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 DBS for Home Monitoring in Children With Kidney Transplantation (NCT01931397), a registered phase not stated study. The primary outcome is Variability of Tacrolimus Blood Levels Measured by DBS Over Time.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01931397 |
| Phase | Phase not stated |
| Condition | Kidney Disease |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 30 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Oregon Health and Science University |
| Results posted | Yes |
2. Clinical Question
Population
Children with kidney transplants are the population described in the study summary. The registry lists Kidney Disease as the condition. It reports enrollment of 30 participants; further participant characteristics are not reported in the registry record.
Intervention
Families were to be taught to collect a dried blood spot at home once a month and mail the filter paper to Oregon Health and Science University for testing. The planned assay measured tacrolimus and creatinine from one spot.
Comparator
A comparison group or alternative monitoring strategy is not reported in the registry record. The registry identifies this as not a randomized comparison and states that allocation was not stated, so the study should not be read as a randomized, like-for-like comparison between arms.
Primary question
The primary outcome concerns the variability of tacrolimus blood levels measured by dried blood spots over 12 months. In particular, the registry describes mean standard deviation scores for tacrolimus levels obtained by dried blood spot for each patient over time. The result for this outcome is not reported in the registry record.
The clinical rationale in the summary is that tacrolimus is used after transplantation to prevent graft rejection, while also being potentially toxic to the kidney. Repeated measurements of tacrolimus and kidney function are described as relevant to dose decisions and to identifying missed medication-taking. Home collection was proposed as a way to obtain measurements without a venous blood draw and to allow families to send samples for testing.
The study also lists the percentage of families preferring the dried blood spot method as a secondary outcome. A preference result is not reported in the registry record. The study therefore raises questions about measurement variability and family preference, but the posted information does not establish how the home method performed relative to another monitoring approach.
3. Trial Design
This completed study is registered as NCT01931397 and is titled DBS for Home Monitoring in Children With Kidney Transplantation. Oregon Health and Science University is listed as the sponsor. The registry reports a start date of 2013-07, a primary completion date of 2015-02, and enrollment of 30 participants.
The summary describes a home-monitoring approach using dried blood spots on filter paper. Families were to learn to collect a sample once a month and mail it to the university laboratory. The assay was intended to measure tacrolimus and creatinine from the same spot, addressing both medication level and kidney function. The registry describes a 12 months timeframe for the primary outcome.
The listed primary outcome is variability of tacrolimus blood levels measured by dried blood spots over time. The secondary outcome listed is the percentage of families preferring the dried blood spot method. The record says there are four outcome measures, but descriptions of the other measures are not reported in the registry record. It also reports zero posted analyses.
The registry does not describe a randomized comparison, and allocation is not stated. A comparator or control arm is not reported in the registry record. Consequently, the study design should be understood from the posted aims and outcome descriptions rather than as evidence from a randomized treatment comparison. Details such as recruitment procedures, eligibility criteria, masking, the planned statistical analysis, and sample-size justification are not reported in the registry record.
For the primary outcome population, the registry states that 9 participants were excluded from final analysis because they submitted two or less evaluable blood samples. It also states that a total of 216 dried blood spot samples were received during the study. The record does not explain how samples were distributed across participants or how the exclusion affected the primary outcome estimate.
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 | Total Cohort |
|---|---|
| STARTED | 30 |
| COMPLETED | 19 |
| NOT COMPLETED | 11 |
Reasons for not completing this period:
| Reason | Total Cohort |
|---|---|
| Physician Decision | 2 |
| Withdrawal by Subject | 8 |
| moved out of state | 1 |
Analysis population for the primary outcome, as defined in the registry: 9 participants were excluded from final analysis because they submitted two or less evaluable blood samples. A total of 216 DBS samples were received during 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.
Population: Descriptive
| Characteristic | Unit | Total Cohort |
|---|---|---|
| Participants analysed | 30 | |
| Age, Continuous | years | 13.6 (SD 5.4) |
| Sex: Female, Male: Female | Participants | 12 |
| Sex: Female, Male: Male | Participants | 18 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 4 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 26 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 1 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 1 |
| Race (NIH/OMB): White | Participants | 26 |
| Race (NIH/OMB): More than one race | Participants | 2 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Region of Enrollment: United States | participants | 30 |
| Number of years post kidney transplantation | years | 5.93 (SD 4.57) |
6. Primary Endpoint
The registry lists the primary outcome as Variability of Tacrolimus Blood Levels Measured by DBS Over Time, measured over 12 months.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | ng/ml |
| Endpoint classification | Continuous Endpoint |
The primary outcome is titled Variability of Tacrolimus Blood Levels Measured by DBS Over Time. Its unit is ng/ml, its summary is a mean, and its dispersion is described as standard deviation. The timeframe is 12 months. The outcome description specifies mean standard deviation scores for tacrolimus blood levels obtained by dried blood spot for each patient over time.
In general, a standard deviation describes how spread out measurements are around their mean. Applied to repeated tacrolimus measurements, it can represent how much a participant’s measured levels vary across the observed samples. The registry’s wording indicates that patient-level variability is then summarized using a mean. This is distinct from reporting only an overall average tacrolimus concentration: an average level and the spread of repeated levels answer different questions.
Variability is relevant to the stated monitoring rationale because the study summary describes repeated tacrolimus measurements as a way to monitor levels over time. However, the registry record does not report the observed mean standard deviation score, its uncertainty, or the individual-level data. It also does not specify in the posted description the precise calculation rules, such as how many measurements were required beyond the stated exclusion criterion. The endpoint therefore identifies the intended measurement, but the posted record does not show its numerical result.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes that the study was completed, lists enrollment of 30, and describes a home dried blood spot approach for measuring tacrolimus and creatinine. It also identifies variability in tacrolimus blood levels as the primary outcome over 12 months. These details describe the study question and data collection approach, not an estimate of how variable the levels were or how the home method compared with another method.
No primary outcome result is reported in the registry record. In particular, the record does not report the mean standard deviation score, a confidence interval, or a p-value for the primary outcome. There are zero analyses listed. A numerical conclusion about the amount of variability, its precision, or whether it changed over time cannot be drawn from the posted information.
The registry reports that 9 participants were excluded from final analysis because they submitted two or less evaluable blood samples, and that 216 dried blood spot samples were received in total. Those details show that the analysis population was not simply all enrolled participants. They do not show how many evaluable samples each included participant contributed, whether collection was regular, or how the excluded participants’ data differed from the remaining data. Such details are not reported in the registry record.
The summary’s rationale presents home collection as a possible alternative to venous blood collection, with potential practical advantages for children and families. But the posted record does not report a direct comparison of collection methods, a measure of agreement between dried blood spot and venous measurements, or a result for family preference. It therefore cannot establish from the posted results whether the proposed home approach was more convenient, acceptable, accurate, or effective than another method.
In general, an estimate paired with a confidence interval communicates both the observed value and the uncertainty around it. Neither is reported for the primary endpoint in the registry record. The absence of a posted estimate is not evidence that variability was high or low; it means the size and precision of the endpoint cannot be assessed from this record. Likewise, the registry’s completion status does not itself provide evidence about the outcome.
The safety entry lists zero serious adverse events among 30 participants at risk and zero other adverse events among 30 participants at risk. These are registry counts, not a comparison against another group. Deaths are not reported in the registry record. The safety figures should be read alongside the limited outcome reporting and should not be treated as a complete account of all possible safety observations.
9. Statistical Methods Explained
The primary endpoint is a continuous measure, meaning it is recorded on a numeric scale rather than as a category. The registry identifies the unit as ng/ml and the summary statistic as a mean, with standard deviation as the measure of dispersion. In general, the mean describes a central value, while the standard deviation describes spread around that value. For repeated measurements, the spread can help describe how much observed tacrolimus levels fluctuate within a person.
What does a mean standard deviation describe?
The outcome description refers to standard deviation scores for each patient over time, then to their mean. Conceptually, this involves describing within-person variation and summarizing those patient-level measures across the analyzed population. That distinction matters: variation among repeated measurements from one person is not the same as variation between different people’s average levels. The registry does not provide a more detailed calculation definition, so the exact computation and handling of irregular numbers of samples are not reported in the registry record.
Repeated measurements also create a data-structure issue. Measurements from the same participant are generally related because they come from the same person. In general, an analysis that treats all repeated samples as independent can misrepresent the amount of information in the data. Methods for repeated observations can account for within-person dependence, but the statistical method used for this endpoint is not reported in the registry record. The total of 216 samples does not, by itself, specify how those samples were distributed or how their dependence was handled.
Why does precision matter?
A confidence interval is a range of values reflecting statistical uncertainty around an estimate under the assumptions of the analysis. A narrower interval indicates greater precision than a wider interval, all else equal. For this endpoint, neither a confidence interval nor another uncertainty measure is reported in the registry record. Without an estimate and its uncertainty, readers cannot judge whether the observed variability was estimated precisely or was compatible with a broad range of values.
A p-value, when reported, describes how compatible the data are with a specified null model, given the statistical assumptions. It does not measure the size or importance of an effect. No p-value or hypothesis test for the primary outcome is reported in the registry record. The record also does not report a prespecified null hypothesis or a statistical analysis plan, so the intended inferential framework cannot be reconstructed from the posted information.
How should the sample-size illustrations be read?
General planning calculations can illustrate how many participants per arm might be needed to detect a specified fraction of an observed effect under stated assumptions. The assumptions described for those illustrations include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They are planning illustrations based on an observed effect, not a record of the study’s original design justification. The sample-size justification is not reported in the registry record, and no sample-size illustration should be read as observed power or as evidence that this study had a particular probability of detecting an effect.
These calculations are framed around two arms, but the registry does not report a randomized comparison or state an allocation scheme. The study’s the registry entries therefore do not establish that a two-arm comparison was conducted. Any planning figures should be interpreted as hypothetical planning scenarios under their stated assumptions, not as a description of the enrolled study or a substitute for its unreported outcome analysis.
What does over-dispersion mean in general?
Over-dispersion occurs when observed variation is greater than a model assumes. In general, ignoring extra variability can make uncertainty estimates too small and can make results appear more precise than they are. The concern is relevant whenever repeated or clustered data are analyzed, but the registry does not report a model for this endpoint or evidence that over-dispersion was assessed. It would be inappropriate to claim that over-dispersion occurred in this study.
The sample counts provide context but do not settle these methodological questions. The registry reports enrollment of 30, exclusion of 9 participants from final analysis for submitting two or less evaluable samples, and receipt of 216 dried blood spot samples. It does not report the final number analyzed for each outcome, the distribution of measurements per participant, missing-data methods, or sensitivity analyses. As a result, the endpoint’s numerical estimate, uncertainty, and robustness cannot be evaluated from the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists four outcome measures, but only the primary outcome title and description and one secondary outcome title are available in the record. Descriptions of the remaining outcome measures are not reported in the registry record. The secondary outcome concerns the percentage of families preferring the dried blood spot method, but no preference result is reported.
When a study evaluates multiple outcomes or performs multiple statistical tests, the chance of obtaining at least one apparently notable finding can increase. In general, multiplicity refers to this issue and to the strategies used to control or interpret it. The registry does not report a multiplicity adjustment, a testing hierarchy, or a statistical plan specifying how multiple outcomes would be handled. Because zero analyses are listed, the posted record does not establish which outcomes were analyzed or what inferential procedures were used.
For the primary outcome population, 9 participants were excluded from final analysis because they submitted two or less evaluable blood samples. The registry also reports 216 samples received. The reason for those exclusions is stated, but missing-data methods and the final analyzed participant count are not reported in the registry record. The record does not describe whether missing samples were imputed, whether participants with incomplete observations contributed partial data, or whether sensitivity analyses were performed.
In general, excluding participants with limited evaluable data can affect the interpretation if the excluded participants differ from those included. The direction or size of any such effect cannot be determined from the registry information. Details about analysis populations, including whether the primary analysis included all enrolled participants or only those meeting an evaluability criterion, are not reported beyond the stated exclusion.
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 |
|---|---|---|---|
| Total Cohort | 0 | 30 | 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 |
|---|---|
| Total Cohort | 0 of 30 |
The registry lists a total cohort of 30 participants at risk for serious adverse events and 0 participants affected. It also lists 30 participants at risk for other adverse events and 0 affected. These are the posted event counts for the total cohort; no separate comparison group is listed. The death count is not reported in the registry record.
In general, a zero count in a registry entry means that no events are recorded in that category for the stated group and reporting period. It does not establish that no event could occur, nor does it by itself describe the completeness of event collection or the duration each participant was observed. The registry entry does not provide further details about event definitions, monitoring procedures, or the period used for the safety counts.
These figures should not be interpreted as a comparison of safety between monitoring methods, because a comparator is not reported in the registry record. They also do not replace the primary outcome: the adverse-event counts concern safety reporting, while the primary endpoint concerns variability of tacrolimus levels. The posted counts are descriptive and should be read with these limitations in mind.
12. What the Result Does, and Does Not, Mean
The study addresses a practical measurement question: whether children and families could collect dried blood spots at home for laboratory measurement of tacrolimus and creatinine. The registry summary explains why repeated tacrolimus and kidney-function measurements are relevant to the study’s rationale and describes a monthly home collection plan. It also identifies variability in tacrolimus levels over 12 months as the primary outcome.
What the posted information does not establish is the measured amount of variability. The primary outcome estimate and its uncertainty are not reported in the registry record, and no analyses are listed. The record also does not report a direct comparison with venous sampling or another monitoring approach. Accordingly, the posted information cannot establish the accuracy or agreement of the dried blood spot assay relative to another method.
The stated rationale includes possible practical advantages, including less painful collection and avoiding a family trip for a blood draw. These are proposed advantages in the summary, not reported comparative findings. The secondary outcome concerning family preference is listed, but its result is not reported in the registry record. Claims about acceptability, convenience, cost, adherence, or clinical consequences cannot be based on the posted results.
In general, a study’s completion status and enrollment count describe conduct and scale, not whether an approach achieved its intended aims. Similarly, a planning illustration based on an observed effect is not an observed-power result and does not supply the missing endpoint analysis. The record supports describing the study question, intended monitoring process, sample collection, and stated exclusions. It does not support a conclusion about the magnitude, precision, or comparative performance of the primary outcome.
The registry reports zero serious and zero other adverse events among 30 participants at risk, while deaths are not reported in the registry record. Those safety entries are descriptive counts and do not establish comparative safety. Overall, the posted record leaves the central outcome question unresolved because its numerical result is absent.
13. Why This Trial Matters Statistically
This study is statistically notable because its primary question concerns repeated measurements within individuals. Measuring a person’s tacrolimus level over time can produce information about both the level and its variability. Those are different summaries, and the endpoint is explicitly framed around variability rather than only an average concentration. Clear reporting of the calculation and the repeated-measures analysis would be important for interpreting that endpoint.
The record also illustrates why sample counts need context. It reports 30 participants enrolled and 216 dried blood spot samples received, but 9 participants were excluded from final analysis because they submitted two or less evaluable samples. Without the participant-level distribution of samples and the analysis method, the total sample count cannot reveal how much information the endpoint contains or how precisely it was estimated.
More broadly, the trial’s registry entry separates a promising measurement rationale from evidence of performance. The summary describes a method intended to combine tacrolimus and creatinine testing from a home-collected spot. The posted record, however, does not include the primary outcome result or a comparison with another sampling method. This distinction is central to statistical interpretation: an intended advantage is not an estimated effect, and a completed study is not itself an outcome finding.
The record is also a reminder that statistical transparency depends on reporting more than an endpoint name. Analysis populations, missing-data handling, uncertainty estimates, and methods for repeated observations all help readers assess what an estimate means. Those details are not reported in the registry record. Their absence limits evaluation of both the endpoint and the study’s scope, without implying that a particular result or bias occurred.
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 limitation of the posted record is that it does not report the primary outcome estimate or any analyses. The size and precision of tacrolimus variability therefore cannot be assessed. The record does not report a confidence interval, p-value, or other uncertainty measure for the endpoint.
A comparator and allocation scheme are not reported, and the registry identifies the study as not a randomized comparison. There is consequently no posted like-for-like control comparison from which to assess differences between home dried blood spot monitoring and another approach. Assay agreement or accuracy against venous measurements is not reported in the registry record.
The analysis population is only partly described. The registry states that 9 participants were excluded from final analysis because they submitted two or less evaluable samples and that 216 samples were received. The final number analyzed, participant-level sample distribution, missing-data handling, and any sensitivity analyses are not reported. These omissions make it difficult to evaluate representativeness and the influence of incomplete sampling.
The record lists four outcome measures, but details for all measures are not available. A family-preference outcome is named without a result. Statistical methods, multiplicity handling, and the sample-size justification are also not reported in the registry record. Further limitations may apply, but cannot be assessed from the posted information.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: DBS for Home Monitoring in Children With Kidney Transplantation — NCT01931397.
- Registry record last updated 2017-03-17; status last verified 2017-03.
- Results first posted 2017-03-17.
- 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
NCT01931397 is a completed study sponsored by Oregon Health and Science University, with enrollment of 30. The registry reports a start date of 2013-07 and a primary completion date of 2015-02. The study summary describes monthly home dried blood spot collection to measure tacrolimus and creatinine in children with kidney transplants.
The primary outcome concerns variability of tacrolimus blood levels measured by dried blood spot over 12 months. The registry reports that 9 participants were excluded from final analysis for submitting two or less evaluable samples and that 216 samples were received. No primary outcome result or statistical analyses are reported. The record lists family preference as a secondary outcome but does not report its result.
The registry lists zero serious and zero other adverse events among 30 participants at risk; deaths are not reported in the registry record. A comparator, detailed statistical methods, and sample-size justification are not reported in the registry record.