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 Supplementation to Obese Chinese Males (NCT01781169), a non-randomized na study. The primary outcome is Plasma 25-hydroxy Vitamin D (25(OH)D) Level (Nmol/L).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01781169 |
| Phase | NA |
| Condition | Obesity, Insulin Resistance |
| Allocation | Non-Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 43 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Shenzhen Center for Chronic Disease Control |
| Results posted | Yes |
2. Clinical Question
Population
Obese Chinese males are the population of interest. The record lists an enrollment of 43 and identifies obesity and insulin resistance as conditions. It also includes a normal-weight group for comparison. Further eligibility criteria and participant characteristics are not reported in the registry record.
Intervention
The obese group received oral cholecalciferol at 50000 IU/wk for 8 weeks. The record describes the intervention as vitamin D supplementation.
Comparator
The normal-weight group also received oral cholecalciferol at 50000 IU/wk for 8 weeks. This is not an untreated or placebo comparator. The allocation is recorded as non-randomized, so the groups are not a like-for-like control comparison.
Primary question
The listed primary endpoint is plasma 25-hydroxy Vitamin D (25(OH)D) level, measured at baseline and endpoint of the eight-week trial. The registry record does not report the group values, change from baseline, or a comparison between groups.
The stated hypothesis concerns whether oral vitamin D supplementation can reduce parathyroid hormone hypersecretion and insulin resistance in obese Chinese males. The registered primary endpoint, however, is plasma 25(OH)D level. These are distinct quantities: the endpoint records a vitamin D measure, while the hypothesis also names parathyroid hormone and insulin resistance. The registry record lists only one outcome measure and does not provide results for it or for those other concepts.
Because both groups are described as receiving the same supplementation, the normal-weight participants provide a comparison across weight groups under supplementation, not a comparison of supplementation against no supplementation. The non-randomized allocation further limits causal interpretation. The record does not report a separate comparison that would isolate the effect of supplementation from differences associated with group membership.
3. Trial Design
The study is recorded as a completed, parallel-group, non-randomized trial with no masking. Its enrollment is 43. The registry record lists an obese group of 22 and a normal-weight group of 21 in the safety information. Both groups are described as receiving oral cholecalciferol at 50000 IU/wk for 8 weeks. The study start is recorded as 2011-04 and primary completion as 2011-12.
A parallel design means that participants are assigned to distinct groups rather than each participant receiving a sequence of study conditions. In this record, the groups are defined by weight status. Because allocation is non-randomized, assignment does not provide the balancing of measured and unmeasured characteristics that random allocation is intended to support. Differences between groups could therefore reflect pre-existing group characteristics as well as any differences during the study.
The record specifies no masking. It does not report whether outcome assessors or laboratory staff were masked, or whether any procedures were used to limit measurement bias. Details about recruitment, eligibility, adherence, co-interventions, and participant flow are not reported in the registry record.
The protocol summary says index measures were conducted at baseline and endpoint. The primary endpoint timeframe is likewise described as endpoint and baseline of the eight weeks' trial. The registry record does not describe the interval between those measurements beyond the eight-week trial period, nor does it provide the actual measurements. The study's phase is recorded as NA. Its sponsor is the Shenzhen Center for Chronic Disease Control.
The record's stated comparison is not a conventional treatment-versus-control contrast: both groups receive the same supplement, while the groups differ by weight status. Consequently, a between-group difference would not on its own estimate what supplementation changed relative to no supplementation. The record does not report a randomized comparison or another analysis designed to estimate that treatment contrast.
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: After enrollment, baseline information of the volunteers including vitamin D nutritional status, health records, etc. were evaluated. Including and excluding criteria were used to select the subjects who were suitable for the intervention trial.
Overall Study
| Stage | Obese Group | Normal-weight Group |
|---|---|---|
| STARTED | 22 | 21 |
| COMPLETED | 21 | 21 |
| NOT COMPLETED | 1 | 0 |
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 | Normal-weight Group | Obese Group | Total |
|---|---|---|---|---|
| Participants analysed | 21 | 21 | 42 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 21 | 20 | 41 |
| Age, Categorical: >=65 years | Participants | 0 | 1 | 1 |
| Age Continuous | years | 34.4 (SD 8) | 44.7 (SD 8.8) | 39.5 (SD 9.8) |
| Sex: Female, Male: Female | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Male | Participants | 21 | 21 | 42 |
| Region of Enrollment: China | participants | 21 | 21 | 42 |
6. Primary Endpoint
The registry lists the primary outcome as Plasma 25-hydroxy Vitamin D (25(OH)D) Level (Nmol/L), measured over Endpoint and baseline of the 8 weeks' trial.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | nmol/L |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is plasma 25-hydroxy Vitamin D (25(OH)D) level, expressed in nmol/L. The registry record specifies a mean as the summary measure and standard deviation as the dispersion measure. The stated timeframe is baseline and endpoint of the eight weeks' trial, indicating that the measure was intended to be assessed at both points.
As general context, 25(OH)D is a circulating measure used to describe vitamin D status. Measuring it can show the concentration recorded in blood at a specified time. A mean summarizes the central level across a group, while a standard deviation describes how dispersed individual measurements are around that mean. These summaries answer different questions: the mean characterizes the group level, and the standard deviation characterizes variability among participants.
The registry record does not report baseline or endpoint means, standard deviations, changes, confidence intervals, or statistical tests. It therefore does not establish the direction or size of any change in this measure. It also does not report the endpoint's relationship to parathyroid hormone or insulin resistance. Although those concepts appear in the stated hypothesis, they are not reported as the listed primary outcome measure.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registered question concerns vitamin D supplementation in obese Chinese males, with normal-weight males included as a comparison group. The record reports that both groups received cholecalciferol at 50000 IU/wk for 8 weeks. It identifies plasma 25(OH)D level as the primary endpoint, assessed at baseline and endpoint, and specifies mean and standard deviation as its summary format.
No endpoint values are reported in the registry record. There is no baseline mean, endpoint mean, change from baseline, standard deviation, confidence interval, or p-value. The number of analyses recorded is 0. As a result, the posted record does not show whether 25(OH)D changed, how variable the measurements were, or how precisely any estimated change was measured. It is not possible to describe the observed magnitude, direction, or statistical uncertainty of an endpoint result from the information recorded.
The group structure matters for interpretation. The obese and normal-weight groups are not randomized, and both are described as receiving the supplement. A difference between their results, if reported, would compare groups with different weight status under supplementation. It would not by itself isolate the effect of supplementation relative to no supplementation. Non-randomized groups can differ in other characteristics as well; the record does not report which characteristics were measured or adjusted for.
The stated hypothesis includes parathyroid hormone hypersecretion and insulin resistance, but the only registered outcome measure is plasma 25(OH)D level. The registry record does not report results for parathyroid hormone or insulin resistance. The endpoint description therefore cannot be used to infer whether those outcomes changed.
General statistical context: an estimate describes the observed data, while a confidence interval, when reported, conveys uncertainty about the estimate under the analysis assumptions. Neither is available for this endpoint in the registry record. Similarly, a p-value, if reported, would summarize how compatible the data are with a specified statistical model and null hypothesis; it would not measure the size or practical importance of an effect. No p-value is reported, and no such interpretation can be made for the registered outcome.
The record marks the study completed, but completion status does not supply missing outcome results. The defensible reading is limited to the study setup, registered endpoint, and recorded safety counts. The endpoint findings and the hypothesis-related clinical outcomes remain unreported in the registry record.
9. Statistical Methods Explained
The study is recorded as parallel and non-randomized, with no masking. A parallel design places participants in separate groups, and the groups are followed over the study period. Here the listed groups are obese and normal-weight males. Both are described as receiving cholecalciferol at 50000 IU/wk for 8 weeks. The design therefore compares weight-defined groups receiving the same stated regimen rather than randomizing participants to supplement or control.
What does non-randomized allocation mean?
General explanation: random allocation is used to make group membership less dependent on participant characteristics, on average. Without random allocation, groups can differ before the intervention begins. Such differences may influence outcomes and can complicate interpretation of a group contrast. The registry record does not describe how participants entered the two groups, whether baseline differences were assessed, or whether any adjusted analysis was planned or performed. The number of analyses recorded is 0.
For this study, the normal-weight group is not a no-supplement comparator: its arm description also specifies vitamin D supplementation. The groups also differ in weight status by definition. Thus, even if group outcome values were available, a simple contrast would not alone identify a supplementation effect. A change over time within a group could describe observed measurements, but without a suitable comparison it would not separate intervention-related change from other time-related influences.
What do mean and standard deviation describe?
The primary endpoint is a continuous measure, plasma 25(OH)D level in nmol/L. The registry specifies the mean and standard deviation. General explanation: the mean is a measure of the center of a set of numerical observations. The standard deviation describes the spread of observations around that mean. They are descriptive summaries and do not, by themselves, show whether an observed difference is statistically distinguishable from random variation or how precisely a treatment effect has been estimated.
The endpoint timeframe is baseline and endpoint of the eight weeks' trial. Repeated measurements can be described as values at each time or as within-participant changes, but these approaches answer somewhat different questions. The registry record does not state which change score, model, or comparison was planned. It does not report group means, standard deviations, individual-level data, or change estimates. No calculation of change or uncertainty can therefore be described from the registered results.
What would uncertainty measures add?
General explanation: a confidence interval gives a range of values compatible with an estimate under the statistical model and its assumptions. Its width reflects precision: wider intervals indicate less precise estimation than narrower intervals. A confidence interval does not remedy a biased design, and it does not establish that an estimate is free of confounding. The registry record does not report a confidence interval for the primary endpoint.
A hypothesis test and p-value are also not reported. In general, a p-value is evaluated in relation to a specified null hypothesis and model. It is not a measure of effect size, clinical importance, or the probability that a hypothesis is true. Without the observed endpoint estimate and its analysis, there is no result to interpret using a test or p-value. The registry record does not provide a statistical analysis plan or a description of any model used.
Why can variability matter?
General explanation: the standard deviation describes variation among individual observations. If data are substantially more variable than a model assumes, methods that rely on that model can produce uncertainty estimates that are too optimistic. This is one reason analysts examine whether model assumptions fit the data and may use methods that account for over-dispersion when relevant. The registry record does not report the endpoint distribution or enough results to assess its variability or whether over-dispersion is a concern. This is general statistical context, not a description of an analysis performed in this study.
The record contains a planning illustration framework based on a stated fraction of an observed effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation. Such planning quantities are not observed trial outcomes. The registry record does not provide calculated participant requirements in the information available for interpretation, and it does not report the trial's own sample-size justification. Any planning illustration based on an observed effect should not be read as observed power or as evidence that the study was adequately powered.
Finally, the absence of masking can matter when outcomes or decisions involve judgment, although a laboratory measurement may be less dependent on subjective assessment than some outcomes. The registry record does not specify the measurement procedures or who conducted them. This general consideration cannot determine whether measurement bias occurred in this study.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists one outcome measure: plasma 25(OH)D level, summarized as a mean with standard deviation and assessed at baseline and endpoint. It records 0 analyses. It does not report a statistical analysis plan, a hierarchy of outcomes, planned contrasts, or how any multiple testing would have been handled. The stated hypothesis also mentions parathyroid hormone and insulin resistance, but the record does not list those as outcome measures or report their analyses.
Multiplicity is a general concern when many outcomes, time points, subgroups, or statistical comparisons are tested. Testing many questions can increase the chance of finding an apparently notable result by chance. Whether that concern applied to the investigators' analyses cannot be assessed because analyses and a full analysis plan are not reported in the registry record. The single listed measure does not establish that no other analyses were conducted.
Missing-data handling is not reported in the registry record. It does not state how many participants completed each measurement, whether any endpoint observations were missing, how missing values were handled, or whether any sensitivity analyses were planned. The enrollment of 43 and the group counts in the safety information do not establish the number with evaluable primary endpoint data.
Analysis populations are also not reported in the registry record. There is no description of whether results were intended for all enrolled participants, participants who completed the intervention, or another defined group. No exclusions or analysis denominators for the primary endpoint are given. Consequently, the endpoint population and the effect of any missing observations on the findings cannot be determined from this record.
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 |
|---|---|---|---|
| Normal-weight Group | 0 | 21 | 0.0% |
| Obese Group | 0 | 22 | 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 |
|---|---|
| Normal-weight Group | 0 of 21 |
| Obese Group | 0 of 22 |
The safety information lists 21 participants at risk in the normal-weight group and 22 in the obese group. It records 0 serious adverse events in each group and 0 other adverse events in each group. These are the event counts recorded for the stated groups; they do not establish that every possible harm was assessed or reported.
Deaths are recorded as null for both groups, so deaths are not reported in the registry record. Null should not be interpreted as a reported zero. The record also does not provide serious adverse event terms; the top serious terms list is empty. It does not describe how adverse events were collected, how long safety follow-up lasted, or whether participants withdrew because of adverse events.
General explanation: a count of zero recorded events is a description of the reported observations, not proof that an event cannot occur. Interpretation depends on how events were defined, sought, and captured, as well as the amount of follow-up. The registry record's counts should therefore be read narrowly as the safety figures entered for these groups, rather than as a complete estimate of risk.
The record describes both groups as receiving the same supplementation, and the groups were not randomized. The safety counts do not provide a randomized comparison of supplement exposure against no exposure. They also do not establish safety beyond the recorded groups and study period.
12. What the Result Does, and Does Not, Mean
The registry record documents a completed, non-randomized parallel study in which obese and normal-weight Chinese males received the same stated cholecalciferol regimen: 50000 IU/wk for 8 weeks. The registered primary endpoint is plasma 25(OH)D level at baseline and endpoint. The record also includes the stated hypothesis about parathyroid hormone and insulin resistance.
What the record does not provide is the primary endpoint result. There are no reported means, standard deviations, changes, confidence intervals, or tests. It does not report findings for parathyroid hormone or insulin resistance. Therefore, the posted results do not establish whether the registered endpoint changed or how precisely any change was estimated. The study's completed status does not fill this outcome-reporting gap.
The comparison also does not answer a simple supplement-versus-no-supplement question. Both groups are described as receiving vitamin D, and the groups are defined by weight status rather than randomized treatment assignment. A difference between them, if one had been reported, would not by itself show what would have happened to the same population without supplementation. Non-randomized group differences may also reflect characteristics other than the intervention.
General explanation: statistical evidence about an effect depends on the comparison, the quality and completeness of the measurements, and the analysis. A precise estimate can still be biased if the design does not support the causal contrast of interest. Conversely, absence of a reported result does not demonstrate that there was no change. Here, the primary outcome findings are not reported in the registry record, so neither a positive nor a null endpoint conclusion is warranted.
The safety entries record no serious or other adverse events in either group, while deaths are not reported. Those entries are limited to the recorded counts and do not establish the absence of all possible harms. Overall, the record supports a description of the study setup and the specific registered measurements, but not a conclusion about efficacy, changes in the hypothesized outcomes, or broader safety.
13. Why This Trial Matters Statistically
This study is statistically informative as an example of why the comparison group and allocation method determine what a result can mean. The two groups are defined by weight status, are not randomized, and both receive the stated vitamin D regimen. That design can describe observations in the two groups, but it does not create a direct randomized contrast between supplementation and no supplementation.
The difference between the stated hypothesis and the registered primary endpoint is also important. The hypothesis names parathyroid hormone and insulin resistance, while the listed outcome is plasma 25(OH)D level. A measure of vitamin D status can describe exposure-related biology, but it cannot stand in for unreported results on the other hypothesized outcomes. Keeping the endpoint and the broader hypothesis distinct avoids over-interpreting what was measured.
Another statistical lesson is that a completed study is not equivalent to a reported outcome analysis. The registry record identifies the endpoint and summary format, but does not report the endpoint values or analyses. Without those, readers cannot assess the magnitude, variability, or precision of the endpoint findings. This limits interpretation independently of the sample size or study duration.
General explanation: study design, measurement, and reporting each contribute to the strength of an inference. Statistical methods can quantify uncertainty in observed data, but they cannot create a missing comparison or recover results that are not reported. In this record, those distinctions clarify what can be said: the groups and regimen are documented, while the primary outcome findings and analysis details are not.
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 most direct limitation for interpretation is that the registry record does not report the primary endpoint results. It gives no baseline or endpoint values, variability estimates, changes, confidence intervals, or tests. It also records 0 analyses. The magnitude and precision of any endpoint finding therefore cannot be assessed.
The comparison is non-randomized and is between obese and normal-weight groups, both of which are described as receiving the same supplementation. This does not isolate supplementation from no supplementation. Group differences could reflect weight status or other characteristics, and the registry record does not describe baseline comparability or adjusted analyses.
The record lists one outcome measure, plasma 25(OH)D level, while the stated hypothesis also concerns parathyroid hormone and insulin resistance. Results for those hypothesized outcomes are not reported in the registry record. The record also does not specify the primary endpoint analysis, analysis populations, missing-data methods, or any multiplicity approach.
Further study details are not reported in the registry record, including eligibility criteria, recruitment procedures, participant flow, adherence, measurement procedures, and whether any outcome assessors were masked. The primary endpoint timeframe is described as baseline and endpoint of the eight weeks' trial, but actual measurement counts and missing observations are not given.
The safety record includes zero recorded serious and other adverse events in both groups, but deaths are not reported, and details about event collection and follow-up are absent. These limitations mean that both outcome and safety interpretation must remain confined to the specific information entered in the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Vitamin D Supplementation to Obese Chinese Males — NCT01781169.
- Registry record last updated 2013-10-30; status last verified 2013-09.
- Results first posted 2013-09-30.
- 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
The registry record describes a completed, parallel, non-randomized study with no masking and enrollment of 43. It compares obese and normal-weight Chinese males; both groups are described as receiving oral cholecalciferol at 50000 IU/wk for 8 weeks. The study start is recorded as 2011-04 and primary completion as 2011-12.
The primary endpoint is plasma 25-hydroxy Vitamin D (25(OH)D) level in nmol/L, summarized as a mean with standard deviation at baseline and endpoint. The record lists one outcome measure and 0 analyses. It does not report endpoint results or results for the hypothesis-related outcomes of parathyroid hormone and insulin resistance.
Safety entries record 0 serious and 0 other adverse events in each group. Deaths are not reported in the registry record. The non-randomized, weight-defined comparison does not provide a supplement-versus-no-supplement contrast.