Magnesium Supplements In The Treatment Of Pseudoxanthoma Elasticum (PXE): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Magnesium Supplements In The Treatment Of Pseudoxanthoma Elasticum (PXE) (NCT01525875), a randomized phase 2 study. The primary outcome is Von Kossa Staining Per Unit Area of Dermis.

2. Clinical Question

The design separates a randomized comparison from a later open-label phase. The first part was intended to provide a placebo-controlled comparison, while the second part was intended to provide additional observation during magnesium oxide use. Because the second part was open-label and did not retain a placebo arm, its changes would not provide the same randomized comparison as the first part.

The registry lists secondary outcomes involving target lesions, visual acuity, and central retinal thickness. It does not report results for those outcomes in the record. The primary endpoint’s planned time points also span both years, but the record contains no estimates with which to judge the direction, size, or precision of the observed changes.

3. Trial Design

This was a randomized, phase 2, parallel-group study with triple masking, according to the registry. The registry lists 44 participants enrolled and a completed study status. It describes two planned parts: a year-long, double-blind, placebo-controlled period, followed by an open-label period of up to one additional year. In the first part, participants were to be allocated in a 1:1 ratio to magnesium oxide or placebo.

The magnesium oxide arm’s first-part regimen was described as 1000 mg elemental magnesium daily, with possible dose decreases depending on tolerability. The placebo arm was described as receiving placebo capsules. For the second part, the registry describes a magnesium oxide regimen of 1500 mg elemental magnesium. It states that participants would receive magnesium oxide in that part barring safety concerns. These descriptions are the planned regimens; the record does not report how many participants completed each part or what doses participants actually received.

Evaluations were planned at baseline and at several follow-up visits during the first year, with evaluations every 3 months during the second part. The registry describes blood tests, clinical evaluations, skin biopsy, eye examination, bone density testing, and skin-lesion photography among the assessments. The primary endpoint was based on skin biopsy staining. The record does not report participant flow, adherence, treatment discontinuation, or the number of observations available at each visit.

The randomized phase is the part suited to a direct comparison between magnesium oxide and placebo, assuming outcome analyses preserve the randomized groups. The later open-label phase has no concurrent placebo group in the described design. Changes during that period may be informative descriptively, but changes over time alone cannot isolate treatment effects from other explanations. The registry record does not report the analysis plan or how the two study parts were analyzed.

The masking label is triple, while the brief description calls the first part double-blind. The record does not specify which roles were masked or provide further detail to resolve that terminology. It also does not report a sample-size justification, interim analyses, or a prespecified statistical analysis plan.

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.

Placebo-controlled Period

Reasons for not completing this period:

Open-label Period

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Estimate: Estimated change from baseline and its standard error (SEM). After 1 year=M12-Baseline, After 2 year=M24-Baseline; during 2nd year =M24-M12.

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.

6. Primary Endpoint

The registry lists the primary outcome as Von Kossa Staining Per Unit Area of Dermis, measured over up to 2 years.

The primary endpoint was Von Kossa staining per unit area of dermis, reported in microns. A blinded dermatopathologist graded skin biopsies for the density of staining. The registry describes the measure as an assessment of changes in calcification of elastic fibers. Thus, the endpoint is a tissue-based measure related to the study’s stated question about skin calcification, rather than a direct measure of symptoms or overall health.

The registry describes estimated change from baseline and its standard error. It defines the first-year change as M12 minus baseline, the second-year change as M24 minus baseline, and change during the second year as M24 minus M12. These contrasts answer different questions: change from baseline describes accumulated change by a visit, whereas the M24-to-M12 contrast describes change over the second-year interval. The record does not provide the estimates, standard errors, or numbers of participants contributing data at these times.

In general, a tissue measure can be useful when the research question concerns a tissue feature that can be assessed in a biopsy. The staining method provides a defined way to quantify that feature, but interpretation depends on how consistently specimens are collected, processed, and graded. Blinded grading can reduce the risk that a grader’s knowledge of treatment influences assessment. The registry states that a blinded dermatopathologist graded the biopsies, but it does not report details about reproducibility or quality-control procedures.

The record’s endpoint description does not establish how a given amount of change should be interpreted clinically. No threshold for a meaningful change, comparison estimate, or inferential result is reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The core design feature is random allocation during the first study part. In general, randomization aims to make treatment groups comparable, on average, with respect to measured and unmeasured factors at the start of a trial. That benefit applies to comparisons that preserve the assigned groups and use an appropriate analysis. The registry describes a 1:1 allocation to magnesium oxide or placebo during the first 12 months. It does not report the method used to generate the allocation sequence, conceal assignments, or analyze participants who did not follow their assigned regimen.

What does the parallel-group design mean?

In a parallel-group design, participants are assigned to one group and followed in that group rather than crossing between treatments during the randomized comparison. Here, the registry describes magnesium oxide and placebo arms during the first part. A direct comparison between their outcome changes can use the randomized assignment as its basis. The later open-label period differs: all participants were to receive magnesium oxide, so there is no longer a placebo group for a concurrent randomized contrast.

How should change scores be understood?

The primary endpoint is expressed as change between visits. A change score is the later measurement minus the earlier measurement; the record specifies M12 minus baseline, M24 minus baseline, and M24 minus M12. In general, comparing change scores between randomized groups asks whether average change differs by assigned group. An alternative general approach is to model follow-up measurements while accounting for baseline values. These approaches can have different assumptions and precision. The registry record does not say which method was used, whether estimates were adjusted, or which contrast was designated as the principal treatment comparison.

The primary measure is described as a mean, with standard error as its dispersion measure. In general, a mean summarizes the central value of a continuous outcome, while a standard error describes the estimated uncertainty of a mean. A standard error is not the same as the spread of individual participant measurements. The record provides no actual mean changes or standard errors, so it is not possible to evaluate their size or uncertainty from the listed results.

What does masking contribute?

Masking is intended to limit the influence of treatment knowledge on trial conduct, participant reports, or outcome assessment. The registry labels the trial triple-masked and states that a blinded dermatopathologist graded biopsies. It does not specify which participants or staff were masked, how masking was maintained, or whether it was assessed. The open-label second part is explicitly different in this respect, and the record does not state how that difference was addressed in analysis.

Why can variability matter?

In general, the precision of a group mean depends on both the number of observations and the variability in the measurements. More variable outcomes tend to produce less precise estimates when other features are similar. Some continuous outcomes may also have variability that changes with their mean or that is not well described by a normal distribution. In such settings, analysts may consider transformations, robust methods, or models that represent the outcome’s distribution more appropriately. These are general methodological considerations, not methods reported for this trial. The registry record does not describe distributional checks, variance assumptions, transformations, or robust analyses.

The stated planning illustration assumptions describe a two-sided significance level of 0.05, equal allocation, and a normal approximation, with effects expressed as fractions of an observed effect. These are planning assumptions rather than evidence about the trial’s actual design justification. The registry record does not report the trial’s own sample-size justification, and no numeric planning illustrations are included in the record. Planning calculations should not be mistaken for observed power or for an analysis of the trial’s results.

There are no reported outcome analyses in the record. Therefore, no fitted model, statistical test, confidence interval, or treatment-effect estimate can be attributed to the trial based on this record. General explanations of those methods do not imply that the trial used them.

10. Multiplicity, Missing Data and Analysis Populations

The primary endpoint is described at multiple time contrasts: M12 minus baseline, M24 minus baseline, and M24 minus M12. The registry also lists secondary outcomes involving target lesions, LogMar, visual acuity, and central retinal thickness. Multiple outcomes and time points create multiple opportunities for statistical testing. In general, when many hypotheses are tested, the chance of at least one apparently notable result can increase unless the analysis plan accounts for multiplicity. Methods can include prespecifying a primary contrast, adjusting inference, or clearly distinguishing confirmatory from exploratory analyses. The registry record does not report a multiplicity strategy or identify a single primary time contrast for a treatment comparison.

Missing data handling is not reported in the registry record. The record does not state how participants with missing biopsies or missed visits were handled, whether reasons for missingness were summarized, or whether sensitivity analyses were performed. In general, missing-data methods rely on assumptions about why values are absent. Different assumptions can lead to different estimates, so transparent reporting of missingness and sensitivity analyses is important. No such details are reported.

The analysis population is not reported in the registry record. The record does not state whether the primary analysis was based on randomized assignment, treatment received, or participants who completed a specified portion of the study. In general, analysis according to randomized assignment helps preserve the comparability created by randomization, while analyses based on treatment received or completion can be affected by post-randomization differences. The record also does not report participant flow, exclusions, or the number contributing to each endpoint analysis.

These omissions limit assessment of whether the analysis addressed the planned question and how robust any estimate might be. Since no outcome analyses are reported, the effects of missing data, multiplicity, and analysis-population choices cannot be evaluated from the registry record.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry lists 22 participants at risk in each arm. It records zero serious adverse events in the magnesium oxide group and zero in the placebo group. For other adverse events, it lists 11 affected participants in each group. No deaths are listed for either group, and no serious adverse-event terms are listed.

These are counts, not a complete account of safety. The record does not describe the types of other adverse events, their severity, timing, duration, or investigators’ assessment of whether they were related to treatment. It also does not explain whether one participant could contribute more than one event or how events were collected. The listed counts therefore cannot show whether the event profiles were otherwise similar.

In general, a zero count in a trial group means that no event of that category was recorded among the participants included in that listing. It does not demonstrate that the risk is absent. Interpretation also depends on follow-up duration, completeness of reporting, and the population observed. Those details are not fully reported for these safety figures. The registry describes a planned two-part study, but the safety listing does not specify the period covered by the counts or exposure time by arm.

The counts should be read as the safety information recorded, not as a standalone estimate of comparative risk or proof of safety. The registry record does not report a statistical comparison of adverse events.

12. What the Result Does, and Does Not, Mean

The record establishes that a randomized, phase 2 study was conducted with a placebo-controlled first part and a planned open-label second part. It identifies a biopsy-based primary measure related to skin calcification and lists selected safety counts. It does not provide the primary outcome estimates or analyses. Therefore, the record does not establish whether the staining measure changed, how large any change was, or whether change differed between randomized groups.

The endpoint itself is a tissue measure. Even if a change estimate were available, its interpretation would depend on precision, the analysis population, missing observations, and the relationship between staining changes and outcomes that matter to participants. The registry does not report a threshold for clinically meaningful change or the results needed to assess that relationship. The stated biological hypothesis is not evidence that the hypothesis was confirmed.

The randomized comparison and the open-label period answer different kinds of questions. A comparison between the randomized groups during the first part can, with an appropriate analysis, estimate differences associated with assigned treatment. Changes during the later period, when all participants were to receive magnesium oxide, do not have a concurrent placebo comparison as described. They should not be interpreted as equivalent evidence of a treatment effect.

The safety listing reports no serious adverse events and equal counts of participants with other adverse events in the two arms. Those figures do not describe event types or establish that treatment effects on safety are equivalent. They also do not replace a complete account of follow-up and safety monitoring.

In general, a trial’s completion status indicates that its administrative status is complete; it does not by itself communicate the findings. Here, the reported enrollment and endpoint definitions do not fill the gap left by absent outcome analyses. The registry record is informative about the study’s design and the kinds of outcomes considered, but it does not support a quantitative conclusion about the primary treatment comparison.

13. Why This Trial Matters Statistically

This study illustrates why an endpoint definition and an outcome result are different kinds of information. The registry identifies a specific biopsy-based measure and describes how change was defined across visits. Without estimates and uncertainty, however, readers cannot judge the direction, size, or precision of any change. A clearly named endpoint is necessary for interpreting a trial, but it does not substitute for reporting its analysis.

The design also highlights the importance of keeping randomized and open-label evidence distinct. The first part was planned to compare magnesium oxide with placebo under random allocation. The second part was open-label, with magnesium oxide offered to all participants barring safety concerns. Statistical interpretation depends on which period and comparison produced an estimate, not simply on the fact that measurements were collected over time.

Multiple outcomes and time contrasts make transparent analysis plans important. Prespecified priorities and clear reporting help readers understand which results were confirmatory and how uncertainty was handled. The registry does not report such analysis details, and no outcome analyses are listed. This absence limits the conclusions possible from the record independently of the trial’s completed status.

The safety counts provide a further example of why simple totals need context. Equal numbers of participants with other adverse events do not show whether the events were alike in type, severity, or timing. Similarly, zero serious events in a listing is a report about observed counts, not proof of no risk. Clear denominators and fuller event descriptions are essential to interpretation.

For biostatistical reading, the central lesson is to distinguish trial design, endpoint measurement, analysis, and inference. Each serves a different role. Here the first two are described more fully than the latter two, so the record allows a careful account of what was planned and measured but not a numerical assessment of the primary result.

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 primary limitation for interpreting efficacy is that no outcome analyses are reported in the registry record. There are no primary endpoint estimates, standard errors, confidence intervals, or comparative tests listed. Although the registry defines several time contrasts, it does not identify a reported result for any of them. The magnitude and precision of change in Von Kossa staining therefore cannot be assessed.

The record does not report participant flow or the number with evaluable skin biopsies at each visit. This matters because the endpoint depends on biopsy measurements over time. Without those counts, readers cannot judge how much information contributed to the planned comparisons or whether missing observations differed across arms or visits. Missing-data methods and sensitivity analyses are also not reported.

The first part is described as double-blind and placebo-controlled, while the overall masking label is triple. The record does not explain which roles were masked. It also does not report allocation-concealment procedures, adherence, dose changes actually made, or treatment discontinuations. These omissions make it difficult to assess implementation of the planned randomized comparison.

The second part was open-label and, as described, had no concurrent placebo arm. Any second-year changes would therefore require cautious interpretation as time trends rather than as a randomized comparison against placebo. The registry does not explain the analysis of this period or whether safety concerns affected who continued.

Finally, the record does not report a sample-size justification, a statistical analysis plan, multiplicity handling, or an analysis population. The safety listing lacks event descriptions and a stated follow-up period. These limitations concern what can be evaluated from the registry record; they do not establish that particular procedures were absent from the conduct of the study.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Magnesium Supplements In The Treatment Of Pseudoxanthoma Elasticum (PXE) — NCT01525875.
• Registry record last updated 2021-03-10; status last verified 2021-02.
• Results first posted 2019-04-25.
• 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.

18. Record Summary

The registry describes a completed, randomized phase 2 parallel-group study of magnesium oxide versus placebo in pseudoxanthoma elasticum. It lists 44 enrolled participants and a triple-masking label. The planned first part was placebo-controlled for 12 months, followed by an open-label period of up to one additional year.

The primary endpoint was Von Kossa staining per unit area of dermis, with changes defined at M12 and M24 and between those visits. The registry record does not report primary outcome analyses or estimates. Secondary outcomes include target lesions, LogMar, visual acuity, and central retinal thickness, but analyses for these outcomes are not reported either.

The safety listing records zero serious adverse events and zero deaths in each arm, with 11 participants recorded as having other adverse events in each group. Event descriptions and fuller analysis details are not reported in the registry record.