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 Dabigatran Adherence Pilot Intervention for Patients With Atrial Fibrillation (NCT01578044), a randomized na study. The primary outcome is Gaps Days Between Prescription Refills for Dabigatran, Rivaroxaban, and Apixaban.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01578044 |
| Phase | NA |
| Condition | Atrial Fibrillation |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 12 |
| Arms in the primary outcome | n/a |
| Lead sponsor | VA Office of Research and Development |
| Results posted | Yes |
2. Clinical Question
Population
The clinical context is patients with atrial fibrillation who are prescribed oral anticoagulants. The primary outcome refers to refill gaps for dabigatran, rivaroxaban, and apixaban. The registry record does not report detailed eligibility criteria or describe the enrolled participants beyond the trial enrollment.
Intervention
The intervention is described as behavioral and includes patient education about dabigatran, with information on risks, benefits, and potential side effects. Education was to be reinforced during monthly interactive voice response calls and pharmacy service calls. Tele-monitoring is also named, but its details are not reported in the registry record.
Comparator
The comparator is usual care. The record does not provide further detail about what usual care involved during the pilot, so its specific activities cannot be characterized from this description.
Primary question
The planned comparison was whether the intervention and usual-care groups differed in the number of days without medication coverage between prescription refills. The registry describes calculating refill-gap days over 3 and 6 months using pharmacy dispensing dates and days posted. It reports no analyzed comparison or result, so the clinical question cannot be answered from the posted results.
The study addresses a practical adherence-measurement question: whether support intended to reinforce medication-taking can be evaluated using pharmacy refill records. Refill gaps capture continuity of medication supply, rather than directly confirming that a patient took each dose. The endpoint also treats an early refill differently from a period without coverage: the record says a negative gap-day value indicates a refill was received before the prior prescription was completed. The registry does not report how participants were selected, how the intervention was delivered beyond the described elements, or whether the planned measure could be calculated for every participant.
3. Trial Design
The registry record describes a completed randomized, parallel-group pilot with single masking. It lists an enrollment of 12 and two groups: an intervention group and a usual-care group. The record lists the phase as NA. It does not identify who was masked, so the meaning and practical scope of single masking cannot be determined from the registry entry.
The intervention is classified as behavioral. Its description includes patient education on dabigatran risks, benefits, and potential side effects, with monthly reinforcement during interactive voice response calls and pharmacy service calls. Tele-monitoring is also mentioned, but the available description is incomplete; its procedures are not reported in the registry record. The control arm is described as usual care, without further specification.
The start is listed as 2012-01, primary completion as 2014-06, and status as completed. These record fields describe the study timeline and administrative status; they do not establish that the primary outcome was analyzed or that results were posted.
The primary measure concerns refill-gap days for dabigatran, rivaroxaban, and apixaban, assessed over 3 and 6 months. The planned calculation uses pharmacy refill data, including dispensing dates and days posted, and calls for comparing total gap days between intervention and usual care. The registry identifies no outcome analysis, and no analysis results are reported. Therefore, the design description documents the intended comparison, but does not provide an estimate of the intervention-control difference or its uncertainty.
The record does not report the randomization procedure, allocation concealment, details of masking, adherence to the assigned intervention, or participant flow. It also does not describe the statistical analysis plan. These omissions limit assessment of how the trial was implemented and how its planned comparison would have been analyzed.
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 | Intervention Group | Usual Care |
|---|---|---|
| STARTED | 6 | 6 |
| COMPLETED | 6 | 6 |
| NOT COMPLETED | 0 | 0 |
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 | Intervention Group | Usual Care Group | Total |
|---|---|---|---|---|
| Participants analysed | 6 | 6 | 12 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 0 | 0 | 0 |
| Age, Categorical: >=65 years | Participants | 6 | 6 | 12 |
| Age, Continuous | Years | 70.5 (67 to 78) | 69.3 (63 to 84) | 69.9 (63 to 84) |
| Sex: Female, Male: Female | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Male | Participants | 6 | 6 | 12 |
| Region of Enrollment: United States | participants | 6 | 6 | 12 |
6. Primary Endpoint
The registry lists the primary outcome as Gaps Days Between Prescription Refills for Dabigatran, Rivaroxaban, and Apixaban, measured over 3 and 6 months.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | days |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the number of days between prescription refills when medication coverage is not available, based on pharmacy refill data. The registry says investigators planned to use the date a prescription was dispensed and the number of days posted to calculate gap days for dabigatran, rivaroxaban, and apixaban. The measure was to be summarized over 3 and 6 months, with total gap days compared between the intervention and usual-care groups.
Refill gaps are used as an indirect measure of medication adherence because they indicate whether refills were obtained in time to maintain a continuous supply. They do not establish whether medication was taken as prescribed on each day. The measure can also reflect factors other than a person's medication-taking behavior, such as changes in dispensing or prescription supply, but the registry does not discuss how such circumstances were handled in this pilot.
The record explicitly notes that a negative gap-day value indicates that a participant received a refill before the previous prescription was completed. Thus, negative values represent early refills under the registry's definition, rather than days without medication coverage. The record does not report how these values were incorporated into any analysis.
No observed endpoint values, group summaries, treatment-effect estimate, confidence interval, or test result are reported. The endpoint description therefore explains what the investigators intended to measure, not what the trial found.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record gives the planned endpoint and trial structure, but not an analyzed primary-outcome comparison. It reports no analysis results for refill-gap days, and the outcome is explicitly not reduced to one comparison because it involves multiple categories or time points. There is consequently no posted estimate of how the groups differed, no measure of precision for such a difference, and no result that can establish whether the intervention changed refill continuity.
The enrollment is listed as 12, with 6 at risk in each group in the adverse-event record. These group counts describe the registered enrollment and safety fields; they do not supply missing outcome data or indicate how many participants contributed to a particular refill-gap calculation. The registry does not report the primary outcome's group-specific sample sizes, observed values, variability, or missingness.
The study is identified as a pilot. In general, pilot studies can help evaluate the feasibility of an intervention and the practical collection of outcome data, while estimates from small pilot samples can be imprecise. That general consideration does not establish what this trial was designed to assess beyond its registered objective. A specific feasibility objective, progression criterion, or sample-size justification is not reported in the registry record.
The endpoint was planned for 3 and 6 months, creating more than one time point for potential description or comparison. The registry does not say whether one time point was primary for inference, whether the two time points were analyzed separately or jointly, or how any repeated measurements would be handled. It also does not report an adjustment for multiple comparisons or identify an analysis population.
The absence of a posted estimate is not evidence that the groups had the same refill gaps. It means the registry record does not provide the outcome data needed to assess the direction, size, or precision of a group difference. Similarly, the zero affected counts in the safety record should be read only as the adverse-event figures entered there, not as evidence about an unreported adherence outcome or as proof that no events occurred outside the recorded categories.
The record gives planning assumptions for sample-size illustrations, including a two-sided significance level of 0.05, equal allocation, a normal approximation, and effects expressed as fractions of an observed effect. Such illustrations are not observed power and do not replace an analysis of trial outcomes. Since no single primary comparison or observed effect is reported, those assumptions cannot support an interpretation of the intervention's effect from this record.
9. Statistical Methods Explained
The registry labels the trial randomized, single-masked, and parallel. These terms describe aspects of the intended design, but the entry does not explain the randomization method or identify who was masked. It also does not provide the statistical analysis plan. The methods that can be described are therefore limited to the registered design and the planned endpoint calculation.
What does randomization contribute?
In general, randomization assigns participants to study groups by chance. When carried out appropriately, it can help make groups comparable with respect to both measured and unmeasured characteristics at the start of a study. This does not guarantee balance in a small trial, and it does not remove the need to report participant flow, outcome completeness, and the analysis approach. The registry confirms randomized assignment but does not describe sequence generation, concealment, or implementation. Those details are not reported in the registry record.
What does the parallel design mean?
In a parallel-group design, participants are assigned to a group and the groups are compared over the study period. This differs from a design in which the same participant receives multiple study conditions in sequence. The record lists intervention and usual-care groups, but does not report whether participants changed treatment, how deviations from assignment were handled, or which analysis population was planned.
How is the refill-gap outcome constructed?
The registered calculation uses pharmacy dispensing dates and the number of days posted for each prescription. The intended measure is the number of gap days between refills, accumulated for the specified assessment periods. In general, this kind of measure translates refill timing into an indicator of medication availability. It is a proxy for adherence, not direct observation of dose-taking. The record notes that negative values indicate early refills; it does not explain how early fills were carried forward, capped, or otherwise treated in the analysis.
The endpoint is described over 3 and 6 months. In general, when outcomes are measured at multiple times, an analysis needs to clarify whether each time point is a separate outcome, whether one is the primary assessment, or whether measurements are combined in a model. The registry does not report which approach was intended. It also does not provide the distribution of gap days or an analysis model, so it is not possible to assess whether a particular model would fit the observed outcome data.
Why does outcome distribution matter?
As a general statistical matter, count-like outcomes may be skewed, may include many zeros, and may show greater variability than a simple model assumes. Over-dispersion means that observed variability exceeds what a chosen model expects; if ignored, uncertainty estimates can be unreliable. Refill-gap days may also include negative values according to the registry's definition, so the exact data structure matters when choosing a model. These are general considerations, not descriptions of the observed data: the registry record reports no endpoint distribution, summary statistics, or model choice.
What does a confidence interval communicate?
In general, a confidence interval expresses the precision of an estimated effect under the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval, while an interval spanning effects in different directions may leave the direction uncertain. This trial record reports no primary-outcome effect estimate or interval, so precision cannot be evaluated. A p-value, if reported, would address compatibility of the data with a specified null model under the analysis assumptions; it would not by itself describe the size or practical meaning of an effect. No primary-outcome p-value is reported.
What can the planning assumptions tell us?
The record describes sample-size illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. It also says the target effect is expressed as a stated fraction of the observed effect. These are planning assumptions, not trial findings. Planning illustrations are not observed power. Because the registry does not report a single analyzed comparison or an observed primary-outcome effect, the assumptions cannot be interpreted as a completed sample-size justification for this study. The trial's own design rationale and sample-size justification are not reported in the registry record.
Overall, the record specifies a randomized comparison and a refill-based measure, but does not provide the analysis methods needed to reproduce or evaluate an outcome estimate. Details of covariate adjustment, handling of missing refills or missing assessments, multiplicity, and analysis populations are not reported.
10. Multiplicity, Missing Data and Analysis Populations
The primary outcome is described at 3 and 6 months and includes refill-gap days for dabigatran, rivaroxaban, and apixaban. These features create potential choices about which comparisons to emphasize and how to interpret multiple results. The registry record does not report a prespecified hierarchy of time points or medications, a multiplicity adjustment, or a plan for controlling the interpretation of multiple tests. No primary-outcome analyses are listed.
Missing data handling is not reported in the registry record. The entry does not say how investigators planned to address absent pharmacy records, incomplete follow-up, medication changes, or participants without a calculable refill-gap measure. It also does not provide the completeness of the outcome data by group. Without these details, the extent to which the planned outcome could be calculated and compared cannot be assessed.
The analysis population is not reported. The registry does not say whether the intended comparison would include all randomized participants, only those with available pharmacy data, or another defined group. It does not describe how departures from assigned group or protocol would be handled.
The record lists no analyses for the primary outcome. Therefore, there are no reported estimates from which to evaluate multiplicity procedures, missing-data assumptions, or differences among analysis populations. These omissions should be distinguished from evidence that any particular method was or was not used; the methods are simply not reported in the registry record.
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 |
|---|---|---|---|
| Intervention Group | 0 | 6 | 0.0% |
| Usual Care Group | 0 | 6 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Intervention Group | 0 of 6 |
| Usual Care Group | 0 of 6 |
The adverse-event record lists an intervention group and a usual-care group, with 6 participants at risk in each group. It records 0 participants affected by serious adverse events and 0 affected by other adverse events in each group. These are the figures entered in the registry record and should be read within the categories and group counts shown there.
The registry does not list any serious adverse-event terms. The deaths field is null for both groups, which means death counts are not reported in the registry record; null should not be interpreted as a reported count of zero. The entry also does not provide event descriptions, severity details, assessment procedures, or information about how completely adverse events were collected.
Zero affected participants in the recorded fields does not establish that the intervention has no safety risks. The record gives limited event information from a pilot enrollment and does not report the primary adherence outcome. These safety entries should not be used to draw conclusions about refill-gap days or the intervention's effect on adherence.
12. What the Result Does, and Does Not, Mean
The record documents a randomized pilot comparing an adherence-support intervention with usual care, and it defines refill-gap days as the intended primary measure. It also records an enrollment of 12 and describes the broad elements of the intervention. These details show what the investigators planned to evaluate and how they intended to measure refill continuity.
The record does not provide observed primary-outcome values, a comparison between groups, an effect estimate, a confidence interval, or an analysis result. It therefore does not show whether refill gaps were shorter, longer, or similar between groups. The lack of a reported result is not evidence of no difference; it is an absence of the information needed to estimate a difference.
Even if a group comparison were available, refill-gap days would represent medication availability inferred from pharmacy records, not direct confirmation of dose-taking. The registry's definition also allows negative values for early refills. Interpreting the measure would require details about its observed distribution and how early refills and incomplete records were handled, which are not reported.
The pilot label and enrollment indicate a small-scale study record, but the registry does not report a specific feasibility objective, progression criterion, or sample-size justification. No conclusion about the study's statistical power can be drawn from the planning assumptions; sample-size illustrations are not observed power. The available information is insufficient to determine the precision of any treatment-effect estimate because none is posted.
The appropriate statistical reading is limited: the registered design and endpoint can be described, but the primary question remains unanswered in the posted results. The safety record contains zero affected counts in the recorded categories, while death counts are not reported. Neither the adherence result nor a broad safety conclusion can be inferred from these entries.
13. Why This Trial Matters Statistically
This trial is statistically notable for the distinction between a clearly described measurement plan and the absence of an analyzed result. A registry can identify the intended endpoint and comparison without supplying the data needed to estimate an effect. Here, refill-gap days are described using pharmacy records, but no endpoint values or group comparison are reported.
The endpoint also illustrates that adherence measures are operational definitions. Refill timing can indicate whether medication was available, yet it cannot verify that doses were taken. The registry explicitly treats early refills as negative gap-day values, making the handling and interpretation of the measure important. Those analytic details are not reported.
Multiple time points and multiple medications appear in the primary outcome description. In general, this can make a prespecified analysis plan important for distinguishing a central comparison from additional descriptive or exploratory results. The record does not identify a hierarchy among these elements or explain how multiplicity would be considered.
The study's pilot context makes precision particularly relevant. A small enrollment can yield uncertain estimates, but no estimate or interval is available to quantify uncertainty. The record's planning assumptions do not remedy that limitation, and planning illustrations should not be confused with observed power or trial findings.
For clinical researchers and biostatisticians, the record demonstrates why outcome definitions, analysis populations, missing-data methods, and reported estimates all matter. Without these elements, readers can understand the intended question but cannot assess the magnitude, direction, or precision of the result. The registry's completed status does not itself substitute for posted outcome analyses.
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 main limitation for interpreting this trial is that the registry record reports no primary-outcome analysis. There are no group summaries, estimates, confidence intervals, or test results for refill-gap days. The intended outcome is described at 3 and 6 months and references three anticoagulant medications, but the record does not reduce those elements to a single comparison.
The enrolled population is not described in detail. Although atrial fibrillation is the listed condition and the trial context concerns oral anticoagulants, eligibility criteria, participant characteristics, and medication-specific enrollment are not reported. The intervention description is also incomplete: tele-monitoring is named, but its details are not reported in the registry record.
Important design and analysis details are absent. The record does not describe the randomization procedure, allocation concealment, who was masked, the statistical model, covariate adjustment, or analysis populations. It also does not report outcome completeness, missing-data handling, the treatment of early refills in analysis, or how multiple time points and medications were addressed.
The safety entry provides affected counts and at-risk counts but lacks event descriptions and broader collection details. Death counts are not reported. These entries therefore offer limited context and should not be treated as a comprehensive safety assessment.
Finally, the registry's completed status and planning assumptions do not provide evidence of an analyzed result. The trial's sample-size justification and any feasibility criteria are not reported. Without outcome estimates, neither the direction of the primary comparison nor its statistical precision can be assessed.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Dabigatran Adherence Pilot Intervention for Patients With Atrial Fibrillation — NCT01578044.
- Registry record last updated 2018-10-10; status last verified 2018-09.
- Results first posted 2015-06-15.
- 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
NCT01578044 is listed as a completed, randomized, single-masked, parallel pilot of an adherence-support intervention versus usual care. The registry lists an enrollment of 12 and identifies atrial fibrillation as the condition. The intervention description includes dabigatran education reinforced during monthly interactive voice response and pharmacy service calls; tele-monitoring is mentioned without further details.
The planned primary outcome is refill-gap days for dabigatran, rivaroxaban, and apixaban over 3 and 6 months, calculated from pharmacy dispensing dates and days posted. The record states that negative gap-day values indicate early refills. No primary-outcome analysis or result is reported, and the record does not provide a single comparison.
The safety entry records 0 serious and 0 other adverse events affecting participants in each group, with 6 at risk in each. Death counts are not reported. Statistical analysis methods, missing-data procedures, analysis populations, and multiplicity handling are not reported in the registry record.