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 Prospective Evaluation of an Extended Interval of INR Follow-up in a VA Anticoagulation Service (NCT02392104), a na na study. The primary outcome is Rates of Participant Accrual.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02392104 |
| Phase | NA |
| Condition | Anticoagulation |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 51 |
| Arms in the primary outcome | n/a |
| Lead sponsor | William S. Middleton Memorial Veterans Hospital |
| Results posted | Yes |
2. Clinical Question
Population
Veterans receiving warfarin at the Anticoagulation Clinic at William S. Middleton Memorial Veterans Hospital were the intended population. The study focused on participants whose warfarin dose remained stable and whose INR values were within the goal range of 2-3, including lab variation. The record reports that 107 individuals were invited and 51 participants enrolled. Further eligibility details are not reported in the registry record.
Intervention
Participants continued to receive usual care from the anticoagulation clinic, with the interval between INR follow-up visits changed under an extended interval protocol when the stable-dose and INR conditions were met. The study intervention is therefore a change in follow-up timing for eligible participants, rather than a comparison of different anticoagulant drugs.
Comparator
There was no separate control arm: the study is described as single-group, and all participants were assigned to the intervention arm. Usual care continued apart from the INR follow-up interval, but the registry record does not describe a concurrent group receiving the usual follow-up schedule. Any comparison with baseline is a within-study comparison, not a randomized comparison between groups.
Primary question
The primary endpoint is rates of participant accrual. It measures the number of people who enrolled relative to the number invited, rather than a clinical effect of the extended interval. The record describes 107 individuals invited and 51 participants enrolled. Feasibility, safety, and acceptability were also aims: the registry description mentions patient satisfaction, provider satisfaction, confidence and knowledge, bleeding and thromboembolic events, and changes in appointment frequency and time in therapeutic range.
3. Trial Design
This is a prospective, single-group study of an extended INR follow-up interval in a Veterans Affairs anticoagulation service. The registry lists the study as completed, with a start date of 2015-03-27 and a primary completion date of 2017-06-25. Enrollment was 51. The phase and allocation are listed as NA, masking is NONE, and the model is SINGLE GROUP. All participants were in the intervention arm; there is no randomized or concurrent control arm described.
Participants continued usual anticoagulation clinic care, except that the interval between INR tests could be extended under the protocol. The brief description states that extended scheduling applied when a participant remained on a stable warfarin dose and INR values were within the goal range of 2-3, including lab variation. The record does not report the exact interval schedule, the operational definition of stable dose, or other detailed eligibility criteria.
The primary outcome is rates of participant accrual, described as the number enrolled compared with the number invited, over up to 2.25 years. Secondary outcomes include change in appointment frequency from baseline to end of study, bleeding and thromboembolic events from baseline, change in time in therapeutic range from baseline, and patient satisfaction through total DASS score. The brief description also says satisfaction was assessed at various points and provider satisfaction, confidence, and knowledge were to be analyzed. The detailed timing and analysis populations are not reported in the registry record.
This design can describe implementation and outcomes among participants who entered the study, but it does not provide a randomized estimate against usual follow-up. The registry record does not report a statistical analysis plan or outcome analyses.
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 | Extended INR Follow-up Interval Group |
|---|---|
| STARTED | 50 |
| COMPLETED | 39 |
| NOT COMPLETED | 11 |
Reasons for not completing this period:
| Reason | Extended INR Follow-up Interval Group |
|---|---|
| discontinuation of warfarin | 3 |
| bleeding event | 1 |
| transferred care to another doctor | 2 |
| INR goal range changed | 1 |
| admitted to skilled nursing facility | 3 |
| INRs drawn by visiting nurse services | 1 |
Analysis population for the primary outcome, as defined in the registry: 107 invited to participate in the study, not all enrolled or started the 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.
| Characteristic | Unit | Intervention Arm |
|---|---|---|
| Participants analysed | 50 | |
| Age, Continuous | years | 71.4 (SD 7.6) |
| Sex: Female, Male: Female | Participants | 1 |
| Sex: Female, Male: Male | Participants | 49 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 |
| Race (NIH/OMB): White | Participants | 49 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 1 |
| Region of Enrollment: United States | participants | 50 |
| HAS-BLED score | units on a scale | 1.8 (SD 0.9) |
6. Primary Endpoint
The registry lists the primary outcome as Rates of Participant Accrual, measured over up to 2.25 years.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is rates of participant accrual. It is described as the number of participants who enroll compared with the number of individuals invited. This outcome addresses a practical feasibility question: whether eligible people approached through the service enter a study that uses an extended follow-up protocol. It is not a measure of INR control, bleeding, thrombosis, or patient satisfaction, and it does not establish the clinical effect of changing visit intervals.
The registry record states that 107 individuals were invited and that 51 participants enrolled. These are the relevant recruitment counts in the record. An accrual proportion or rate is not reported in the registry record, and no separate endpoint result or statistical analysis is posted. The overall enrollment figure should not be mistaken for an analysis of the number who completed the protocol or met its stable-dose and INR conditions; those counts are not reported.
Accrual is useful in an implementation study because a protocol may be operationally feasible only if people can be recruited and enrolled in the intended setting. However, interpretation depends on how invitations were made, who was eligible, and why invited individuals did or did not enroll. Those details are not reported in the registry record. The endpoint therefore gives a limited view of recruitment feasibility, rather than a comprehensive account of acceptability or safety.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The record describes an implementation study with 51 enrolled participants and 107 individuals invited. Its primary endpoint concerns accrual, not comparative treatment efficacy. The study has one intervention arm, and all participants were assigned to it. There is no randomized control group against which to estimate what would have happened under a usual follow-up schedule. The posted information therefore supports description of the study setup and selected counts, but not a causal conclusion about the effect of extended INR intervals.
The primary outcome description calls for comparing enrollment with invitations, but no accrual result or statistical analysis is posted separately. The record also lists secondary outcomes addressing appointment frequency, bleeding and thromboembolic events, time in therapeutic range, and patient satisfaction. It does not post outcome analyses, estimates of change, confidence intervals, or p-values. The direction and precision of any change in these outcomes cannot be assessed from the registry record.
The safety record lists 50 participants at risk for serious events, with 15 affected, and 50 at risk for other events, with 19 affected. It reports zero deaths. These counts describe events in the intervention arm; without a concurrent comparison arm, they do not quantify how safety would differ under another follow-up schedule. The serious-event terms and their listed percentages provide additional descriptive information, but they do not establish whether events were caused by the protocol. Causal attribution is not reported in the registry record.
The study's stated aims include feasibility, safety, and acceptability among Veterans on stable-dose warfarin. Its description specifies that extended scheduling was intended for participants who remained on a stable dose and had INR values within the goal range of 2-3, including lab variation. Results among such participants would need to be interpreted with attention to how eligibility, follow-up, and outcome ascertainment were handled; those details are not reported. The record also does not report the number who actually followed the extended interval or completed follow-up.
Accordingly, the available information is best read as a registry description with enrollment and adverse-event counts, not as a complete report of the study's clinical outcomes. The absence of posted analyses means there is no reported estimate of changes in appointment frequency or time in therapeutic range, and no reported patient satisfaction result. It also means the precision of the listed counts and their relationship to the study's objectives cannot be evaluated through inferential statistics.
9. Statistical Methods Explained
The registry record identifies a single-group design and lists no statistical analyses. The following statistical concepts explain how the listed outcomes would ordinarily be interpreted; they are general explanations, not claims about analyses performed in this study.
What does a single-group design allow?
A single-group study follows participants under one intervention condition. It can describe who enrolled, what events were recorded, and how measured outcomes changed over time if those results are reported. For outcomes measured at baseline and later follow-up, a within-person comparison can describe observed change among participants with measurements at both times. Such a comparison does not by itself isolate the effect of the intervention: changes could also reflect time, other care, participant characteristics, or incomplete follow-up. A concurrent control group and an appropriate design would be needed to make a stronger comparative causal assessment.
Here, the record says all participants were in the intervention arm and describes usual clinic care except for the interval between INR tests. It does not report a control arm or a statistical analysis plan. The registry's allocation entry is NA, and the study model is SINGLE GROUP. These design features limit interpretation to descriptive evidence unless additional comparative information is reported elsewhere.
How should accrual be understood?
Accrual is a recruitment outcome. In general, it is assessed by relating the number who enroll to the number invited or found eligible, with a clear definition of the recruitment denominator and time period. The record describes the primary endpoint as enrolled participants versus invited individuals and gives 107 invited and 51 enrolled. It does not report an accrual analysis or explain whether all invited individuals met eligibility criteria. No accrual rate should be inferred from the counts without an explicitly reported result.
What does a confidence interval communicate?
In general, a confidence interval expresses the statistical uncertainty around an estimated quantity under a specified analysis and its assumptions. A narrow interval indicates greater precision than a wide interval, but neither width nor statistical significance alone establishes clinical importance or freedom from bias. No confidence intervals or other uncertainty estimates for the outcomes are reported in the registry record. The counts alone cannot show how precisely an underlying event frequency or change has been estimated.
Why do outcome definitions and analysis populations matter?
In general, an outcome needs a clear definition, observation window, and method of ascertainment. An analysis population should also specify which enrolled participants contribute to each result, including how missing measurements, withdrawals, or protocol deviations are handled. The registry describes several outcomes, including appointment frequency, bleeding and thromboembolic events, time in therapeutic range, and patient satisfaction through total DASS score. Detailed definitions, denominators for these outcomes, and rules for incomplete observations are not reported in the registry record. Consequently, their measurement and comparability over time cannot be assessed.
How should safety counts and planning illustrations be read?
In general, an adverse-event count is descriptive unless the analysis defines the relevant denominator, follow-up period, and method for attributing events. An event count is not automatically a rate, and participants with events are not necessarily the same as the total number of events. The registry lists numbers at risk and affected for serious and other events, but does not report a comparative safety analysis or a causal attribution method.
Any hypothetical sample-size illustration based on an observed effect is a planning exercise, not evidence of achieved power and not a replacement for the study's design. The record's planning assumptions describe a two-arm calculation with equal allocation, a two-sided significance level of 0.05, and a normal approximation. Those assumptions do not match the listed single-group design and should not be read as the trial's actual allocation or as a reported protocol justification. The sample-size justification and statistical plan are not reported in the registry record. No observed-effect estimate or resulting planning value is reported in the information available for interpretation.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists eight outcome measures and identifies several secondary outcomes: appointment frequency, bleeding and thromboembolic events, time in therapeutic range, and patient satisfaction through total DASS score. The brief description also mentions patient satisfaction at various points and provider satisfaction, confidence, and knowledge. When multiple outcomes or repeated assessments are considered, the chance of finding an apparently notable result can increase if many statistical tests are conducted. General approaches include prespecifying a primary comparison, controlling an overall error rate, or treating secondary results as exploratory. The registry record does not report a multiplicity strategy or a detailed statistical analysis plan.
The record reports zero analyses. It does not provide estimates, uncertainty intervals, p-values, or results for the listed changes and satisfaction outcomes. It is therefore not possible to determine which analyses were conducted, whether any multiplicity adjustment was used, or how outcomes were prioritized in analysis. A count of outcome measures does not establish that each was analyzed or that the measures were all defined in the same way.
Missing-data handling and analysis populations are also not reported in the registry record. There is no description of the number of participants with completed follow-up, the number contributing to each outcome, reasons for missing observations, or methods for handling missing values. These details matter because analyses based only on participants with complete data can differ from analyses that account for all enrolled participants, particularly when missingness is related to health, treatment, or satisfaction. The registry record does not state whether results were intended to be analyzed by enrollment, protocol adherence, or another population definition.
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 Arm | 15 | 50 | 30.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Intervention Arm | 0 of 50 |
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 Arm | 19 of 50 |
Most frequent serious adverse event terms
| Event term | Organ system | Intervention Arm |
|---|---|---|
| Heart failure | Cardiac disorders | 3 of 50 |
| Aortic valve disease | Cardiac disorders | 2 of 50 |
| Hemorrhoids | Gastrointestinal disorders | 2 of 50 |
| Multiple myeloma | Blood and lymphatic system disorders | 1 of 50 |
| Chest pain - cardiac | Cardiac disorders | 1 of 50 |
| Colitis | Gastrointestinal disorders | 1 of 50 |
| Colonic hemorrhage | Gastrointestinal disorders | 1 of 50 |
| Hemorrhoidal hemorrhage | Gastrointestinal disorders | 1 of 50 |
| Small intestinal obstruction | Gastrointestinal disorders | 1 of 50 |
| Upper gastrointestinal hemorrhage | Gastrointestinal disorders | 1 of 50 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Intervention Arm |
|---|---|---|
| Serious bleeding | Blood and lymphatic system disorders | 16 of 50 |
| Major bleeding | Blood and lymphatic system disorders | 6 of 50 |
| Thromboembolism | Vascular disorders | 1 of 50 |
Serious events with the highest arm-level rate: heart failure (6.0%), aortic valve disease (4.0%), hemorrhoids (4.0%), multiple myeloma (2.0%), chest pain - cardiac (2.0%).
The registry lists an intervention arm with 50 participants at risk for serious events and 15 affected. For other events, it lists 50 at risk and 19 affected. Deaths are listed as 0. These are descriptive counts in the intervention arm, not estimates of a difference between extended and usual follow-up. No concurrent control arm is reported, so the counts cannot establish how event occurrence compares with another schedule.
The serious-event terms listed most often include Heart failure at 6.0%, Aortic valve disease at 4.0%, and Hemorrhoids at 4.0%. Multiple myeloma, Chest pain - cardiac, and Colitis are each listed at 2.0%. These percentages are reproduced as recorded; the registry description does not provide further detail about event timing, duration, recurrence, or causal attribution. The listed terms should not be interpreted as evidence that the follow-up protocol caused an event.
Event counts and the number of participants affected are not interchangeable in general: one participant may experience more than one event. The registry's event definitions and counting rules are not reported in the registry record. The safety figures therefore offer a descriptive account, but cannot alone establish comparative risk, statistical precision, or a causal relationship.
12. What the Result Does, and Does Not, Mean
The record documents a prospective, single-group evaluation of extended INR follow-up in a VA anticoagulation service. It reports 51 enrolled participants and 107 individuals invited. The intervention was designed for participants who continued on a stable dose of warfarin and had INR values within the goal range of 2-3, including lab variation. The record also lists counts of serious and other adverse events and zero deaths in the intervention arm.
These registry entries do not establish that extending the interval between INR tests improves or worsens clinical outcomes. There is no separate usual-follow-up control group, and the registry lists no statistical analyses. Results for changes in appointment frequency, time in therapeutic range, bleeding and thromboembolic events, and patient satisfaction are not reported in the registry record. No effect estimates or confidence intervals are available to describe the size or precision of changes.
The study's accrual endpoint is relevant to whether recruitment into this protocol was achieved, but the record does not post a separate accrual result or explain the full eligibility and invitation process. The enrollment and invitation counts alone do not describe why people did or did not enroll, whether enrollees completed follow-up, or how broadly the findings would apply to other services or patients.
The safety counts also require restraint. They describe events recorded among participants in the intervention arm, but without a comparator they cannot show whether the event burden was higher, lower, or similar under another follow-up schedule. The registry does not report causal attribution or a complete account of event ascertainment. In general, a lack of a reported event analysis is not evidence that no event occurred; the record specifically lists affected participants and deaths.
Overall, the posted information supports a description of the study's purpose, design, recruitment, and recorded safety counts. It does not provide a statistical demonstration of feasibility, safety, acceptability, or clinical effect. Those conclusions would require outcome definitions, follow-up information, analysis methods, and results that are not reported in the registry record.
13. Why This Trial Matters Statistically
This study addresses a practical statistical question in clinical service delivery: whether an extended INR follow-up schedule can be evaluated among Veterans receiving stable-dose warfarin. Recruitment, visit frequency, time in therapeutic range, satisfaction, and safety are distinct dimensions of such an evaluation. A feasibility endpoint can help characterize whether a protocol reaches participants, while clinical and patient-reported outcomes address different aspects of what happens after enrollment.
The design also illustrates why the research question and comparison structure must be kept aligned. A single-group study can describe implementation and observed outcomes, but it lacks a concurrent group representing what would have occurred under another follow-up schedule. Any change from baseline would therefore be difficult to attribute specifically to the interval protocol. This is a design limitation, not a matter that can be corrected simply by applying a statistical test.
The record's primary endpoint is accrual, and the listed counts give context for recruitment. The safety counts further illustrate the difference between documenting events and estimating comparative risk. Without a control group, outcome analyses, and uncertainty estimates, descriptive counts cannot answer whether outcomes differ under extended versus usual follow-up. The registry record reports no statistical analyses, so it does not allow readers to assess the precision of outcome estimates or the planned approach to multiple measures.
For biostatisticians and clinical researchers, this record underscores the importance of linking implementation aims to measurable endpoints and reporting denominators, follow-up, missingness, and analysis populations. It also shows why planning assumptions must not be mistaken for the actual trial design: the listed study is single-group, while the planning description refers to a hypothetical two-arm calculation. Clear distinction between design, descriptive results, and planning illustrations helps prevent stronger conclusions than the record supports.
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.
Several trial-specific limitations constrain interpretation. First, the design is single-group, with all participants in the intervention arm and no concurrent comparator. The record therefore cannot support a direct comparison with usual INR follow-up. The allocation field is NA, and masking is listed as NONE. The phase is also listed as NA.
Second, the primary endpoint concerns accrual, while the study description also names safety, acceptability, and clinical outcomes. The registry gives 107 invited and 51 enrolled but does not report a separate accrual analysis. It does not report the number who met the stable-dose and INR criteria, began extended scheduling, completed follow-up, or contributed to each outcome. Eligibility details beyond the stated stable-dose and INR conditions are not reported in the registry record.
Third, outcome results are limited. The registry lists eight outcome measures and zero analyses, but does not report estimates of change, confidence intervals, p-values, or detailed results for appointment frequency, time in therapeutic range, bleeding and thromboembolic events, or satisfaction. Outcome definitions, observation windows, and methods for assessing provider outcomes are not described in sufficient detail to evaluate measurement consistency.
Finally, the registry does not report the statistical analysis plan, multiplicity approach, handling of missing data, or analysis populations. The serious and other event counts are descriptive and do not provide comparative risk or causal attribution. Generalizability is also uncertain because the study was conducted in one named VA anticoagulation service and the record does not describe how the enrolled participants compare with other warfarin users or services.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Prospective Evaluation of an Extended Interval of INR Follow-up in a VA Anticoagulation Service — NCT02392104.
- Registry record last updated 2019-12-11; status last verified 2019-11.
- Results first posted 2019-12-11.
- 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
NCT02392104 is a completed, prospective, single-group study titled Prospective Evaluation of an Extended Interval of INR Follow-up in a VA Anticoagulation Service. The sponsor is William S. Middleton Memorial Veterans Hospital. The record lists a start date of 2015-03-27, a primary completion date of 2017-06-25, and enrollment of 51. All participants were in the intervention arm, and the intervention involved extended INR follow-up for participants continuing on stable-dose warfarin with INR values within the goal range of 2-3, including lab variation.
The primary endpoint is rates of participant accrual, described as enrolled participants compared with invited individuals. The record states that 107 individuals were invited. Secondary outcomes address appointment frequency, bleeding and thromboembolic events, time in therapeutic range, and patient satisfaction through total DASS score. Safety counts list 15 participants affected among 50 at risk for serious events, 19 affected among 50 at risk for other events, and zero deaths.
The registry lists eight outcome measures and zero analyses. Detailed outcome results, inferential analyses, missing-data methods, and a statistical analysis plan are not reported in the registry record.