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 Effect of Vitamin D Treatment in Primary Hyperparathyroidism (NCT00674154), a randomized phase 2, phase 3 study. The primary outcome is Decrease in Preoperative P-PTH.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00674154 |
| Phase | Phase 2, Phase 3 |
| Condition | Vitamin D Deficiency, Primary Hyperparathyroidism, Hypercalcemia |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 46 |
| Arms in the primary outcome | 2 |
| Lead sponsor | University of Aarhus |
| Results posted | Yes |
2. Clinical Question
Population
People with primary hyperparathyroidism were studied. The registry also lists vitamin D deficiency and hypercalcemia as conditions. Further eligibility criteria and a more detailed description of the analyzed population are not reported in the registry record.
Intervention
The active group received cholecalciferol, described as 1400 IU in 2 tablets once daily for 52 weeks. The brief study summary describes the primary aim as assessing 6-months of vitamin D supplements, while the posted primary endpoint is measured at 25 weeks. The record does not explain these differing durations.
Comparator
The comparison group received placebo, described as two tablets daily for 52 weeks. The registry labels the trial randomized and reports a parallel-group design with quadruple masking.
Primary question
The primary question is whether vitamin D treatment changes preoperative plasma PTH compared with placebo. The posted endpoint is the decrease in P-PTH after 25 weeks, measured in pmol/l. Results are reported as group means and a between-group mean difference.
3. Trial Design
The registry describes a randomized, parallel-group trial with quadruple masking and lists its phase as phase 2 and phase 3. The sponsor is the University of Aarhus. The record lists enrollment as 46 and the study status as completed. The recorded start is 2008-05, and primary completion is listed as 2013-08.
The active intervention was cholecalciferol, described as 1400 IU, 2 tablets once daily in 52 weeks. The placebo group is described as taking two tablets daily in 52 weeks. The brief study summary states that the primary aim was to assess whether 6-months of vitamin D supplements could decrease PTH compared with placebo. The primary outcome entry, however, gives a timeframe of 25 weeks. The registry record does not explain the difference between these descriptions.
For the posted primary outcome, the Vitamin D group has 20 participants and the Placebo group has 22 participants. These group counts do not account for the enrollment figure of 46; the record does not explain the relationship between enrollment and the analyzed outcome groups. The reason for any difference is not reported in the registry record.
The record identifies five secondary outcomes: muscular function, postoperative hypocalcemia, quality of life, bone mineral density, and trabecular and cortical volumetric bone mineral density measured by QCT and pQCT of the hip, spine and forearm. It lists six outcome measures overall, but the results available for this analysis include five posted secondary outcomes and no posted analyses. The registry does not provide further details about the trial’s allocation procedure, masking implementation, or the analysis populations.
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: We screened 227 PHPT patients. A total of 46 patients were included.
Overall Study
| Stage | Vitamin D | Placebo |
|---|---|---|
| STARTED | 23 | 23 |
| COMPLETED | 20 | 20 |
| NOT COMPLETED | 3 | 3 |
Reasons for not completing this period:
| Reason | Vitamin D | Placebo |
|---|---|---|
| Withdrawal by Subject | 3 | 1 |
| Did not want parathyroidectomy | 0 | 2 |
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 | Vitamin D | Placebo | Total |
|---|---|---|---|---|
| Participants analysed | 23 | 23 | 46 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 16 | 14 | 30 |
| Age, Categorical: >=65 years | Participants | 7 | 9 | 16 |
| Age Continuous | years | 58 (SD 14) | 57 (SD 13) | 58 (SD 13) |
| Sex: Female, Male: Female | Participants | 16 | 19 | 35 |
| Sex: Female, Male: Male | Participants | 7 | 4 | 11 |
| Region of Enrollment: Denmark | participants | 23 | 23 | 46 |
6. Primary Endpoint
The registry lists the primary outcome as Decrease in Preoperative P-PTH, measured over 25 weeks.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Error |
| Unit | pmol/l |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is the decrease in preoperative P-PTH, or plasma parathyroid hormone, after 25 weeks. It is expressed in pmol/l and treated as a continuous measure, with results reported as means. PTH is the measure named in the study’s primary aim: the trial sought to compare its change with vitamin D treatment against its change with placebo.
The reported group means describe the decrease from the relevant baseline measure, rather than an endpoint value alone: the Vitamin D group mean is -2.2 pmol/l and the Placebo group mean is 0.2 pmol/l. The registry’s description calls this a decrease in plasma PTH after 25 weeks of preoperative treatment. The posted between-group mean difference is -2.4 pmol/l, calculated as Vitamin D minus Placebo. In the direction used by the registry, a more negative mean represents a larger decrease.
Using a continuous endpoint preserves the magnitude of the measured change rather than reducing it to a yes-or-no outcome. A mean difference directly describes the difference between the groups’ average changes. It does not, by itself, show how individual participants’ values varied, and the registry record does not give the distribution of individual changes.
The record gives the endpoint timeframe as 25 weeks, while the intervention descriptions specify 52 weeks and the brief summary describes 6-months of supplements. No further explanation reconciling these time references is reported in the registry record.
7. Results Posted in the Registry
- Vitamin D: mean -2.20 versus 0.20 on control; difference -2.40 (95% CI -4.79 to -0.01), standardized effect d = -0.60; z-test p = 0.049.
Mean difference: Vitamin D
95% CI: -4.79 to -0.01
Recalculated from the posted summary statistics
8. Statistical Interpretation
For the primary outcome, the mean decrease was -2.2 pmol/l in the Vitamin D group and 0.2 pmol/l in the Placebo group. The posted mean difference, defined as Vitamin D minus Placebo, is -2.4 pmol/l. Thus, the posted group averages differ in the direction of a greater decrease in the Vitamin D group. This is a description of the recorded outcome, not a conclusion about what treatment should be used.
The interval attached to the mean difference runs from -4.792 to a value just below zero on the negative side. The interval therefore includes effects ranging from a comparatively larger negative difference to one very close to no difference. The registry also reports an unadjusted p-value of 0.049. That value describes the compatibility of the observed result with a statistical null model under the test’s assumptions; it does not measure the probability that the null hypothesis is true, nor does it establish the size or importance of an effect.
There is no posted adjusted analysis for the primary outcome in the record. The reported p-value should therefore be read as unadjusted. The registry record does not report whether the outcome was analyzed under a prespecified statistical plan, whether there were interim analyses, or how multiplicity across outcomes was handled. Those omissions matter because interpretation can depend on whether an outcome and analysis were selected in advance and how many comparisons were examined.
The reported standard errors are 0.7 for Vitamin D and 1.0 for Placebo. A standard error describes uncertainty around an estimated group mean, not the spread of individual participant values. The arm sizes reported for this outcome are 20 and 22. The registry does not supply standard deviations for the observed group changes, nor does it describe missing observations or the method used to handle them.
These results are limited to the posted primary outcome and its stated timeframe. The registry lists secondary outcomes concerning muscular function, postoperative hypocalcemia, quality of life, and bone measures, but secondary result details are not included in the registry record for this analysis. The record also describes the intervention over 52 weeks, while the primary endpoint is at 25 weeks and the brief summary refers to 6-months. The timing discrepancy is not explained. Accordingly, the numerical findings should be interpreted as the posted comparison at the registry’s stated primary endpoint, without assuming how they relate to other time points or outcomes.
9. Statistical Methods Explained
The registry reports a continuous primary outcome, summarized as a mean, and a comparison between two groups. The posted contrast is a mean difference: the Vitamin D group mean minus the Placebo group mean. This makes the sign interpretable in relation to the group order. Here, the posted mean difference is -2.4 pmol/l, with group means of -2.2 pmol/l and 0.2 pmol/l. A negative contrast indicates that the first group’s mean is lower than the second group’s mean on the recorded change scale.
What does a mean difference describe?
A mean is a measure of the center of a set of observations. For a continuous outcome, it summarizes the average value or change in a group. A mean difference compares these averages on the outcome’s original scale, so the result retains the unit: pmol/l. It does not describe every participant’s experience, and a group mean can conceal variation among individual values. The registry’s posted result is a group-level summary; individual observations are not reported in the registry record.
The arm-level spread is reported as standard error. In general, a standard error describes the precision of an estimated mean, whereas a standard deviation describes the variability of individual observations. They answer different questions. The values 0.7 and 1.0 are the posted standard errors for the Vitamin D and Placebo groups, respectively. The registry does not report the group standard deviations for this outcome.
What is the role of a confidence interval?
In general, a confidence interval gives a range of estimates compatible with the observed data under the statistical model and its assumptions. It communicates uncertainty about the estimated contrast, rather than the range of individual participant outcomes. The interval for this result extends from -4.792 to just below zero. Its position on the negative side conveys the direction of the posted estimate, while its proximity to zero at one end indicates that estimates close to no difference are also compatible with the interval.
The registry reports an unadjusted p-value of 0.049. In general, a p-value measures how unusual data at least as incompatible with a specified null model would be if that model and the test assumptions held. It is not the probability that the null model is correct, and it does not quantify clinical importance. The word “unadjusted” is important: the record does not state that this p-value accounts for multiple outcomes or analyses. No adjusted primary analysis is posted in the record.
Why can over-dispersion matter?
General explanation: over-dispersion arises when observations vary more than a statistical model expects. If a model assumes less variation than is present, standard errors can be too small and intervals too narrow, making estimates appear more precise than they are. This is especially relevant for some count outcomes, where a simple model may not capture extra variability. The primary endpoint is continuous, and the registry record does not report an over-dispersion assessment or the model details needed to evaluate it. It would not be justified to infer whether over-dispersion was present or affected the reported analysis.
What can be inferred from the design labels?
The record labels the study randomized, parallel, and quadruple-masked. In general, random allocation is intended to reduce systematic differences between groups, a parallel design assigns participants to one treatment group for comparison, and masking is intended to limit the influence of knowledge about assignment. These design features describe the trial structure, but they do not establish that every possible bias was avoided. The registry record does not give details of sequence generation, allocation concealment, or who was included in the “quadruple” masking description.
The record identifies the phases as phase 2 and phase 3. It does not report a statistical analysis plan, the original sample-size justification, interim analyses, missing-data methods, or analysis populations. These details cannot be reconstructed from the posted outcome summaries. The primary outcome’s group counts are 20 and 22, while enrollment is listed as 46; the registry does not explain this difference. The labels and summaries therefore support a focused reading of the reported contrast, but not a full audit of the trial’s analysis procedures.
10. Confidence Intervals and Precision
The posted mean difference is -2.4 pmol/l, and its confidence interval runs from -4.792 to just below zero. The width of an interval conveys how much uncertainty surrounds an estimate: a broader range allows a wider set of plausible values, while a narrower range indicates greater precision under the analysis assumptions. This interval includes a comparatively large negative difference and values very close to no difference. It does not establish which value is the true effect.
The reported unadjusted p-value is 0.049. Read alongside the interval, it indicates that the estimate lies close to the boundary between a negative difference and no difference under the model used for the calculation. The record does not report an adjusted p-value or describe any multiplicity procedure, so the unadjusted result should not be treated as if it incorporated adjustment for other outcomes or analyses.
Precision is also affected by the amount of information available and the variability of the measurements. The posted arm sizes are 20 and 22, and the standard errors are 0.7 and 1.0. The registry does not give the standard deviations or individual measurements, so the distribution and heterogeneity of participant changes cannot be assessed from these summaries. Nor does the registry explain why enrollment is listed as 46 while the primary outcome groups have the reported counts.
In general, an interval quantifies sampling uncertainty conditional on the analysis model; it does not account automatically for bias, missing data, outcome selection, or an unreported analysis decision. Those aspects are not detailed in the registry record. The interval is therefore useful for judging the statistical precision of the posted contrast, but it cannot resolve those other uncertainties.
11. Planning a Similar Trial: Sample Size
This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.
| Effect to detect | Participants per arm, 80% power | Participants per arm, 90% power |
|---|---|---|
| 100% of the observed effect | 45 | 60 |
| 75% of the observed effect | 79 | 106 |
| 50% of the observed effect | 177 | 237 |
The sample-size figures are planning illustrations based on fractions of the observed mean difference. For this continuous outcome, the figures are participants per arm, not total events. The rows describe planning for 100%, 75%, and 50% of the observed effect. The corresponding figures are 45, 79, and 177 participants per arm for 80% power, and 60, 106, and 237 participants per arm for 90% power.
The planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is the stated fraction of the observed effect. The registry record does not report the assumptions used for the trial’s original design, so these illustrations should not be read as a reconstruction of that design.
In plain language, the 80% power column gives the planned number of participants per arm under those assumptions for an 80% chance of detecting the specified effect if that effect were the true effect and the model assumptions held. The 90% power column describes the corresponding planning target for a 90% chance. These are prospective planning concepts, not guarantees about the result of a study.
Smaller effects require more participants to detect under otherwise unchanged assumptions. That pattern is reflected in the increasing per-arm figures as the planning effect moves from the full observed effect to a smaller fraction. These values are not observed power; they are illustrations calculated from the observed effect, not a measure of how much power the completed trial actually had.
12. How the Sample Size Is Derived
Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z1−α/2 = 1.960) and the desired power (z1−β = 0.842 for 80% and 1.282 for 90%).
Formula
n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.
Worked calculation for this trial
- Observed difference Δ = -2.400; pooled standard deviation σ = 4.026.
- n = 2 × (1.96 + 0.842)2 × 4.0262 / -2.4002 = 44.2, rounded up to 45 participants per arm for 80% power.
The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).
R code
alpha <- 0.05
z_a <- qnorm(1 - alpha / 2) # two-sided
delta <- -2.4 # observed difference in means
sigma <- 4.02554344157407 # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))
# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")
# Simulation: exact two-sample t-test using simulated means and variances
set.seed(674154)
n <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n)) # difference in sample means
s2 <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1)) # pooled sample variance
tstat <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))
Output from running the code
100% of observed effect: n per arm = 45 (80% power), 60 (90% power)
75% of observed effect: n per arm = 79 (80% power), 106 (90% power)
50% of observed effect: n per arm = 177 (80% power), 237 (90% power)
power.t.test: 45.1
Simulated power at n = 45 per arm: 0.796 (20000 replicates)The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.
13. Multiplicity, Missing Data and Analysis Populations
The registry lists six outcome measures overall and five posted secondary outcomes. Those secondary outcomes concern muscular function, postoperative hypocalcemia, quality of life, bone mineral density, and trabecular and cortical volumetric bone mineral density measured by QCT and pQCT of the hip, spine and forearm. The registry entries available for this analysis do not include results for those outcomes. The registry lists zero analyses, so it does not provide posted analysis details beyond the reported comparison summarized for the primary endpoint.
Multiplicity arises when several outcomes, time points, or statistical comparisons are examined. In general, the more tests that are conducted, the greater the chance that at least one result will appear unusual by chance alone. Methods to address multiplicity may adjust the interpretation or the statistical threshold, but the registry record does not report whether any such method was planned or used. The primary p-value is identified as unadjusted; it should not be interpreted as accounting for other possible comparisons.
The record does not report the statistical analysis plan, the prespecified order of outcomes, interim analyses, or a method for controlling multiplicity. It also does not state whether analyses were planned for all randomized participants, participants who completed treatment, or another analysis population. The group counts associated with the primary outcome are 20 for Vitamin D and 22 for Placebo. The record lists enrollment as 46 but does not explain how those figures relate or whether outcome data were missing.
Missing-data methods, reasons for missingness, and participant flow by analysis population are not reported in the registry record. Without these details, it is not possible to determine whether the posted means reflect all randomized participants or a subset, or how missing outcomes may have been handled. These are limitations in what can be evaluated from the registry record, not evidence that a particular analysis or data problem occurred.
14. 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 |
|---|---|---|---|
| Vitamin D | 1 | 20 | 5.0% |
| Placebo | 1 | 22 | 4.5% |
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 |
|---|---|
| Vitamin D | 4 of 20 |
| Placebo | 6 of 22 |
Most frequent serious adverse event terms
| Event term | Organ system | Vitamin D | Placebo |
|---|---|---|---|
| Nephrolithiasis | Renal and urinary disorders | 1 of 20 | 0 of 22 |
| Eye operation | Eye disorders | 0 of 20 | 1 of 22 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Vitamin D | Placebo |
|---|---|---|---|
| Eye infection | Eye disorders | 1 of 20 | 1 of 22 |
| Lower leg cramp | Musculoskeletal and connective tissue disorders | 1 of 20 | 1 of 22 |
| Pneumonia | Respiratory, thoracic and mediastinal disorders | 2 of 20 | 0 of 22 |
| Abdominal pain | Gastrointestinal disorders | 0 of 20 | 1 of 22 |
| Steatosis hepatis | Gastrointestinal disorders | 0 of 20 | 1 of 22 |
| Hand eczema | Skin and subcutaneous tissue disorders | 0 of 20 | 1 of 22 |
| Cystitis | Renal and urinary disorders | 1 of 20 | 0 of 22 |
| Heamatoma | Skin and subcutaneous tissue disorders | 0 of 20 | 1 of 22 |
| Voice change | Nervous system disorders | 0 of 20 | 1 of 22 |
| Changed sense of touch | Nervous system disorders | 0 of 20 | 1 of 22 |
Serious events with the highest arm-level rate: nephrolithiasis (5.0%), eye operation (4.5%).
The registry reports serious adverse events for 1 of 20 participants at risk in the Vitamin D group and 1 of 22 at risk in the Placebo group. For other, non-serious adverse events, it reports 4 of 20 at risk in the Vitamin D group and 6 of 22 at risk in the Placebo group. These are recorded affected-participant counts and denominators, not measures of the primary PTH outcome.
The registry lists nephrolithiasis at 5.0% and eye operation at 4.5% among its top serious terms. It does not provide further context in the registry record about how these terms relate to the treatment groups or the serious-event counts. Death counts are not reported in the registry record.
These safety figures should be read as event reporting within the recorded groups, not as a complete comparison of safety. The registry record does not give event timing, severity detail beyond the serious/non-serious grouping, relatedness to treatment, or a fuller account of how events were collected. The counts alone do not establish whether an event was caused by treatment, and they do not support medical advice.
15. What the Result Does, and Does Not, Mean
The posted primary outcome shows a mean decrease in P-PTH of -2.2 pmol/l in the Vitamin D group and a mean of 0.2 pmol/l in the Placebo group at the stated 25-week endpoint. The mean difference is -2.4 pmol/l, with a confidence interval extending from -4.792 to just below zero and an unadjusted p-value of 0.049. These figures describe the registry’s reported comparison and its statistical uncertainty.
The result does not, on its own, establish how important the difference is for patients or how it relates to the secondary outcomes. The registry’s stated secondary outcomes include muscular function, postoperative hypocalcemia, quality of life, and bone measures, but their results are not included in the available record. The primary endpoint is a laboratory measure of PTH; it is not itself a report of symptoms or other clinical outcomes.
The result also does not resolve whether findings would be similar at another time point or in a different population. The intervention descriptions specify 52 weeks, the brief summary describes 6-months of supplementation, and the primary outcome is listed at 25 weeks. The registry does not explain the difference. Further population details, including eligibility criteria and the analysis population, are not reported in the registry record.
The interval includes values close to no difference, and the record provides an unadjusted p-value without a reported multiplicity procedure. The statistical summaries therefore should not be treated as proof of a definitive effect or as evidence of no effect. They also do not replace information about missing observations, the prespecified analysis, or the broader context of outcomes and safety. The appropriate reading is limited to the posted group means and contrast, under the assumptions of the analysis used.
16. Why This Trial Matters Statistically
This trial is statistically informative as an example of how a point estimate, uncertainty interval, and p-value contribute different information. The mean difference of -2.4 pmol/l describes the direction and size of the posted group contrast on the outcome’s measurement scale. The confidence interval expresses uncertainty around that contrast, while the unadjusted p-value gives a test-based summary under a statistical model. None of these quantities alone describes every participant’s outcome or the clinical importance of the result.
The interval reaches very close to zero, making precision central to interpretation. A point estimate can look distinct from zero while the range of compatible estimates still extends to values near no difference. The posted p-value of 0.049 should therefore be read together with the interval and with the fact that it is unadjusted. The record does not report how multiplicity was handled.
The registry also illustrates why trial design and registry reporting must be considered separately. The design is labeled randomized, parallel, and quadruple-masked, but important details of allocation and analysis are not reported. Enrollment is listed as 46, while the primary outcome groups have counts of 20 and 22; the record does not explain their relationship. The endpoint is recorded at 25 weeks, whereas the intervention descriptions refer to 52 weeks and the summary describes 6-months. These unresolved details constrain what can be inferred from the numerical summaries.
Finally, the posted sample-size illustrations show how planning targets depend on the effect size chosen: smaller target effects require larger per-arm sample sizes under the stated assumptions. They are planning calculations based on the observed effect, not a report of the study’s original design or its observed power. Together, these features make careful distinction between observed results, statistical uncertainty, and unreported design information especially important.
17. 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 leaves several trial-specific questions unresolved. It lists enrollment as 46, but the primary outcome group counts are 20 and 22. It does not explain whether the difference reflects missing outcome data, eligibility for the analysis, or another reason. The analysis population and participant flow are not reported, and no missing-data method is described.
Timing is also not fully clear. The brief summary describes a 6-months treatment aim, the intervention descriptions specify 52 weeks, and the primary outcome timeframe is 25 weeks. The record does not reconcile these time references or report how the 25-week endpoint relates to the full intervention period.
The registry does not report the statistical analysis plan, the original sample-size justification, interim analyses, model details, or multiplicity handling. The primary p-value is unadjusted. Although the outcome is reported as a mean with standard errors, standard deviations and individual-level data are not available in the registry record for this analysis. The five listed secondary outcomes do not have result details.
The safety record includes serious and other adverse-event counts and two listed serious terms, but does not provide timing, treatment relatedness, or group attribution for the listed terms in the registry entries. Death counts are not reported in the registry record. These reporting limits prevent a more complete assessment of the primary analysis, secondary findings, and safety profile from the registry summaries alone.
18. Related Tutorials
19. Related Statistical Calculators
20. Sources
- ClinicalTrials.gov: Effect of Vitamin D Treatment in Primary Hyperparathyroidism — NCT00674154.
- Registry record last updated 2013-11-18; status last verified 2013-08.
- Results first posted 2013-10-16.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
21. Record Summary
The registry record describes a completed, randomized, parallel-group trial with quadruple masking, listed as phase 2 and phase 3 and sponsored by the University of Aarhus. Enrollment is recorded as 46. The study compared cholecalciferol with placebo in people with primary hyperparathyroidism, with vitamin D deficiency and hypercalcemia also listed as conditions.
The primary outcome is decrease in preoperative P-PTH at 25 weeks, measured in pmol/l. The posted mean difference is -2.4, with a confidence interval from -4.792 to just below zero and an unadjusted p-value of 0.049. Group means are -2.2 for Vitamin D and 0.2 for Placebo.
The registry lists five secondary outcomes, but their results are not included in the record details available for this analysis. The original statistical plan, missing-data handling, multiplicity procedures, and the relationship between the enrollment figure and outcome group counts are not reported in the registry record.