Antioxidant Therapy in RYR1-Related Congenital Myopathy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Antioxidant Therapy in RYR1-Related Congenital Myopathy (NCT02362425), a randomized phase 1, phase 2 study. The primary outcome is Urine 15-F2t Isoprostane Concentration.

2. Clinical Question

The clinical question is whether N-acetylcysteine changes a urinary biomarker of oxidative stress in people with RYR1-related myopathy, compared with placebo. The registry also describes exercise tolerance and other functional or biomarker outcomes, but the primary endpoint is urine 15-F2t isoprostane concentration at 12 months.

3. Trial Design

The registry describes a randomized, triple-masked, parallel-group phase I/phase II trial. It lists N-acetylcysteine and placebo as the interventions and reports an enrollment of 63. The registry record does not identify which trial roles were masked or provide further detail about the randomization procedure.

Eligible participants were age 7 and older and had either a confirmed genetic diagnosis of RYR1 or a clinical diagnosis with a family member who had a confirmed genetic diagnosis. The brief summary describes screening, clinical assessments, blood and other samples, walking and heart and lung tests, muscle testing, and ultrasound. Adult participants might have a muscle biopsy. These procedures describe the study visits; they are not the primary outcome.

The brief summary states that participants would begin taking N-acetylcysteine or placebo dissolved in water three times a day for 6 months. The primary outcome timeframe is 12 months. The registry record does not report a more detailed schedule connecting each treatment and assessment period.

Healthy volunteers appear as a separate group in the arm descriptions. They had a physical examination, biomarker testing, near-infrared spectroscopy testing, and muscle ultrasound at one visit. The registry specifically states that healthy volunteers were not included in the post-baseline primary outcome analysis.

The sponsor is the National Institute of Nursing Research. The trial is listed as completed, with a start date of 2015-02-12 and a primary completion date of 2018-05-30. These design details help define the setting and comparison, but they do not by themselves establish the precision or importance of the treatment estimate.

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.

Phase 1 (up to 6 Months)

Reasons for not completing this period:

Phase 2 (up to 6 Months, Randomized)

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Outcome measures are reported for participants who were randomized and continued into the randomized, double-blind period of the trial. Missing data was not imputed. This measure was not collected for Healthy Volunteers post-baseline (months 6 and 12), thus they are not included in the analysis.

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.

Population: The baseline analysis population contains the healthy volunteer participants, who only had one visit to determine normal values of biomarkers, muscle ultrasound, and near infrared spectroscopy in this rare disease, in order to develop a comparison between healthy and RYR1-RM individuals.

6. Primary Endpoint

The registry lists the primary outcome as Urine 15-F2t Isoprostane Concentration, measured over 12 months.

The primary endpoint is urine 15-F2t isoprostane concentration, measured in ng/mg Cr at 12 months. The registry describes 15-isoprostane-F2 as a product formed when arachidonic acid reacts with reactive oxygen species. It says urine samples were assessed using a validated gas chromatography-mass spectrometer method.

This endpoint was selected to measure a biological signal related to oxidative processes. A urine biomarker can provide a measurable laboratory outcome, whereas a functional measure such as walking or climbing steps describes performance. The registry's brief summary also identifies exercise tolerance as an objective, and the listed secondary outcomes include functional tests and motor-function domains. Those outcomes address related but distinct questions; a change in a biomarker alone does not establish a change in physical function.

The primary endpoint is reported as a least-squares mean with a 95% confidence interval for each treatment group. The sponsor's comparison is a regression estimate of the mean difference in final values. The registry record does not report a threshold for a clinically important difference or establish that this biomarker is a surrogate for a patient-important outcome. Accordingly, the endpoint is best interpreted as a laboratory measure, not as a direct measure of symptoms or everyday ability.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: it is a measured concentration rather than a count or a yes/no event. The registry reports least-squares means for the treatment groups and a regression comparison of final values. These statistics describe the outcome on its measurement scale, while the confidence interval communicates uncertainty around the estimated group contrast.

What does a confidence interval convey?

General explanation: a confidence interval is a range produced by a statistical procedure to represent uncertainty about an estimate. A narrower interval indicates greater precision than a wider interval, all else equal. It is not a range that guarantees the true value lies inside it, and it does not identify which values are clinically important. For the primary comparison, the reported 95% confidence interval for the difference runs from -1.4 to 1.6. Because that interval includes zero, the data are compatible with no difference as well as with differences in either direction.

How should the reported p-value be read?

General explanation: a p-value describes how unusual data at least as inconsistent with a specified null hypothesis would be under the statistical model, if that null hypothesis and model assumptions held. It is not the probability that the null hypothesis is true, nor a measure of the size or importance of an effect. The registry reports p = 0.88 for the regression comparison. Read alongside the estimate and confidence interval, this does not provide statistically clear evidence of a group difference for the primary endpoint.

What does the regression contrast represent?

The registry identifies the method as linear regression and the parameter as the mean difference in final values. The reported estimate is 0.1. The registry record does not describe the covariates, any baseline adjustment, or other model details, so those should not be inferred. The group-specific least-squares means and the regression contrast are related summaries, but the reported contrast is the sponsor's stated analysis and is the appropriate primary comparison to cite.

Why is the analysis population important?

The registry says the outcome was reported for participants who were randomized and continued into the randomized, double-blind period. This wording defines the population represented by the result; it does not establish that every randomized participant contributed an outcome. Missing data were not imputed. The record does not report the number or reasons for missing primary measurements, nor does it describe a sensitivity analysis for missing outcomes. As a result, the possible influence of missingness cannot be assessed from the reported information.

What can a simple recalculation add?

General explanation: a recalculation from group summaries can be useful as a check on a contrast when the necessary summary statistics are available. Such a calculation is generally unadjusted and may not reproduce a regression model that uses additional information or assumptions. For this primary endpoint, the registry record reports a sponsor regression result but does not provide a separate recalculated primary contrast. There is therefore no independent primary recalculation to use as a competing estimate.

The record includes a secondary baseline comparison for the blood glutathione reduced-to-oxidized ratio between RYR1-RM volunteers and healthy volunteers. That comparison is not the randomized N-acetylcysteine-versus-placebo primary contrast, and it is measured at baseline. Its unadjusted significance should not be treated as a treatment effect. The registry's sample-size illustrations for that secondary comparison are planning scenarios based on the observed effect, not observed power and not the trial's original design justification.

Why do multiple outcomes affect interpretation?

General explanation: when many outcomes or comparisons are examined, the chance of finding at least one apparently unusual result by chance can increase. A prespecified outcome hierarchy or a multiplicity adjustment can help address that issue, but the registry record does not report a multiplicity strategy for the posted outcomes. An unadjusted secondary result should therefore be treated as exploratory unless further analysis documentation establishes how it was selected and interpreted.

The clinical and statistical questions also differ by outcome. A biomarker, a timed task, and a motor-function measure have different scales and meanings. Their results cannot simply be combined into one conclusion without a stated method. The primary endpoint remains the registry's designated primary measure; secondary results can offer context but do not replace that comparison.

10. Analyses Reported by the Sponsor

The sponsor's reported primary analysis is a linear regression comparison of final values. It estimates a mean difference of 0.1 for N-acetylcysteine versus placebo, with a 95% confidence interval from -1.4 to 1.6 and p = 0.88. This is the principal reported inferential result for the primary endpoint.

The registry record does not include a separate recalculated primary contrast from the arm-level summaries. Consequently, there is no independent unadjusted primary estimate to compare with the regression result. The reported group means and confidence intervals give descriptive context, while the regression estimate is the stated between-group analysis.

For the secondary baseline glutathione ratio comparison, the registry includes an unadjusted recalculation and planning illustrations, but no sponsor-reported analysis for that outcome. That secondary comparison is between RYR1-RM volunteers and healthy volunteers at baseline, not a randomized treatment comparison. It cannot serve as a check on, or substitute for, the sponsor's primary regression analysis.

The registry record does not identify additional model specifications or sensitivity analyses for the primary result. Interpretation should therefore stay with the reported estimate, its confidence interval, and the stated analysis population. No discrepancy is reported between a sponsor analysis and a recalculated primary result.

11. Multiplicity, Missing Data and Analysis Populations

The registry counts 56 outcome measures and 27 analyses, and it lists 26 posted secondary outcomes. Examining multiple outcomes and analyses creates a multiplicity concern: without appropriate planning and interpretation, an apparently unusual result may arise by chance. The registry record does not report whether a formal multiplicity adjustment was used, whether outcomes were ranked in a prespecified hierarchy, or how secondary analyses were selected. No correction or hierarchy should therefore be assumed.

The primary outcome population is described as participants who were randomized and continued into the randomized, double-blind period. The record states that missing data were not imputed. It does not report the number of missing primary measurements, the reasons for missingness, or a sensitivity analysis showing how different assumptions about missing values might affect the result. The reported group sizes for the primary outcome are 16 for N-acetylcysteine and 17 for placebo; they should not be mistaken for the overall enrollment.

The registry record does not report a sample-size justification, interim analyses, or details of a formal statistical analysis plan. It also does not provide enough information to determine whether the reported analysis population matches an intention-to-treat population. These omissions limit assessment of the prespecification and robustness of the analysis; they do not establish that a particular procedure was or was not used outside what the record states.

General explanation: missing-data methods matter because results can be biased if the likelihood of an outcome being observed is related to its value or to a participant's condition. Not imputing missing values avoids making one particular imputation, but it does not by itself remove the potential influence of missingness. Similarly, multiplicity procedures affect how evidence from several comparisons should be interpreted. Both issues are relevant to the overall reading of trial results, especially secondary findings, and should be considered alongside the primary estimate and its uncertainty.

12. 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 serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: intestinal malrotation (6.2%), ovarian cyst (6.2%), chest discomfort (6.2%), hypotension (6.2%), diarrhoea (5.9%).

The registry lists serious adverse events for several groups: RYR1-RM volunteers overall, RYR1-RM volunteers receiving N-acetylcysteine, RYR1-RM volunteers receiving placebo, and healthy volunteers. The corresponding serious-event counts are 1 among 53, 4 among 16, 5 among 17, and 0 among 10. The group labels include an overall RYR1-RM volunteer group as well as treatment groups; these figures should not be added together or treated as mutually exclusive without further information from the registry.

The record lists zero deaths in each group. It also lists intestinal malrotation, ovarian cyst, chest discomfort, and hypotension at 6.2% each, and diarrhoea and arthralgia at 5.9% each, among the top serious event terms. Those terms and percentages are registry entries; the record excerpt does not establish their causal relationship to treatment or provide enough context to attribute each term to a particular group.

These counts describe reported events in the listed groups. They are not, by themselves, a comparative safety analysis, and the groups have different reported sizes. The registry record does not provide a statistical comparison of serious adverse events. Interpretation should therefore remain descriptive rather than treating the figures as proof of a treatment-related risk or absence of risk.

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

The primary result estimates the difference between N-acetylcysteine and placebo in urine 15-F2t isoprostane concentration at 12 months among participants in the stated analysis population. The reported estimate is close to zero, but its confidence interval spans values on both sides of zero. The result does not provide statistically clear evidence of a difference in this biomarker in the reported analysis.

That conclusion is narrower than saying the treatments are equivalent. The registry does not state an equivalence margin, and the confidence interval does not rule out every potentially meaningful difference. The record also does not give a threshold that would establish whether a particular biomarker change is clinically important. Statistical uncertainty and clinical importance are related questions, but they are not interchangeable.

The primary outcome is a laboratory measure associated in the registry description with reactive oxygen species. It is not a direct measure of walking, exercise tolerance, symptoms, or quality of life. The registry lists functional secondary outcomes, but the primary biomarker result cannot establish what happened on those measures. Nor does it establish a change in the underlying disease process or predict a longer-term outcome.

The study's eligibility criteria and analysis population define who is represented in the primary comparison. The result should not automatically be generalized to people who do not meet those criteria, to healthy volunteers, or to participants who did not continue into the randomized, double-blind period. Missing data were not imputed, and the registry does not describe missingness in enough detail to determine its potential effect.

Overall, the registry reports an uncertain treatment-group contrast for a specific biomarker and follow-up time. It does not demonstrate equivalence, establish a functional benefit or harm, or answer every question about treatment and RYR1-related myopathy.

14. Why This Trial Matters Statistically

This trial is statistically informative because it places a biomarker question in a randomized, placebo-controlled comparison rather than relying only on a difference between people with myopathy and healthy volunteers. Randomization is intended to support a fair treatment comparison, while masking can reduce some influences on assessment and reporting. The registry identifies the design as randomized and triple-masked, although it does not specify which roles were masked.

The result also illustrates why an estimate should be read together with its uncertainty. The point estimate alone is not enough to decide whether the data distinguish the groups. The confidence interval and p-value show that the primary analysis does not provide a statistically clear separation, while the interval still permits differences in either direction. This is a more careful conclusion than interpreting a small point estimate as proof of no effect.

Another important statistical distinction is between a biological marker and a functional outcome. The trial's primary measure captures a urine biomarker, while secondary outcomes include timed tasks and motor-function domains. A biomarker finding cannot stand in for functional evidence unless that relationship is established; the registry record does not establish it.

The record also highlights limits that arise when many outcomes are measured and when missing data are not imputed. Multiplicity strategy, missingness details, and a sample-size justification are not reported in the registry record. Their absence from the record restricts how confidently the full set of findings can be interpreted, particularly for secondary analyses. The primary comparison remains the clearest stated treatment contrast, and its uncertainty should guide the statistical reading.

15. 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 outcome groups were reported as 16 participants receiving N-acetylcysteine and 17 receiving placebo. The confidence interval is wide enough to include differences in either direction, so the estimate is not precise enough to establish equivalence or exclude all potentially important differences. The registry record does not give a clinical-importance threshold for the biomarker.

The analysis population was limited to participants randomized and continuing into the randomized, double-blind period. Missing data were not imputed, but the record does not report missing outcome counts, reasons for missingness, or sensitivity analyses. It is therefore not possible to assess from the record whether missing outcomes could have influenced the result.

The primary outcome is a laboratory biomarker, not a direct functional measure. The registry describes a 12-month endpoint and a treatment course of 6 months, but does not provide further detail in the record excerpt about the assessment schedule or the persistence of any effect. The result does not settle questions about exercise tolerance, motor function, or longer-term outcomes.

The registry does not report a multiplicity strategy, a formal sample-size justification, interim analyses, or details of the statistical analysis plan. It also does not identify which trial roles were covered by triple masking or describe model covariates for the primary regression. These are limits on what can be evaluated from the registry record, not proof that the trial lacked procedures that are not described there.

Finally, the primary analysis excluded healthy volunteers after baseline, and the reported randomized comparison concerns the RYR1-RM treatment groups. Results should not be generalized to the healthy volunteer group or to populations outside the eligibility description without supporting evidence.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Antioxidant Therapy in RYR1-Related Congenital Myopathy — NCT02362425.
• Registry record last updated 2019-12-24; status last verified 2019-10-05.
• Results first posted 2019-12-24.
• 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.

19. Record Summary

The registry identifies NCT02362425 as a completed randomized, triple-masked, parallel-group phase I/phase II trial of N-acetylcysteine versus placebo in RYR1-related congenital myopathy. Enrollment was 63. The listed eligibility criteria include people age 7 and older with a confirmed genetic diagnosis of RYR1 or a clinical diagnosis and an affected family member with a confirmed genetic diagnosis.

The primary endpoint was urine 15-F2t isoprostane concentration at 12 months. The reported regression estimate for the difference in final values was 0.1, with a 95% confidence interval from -1.4 to 1.6 and p = 0.88. The result does not show a statistically clear difference in the primary biomarker analysis.

The registry reports that missing data were not imputed and that healthy volunteers were not included in post-baseline primary analyses. It also lists functional and biomarker secondary outcomes and adverse-event counts. The registry record does not report multiplicity procedures, a sample-size justification, interim analyses, or detailed missingness information.