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 Vitamin D in Preschoolers With Viral-induced Asthma (NCT02197702), a randomized phase 2, phase 3 study. The primary outcome is Change From Baseline in Serum 25OHD.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02197702 |
| Phase | Phase 2, Phase 3 |
| Condition | Asthma |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 47 |
| Arms in the primary outcome | 2 |
| Lead sponsor | St. Justine's Hospital |
| Results posted | Yes |
2. Clinical Question
Population
The trial enrolled children aged 1–6 years with asthma attacks triggered mostly by colds. The condition listed in the registry record is asthma. The record does not give further eligibility details, such as how asthma severity was defined or what criteria were used to establish that attacks were predominantly viral-triggered.
Intervention
Children assigned to vitamin D received 100,000IU in a 2 ml oral dose at baseline and 3.5 months. The study description characterizes the strategy as a high dose given during usual clinic visits. The trial also set out to document the safety profile of this approach.
Comparator
The comparison group received 2 ml of an identical placebo by mouth at baseline and 3.5 months. The intervention and placebo were assigned in a randomized, parallel-group design, and masking was listed as quadruple. The record does not describe the identities of the groups covered by masking.
Primary question
The primary endpoint asks whether the adjusted change from baseline in serum 25OHD differed between groups over the 7-month follow-up period. This is a biomarker question, not a direct measure of the frequency or severity of asthma exacerbations. The trial description also identifies exacerbations and safety as broader study interests, while the posted primary result is the change in serum 25OHD.
3. Trial Design
NCT02197702, titled “Vitamin D in Preschoolers With Viral-induced Asthma,” is listed as a completed randomized controlled trial with a parallel design. Its phases are recorded as Phase 2 and Phase 3. The registry lists St. Justine's Hospital as the sponsor. Enrollment is recorded as 47. The study began in 2014-09, and primary completion was in 2016-07.
The study description specifies a 7-month trial in children aged 1–6 years with asthma attacks triggered mostly by colds. Participants were assigned to vitamin D or placebo. The vitamin D arm received 100,000IU in a 2 ml oral dose at baseline and 3.5 months; the placebo arm received 2 ml of an identical placebo at those times. Masking is recorded as quadruple, though the registry record does not identify which parties were masked or explain how masking was maintained.
The posted primary endpoint is change from baseline in serum 25OHD, expressed in nmol/L, with a group difference in adjusted change described over the 7-month follow-up. The registry also lists emergency department visits for asthma flare-up and the number of participants with total 25OHD at least 75 nmol/L among the secondary outcomes. The record lists 16 outcome measures, but only 2 secondary outcomes are named in the available summary. It does not report a protocol rationale for the enrollment target, or detailed information about recruitment, adherence, or the conduct of follow-up.
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 | Placebo | Vitamin D |
|---|---|---|
| STARTED | 24 | 23 |
| Withdrew at Visit 1 | 0 | 1 |
| Withdrew at Visit 2 | 1 | 1 |
| Withdrew at Visit 3 | 0 | 2 |
| Analysed for Main Outcome | 23 | 22 |
| COMPLETED | 23 | 19 |
| NOT COMPLETED | 1 | 4 |
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 | Placebo | Vitamin D | Total |
|---|---|---|---|---|
| Participants analysed | 24 | 23 | 47 | |
| Age, Continuous | years | 2.9 (SD 1.2) | 2.9 (SD 0.9) | 2.9 (SD 1.0) |
| Sex: Female, Male: Female | Participants | 10 | 7 | 17 |
| Sex: Female, Male: Male | Participants | 14 | 16 | 30 |
| Race/Ethnicity, Customized: Ethnicity – Caucasian | Participants | 16 | 12 | 28 |
| Race/Ethnicity, Customized: Ethnicity – Other | Participants | 8 | 11 | 19 |
| Region of Enrollment: Canada | participants | 24 | 23 | 47 |
| Vitamin D intake IU/day -Median (25%, 75%) | IU/day | 238 (162 to 270) | 182 (125 to 425) | 215 (165 to 356) |
| Serum vitamin D <75 nmol/L - n (%) | Participants | 13 | 15 | 28 |
6. Primary Endpoint
The registry lists the primary outcome as Change From Baseline in Serum 25OHD, measured over During the 7-month follow-up period.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | nmol/L |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is change from baseline in serum 25OHD, measured in nmol/L. 25OHD is a circulating marker of vitamin D status. The registry describes the target comparison as the difference between groups in adjusted change over the 7-month follow-up. The posted arm-specific results give a mean change of 4.3 nmol/L for placebo, with a 95% confidence interval from -6.6 to 15.1, and 9.6 nmol/L for vitamin D, with a 95% confidence interval from -6.6 to 19.6.
A continuous measure such as serum 25OHD can retain information about the size of a change rather than reducing the result to categories such as above or below a threshold. In general, a biomarker endpoint can help assess whether an intervention is associated with a change in the biological measure it targets. It is not automatically a measure of a clinical benefit. For this trial, the primary endpoint does not directly count asthma exacerbations or describe their severity. The study description identifies exacerbation frequency and severity as interests, and emergency department visits for an asthma flare-up are listed as a secondary outcome. The registry record does not report a primary clinical exacerbation endpoint.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted results give arm-specific mean changes in serum 25OHD, alongside confidence intervals. The placebo estimate is 4.3 nmol/L (95% confidence interval -6.6 to 15.1), and the vitamin D estimate is 9.6 nmol/L (95% confidence interval -6.6 to 19.6). Both intervals extend from a negative value to a positive value, so each includes no change within that arm. These are arm-level intervals; they are not the confidence interval for the adjusted between-group contrast described as the primary question.
The registry record describes the primary comparison as an adjusted group difference, but the result details available in this record do not give the adjusted contrast, its confidence interval, or a p-value. Those quantities should not be reconstructed from the arm-specific estimates. In particular, comparing the two arm estimates by subtraction would not reproduce an adjusted analysis, and the uncertainty for a between-group contrast cannot be obtained by simply treating the arm intervals as if they were the contrast interval. The sponsor's own analysis does not conflict with a recalculation in this record; no discrepancy is flagged.
The arm-specific intervals convey uncertainty about the estimated mean changes. In general, a confidence interval describes a range of values compatible with the data and the method used to construct it; it is not a guarantee that the true value lies in that range. Here, the posted intervals are broad enough to include values on either side of no change. That feature cautions against reading the point estimates alone as a precise account of change. It does not, by itself, answer whether the adjusted difference between arms is statistically distinguishable from zero.
The endpoint is a biomarker, while the study description is also concerned with asthma exacerbations and safety. A result about serum 25OHD cannot, without the relevant clinical outcome results, establish the effect of the intervention on flare frequency, flare severity, or emergency care. The record lists emergency department visits for an asthma flare-up as a secondary outcome, but does not post its result in the registry record for interpretation. It also does not provide results for the listed threshold outcome in the information summarized by the registry record.
The enrollment and arm-specific outcome counts are modest, and the interval estimates reflect uncertainty in the posted endpoint results. The record lists 23 participants for placebo and 22 for vitamin D in these arm-level endpoint results. No analysis-level entries are listed, even though endpoint estimates are posted. Without the adjusted contrast, analysis details, and results for the clinical outcomes, the primary biomarker estimates provide only a limited picture of the trial's questions.
9. Statistical Methods Explained
The primary result concerns a continuous outcome: change in serum 25OHD from baseline, in nmol/L. The registry identifies the summary as a mean and the uncertainty measure as a 95% confidence interval. It describes the intended primary comparison as the group difference in adjusted change over the 7-month follow-up. The posted arm estimates are means with intervals, but an adjusted contrast and its uncertainty are not reported in the result details available in the registry record.
What does a mean change describe?
In general, a mean summarizes the central value of a continuous measurement across the analyzed observations. A mean change describes the average difference between a participant's follow-up measurement and their baseline measurement, aggregated within an arm. It does not show how much individual participants varied, whether changes were similar across participants, or whether a small number of values strongly influenced the average. The registry lists 23 participants for placebo and 22 for vitamin D for the posted endpoint results, but does not provide individual-level values or a measure of spread beyond the confidence intervals.
Change from baseline uses each participant's starting measurement as a reference. In general, this can focus the analysis on change during follow-up rather than on follow-up values alone. The registry describes the target outcome as adjusted change, but does not report which covariates were included, how the adjustment was performed, or whether all participants had measurements at every intended time. Therefore, the mean changes posted for the arms should not be assumed to reveal the complete adjusted analysis.
How should a confidence interval be read?
In general, a confidence interval communicates statistical uncertainty around an estimate under a particular analysis method. A narrower interval indicates greater precision under that method; a wider interval indicates greater uncertainty. A 95% confidence interval is not a range containing 95% of participant measurements. It is also not a probability statement that the particular interval contains the true parameter. Its interpretation depends on the analysis and the assumptions used to construct it.
For placebo, the posted mean change is 4.3 nmol/L, with a 95% confidence interval from -6.6 to 15.1. For vitamin D, the mean change is 9.6 nmol/L, with a 95% confidence interval from -6.6 to 19.6. Since each interval includes zero, the arm-level data are compatible with no mean change as well as with changes in either direction under the reported interval method. These intervals do not directly test the difference between arms. A contrast has its own estimate and uncertainty, accounting for the variability in both groups and for any adjustment specified in the analysis.
Why does the adjusted between-group contrast matter?
The study's stated primary question is comparative: whether adjusted change differed between vitamin D and placebo. An arm's mean change answers a within-arm descriptive question. The between-arm contrast addresses whether the average changes differ. In general, the comparative estimate is the central quantity for a randomized trial because changes could occur in either group over time, including changes unrelated to the assigned intervention. The registry record does not report the numerical adjusted contrast or its confidence interval in the result details, so the comparative magnitude and precision cannot be described from the arm means alone.
Random assignment is intended, in general, to create groups whose differences at entry are not systematically determined by treatment choice. A parallel design assigns participants to a group that remains their assigned comparison group during the trial. Masking can reduce the chance that knowledge of assignment influences care, outcome assessment, or reporting. The record describes the trial as randomized, parallel, and quadruple-masked, but does not provide the randomization procedure, allocation concealment details, or the parties covered by masking.
What do the planning calculations represent?
The sample-size planning illustrations use the observed effect as a basis, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. They consider an effect to detect expressed as a fraction of the observed effect. In general, such calculations illustrate how a future study's required sample size can depend on the effect size being targeted, the significance threshold, and the desired power. A smaller target effect generally requires more information to detect, while a larger target effect generally requires less, under otherwise comparable assumptions.
These are planning illustrations, not observed power and not evidence that the original trial had a particular probability of detecting an effect. The assumptions do not establish that the original enrollment was selected using this calculation. The trial's own sample-size justification and design assumptions are not reported in the registry record. No further numerical planning results are stated in the record details, so no required sample size for a future trial can be inferred from the posted arm means alone.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists 16 outcome measures and names 2 secondary outcomes: participants with total 25OHD at least 75 nmol/L, and emergency department visits for an asthma flare-up. The primary outcome is change from baseline in serum 25OHD. Considering multiple outcomes can raise a multiplicity issue: in general, testing many outcomes may increase the chance that at least one result appears notable by chance if each is assessed separately. The record does not report whether the investigators prespecified a hierarchy, adjusted for multiple comparisons, or used another approach to address multiplicity. It is not possible to infer that no adjustment was used merely because the record does not describe one.
Missing-data handling is also not reported in the registry record. The available information does not state how missing baseline or follow-up serum measurements were handled, whether observations were excluded, or whether imputation was used. The analysis population is not specified, including whether the posted estimates represent all randomized participants or a subset defined by available measurements or other criteria. The endpoint arm counts are listed as 23 for placebo and 22 for vitamin D, while the safety at-risk counts differ; the record does not explain the relationship between these sets of counts.
The record lists zero analysis-level entries, although it does post arm-specific estimates for the primary endpoint. It does not report interim analyses, detailed statistical methods, or a prespecified analysis plan. The adjusted primary contrast is not included in the result details. These omissions limit assessment of how outcomes were selected, how incomplete data may have affected the estimates, and whether the posted analyses followed a prespecified plan.
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 |
|---|---|---|---|
| Placebo | 1 | 24 | 4.2% |
| Vitamin D | 0 | 23 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Placebo | 0 of 24 |
| Vitamin D | 0 of 23 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 1% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Placebo | 17 of 24 |
| Vitamin D | 19 of 23 |
Most frequent serious adverse event terms
| Event term | Organ system | Placebo | Vitamin D |
|---|---|---|---|
| peribronchitis | Respiratory, thoracic and mediastinal disorders | 1 of 24 | 0 of 23 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Placebo | Vitamin D |
|---|---|---|---|
| infections and infestations (SOC) | Infections and infestations | 17 of 24 | 19 of 23 |
| General (SOC) | General disorders | 17 of 24 | 13 of 23 |
| Investigations (SOC) | Investigations | 9 of 24 | 7 of 23 |
| Respiratory (SOC) | Respiratory, thoracic and mediastinal disorders | 7 of 24 | 4 of 23 |
| Gastrointestinal disorders (SOC) | Gastrointestinal disorders | 8 of 24 | 3 of 23 |
| Skin and subcutaneous tissue disorders (SOC) | Skin and subcutaneous tissue disorders | 4 of 24 | 7 of 23 |
| Immune system disorders (SOC) | Immune system disorders | 5 of 24 | 2 of 23 |
| Blood and lymphatic system disorders (SOC) | Blood and lymphatic system disorders | 1 of 24 | 3 of 23 |
| Ear and labyrinth disorders (SOC) | Ear and labyrinth disorders | 2 of 24 | 0 of 23 |
| Nervous system disorder (SOC) | Nervous system disorders | 1 of 24 | 1 of 23 |
Serious events with the highest arm-level rate: peribronchitis (4.2%).
The registry reports serious adverse events by arm. In placebo, 1 participant was affected among 24 at risk; in vitamin D, 0 participants were affected among 23 at risk. Deaths are recorded as 0 in each arm. These are counts within the safety populations listed in the record. They are not the same denominators as the endpoint arm counts, which are listed as 23 for placebo and 22 for vitamin D. The record does not explain the difference between these safety and endpoint counts.
The registry also reports other adverse events affecting 17 participants among 24 at risk in placebo and 19 among 23 at risk in vitamin D. The top serious adverse event term is listed as peribronchitis, with 4.2%. The record does not clarify the event-count basis or denominator for that term in the registry record, so that percentage should not be converted into a participant count or assigned to an arm.
In general, adverse-event counts describe events recorded under a study's collection and classification procedures. They do not establish that an event was caused by the assigned intervention, and comparisons can be difficult to interpret without definitions, timing, severity, and exposure details. The registry record does not report those details for these figures. These results are a description of the posted safety data, not a complete assessment of risk.
12. What the Result Does, and Does Not, Mean
The posted primary endpoint estimates describe mean changes in serum 25OHD during the 7-month follow-up. The placebo arm estimate is 4.3 nmol/L, with a 95% confidence interval from -6.6 to 15.1; the vitamin D arm estimate is 9.6 nmol/L, with a 95% confidence interval from -6.6 to 19.6. Both intervals include zero, and the registry does not report the adjusted between-arm estimate, its confidence interval, or a p-value in the result details. The arm estimates therefore do not provide a precise numerical answer to the stated comparative primary question.
These data concern serum 25OHD, not a direct clinical outcome. The study description identifies asthma exacerbation frequency and severity as interests, and the registry lists emergency department visits for asthma flare-up as a secondary outcome. The result for that outcome is not reported in the registry record details. The number of participants with total 25OHD at least 75 nmol/L is also listed as a secondary outcome, but its result is not reported in those details. No conclusion about those outcomes follows from the arm-specific biomarker changes alone.
The record's safety figures describe serious and other adverse events recorded in each arm, as well as deaths and a listed serious-event term. They are useful as descriptive counts, but they do not establish causation or provide a full account of event timing, severity, or attribution. The safety denominators differ from the endpoint counts, and no explanation is reported.
In general, a trial result is best interpreted in relation to its estimate, uncertainty, outcome definition, and analysis population. Here, the registry record supplies some arm-level estimates and safety counts, but does not report several details needed for a full evaluation of the primary comparison and clinical outcomes. The results should not be read as establishing the effect on asthma attacks or as a complete safety assessment.
13. Why This Trial Matters Statistically
This trial is statistically informative because it illustrates the distinction between an intervention's biological endpoint and the clinical questions motivating its study. Serum 25OHD is the posted primary measure, while the study description focuses more broadly on asthma exacerbations and safety. A change in a biomarker can be relevant to understanding an intervention, but it is not interchangeable with a change in symptoms, exacerbations, or emergency care. Keeping those outcomes separate helps prevent a biomarker result from being treated as direct evidence about a clinical event.
It also illustrates why arm-specific estimates are not a substitute for the between-group comparison in a randomized trial. The registry reports mean changes and confidence intervals for placebo and vitamin D, while describing the primary question as an adjusted difference between groups. The contrast is the quantity that directly addresses the comparative question. Without its estimate and uncertainty, the arm-level results leave the comparative magnitude and precision unresolved. In general, confidence intervals help convey uncertainty, but an interval for each arm does not stand in for an interval around the contrast.
The record also draws attention to reporting completeness. It names secondary outcomes and lists 16 outcome measures, yet only 2 secondary outcomes are named in the available record details. It does not report the adjustment strategy for multiple outcomes, missing-data methods, analysis population, or detailed statistical plan. Such information matters because outcome selection and incomplete follow-up can affect how results are interpreted.
Finally, safety counts require their own careful reading. The at-risk counts for safety differ from the endpoint arm counts, and the registry does not explain why. Reporting those denominators alongside event counts is useful, but does not answer questions about timing, severity, or attribution. These features make clear why trial interpretation depends not only on numerical results but also on transparent descriptions of design and analysis.
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 registry record gives limited detail about eligibility beyond age and asthma attacks triggered mostly by colds. It does not report recruitment setting, diagnostic criteria, severity definitions, or other inclusion and exclusion criteria. The follow-up is described as 7 months, so the record does not establish what happened beyond that period. It also does not provide adherence information or describe whether participants received the assigned oral doses as intended.
The primary endpoint is a biomarker, and the adjusted between-group result is not reported in the result details. The arm-level estimates and intervals do not recover that contrast. The registry also does not report the results for the listed secondary outcomes in the registry record, limiting interpretation of the study's stated clinical aims. There is no detailed account of how the 16 outcome measures were prioritized or analyzed.
Important analysis details are not reported: covariate adjustment, missing-data handling, analysis population, multiplicity procedures, and the trial's statistical plan. The record does not explain why the endpoint counts differ from the safety at-risk counts. It also does not describe how adverse events were defined, assessed, or attributed. These gaps prevent a full assessment of potential bias, precision, and the relationship between the safety figures and the outcome estimates.
The enrollment is recorded as 47, but the registry does not provide a sample-size justification for the trial. Planning calculations based on the observed effect are illustrations and cannot establish what the original design was intended to detect. These limitations concern what can be concluded from the registry record; they do not, on their own, indicate the direction or size of any unreported result.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Vitamin D in Preschoolers With Viral-induced Asthma — NCT02197702.
- Registry record last updated 2024-12-09; status last verified 2024-12.
- Results first posted 2024-12-09.
- 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
NCT02197702 is a completed randomized, parallel-group trial with quadruple masking, sponsored by St. Justine's Hospital. It is listed as Phase 2 and Phase 3, with enrollment of 47. The recorded study dates are 2014-09 for start and 2016-07 for primary completion. The study description concerns children aged 1–6 years with asthma attacks triggered mostly by colds and compares oral vitamin D with an identical placebo.
The primary endpoint is change from baseline in serum 25OHD over the 7-month follow-up. Posted mean changes are 4.3 nmol/L for placebo and 9.6 nmol/L for vitamin D, with the respective 95% confidence intervals -6.6 to 15.1 and -6.6 to 19.6. The adjusted between-group estimate is not reported in the result details. The registry names 2 secondary outcomes and lists 16 outcome measures. It also reports serious and other adverse-event counts, but does not provide a full account of analysis methods, missing data, or adverse-event attribution.