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 Personalized Vitamin D Supplementation in European and African Americans (NCT02362269), a randomized na study. The primary outcome is Efficacy of the Dosing Algorithm in Achieving Total 25(OH)D as Measured by the Percentage of Participants Ending With Concentrations of 35-50 ng/mL.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02362269 |
| Phase | NA |
| Condition | Vitamin D Deficiency |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 169 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Wisconsin, Madison |
| Results posted | Yes |
2. Clinical Question
Population
The planned population was community-dwelling post-menopausal women of European and African descent with vitamin D deficiency. The registry record lists 169 participants enrolled, but does not report the enrolled participants’ ancestry, menopausal status, or baseline vitamin D status.
Intervention
The dosing algorithm group was planned to receive daily vitamin D3 at an initial dose of 1000, 2500, or 4000 IU, selected according to baseline 25(OH)D. The dose could be adjusted at the 3-month visit. The study description specifies six months of daily supplementation.
Comparator
The control group was planned to receive 2500 IU of vitamin D3 daily. The record describes the trial as randomized and double-blind, with parallel groups. Details about how masking was maintained or assessed are not reported in the registry record.
Primary question
The primary outcome concerns the percentage of participants ending with total 25(OH)D concentrations in the 35-50 ng/mL goal range, with assessments at 3 and 6 months. The clinical question is whether the proportion in that range differs between the algorithm and fixed-dose groups. The registry record does not report the observed percentages or a statistical comparison, so it does not establish the direction or precision of any group difference.
3. Trial Design
The registry describes a randomized, double-blind, controlled, parallel-group trial of vitamin D3 supplementation. Its study description calls the trial multi-center and proposes six months of daily oral cholecalciferol. The planned population was community-dwelling post-menopausal women of European and African descent. The description places European ancestry participants at the Madison clinic and African ancestry participants at the Milwaukee clinic.
The planned allocation was 1:1 between the control group and the dosing algorithm group, using stratified block randomization with a block size of six and stratification by site, identified with ancestry. These are details of the proposed design; the registry does not report whether each design feature was implemented as planned. The listed enrollment is 169, while the study description gives a planned enrollment of 334, including 10% over-recruitment for loss to follow-up. The reason for the difference between the listed enrollment and planned enrollment is not reported in the registry record.
The control group was assigned 2500 IU daily. The algorithm group was assigned an initial daily dose of 1000, 2500, or 4000 IU based on baseline 25(OH)D, with possible adjustment at the 3-month visit. The trial status is completed; the listed start date is 2015-10-30 and the primary completion date is 2019-05-03. Participant flow, including the numbers who completed follow-up or were included in each analysis, is not reported in the registry record.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Overall Study
| Stage | Control Group | Dosing Algorithm Group |
|---|---|---|
| STARTED | 83 | 86 |
| COMPLETED | 82 | 80 |
| NOT COMPLETED | 1 | 6 |
Reasons for not completing this period:
| Reason | Control Group | Dosing Algorithm Group |
|---|---|---|
| Moved | 1 | 0 |
| Lost to Follow-up | 0 | 6 |
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 | Control Group | Dosing Algorithm Group | Total |
|---|---|---|---|---|
| Participants analysed | 83 | 86 | 169 | |
| Age, Continuous | years | 63.3 (SD 10.9) | 63.6 (SD 6.7) | 63.5 (SD 7.5) |
| Sex: Female, Male: Female | Participants | 83 | 86 | 169 |
| Sex: Female, Male: Male | Participants | 0 | 0 | 0 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 1 | 0 | 1 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 82 | 86 | 168 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 14 | 15 | 29 |
| Race (NIH/OMB): White | Participants | 69 | 71 | 140 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Baseline 25(OH)Vitamin D | ng/mL | 26.4 (SD 7.5) | 27.8 (SD 7.6) | 27.0 (SD 7.5) |
6. Primary Endpoint
The registry lists the primary outcome as Efficacy of the Dosing Algorithm in Achieving Total 25(OH)D as Measured by the Percentage of Participants Ending With Concentrations of 35-50 ng/mL, measured over 3 and 6 months.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | percentage of participants in goal range |
| Endpoint classification | not reduced to a single comparison |
The primary outcome is the percentage of participants ending with total 25(OH)D concentrations in the 35-50 ng/mL goal range. It is listed as a number outcome expressed as a percentage of participants in the goal range, with a timeframe of 3 and 6 months. The study description says a vitamin D panel would be run on blood samples collected at baseline and those follow-up visits. The panel includes serum vitamin D3, 25(OH)D3, 25(OH)D2, the C3-epimer of 25(OH)D3, 24,25(OH)2D, and an assay for free serum 25(OH)D.
As a general statistical concept, a percentage in a target range turns a continuous measurement into a category: each participant either meets the stated range criterion at an assessment or does not. This can make the outcome straightforward to interpret against a prespecified goal, but it does not describe how far measurements fall from the range or how values vary within it. The registry record does not report observed percentages, the rule for handling values exactly at the range limits, or a single comparison combining the 3- and 6-month assessments. It therefore does not report an efficacy estimate for this endpoint.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies the goal-range percentage as the primary outcome, but it does not report outcome values for either group at 3 or 6 months. It also lists zero analysis entries. Consequently, the record does not provide a group contrast, an uncertainty interval, a test statistic, or a p-value for the primary outcome. There is no posted efficacy result from which to judge the size, direction, or precision of a difference between the dosing strategies.
The outcome includes assessments at two follow-up times. The registry’s note indicates that the primary outcome has several categories or time points and was not reduced to one comparison. This matters for interpretation: a result at one visit would not automatically answer the question at the other visit, and a combined claim would require a clearly defined comparison and analysis. Neither a combined estimate nor separate visit-specific estimates are reported in the registry record.
The record lists enrollment of 169, while the study description planned enrollment of 334. This difference is relevant when considering the amount of information potentially available, but the registry does not give participant flow or outcome denominators. The enrollment figure alone does not establish how many participants contributed endpoint data at each visit, whether groups remained balanced, or why the listed enrollment differs from the planned enrollment.
The serious adverse event entries are separate from the efficacy outcome. The record lists two serious events among 82 participants at risk in the control group and three among 80 at risk in the dosing algorithm group, with no deaths in either group. These counts do not supply evidence about the goal-range outcome. They also should not be treated as a comparative safety analysis: event attribution, follow-up completeness, and uncertainty for a between-group contrast are not reported.
Overall, the posted registry information describes the intended comparison and includes limited safety counts, but does not report the primary outcome results or the analysis needed to interpret efficacy. A conclusion about the relative outcome in the two groups cannot be drawn from the registry record alone.
9. Statistical Methods Explained
The statistical methods used to analyze the primary outcome are not reported in the registry record. The trial is described as randomized, double-blind, and parallel group, but the record does not specify a statistical model, an estimation method, a hypothesis test, or an approach to uncertainty. The following concepts are general explanations of how such features can matter; they are not claims about methods used in this trial.
What does randomization contribute?
In general, randomization assigns participants to groups by chance and is intended to make the groups comparable at the start of a trial, including with respect to factors that may not have been measured. That rationale depends on the allocation process being implemented and on analyzing participants in a way consistent with the assigned groups. The registry description says allocation was randomized and planned as 1:1, with stratified blocks by site or ancestry. It does not report the sequence-generation procedure, allocation concealment, randomization checks, or the analysis population. Thus the record identifies the planned allocation approach but does not document all operational or analytic details.
How should a percentage outcome be understood?
As a general concept, a percentage in a target range summarizes the share of participants whose measurements satisfy a defined criterion. For each assessment, the underlying participant-level outcome is categorical: in range or not in range. Group percentages can be compared as an absolute difference, a relative measure, or through a model for categorical data, but those approaches answer questions on different scales and can have different assumptions. No effect measure or model is reported for this trial, so none can be attributed to its analysis.
The endpoint is assessed at 3 and 6 months. General statistical practice must distinguish a comparison at each time from a single summary across visits. If measurements are taken repeatedly from the same participants, their outcomes may be related; a method that treats them as independent may not represent that relationship. Conversely, separate tests at multiple visits raise questions about how to interpret the set of results. The registry record does not report whether results were analyzed separately, jointly, or with a repeated-measures method.
What do uncertainty intervals and tests add?
In general, an estimate describes the observed contrast, while a confidence interval describes the range of values compatible with the data under the method’s assumptions. A p-value, when used, addresses how unusual data at least as incompatible with a specified null hypothesis would be under that hypothesis and model. Neither quantity replaces the effect estimate or determines clinical importance. Here, no primary-outcome estimate, confidence interval, or p-value is reported, so the precision of the result cannot be assessed. The registry record also does not state a significance threshold or whether a test was planned.
What can the planning illustrations establish?
The stated planning assumptions describe illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation; the target effect is a stated fraction of the observed effect. For outcomes other than time-to-event outcomes, those illustrations are expressed as participants per arm. They are planning illustrations, not observed power and not a substitute for the trial’s reported findings. Because the primary outcome has multiple categories or time points and was not reduced to one comparison, a single primary contrast is not specified in the record. The trial’s own sample-size justification is not reported in the registry record.
In general, over-dispersion means that observed variability is greater than a statistical model expects. When it is relevant, ignoring it can make uncertainty estimates too narrow. The registry record does not report a model for this outcome or indicate whether over-dispersion was assessed, so this is a general consideration rather than a trial-specific finding. Likewise, no interim-analysis plan, stopping rule, or statistical analysis plan is reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The primary outcome is described at 3 and 6 months, and the study description lists blood collection at baseline and both follow-up visits. The registry record does not specify whether the two follow-up assessments were treated as separate primary comparisons, whether one visit had priority, or whether an overall summary was planned. Its note that the outcome has several categories or time points and was not reduced to one comparison reinforces that no single contrast is available to interpret.
As a general statistical concept, examining several outcomes, time points, or subgroup comparisons can increase the chance of a misleading finding if each is treated as a separate opportunity for a positive result. Multiplicity procedures can address that issue, but their choice depends on which comparisons were prespecified and how they relate to one another. Any multiplicity strategy, hierarchy of outcomes, or prespecified subgroup analysis is not reported in the registry record. No adjustment or unadjusted efficacy results are posted.
Missing-data handling is also not reported in the registry record. The study description mentions planned over-recruitment to allow for loss to follow-up, but that does not show how much follow-up was missing or how missing measurements were handled. The record does not state whether analyses used observed cases, imputation, or another approach, nor does it describe sensitivity analyses for missing outcomes.
The registry lists no analysis entries and does not identify an intention-to-treat, per-protocol, or other analysis population. It does not report participant disposition by group or the number with measurements at each visit. As a result, the endpoint denominators and the consequences of any exclusions or incomplete follow-up cannot be assessed.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Control Group | 2 | 82 | 2.4% |
| Dosing Algorithm Group | 3 | 80 | 3.8% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Control Group | 0 of 82 |
| Dosing Algorithm Group | 0 of 80 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Control Group | 0 of 82 |
| Dosing Algorithm Group | 0 of 80 |
Most frequent serious adverse event terms
| Event term | Organ system | Control Group | Dosing Algorithm Group |
|---|---|---|---|
| Hemorrhagic stroke | Cardiac disorders | 1 of 82 | 0 of 80 |
| Hip replacement | Musculoskeletal and connective tissue disorders | 1 of 82 | 0 of 80 |
| Pulmonary embolism | Respiratory, thoracic and mediastinal disorders | 0 of 82 | 1 of 80 |
| Viral gastroenteritis | Gastrointestinal disorders | 0 of 82 | 1 of 80 |
| Urothelial carcinoma | Renal and urinary disorders | 0 of 82 | 1 of 80 |
Serious events with the highest arm-level rate: pulmonary embolism (1.2%), viral gastroenteritis (1.2%), urothelial carcinoma (1.2%), hemorrhagic stroke (1.2%), hip replacement (1.2%).
The registry lists serious adverse events for each group using participants at risk and participants affected. In the control group, 82 participants were listed as at risk and two were affected; in the dosing algorithm group, 80 were listed as at risk and three were affected. No deaths are listed in either group. The record also lists zero other adverse events in each group. These are counts from the posted safety record, not estimates of a treatment effect.
The registry lists pulmonary embolism, viral gastroenteritis, urothelial carcinoma, hemorrhagic stroke, and hip replacement among the top serious event terms, each at 1.2%. It does not report which group each term occurred in, the number of events associated with each term, or whether investigators considered the events related to study supplementation. The listed serious-event counts should not be combined with the term percentages because the record does not explain their relationship or denominators.
In general, adverse-event counts describe events recorded during the stated observation and do not by themselves establish causation. The record does not describe safety ascertainment, event severity criteria beyond the serious-event classification, duration of safety follow-up, or a comparative statistical analysis. With those details absent, the figures are descriptive and do not support a precise between-group safety conclusion.
12. What the Result Does, and Does Not, Mean
The registry record establishes that a randomized, double-blind, parallel-group trial was completed and describes a comparison between a fixed daily vitamin D3 dose and a dosing algorithm based on baseline 25(OH)D, with possible adjustment at the 3-month visit. It also identifies the intended primary endpoint: the percentage ending within the 35-50 ng/mL total 25(OH)D range at 3 and 6 months. These details define the planned research question, not its answer.
The primary endpoint values and statistical comparisons are not reported in the registry record. It is therefore not possible to determine from this record whether the groups differed, which group had a higher goal-range percentage, or how precise any difference would be. The absence of a posted result is not evidence that the groups were the same, nor does it establish that the algorithm achieved or failed to achieve its intended goal.
The listed serious adverse event counts provide limited descriptive information. They do not establish that an event was caused by supplementation, and the record does not provide enough detail to interpret the listed serious-event terms by group or to quantify uncertainty in a safety comparison. No deaths are listed, but that observation alone does not characterize all aspects of safety.
In general, a completed trial status indicates that the study is recorded as completed; it does not mean that every outcome or analysis is available in the registry. The difference between planned enrollment of 334 and listed enrollment of 169 also does not, by itself, explain recruitment, follow-up, or analysis decisions. The registry record does not report those details. The defensible interpretation is limited to the design description, enrollment listing, and posted safety counts; efficacy conclusions and a full assessment of precision remain unavailable.
13. Why This Trial Matters Statistically
This trial raises a useful statistical question about tailoring a dosing strategy using a baseline biomarker and evaluating whether participants reach a defined concentration range. The contrast is not simply between supplementation and no supplementation: the control group was assigned 2500 IU of vitamin D3 daily, while the algorithm group could start at 1000, 2500, or 4000 IU daily according to baseline 25(OH)D and could have its dose adjusted at the 3-month visit. That structure makes clear why the intervention being evaluated is a dosing strategy rather than one uniform dose.
Statistically, the endpoint illustrates the distinction between analyzing a measured concentration and analyzing whether it falls within a target range. A range-based outcome may be easy to interpret as a participant-level goal, but it does not preserve all information about the underlying measurements. Participants just inside and far inside the range count alike, while values just outside and far outside are also grouped together. This is a general property of categorization, not a reported trial finding.
The assessment schedule also matters. Results at 3 and 6 months could address different aspects of the outcome over time, but they require a clearly stated analysis and interpretation. The registry does not report how those visits were compared or how multiplicity was handled, and it posts no primary outcome estimates. That absence makes the record an example of why design information and outcome reporting are both necessary for statistical interpretation.
Finally, the registry’s planned enrollment and listed enrollment differ, while participant flow and endpoint denominators are not reported. Those omissions limit assessment of the information available for the primary outcome. The trial design is identifiable, but the posted record does not provide the results needed to evaluate the intended statistical question.
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 for interpreting this trial is that the registry record does not report the primary outcome results or any analyses. It gives the outcome definition and assessment times, but not the percentage in the goal range in either group, the estimated contrast, or its uncertainty. The record lists zero analysis entries. As a result, the intended efficacy question cannot be answered from the posted registry information.
Enrollment and follow-up information are incomplete. The listed enrollment is 169, whereas the study description planned 334 participants. The reason for this difference is not reported in the registry record. The numbers with available outcome measurements at 3 and 6 months, withdrawals, exclusions, and analysis denominators are also not reported. The planned allowance for loss to follow-up does not establish what actually occurred.
The statistical analysis plan is not reported in the registry record. In particular, the record does not state how the two assessment times were analyzed, how missing measurements were handled, which analysis population was used, or whether multiplicity was addressed. It also does not report confidence intervals, hypothesis tests, or any interim-analysis plan. These absences prevent evaluation of the precision and robustness of a primary-outcome result.
Some design details appear in the study description as plans, including stratified block randomization and possible dose adjustment. The record does not document whether those details were implemented as planned. The participant characteristics actually enrolled and their baseline outcome measurements are not reported, so the extent to which the recruited sample matched the proposed population cannot be assessed. Safety details are likewise limited: serious-event counts are listed, but attribution, group allocation of the listed event terms, and comparative uncertainty are not reported.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Personalized Vitamin D Supplementation in European and African Americans — NCT02362269.
- Registry record last updated 2020-12-01; status last verified 2020-11.
- Results first posted 2020-11-13.
- 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
NCT02362269 is listed as a completed randomized, double-blind, parallel-group trial of personalized vitamin D supplementation in European and African Americans. The study description planned six months of daily vitamin D3 in community-dwelling post-menopausal women of European and African descent. It proposed comparing a baseline-25(OH)D-based dosing algorithm with 2500 IU daily in the control group. Listed enrollment is 169; planned enrollment in the study description is 334.
The primary outcome is the percentage of participants with total 25(OH)D in the 35-50 ng/mL range at 3 and 6 months. Primary outcome results and statistical analyses are not reported in the registry record. The record lists two serious adverse events among 82 participants at risk in the control group and three among 80 in the dosing algorithm group, with no deaths listed.