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 Etexilate for Stroke Prevention in Patients With Atrial Fibrillation and Mild to Moderate Renal Impairment (NCT01721837), a registered phase not stated study. The primary outcome is Creatinine Clearance (Recalculated Using Entries of Age, Gender, Body Weight and Serum Creatinine Made by the Physician).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01721837 |
| Phase | Phase not stated |
| Condition | Atrial Fibrillation |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 4340 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Boehringer Ingelheim |
| Results posted | Yes |
2. Clinical Question
Population
Patients with non-valvular atrial fibrillation and documented mild or moderate renal impairment. The study enrolled 4340 participants, while the primary measure’s stated population is the subset with evaluable age, gender, body weight, and serum creatinine data.
Intervention
Physicians’ use of dabigatran etexilate for stroke prevention. This was a non-interventional, observational study, so the registry record does not describe treatment assignment by the study.
Comparator
No comparator group is described. The record lists a single study group and does not establish a like-for-like control comparison.
Primary question
What is the distribution of creatinine clearance recalculated from age, gender, body weight, and serum creatinine at the time of prescription, before the first dabigatran intake? The registry lists a median and inter-quartile range as the summary measures, but the actual result is not reported in the registry record.
3. Trial Design
This completed study examined physicians’ use of dabigatran etexilate in routine care for stroke prevention among patients with atrial fibrillation and mild to moderate renal impairment. The registry classifies it as non-interventional and observational. It reports enrollment of 4340 and lists Boehringer Ingelheim as the sponsor. The study start is recorded as 2012-10 and primary completion as 2013-06.
The record describes one group, consisting of patients with atrial fibrillation and mild to moderate renal impairment. It does not describe a randomized allocation or a control arm. The record specifically cautions that this is not a randomized comparison and that the listed arms are not a like-for-like control comparison. Because treatment assignment was not stated, the registry does not establish how physicians decided which patients received dabigatran or whether other treatments were used.
The primary measure is a single observation at the time of prescription, before the first dabigatran intake. Creatinine clearance was recalculated using the Cockcroft-Gault formula from age, gender, body weight, and serum creatinine. The stated population for this measure is patients with documented mild or moderate renal impairment and non-valvular atrial fibrillation who had evaluable data for those inputs. The record notes that 145 patients lacked one or more of the required inputs.
The registry lists one outcome measure and no analysis entries. A study protocol, statistical analysis plan, sample-size justification, and details of any interim analyses are not reported in the registry record. The study’s observational design and single-time-point measurement describe the available information; they do not establish a treatment effect or a comparison between treatment strategies.
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.
Before assignment: 4340 patients were enrolled in the study, 2220 patients had no documented mild or moderate renal impairment or no documented non valvular atrial fibrillation. Therefore, 2120 patients remained for analysis.
Overall Study
| Stage | All Patients |
|---|---|
| STARTED | 2120 |
| COMPLETED | 2120 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: All patients with documented mild or moderate renal impairment and non-valvular atrial fibrillation (PPS) having evaluable data for age, gender, body weight, and serum creatinine. In 145 patients age, gender, serum creatinine or weight was missing so that Creatinine Clearance according to the Cockcroft Gault formula could not be recalculated.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
Population: All patients with documented mild or moderate renal impairment and non valvular atrial fibrillation (PPS).
| Characteristic | Unit | All Patients |
|---|---|---|
| Participants analysed | 2120 | |
| Age, Continuous | years | 75.2 (SD 8.8) |
| Gender: Female | participants | 1015 |
| Gender: Male | participants | 1101 |
6. Primary Endpoint
The registry lists the primary outcome as Creatinine Clearance (Recalculated Using Entries of Age, Gender, Body Weight and Serum Creatinine Made by the Physician), measured over One single observation time point: at the time of prescription before the first intake of dabigatran etexilate.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | ml/min |
| Endpoint classification | not reduced to a single comparison |
The listed primary measure is creatinine clearance, expressed in ml/min, recalculated using the Cockcroft-Gault formula. The inputs named in the registry are age, gender, body weight, and serum creatinine. The measurement is intended to characterize renal function at the time dabigatran is prescribed, before the first intake. The registry specifies a median and inter-quartile range, which describe the center and spread of the calculated values without requiring the values to follow a symmetric distribution.
In general, creatinine clearance is used as an estimate of kidney filtration based on patient characteristics and serum creatinine. A recalculated measure makes explicit which recorded inputs were used and can provide a description of the study group’s renal-function profile at the specified time. It is not, by itself, a measure of stroke prevention, bleeding, change in renal function, or comparative treatment effect.
The endpoint population is restricted to participants with evaluable data for all named inputs. The record notes missing age, gender, serum creatinine, or weight for 145 patients. It does not report the median, inter-quartile range, or any other numerical result for creatinine clearance. Consequently, the endpoint’s observed distribution and its precision cannot be assessed from the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry describes a completed observational study of dabigatran etexilate use, but it does not report the numerical result for its primary measure. It identifies the measure as creatinine clearance recalculated from age, gender, body weight, and serum creatinine, with the value assessed at prescription before the first intake. The specified summary is a median with an inter-quartile range. Without those results, the renal-function distribution in the endpoint population cannot be characterized from this record.
The measure is descriptive rather than a direct test of stroke prevention. It does not report stroke events, treatment effectiveness, change in kidney function, or an outcome comparison between dabigatran and another treatment. The registry lists a single study group, and there is no described control group. Its warning that the study is not a randomized comparison is important: an observational record of physician use cannot, on its own, separate treatment effects from patient characteristics, clinical decisions, or other differences between groups.
The full enrollment is 4340, but the primary measure is defined for participants with evaluable information on all four inputs. The record notes that 145 patients had age, gender, serum creatinine, or weight missing. It does not give the final number with evaluable endpoint data or explain whether any missing values were handled through exclusion, imputation, or another approach. The relationship between the total enrollment and the analyzed endpoint population therefore cannot be fully reconstructed.
The record lists one outcome measure and no analysis entries. It does not report an estimate, confidence interval, hypothesis test, or detailed statistical analysis plan. A confidence interval, in general, expresses the uncertainty around an estimated quantity under a specified statistical procedure; it is not available for this measure in the registry record. No conclusion about the precision of the endpoint estimate is possible without a reported estimate and its uncertainty.
Any sample-size calculations associated with the statistical material are planning illustrations, not observed power and not evidence that the study was designed to detect a particular treatment effect. The stated illustration assumptions include a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a fraction of an observed effect. The record does not describe a randomized two-arm comparison for this study, and it does not report a primary endpoint effect estimate. Those planning assumptions should not be interpreted as the design or findings of the observational study.
9. Statistical Methods Explained
The primary measure is a recalculation, not a direct report of an assay called creatinine clearance. The registry says that age, gender, body weight, and serum creatinine were entered into the Cockcroft-Gault formula. This defines how the reported measure was derived, but the record does not provide the actual calculated values or summarize them numerically.
In general, a formula-based estimate combines recorded patient characteristics and laboratory information according to a specified relationship. The result depends on the input values and the formula used. Reporting the formula and inputs helps readers understand what the measure represents, but it does not show whether the input data were accurate, how they were collected, or whether any additional data-cleaning steps were applied. Those details are not reported in the registry record.
The registry specifies a median and inter-quartile range. In general, the median is the central value after observations are ordered, while the inter-quartile range describes the spread of the central portion of the observations. These summaries can be useful when data are skewed or contain extreme values, because they are less influenced by extremes than the mean and standard deviation. This is a general explanation of the statistics; the registry record does not report the endpoint’s median or inter-quartile range.
The measurement was planned for one observation time point: at prescription before the first intake of dabigatran etexilate. In general, a single time-point description can characterize a group at a particular moment but cannot establish change over time. It also cannot show whether renal function later changed or whether any change was associated with treatment. No repeated measurement schedule is reported for this endpoint.
The registry classifies the study as non-interventional and observational. In general, observational studies record care as it occurs rather than assigning participants to treatments for purposes of the study. This can be appropriate for describing prescribing and patient characteristics, but treatment groups may differ in ways that influence outcomes. Randomization is not described, and the registry says allocation was not stated. It also cautions that the arms are not a like-for-like control comparison. Therefore, causal interpretations or direct treatment contrasts are not supported by the design information in the record.
There is no comparator group described for the primary measure. In general, a comparative analysis requires a clear definition of the groups being contrasted and an appropriate method for estimating their difference. The record does not report such an analysis, nor does it provide an effect estimate or uncertainty interval. It lists no analysis entries, so no inferential result for the primary measure can be interpreted from the registry record.
The sample-size assumptions described for planning illustrations are a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of the observed effect. The assumptions also distinguish total event counts for time-to-event illustrations from participants per arm for other illustrations. In general, a planning calculation estimates the sample size needed under specified assumptions; it does not establish the number needed for this particular observational study unless its design, endpoint, effect, and analysis match those assumptions. Such illustrations are not observed power. The record does not report that these assumptions were the study’s own design plan or give a sample-size justification.
Over-dispersion is a general statistical concern when outcome variability exceeds what a chosen model assumes; if ignored, uncertainty can be understated. It is not possible to assess over-dispersion for this endpoint from the registry record, which does not report a model, outcome distribution, or inferential analysis. Likewise, the record does not identify adjustment variables or specify how potential confounding was addressed.
Missing input data affect who can contribute to a formula-based endpoint. The registry identifies 145 patients with missing age, gender, serum creatinine, or weight, but does not report a missing-data method or the number remaining in the evaluable endpoint population. In general, excluding incomplete records and imputing missing inputs are different approaches that can lead to different estimates, particularly if missingness is related to patient characteristics. No method or assumption about the missingness mechanism is reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one primary outcome measure: recalculated creatinine clearance. It does not report a multiplicity strategy, such as how several statistical tests or endpoints would be handled if analyzed together. The presence of one listed outcome does not establish that no additional analyses were planned or conducted; the registry records no analysis entries, and any broader analysis plan is not reported in the registry record.
The endpoint is defined for patients with evaluable age, gender, body weight, and serum creatinine. The registry notes that 145 patients were missing one or more of these inputs. It does not report the final endpoint sample size, whether those records were excluded, whether values were imputed, or whether another missing-data approach was used. The criteria for the stated PPS population are described in part, but the exact construction of that analysis population beyond the stated eligibility and evaluability requirements is not reported in the registry record.
In general, missingness can affect both the number of observations available and the representativeness of the analyzed group. If records with missing inputs differ from records with complete inputs, the endpoint summary among evaluable patients may not describe all enrolled patients equally well. That is a general consideration, not a finding about this study; the record does not report why the inputs were missing or compare patients with and without evaluable data.
Subgroup analyses, sensitivity analyses, covariate adjustment, and methods for controlling multiplicity are not reported in the registry record. The record also lists no analysis results from which to assess whether these methods were used. Thus, the analysis population and missing-data handling cannot be fully evaluated, and the endpoint result cannot be independently interpreted from the registry entry.
11. What the Result Does, and Does Not, Mean
The registry record describes a study of physicians’ use of dabigatran etexilate in patients with atrial fibrillation and mild to moderate renal impairment. Its primary measure concerns a calculated renal-function estimate at prescription, before the first dabigatran intake. This can describe the renal-function profile of participants with complete required inputs if the summary result is reported.
The record does not report the primary measure’s median or inter-quartile range, so it does not establish the observed creatinine-clearance distribution. It also does not report a treatment-effect estimate, a confidence interval, or a hypothesis test. No claim about the size or precision of an endpoint result can be made from the information recorded.
The study is observational and does not describe a control group or randomized treatment assignment. Accordingly, the registry entry cannot establish whether dabigatran changes renal function, prevents stroke, or produces different outcomes compared with another treatment. The primary measure is not itself a clinical outcome of stroke prevention, and a single pre-intake measurement cannot establish subsequent change.
The enrollment of 4340 should not be treated as the number contributing to the primary measure: that measure requires evaluable age, gender, body weight, and serum creatinine, and the record identifies 145 patients with missing input data. The exact analyzed endpoint population and missing-data handling are not reported in the registry record.
In general, observational studies can describe clinical practice and patient characteristics, while causal conclusions require a design and analysis that address alternative explanations. The registry does not report enough detail to assess such adjustment or to support a comparative treatment conclusion. The appropriate interpretation is therefore limited to the study’s stated purpose and measurement framework, not efficacy or safety claims.
12. Why This Trial Matters Statistically
This study is statistically notable for the distinction between describing prescribing practice and estimating a treatment effect. The registry describes a non-interventional observational study, not a randomized comparison. It lists one group and warns that the arms are not a like-for-like control comparison. That distinction matters because a record of physician use can characterize care without establishing what would have happened under a different treatment strategy.
The primary measure also illustrates how a derived endpoint depends on its inputs. Creatinine clearance was recalculated with the Cockcroft-Gault formula from age, gender, body weight, and serum creatinine. The endpoint is tied to one specified time point before the first dabigatran intake. This makes the intended measurement interpretable, but the absence of the numerical summary means that its observed distribution cannot be assessed.
Missing inputs are another important feature: the record identifies 145 patients without one or more required values. The handling of those records and the final endpoint population are not reported. In general, transparent reporting of missingness and analysis populations helps readers judge how well an endpoint summary represents the enrolled group.
Finally, the registry lists one outcome measure but no analysis entries. It does not report an estimate, uncertainty interval, or analysis plan. The record therefore highlights why statistical interpretation requires not only an endpoint definition and enrollment figure, but also a result, a clear analysis population, and methods suited to the study design. Without those elements, the study’s measurement framework can be described, but its endpoint findings cannot be evaluated.
13. 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 limitation for interpreting the primary measure is that the registry does not report its numerical result. Although the measure, unit, summary type, calculation inputs, and timing are specified, no median or inter-quartile range is available. The endpoint’s observed level and spread therefore cannot be described.
The record identifies 145 patients with missing age, gender, serum creatinine, or weight, all of which are required for the stated recalculation. It does not report the final number of participants with evaluable endpoint data, the handling of incomplete records, or whether imputation was considered. The stated PPS label is not accompanied by a complete description of its construction.
The design is observational, with no randomized assignment or comparator group described. The registry cautions that the arms are not a like-for-like control comparison. Allocation, confounding adjustment, and the statistical analysis plan are not reported in the registry record. Consequently, the listed measurement cannot support a causal treatment comparison on the basis of this record.
The measure is a single observation at prescription before first intake. No later measurement or change-from-baseline result is described. The record also does not report an estimate of precision, such as a confidence interval, or any hypothesis test. Although the registry lists one outcome measure, it does not explain how multiplicity or any additional analyses were handled.
These limitations concern what can be interpreted from the registry record; they do not establish that unreported methods were absent from the study itself. The protocol, sample-size justification, interim analyses, detailed outcome findings, and other analysis details are not reported in the registry record.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: Dabigatran Etexilate for Stroke Prevention in Patients With Atrial Fibrillation and Mild to Moderate Renal Impairment — NCT01721837.
- Registry record last updated 2014-07-31; status last verified 2014-06.
- Results first posted 2014-07-31.
- 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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17. Record Summary
The registry describes a completed, non-interventional observational study of physicians’ use of dabigatran etexilate for stroke prevention in patients with atrial fibrillation and mild to moderate renal impairment. Enrollment was 4340, and Boehringer Ingelheim is listed as the sponsor. The recorded study start is 2012-10 and primary completion is 2013-06.
The primary measure is creatinine clearance, recalculated with the Cockcroft-Gault formula from age, gender, body weight, and serum creatinine. It is specified as a median with inter-quartile range at one time point, before the first dabigatran intake. The record identifies 145 patients with one or more required inputs missing.
The registry lists one outcome measure and no analysis entries. It does not report the primary measure’s numerical result, its uncertainty, the final endpoint population, or details of missing-data handling. No randomized comparator is described, and the record cautions that the study is not a like-for-like control comparison.