This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Usability Study to Assess the Reveal LINQ Insertable Cardiac Monitor System (NCT01965899), a na na study. The primary outcome is Success of Wireless Transmissions.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01965899 |
| Phase | NA |
| Condition | Syncope, Recurrent Symptomatic Atrial Fibrillation |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 151 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Medtronic Cardiac Rhythm and Heart Failure |
| Results posted | Yes |
2. Clinical Question
Population
The study enrolled patients indicated for an insertable cardiac monitor. The registry record lists syncope and recurrent symptomatic atrial fibrillation as conditions and reports enrollment of 151 subjects. All 151 received a CareLink monitor software update.
Intervention
The intervention was implant of the Reveal LINQ insertable cardiac monitor system. The study purpose was to assess the functionality of the monitor and accompanying system in patients indicated for an insertable cardiac monitor.
Comparator
The study used a single-group model. The registry record does not report a control group or a like-for-like comparator. The listed Holter monitor comparison is a secondary outcome, not a separate randomized study arm.
Primary question
The primary question was what percentage of automatic wireless transmissions from the system were successful within 30 days of implant. The registry record gives the endpoint definition and follow-up context, but the estimate and its 95% confidence interval are not reported in the registry record.
This is a device-usability and system-functionality question, rather than a randomized comparison of alternative treatments. The endpoint concerns the operation of automatic wireless transmission during the stated follow-up period. It does not, on its own, describe the accuracy of atrial fibrillation detection, safety, or patient experience; those topics appear among the secondary outcomes.
The registry record reports 4,511 follow-up days contributed by subjects during their first 30 days. That information describes follow-up exposure, but it does not give the number of transmission attempts, the number that succeeded, or the endpoint percentage. Without those counts or the reported estimate, the extent of transmission success and the precision of the result cannot be assessed from the registry record.
3. Trial Design
The Reveal LINQ Usability Study was registered as NCT01965899 and is listed as completed. Its start is recorded as 2013-09 and its primary completion as 2014-07. The sponsor was Medtronic Cardiac Rhythm and Heart Failure. The phase is listed as NA.
The record describes a single-group study of the Insertable Cardiac Monitor Implant. Allocation is listed as NA, and masking is listed as NONE. These entries do not describe a randomized or masked comparison. The registry record gives enrollment as 151 and states that all 151 subjects received a CareLink monitor software update. Subjects contributed 4,511 follow-up days in their first 30 days.
The study's stated purpose was to assess the functionality of the Reveal LINQ insertable cardiac monitor and accompanying system in patients indicated for an insertable cardiac monitor. The primary endpoint focused on the percentage of successful automatic wireless transmissions within 30 days of implant. Listed secondary outcomes address accuracy of device-detected atrial fibrillation, safety, comparison of device-detected atrial fibrillation with Holter monitoring, implanting physician surveys, and patient experience over time.
The record lists eight outcome measures and zero analyses. It does not report a separate control arm, allocation procedure, or masking procedure beyond the entries noted above. The description of the intervention arm contains no additional details. The registry record does not report a protocol-level account of how implant procedures, follow-up visits, or transmission opportunities were managed, so those aspects should not be inferred from the study title or endpoint description.
Because the design is single-group, the primary endpoint is interpreted as a system performance measure during follow-up, not as an estimate of a difference between treatment groups. The secondary Holter comparison may address agreement or accuracy, but its analysis details and results 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
| Stage | Insertable Cardiac Monitor Implant |
|---|---|
| STARTED | 151 |
| COMPLETED | 145 |
| NOT COMPLETED | 6 |
Analysis population for the primary outcome, as defined in the registry: All 151 subjects received a CareLink monitor software update. Subjects contributed 4,511 follow-up days in their first 30 days.
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.
| Characteristic | Unit | Insertable Cardiac Monitor Implant |
|---|---|---|
| Participants analysed | 151 | |
| Age, Continuous | years | 56.6 (SD 12.1) |
| Sex: Female, Male: Female | Participants | 50 |
| Sex: Female, Male: Male | Participants | 101 |
| Region of Enrollment: Russian Federation | participants | 7 |
| Region of Enrollment: Netherlands | participants | 40 |
| Region of Enrollment: Austria | participants | 28 |
| Region of Enrollment: Belgium | participants | 10 |
| Region of Enrollment: United Kingdom | participants | 8 |
| Region of Enrollment: Slovakia | participants | 25 |
| Region of Enrollment: Australia | participants | 33 |
6. Primary Endpoint
The registry lists the primary outcome as Success of Wireless Transmissions, measured over 30 days.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | 95% Confidence Interval |
| Unit | percentage of successful transmissions |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the percentage of successful automatic wireless transmissions from the system within the first 30 days after implant. It is intended to describe whether the monitor system can transmit automatically during the specified early follow-up period. This is relevant to evaluating system functionality because transmission is part of the accompanying monitoring process.
The registry record identifies the measure as a number expressed in percentage units and specifies a 95% confidence interval as its dispersion measure. It also states that all 151 subjects received a CareLink monitor software update and that subjects contributed 4,511 follow-up days in their first 30 days. The actual percentage, confidence interval limits, and underlying transmission counts are not reported in the registry record.
To interpret a percentage of successful transmissions, it is important to know what counts as a transmission opportunity and how success is defined. The endpoint description does not state those operational details or explain whether the percentage is calculated across all transmission attempts, summarized by participant, or constructed in another way. Those details affect the meaning and precision of a percentage, particularly when participants contribute different numbers of attempts.
The endpoint is distinct from the secondary outcomes concerning atrial fibrillation detection, safety, and survey responses. A transmission success estimate would describe the specified system function; it would not by itself establish detection accuracy, clinical benefit, or the experience of participants. Since the estimate is not reported, the registry record does not allow the endpoint's observed performance or precision to be judged.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a clear primary measurement target: the percentage of successful automatic wireless transmissions within 30 days of implant. It also identifies the intended precision summary as a 95% confidence interval. However, it does not report the observed percentage or the interval limits. The central result therefore cannot be interpreted quantitatively from this record. No statement about the level of transmission success or how precisely it was estimated is supported by the posted results in this record.
The follow-up context is informative but does not replace the endpoint result. The record reports that all 151 subjects received a CareLink monitor software update and that subjects contributed 4,511 follow-up days in their first 30 days. Follow-up days are not transmission attempts, and they do not reveal how many attempts occurred or how many succeeded. They therefore cannot be used to reconstruct the endpoint or its uncertainty.
The single-group design also sets limits on interpretation. The primary endpoint describes system performance during the observed follow-up; it is not a randomized contrast against another monitor or a control group. The record lists a secondary comparison of device-detected atrial fibrillation with Holter monitoring, but its results and analysis details are not reported in the registry record. That outcome should not be conflated with the primary transmission endpoint.
Several other outcomes are listed, including safety, device-detected atrial fibrillation accuracy, and surveys. Their presence indicates that the study addressed multiple aspects of usability and system performance, but the record does not provide corresponding results or analysis details. The record lists eight outcome measures and zero analyses, so outcome names alone should not be treated as findings.
The record's adverse-event entries report 31 affected among 151 at risk for serious adverse events and 39 affected among 151 at risk for other adverse events. Those counts describe the safety entries and are separate from the primary endpoint. The record also lists serious adverse-event terms with percentages. These entries do not explain whether events were considered related to the device or procedure, how event collection was conducted, or how the terms were selected.
Accordingly, the registry record supports a description of the design, endpoint, follow-up context, and recorded safety counts, but not a conclusion about the magnitude or precision of the primary result. Missing outcome estimates should not be replaced by assumptions based on study purpose, follow-up exposure, or the existence of listed secondary outcomes.
9. Statistical Methods Explained
What does a percentage endpoint represent?
In general, a percentage is a ratio of a count meeting a defined condition to a count of eligible opportunities, expressed on a percentage scale. For this study, the condition is a successful automatic wireless transmission. To interpret the percentage, readers need a clear definition of both success and the opportunities included in the denominator. The registry record states the endpoint purpose and timeframe but does not report those operational definitions or the underlying counts.
Repeated transmission attempts can create a statistical complication: attempts from the same participant may be more alike than attempts from different participants. If each attempt is treated as independent when attempts within a participant are correlated, the analysis may overstate the amount of independent information and produce an interval that is too narrow. In general, methods that account for clustering or summarize information at the participant level can address this dependence, but the registry record does not report which approach was used.
Variation in the number of attempts per participant also matters. A percentage pooled over all attempts gives more weight to participants with more attempts, while a participant-level summary gives each participant a different role in the estimate. Those approaches answer different questions. The record reports 4,511 follow-up days in the first 30 days, but not the distribution of days or transmission attempts by participant, so the exact weighting implied by the endpoint cannot be identified.
What does the confidence interval communicate?
In general, a confidence interval expresses uncertainty around an estimated quantity under the assumptions of the analysis method. A narrower interval indicates greater statistical precision for that estimate; a wider interval indicates less precision. It does not show whether the endpoint is clinically important, whether the design rules out bias, or whether the result applies to other settings. The registry record names a 95% confidence interval as the dispersion measure but does not report its limits or the method used to calculate it. Precision therefore cannot be assessed from the posted information.
A confidence interval for a percentage depends on the amount and structure of information, not just the nominal number of participants. When observations are clustered, an interval that ignores this structure may not reflect the uncertainty appropriately. When the number of eligible opportunities is not reported, readers cannot independently assess the amount of information behind the estimate. No recalculated endpoint estimate or interval can be obtained from the counts and follow-up exposure stated in the registry record.
How should a single-group result be read?
In general, a single-group endpoint estimates a quantity within the studied group over the defined observation period. It does not estimate a between-group treatment effect. That distinction is important because the registry design is single-group, allocation is listed as NA, and masking is listed as NONE. The primary endpoint is consequently a system-function measure, not evidence from a randomized contrast. A separate secondary outcome compares device-detected atrial fibrillation with Holter monitoring, but the registry record does not report its methods or results.
Comparisons with a benchmark would require a stated benchmark and an analysis plan appropriate to it. Neither is reported for the primary endpoint in the registry record. Without a comparator or an explicitly reported benchmark, a high or low result cannot be interpreted as a relative effect. The primary estimate itself is also absent, so even a descriptive characterization is unavailable.
What do the planning illustrations mean?
In general, sample-size planning calculations ask how much information a future study might need to detect a specified effect under stated assumptions. They are not observed outcomes and do not measure the probability that a completed study has detected a real effect. The planning assumptions associated with this study describe a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and effects defined as fractions of the observed effect. Those assumptions describe planning illustrations, not the actual single-group design recorded for this study.
The planning notes distinguish participant counts per arm for outcomes other than time-to-event outcomes, and total event counts for time-to-event calculations using the Schoenfeld approach. This distinction is general: a time-to-event calculation is typically driven by the number of observed events, whereas other calculations may be expressed as participants per arm. The registry record does not report the calculation results in the information available for this analysis, and no sample-size value should be inferred from the assumptions alone. Such calculations are planning illustrations, not observed power.
How does over-dispersion affect a count or proportion?
In general, over-dispersion means that observed variability is greater than a simple statistical model expects. For repeated device transmissions, extra variation can arise when participants differ in their transmission patterns or when attempts within a participant are dependent. A model that does not account for this variability can give uncertainty estimates that are too optimistic. Appropriate methods depend on the data structure and the estimand, such as whether the target is success per transmission attempt or a participant-level average. The registry record does not report a model, a dispersion assessment, or an adjustment for repeated observations.
These methodological considerations explain why an endpoint label and follow-up exposure alone are insufficient for a full statistical interpretation. The numerator, denominator, participant-level structure, estimate, interval, and analysis method are all relevant. The registry record does not report enough detail to reproduce or independently assess the primary analysis.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists eight outcome measures, including the primary transmission endpoint and secondary outcomes concerning atrial fibrillation detection, safety, Holter comparison, and surveys. When a study assesses multiple outcomes, general statistical practice distinguishes the primary question from additional or exploratory questions. Testing many outcomes can increase the chance of finding a nominally unusual result by chance. Possible approaches include prespecifying a hierarchy, adjusting for multiple testing, or treating secondary analyses as descriptive. Which approach was used in this study is not reported in the registry record.
The record lists zero analyses. It does not provide test results, confidence intervals for outcomes, or a multiplicity procedure. It also does not report whether analyses were prespecified, whether interim analyses occurred, or whether any outcome definitions changed. These details should not be inferred from the list of outcomes.
Missing-data handling and analysis populations are also not described. The record does not state how incomplete transmission records, missed follow-up, withdrawals, or unavailable survey responses were handled. It does not define an intention-to-treat, per-protocol, safety, or other analysis population for the primary endpoint. Although it reports that all 151 subjects received a CareLink monitor software update and that subjects contributed 4,511 follow-up days in their first 30 days, these details do not establish which observations were included in the endpoint analysis.
In general, missingness can affect interpretation if the probability of an unobserved measurement is related to the outcome or participant characteristics. Methods may depend on why data are missing and on the target estimand. Since neither the amount nor handling of missing primary endpoint data is reported, the effect of missingness on the result cannot be assessed.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Insertable Cardiac Monitor Implant | 31 | 151 | 20.5% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Insertable Cardiac Monitor Implant | 39 of 151 |
Most frequent serious adverse event terms
| Event term | Organ system | Insertable Cardiac Monitor Implant |
|---|---|---|
| Atrial fibrillation | Cardiac disorders | 9 of 151 |
| Atrial flutter | Cardiac disorders | 3 of 151 |
| Ventricular tachycardia | Cardiac disorders | 3 of 151 |
| Atrial tachycardia | Cardiac disorders | 2 of 151 |
| Syncope | Nervous system disorders | 2 of 151 |
| Lung disorder | Respiratory, thoracic and mediastinal disorders | 1 of 151 |
| Implant site pain | General disorders | 1 of 151 |
| Urinary tract infection | Infections and infestations | 1 of 151 |
| Cerebral haemorrhage | Nervous system disorders | 1 of 151 |
| Ligament sprain | Injury, poisoning and procedural complications | 1 of 151 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Insertable Cardiac Monitor Implant |
|---|---|---|
| Implant Site Pain | General disorders | 39 of 151 |
Serious events with the highest arm-level rate: atrial fibrillation (6.0%), atrial flutter (2.0%), ventricular tachycardia (2.0%), atrial tachycardia (1.3%), syncope (1.3%).
The registry record reports a single intervention group, with 151 at risk for serious adverse events and 31 affected. For other adverse events, it reports 151 at risk and 39 affected. These are safety counts, not estimates of the primary wireless-transmission endpoint. The registry record does not report deaths; the death entry is not reported in the registry record.
The listed serious adverse-event terms and percentages are atrial fibrillation, 6.0%; atrial flutter, 2.0%; ventricular tachycardia, 2.0%; atrial tachycardia, 1.3%; syncope, 1.3%; and lung disorder, 0.7%. The record does not provide event counts for each term or explain whether the percentages refer to participants, events, or another denominator. The term list should therefore be read as reported, without converting the percentages into counts or assuming that the categories are mutually exclusive.
In general, adverse-event counts describe events observed and recorded under a study's safety procedures. They do not by themselves establish that an event was caused by the device or implant. The registry record does not report attribution, event-collection procedures, or comparative safety data. With a single group and no like-for-like control, these figures cannot quantify a relative safety difference.
12. What the Result Does, and Does Not, Mean
The record establishes the study's purpose and primary measurement target: assessing the percentage of successful automatic wireless transmissions during the first 30 days after implant. It also reports enrollment of 151, the CareLink monitor software update, and 4,511 follow-up days contributed during that period. These details describe the study context, not the primary endpoint result.
The key limitation for interpreting the central question is that the registry record does not report the observed transmission percentage or its 95% confidence interval. It also does not report transmission counts or the operational definition of a successful attempt. As a result, the posted information cannot establish the observed level of system performance or how precisely it was estimated.
The single-group design means the primary endpoint is descriptive of system function in the study group; it is not a randomized comparison against an alternative system. The secondary outcome comparing device-detected atrial fibrillation with Holter monitoring is distinct, and its results are not reported in the registry record. The listed safety counts and serious adverse-event terms likewise do not supply evidence about transmission success or detection accuracy.
In general, a measured system-function outcome is only one component of a broader assessment. It does not alone establish diagnostic accuracy, clinical effectiveness, safety relative to another device, or the experience of patients and clinicians. Those questions require their own outcomes and analysis details. Although such outcomes are listed in the record, their results and analytic methods are not reported.
The appropriate reading is therefore bounded: the registry record describes a completed, single-group usability study and names its primary endpoint, but it does not provide the primary numerical result needed to judge that endpoint. It is not possible to infer success or failure from the study's title, purpose, follow-up exposure, or the existence of secondary outcomes.
13. Why This Trial Matters Statistically
This study raises a useful statistical distinction between a device-function target and a comparative treatment effect. The primary question concerns successful automatic wireless transmissions over a defined follow-up period. Because the design is single-group, the endpoint is not a randomized estimate of a difference between systems or treatment strategies. Recognizing that distinction helps prevent a within-group performance measure from being interpreted as a comparative effect.
The endpoint also illustrates why repeated observations require careful definition. A percentage based on transmission attempts can be affected by how attempts are counted, how success is defined, and whether multiple attempts from the same participant are treated as related. In general, dependence among repeated observations affects uncertainty estimates. The registry record does not report the details needed to assess how this issue was handled, making the gap between a stated endpoint and an interpretable estimate especially important.
The record names a 95% confidence interval, which signals that precision was intended to accompany the primary estimate. Yet without the estimate, interval limits, and analytic details, readers cannot judge either the result's magnitude or its uncertainty. This demonstrates that outcome definitions alone are not a substitute for posted results.
Finally, the study lists outcomes spanning system function, detection accuracy, safety, and user experience. These are related aspects of usability but answer different questions and may require different statistical methods. The record's outcome list helps define the scope of the investigation; the absence of reported analyses means the listed questions cannot be treated as answered findings.
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 principal trial-specific limitation in the registry record is the absence of the primary endpoint estimate and its confidence interval. The record states that the endpoint is the percentage of successful automatic wireless transmissions within 30 days, but does not report the percentage, interval limits, transmission counts, or a detailed success definition. The result and its precision therefore cannot be assessed.
The endpoint's denominator and unit of analysis are not described in enough detail to determine whether the analysis is based on attempts, participants, or another summary. The record reports 4,511 follow-up days, but not the distribution of follow-up or transmissions across subjects. It also does not report whether repeated attempts were accounted for statistically.
The single-group design has no reported like-for-like control arm, limiting comparative interpretation. Allocation is listed as NA and masking as NONE. The record does not report a protocol-level analysis plan, multiplicity approach, missing-data procedure, analysis population, interim analyses, or sample-size justification. These items are not reported in the registry record.
Although the registry lists secondary outcomes, their results and analysis details are not reported. Safety entries include affected counts and percentages for selected serious adverse-event terms, but the record does not specify event attribution or the denominator used for the term percentages. Deaths are not reported in the registry record. These gaps constrain interpretation of both the system-function question and the broader safety and usability questions.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Usability Study to Assess the Reveal LINQ Insertable Cardiac Monitor System — NCT01965899.
- Registry record last updated 2016-09-23; status last verified 2016-06.
- Results first posted 2016-09-23.
- 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.
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18. Record Summary
NCT01965899, titled “Usability Study to Assess the Reveal LINQ Insertable Cardiac Monitor System,” is listed as completed. The record gives a start of 2013-09, primary completion of 2014-07, sponsor Medtronic Cardiac Rhythm and Heart Failure, enrollment of 151, phase NA, allocation NA, and masking NONE. The model is single-group.
The primary endpoint was the percentage of successful automatic wireless transmissions within 30 days of implant, with a 95% confidence interval specified as the dispersion measure. The record states that all 151 subjects received a CareLink monitor software update and contributed 4,511 follow-up days in their first 30 days. The primary estimate and interval are not reported in the registry record.
The record lists eight outcome measures and zero analyses. Safety entries report 31 affected among 151 at risk for serious adverse events and 39 affected among 151 at risk for other adverse events. Deaths are not reported in the registry record.