describe and helps readers understand what counts as an event. Here, the endpoint is intended to capture significant rhythm findings in relation to unexplained syncope, rather than every rhythm variation that might be detected during monitoring. The registry's detailed criteria matter because changing a threshold or symptom requirement could change which participants qualify.

The available record does not report the observed primary endpoint count, a proportion, or an uncertainty interval. As a result, the endpoint's definition can be explained, but its frequency in the study cannot be interpreted from the registry information available for this analysis.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes PATCH-ED as a single-group study, with one arm and no masking. This design is important for interpreting all of its statistics. An outcome count in one group can describe what was observed in that group, but it does not provide a direct estimate of a difference between two assigned treatments. In a randomized comparison, allocation can support a balanced comparison of groups; no such randomized comparison is recorded.

What does a participant count represent?

The primary outcome is defined as a count of participants meeting the significant symptomatic arrhythmia criteria during the 90-day timeframe. A count answers how many participants met the definition, not how many rhythm episodes occurred. If one participant had multiple qualifying episodes, a participant-level count would still count that participant once. That distinction is general to outcomes defined as participants with an event; the registry does not report the primary count for PATCH-ED.

Counts are often interpreted alongside the number of participants assessed for the outcome. A proportion can express the count relative to an eligible denominator, while an uncertainty interval can show the statistical imprecision in that estimate. The record lists enrollment and safety denominators, but it does not report the denominator used for the primary outcome or its result. It would not be appropriate to infer that every enrolled participant contributed complete primary-outcome data.

Why do endpoint definitions matter?

Definitions set the boundary between an event and a non-event. The primary definition lists rhythm types and rate or duration criteria, and it also distinguishes symptoms occurring with an arrhythmia from asymptomatic findings. This specificity helps make the intended classification more reproducible. At the same time, interpretation depends on how each criterion was applied, how rhythm recordings were reviewed, and how symptoms were linked to a recording. Those operational details are not reported in the registry record.

As a general point, a broad composite definition can capture several clinically different event types in one endpoint. The total count then reflects the combined definition, while the individual components may have different implications and frequencies. Readers would need component results and clear adjudication methods to understand which findings contributed to an overall endpoint. Such primary component results and adjudication details are not reported in this record.

What can a confidence interval tell the reader?

In general, a confidence interval expresses sampling uncertainty around an estimate. It is not a guarantee that the true value lies within a particular interval, nor does it account automatically for bias, missing outcomes, measurement errors or limits of the study design. A point estimate without an interval gives less information about precision. For PATCH-ED, the record does not report the primary estimate or a confidence interval, so neither the event frequency nor its precision can be assessed.

A p-value, when used, evaluates how compatible data are with a specified null model under the assumptions of a test. It does not measure the size or importance of an effect, and it does not correct shortcomings in design. The registry entries for this analysis report no outcome analyses or p-values. There is also no treatment contrast to test in the single-group design. Any analysis comparing the group with an external benchmark would require details and assumptions not reported in the registry record.

How should the sample-size illustration be read?

The planning illustration is described as using an effect based on the observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It describes planning for a stated fraction of that effect, not a feature of the registered single-group design. The record also says that time-to-event planning uses a total event count, while other planning results are expressed as participants per arm. No numerical planning outputs are reported in the registry record for this analysis.

In general, a sample-size calculation is a planning exercise based on assumptions about the target effect, variability or event rate, type I error and desired power. It does not show that a study had a particular probability of detecting an effect after the data were collected. Sample sizes derived from observed effects are especially sensitive to how those effects were estimated; an unstable estimate can produce misleading planning targets. The illustration should therefore be treated as hypothetical planning information, not as evidence that the PATCH-ED study had a particular power. It is not an observed-power result, and its two-arm assumptions should not be mistaken for the study's actual single-group design.

Why can over-dispersion matter?

As a general statistical concept, over-dispersion occurs when count data vary more than a model assumes. If a model underestimates that variability, its uncertainty estimates can be too small and its inferences too confident. The registry entries do not identify a count model, a dispersion estimate or an analysis of over-dispersion for PATCH-ED. Since the primary result and analysis are not reported, there is no basis to say whether this issue affected the study's results.

More broadly, a statistical method should match the endpoint, data structure and design. Repeated rhythm events, participant-level event status and time until detection are different data structures and may call for different methods. The registry lists outcomes of these different kinds but does not report the methods used to analyse them. A method cannot be inferred solely from the name of an outcome.

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("Study Group")
n      <- c(86)
events <- c(9)
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  Study Group  86  9  10.5  4.9  18.9  5.6  18.7  5.7  18.7

11. Multiplicity, Missing Data and Analysis Populations

The registry lists seven outcome measures and identifies one primary endpoint: the count of participants with significant symptomatic arrhythmia. It also lists secondary outcomes involving detection time, arrhythmia, ease of use, device wear time, referral and all-cause serious outcome. The registry record lists zero analyses. It does not report a multiplicity strategy, such as a prespecified hierarchy or adjustment for examining multiple outcomes.

As a general statistical issue, when several outcomes or analyses are examined, the chance of finding at least one apparently unusual result can increase if each is interpreted independently. Adjustment or a clearly prespecified testing hierarchy can help control that issue, but the appropriate approach depends on the study aims and analysis plan. Without a reported plan and results, it is not possible to determine how multiplicity was handled or whether it materially affects interpretation.

The record does not report a missing-data plan, outcome-specific completion counts, or methods for handling missing measurements. This matters because the patch's intended wear period, symptom reports, laboratory measurements and later outcomes may have different completeness. In general, complete-case analysis, imputation and other approaches rely on different assumptions; missingness can affect both the estimate and its precision.

Analysis populations are also not described in the registry entries. The enrollment count alone does not establish how many participants were included in each outcome analysis or whether all enrolled participants were analysed. The record does not report an intention-to-treat population, a per-protocol population, or another defined analysis set. Consequently, the scope of any outcome estimate cannot be assessed from the available registry information.

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.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: major adverse cardiac events [mace] (30.2%), significant arrhythmia (27.9%), permanent pacemaker or defibrillator placement (4.7%), coronary artery bypass graft or coronary artery stent (2.3%), initiation of antiarrhythmia medical therapy (2.3%).

The safety record lists 86 participants at risk for serious adverse events and 26 affected, alongside 86 at risk and 0 affected for other adverse events. It lists one death. These figures describe the registry's adverse-event reporting; they do not identify the cause of each event or establish whether an event was related to the patch, the monitoring process, or another aspect of care.

The serious-event terms listed include major adverse cardiac events at 30.2%, significant arrhythmia at 27.9%, permanent pacemaker or defibrillator placement at 4.7%, coronary artery bypass graft or coronary artery stent at 2.3%, initiation of antiarrhythmia medical therapy at 2.3%, and significant structural heart disease at 1.2%. The record does not explain whether these categories overlap, how terms were assigned, or the denominator underlying each percentage. They should not be added together or read as mutually exclusive categories.

Serious adverse events and the primary endpoint are distinct reporting concepts, even when their terminology may overlap. The safety figures do not supply the missing primary endpoint count and cannot be used to infer it. A single-group safety description also cannot establish comparative risk: there is no control arm against which to assess whether event frequency differed under another approach.

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

PATCH-ED addresses a diagnostic-monitoring question in a group of patients with syncope that remained unexplained after emergency department evaluation. The registry describes an ambulatory patch that records heartbeats for up to 14 days, alongside BNP and hs-troponin I testing at 0 and 3 hours after emergency department attendance. Its primary endpoint is defined around participants with significant symptomatic arrhythmia within 90 days. These features explain what the study set out to observe.

The central limitation for interpreting results from this record is that the primary endpoint result is not reported in the registry record. Without that result, the frequency of the endpoint cannot be stated, and its precision cannot be evaluated. Other outcomes are named, but their numerical results are not included in the registry record for this analysis. The serious-event counts provide safety-record information, not the missing primary-outcome result.

The design also limits what any single-group outcome could establish. Without a concurrent comparator, an observed event count cannot show how outcomes would differ under another monitoring strategy, or whether the monitoring approach caused a change. Patient characteristics, other care and event ascertainment could all contribute to the observed experience. The record does not report an analysis that addresses these alternatives.

General interpretation of diagnostic monitoring also depends on how often participants wore the device, whether symptoms were recorded accurately, how rhythm findings were reviewed, and whether follow-up was complete. The registry lists device wear time and ease of use among its outcomes, but does not report their values. It therefore does not allow assessment of monitoring completion or participant experience from the available record.

The study is best read as a registered pilot investigation with a defined monitoring strategy and clinically focused outcome definitions, alongside reported serious-event entries. It does not, on this record, provide a quantitative primary-endpoint result or a controlled estimate of comparative benefit or harm. Such conclusions would require outcome estimates, their uncertainty, fuller methods and, for comparative claims, a suitable comparison design.

14. Why This Trial Matters Statistically

This study raises statistical questions that recur in diagnostic monitoring research. A device can record events over time, while the clinical endpoint may depend on whether a rhythm finding meets a threshold and coincides with symptoms. Defining the endpoint at the participant level, specifying the observation window, and distinguishing symptomatic from asymptomatic findings are important for making an outcome interpretable.

The design also illustrates the difference between describing detection and estimating a comparative effect. A single group can provide a setting for reporting event types, participant experience and device wear time. It cannot by itself separate the contribution of monitoring from other influences. This distinction is essential when interpreting a pilot study: feasibility or descriptive information and causal evidence answer different questions.

Precision is another key issue. A count without an estimate of uncertainty can be difficult to generalize beyond the people observed, especially when outcome frequency is unknown. The registry record does not report the primary endpoint result or an interval, so readers cannot judge how precise the primary finding would be. This gap is distinct from the question of whether an endpoint definition is clinically relevant.

Finally, the registry illustrates why analytic transparency matters. Multiple outcomes are listed, but the analysis plan, missing-data approach, analysis populations and multiplicity handling are not reported in the available record. Those details help readers distinguish prespecified analyses from exploratory ones and understand which participants contributed to each estimate. Together, clear endpoint rules, complete reporting, and a design aligned with the intended inference are central to sound interpretation of clinical monitoring studies.

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 available registry record has important limitations for statistical interpretation. It identifies the primary endpoint and its timeframe but does not report the primary endpoint result, its denominator, an uncertainty interval, or a test statistic. The listed secondary outcomes likewise have no numerical results in the registry record for this analysis. The record therefore permits explanation of the study question and endpoint definition, but not a quantitative assessment of the main outcome.

The single-group design has no concurrent control and is not randomized. Any descriptive outcome cannot establish a difference relative to another monitoring strategy or usual care. The registry does not report detailed eligibility criteria, participant characteristics, outcome adjudication procedures, or how arrhythmia recordings were linked to symptoms. These omissions limit assessment of applicability and measurement reliability.

Important analysis details are also not reported in the registry record: the statistical methods, analysis populations, missing-data handling, multiplicity plan, and outcome-specific numbers assessed. The record does not indicate how completely participants wore the patch or completed follow-up, despite listing wear time as an outcome. These details would be needed to assess the potential effects of incomplete monitoring or missing outcome information.

The safety listing is informative as a record of reported events, but the available information does not establish event attribution, category overlap, or the denominator for each listed percentage. The single-group design also prevents comparative safety inference. Finally, a planning illustration based on an observed effect and two-arm assumptions does not describe the actual single-group design or establish observed power. Its numerical outputs are not reported in the registry record for this analysis.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Diagnostic Yield of an Ambulatory Patch Monitor in Unexplained Emergency Department Syncope: A Pilot Study (PATCH-ED) — NCT02683174.
• Registry record last updated 2019-12-03; status last verified 2016-09.
• Results first posted 2019-12-03.
• 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.

19. Record Summary

PATCH-ED is a completed, single-group pilot study sponsored by NHS Lothian. The registry reports enrollment of 86 and describes ambulatory patch monitoring for patients with syncope unexplained after emergency department evaluation. The patch continuously records heartbeats for up to 14 days; the study arm also includes BNP and hs-troponin I testing at 0 and 3 hours after emergency department attendance.

The primary endpoint is the count of participants with significant symptomatic arrhythmia within 90 days. Its definition includes specified rhythm criteria and classification of arrhythmias as symptomatic or asymptomatic. The primary endpoint result and its precision are not reported in the registry record. The record lists 26 participants with serious adverse events among 86 at risk, 0 with other adverse events among 86 at risk, and one death. These safety entries do not provide a controlled comparison or replace the absent primary outcome result.