Antioxidant Therapy With N-acetylcysteine for Children With Neurofibromatosis Type 1: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Antioxidant Therapy With N-acetylcysteine for Children With Neurofibromatosis Type 1 (NCT04481048), a randomized phase 2 study. The primary outcome is Change From Baseline in Motor Function Measured by Physical and Neurological Examination for Soft Signs (PANESS).

2. Clinical Question

The clinical rationale in the registry record concerns cognitive, behavioral, and motor impairments associated with NF1. The trial was intended to explore NAC safety, tolerability, and possible clinical benefit, with motor behavior and/or learning among the areas of interest. The primary endpoint specifically focused on motor function rather than combining all those domains into a single outcome.

The trial record reports the primary comparison at the end of treatment, 8 weeks after treatment began. It does not report a numerical estimate of the between-group difference or a confidence interval for that difference. The available group summaries and p-value therefore describe the comparison less fully than an effect estimate accompanied by its uncertainty would.

3. Trial Design

This was a Phase II, randomized, parallel-group trial of NAC versus placebo in children with NF1. The registry record lists the study as completed, with a start date of 2021-02-23 and a primary completion date of 2024-06-25. Enrollment was 25. The trial description identifies it as a single-center, prospective, placebo-controlled study. The registry metadata lists quadruple masking, while the description uses the term double-blind; further detail on masking roles is not reported in the registry record.

The intervention period was 8 weeks. The NAC arm description specifies approximately 70 mg/kg/day and describes three dose tiers according to body weight. The placebo arm description specifies placebo for 8 weeks. The primary assessment compared baseline with the end of treatment at week 8. The registry record also says that primary and secondary measures were administered at baseline, follow-up, and post-treatment, but the exact timing of every secondary assessment is not reported in the registry record.

The record states that 25 children were randomized, with 12 assigned to NAC and 13 to placebo. Two participants in the NAC group were withdrawn after randomization but before receiving drug and were not analyzed. Two more participants in the NAC group withdrew during treatment before the week-8 primary assessment. The reported completer analysis included 8 in the NAC group and 13 in the placebo group. The record does not provide a corresponding detailed account of all analysis populations or explain whether any other analyses included participants who did not complete treatment.

The registry lists one primary outcome, change from baseline in motor function measured by PANESS, and four secondary outcomes concerning ADHD symptoms, motor-cortex measures, and brain-tissue microstructure. The record lists 5 outcome measures and 16 analyses overall. Detailed protocol information about the planned statistical methods, sample-size justification, interim analyses, and handling of missing data is not reported in the registry record.

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 screening and baseline assessments, participants were randomized 1:1 to receive N-acetylcysteine (NAC) or matching placebo using permuted block randomization stratified by age, sex, and ADHD status. The study was double-blind; only the investigational pharmacy was unblinded. NAC was administered orally for 8 weeks at \~70 mg/kg/day divided BID with weight-based dosing. Placebo was identical in appearance and schedule.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: 25 were enrolled and randomized (12 active NAC; 13 placebo). 2 (NAC group) were withdrawn after randomization, before receiving drug and were not analyzed. 2 (NAC group) withdrew during treatment, prior to primary outcome assessment at week 8. Therefore, completer analysis was done with 8 NAC, 13 placebo, at week 8. We also did intention to treat with 10 NAC, 13 placebo, using last observation carried forward. For the 12-week washout analysis, one NAC was lost to follow up.

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: Study participation at baseline was exactly the same for participants in both arms.

6. Primary Endpoint

The registry lists the primary outcome as Change From Baseline in Motor Function Measured by Physical and Neurological Examination for Soft Signs (PANESS), measured over Baseline vs. end of treatment, 8 weeks.

The primary endpoint was change from baseline in motor function measured with the Physical and Neurological Examination for Soft Signs (PANESS), comparing baseline with the end of treatment at 8 weeks. The registry describes PANESS as a validated scale and gives a range of 0-119. Higher scores correlate with greater symptom severity and therefore a worse outcome. The endpoint is expressed in units on a scale, with the group summaries reported as means and standard deviations.

In general, a change score expresses how a measurement at follow-up differs from its baseline value. With a scale on which higher scores indicate greater severity, a negative change corresponds to a lower score at follow-up than at baseline. That direction alone does not establish that one treatment group improved more than the other: the comparison between groups is the relevant randomized-trial question. Both group means are negative in the posted results, and the means are close in magnitude, but no between-group difference or confidence interval is reported in the registry record.

The registry description explains why PANESS was selected: it has been used to assess motor function and has demonstrated impairments in children with ADHD; preliminary data described in the record suggested possible impairments in children with NF1. Those preliminary data are described as unpublished in the registry record. The scale is therefore the trial’s specified motor-function measure, not a direct measurement of every cognitive, behavioral, or learning outcome mentioned in the broader study rationale.

The record reports group-level change summaries and a nonparametric comparison. It does not report an individual-level distribution, a confidence interval for the treatment contrast, or a threshold for a clinically important PANESS change. Those omissions limit assessment of the magnitude and precision of the group difference.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is continuous: PANESS change is measured in units on a scale, and the registry reports a mean and standard deviation for each group. The sponsor’s reported comparison uses the Wilcoxon (Mann-Whitney) method. These summaries and the test answer related but different questions: group means describe average change, while the Wilcoxon comparison uses the ordering of observations between groups rather than directly testing a difference in means.

What does the reported p-value mean?

In general, a p-value describes how unusual data at least as incompatible with a specified null model would be if that model and the test assumptions were true. It is not the probability that the null hypothesis is true, nor does it measure the size or clinical importance of an effect. The reported p-value is 0.9. It does not provide an estimate of the treatment contrast and should be interpreted together with the group summaries and the uncertainty around the contrast. A confidence interval for the between-group comparison is not reported in the registry record.

The Wilcoxon (Mann-Whitney) test is a rank-based method. In general, it compares the relative ordering of observations across two independent groups. It is often described as a test of whether one group tends to have higher or lower values than the other. It is not automatically a test of a difference in medians under all possible distribution shapes; interpretation depends on the distributions and assumptions. The registry record does not provide the individual observations or additional distributional details needed to examine those features.

Why consider the mean and standard deviation?

A mean is the arithmetic average of the observed change scores. A standard deviation describes how spread out those scores are around the mean. Here, the reported mean changes are -3.3 for NAC and -3.1 for placebo; the corresponding standard deviations are 9.3 and 12.7. These summaries make the scale and variability of the observed changes visible. They do not reveal the full shape of the distributions, outliers, or how many participants had decreases or increases. In general, a standard deviation is not a confidence interval and should not be read as one.

Because the reported test is rank-based while the descriptive summaries are means and standard deviations, they should not be conflated. The p-value is the result of the sponsor’s Wilcoxon comparison, not a test derived directly from the two means. A recalculated comparison would require a stated method and relevant data or sufficient summary statistics. No recalculated between-group estimate is reported in the registry record.

What would a confidence interval add?

In general, a confidence interval expresses the uncertainty of an estimated effect under a specified statistical procedure. Its width conveys precision: a narrower interval indicates a more precise estimate than a wider interval, while the interval’s position shows which effect values are compatible with the data under that procedure. A confidence interval can help distinguish a precise estimate near no difference from an imprecise estimate that includes a range of potentially important differences. The registry record does not report a confidence interval for the primary comparison, so this kind of precision assessment cannot be made from the posted result.

Why does over-dispersion matter?

In general, over-dispersion means that observed variability is greater than a model expects. When a method assumes less variability than is actually present, standard errors may be too small and uncertainty may be understated. The posted primary result gives standard deviations for the groups, but it does not identify a count model or report an over-dispersion analysis. Since PANESS change is a continuous score and the reported method is Wilcoxon, over-dispersion is not a specific reported feature of this analysis. The broader lesson is that the model or test should match the outcome and its observed distribution.

Sample-size illustrations, when based on an observed effect, are planning calculations rather than evidence about the precision of this completed trial. The stated illustration assumptions are a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the target effect expressed as a fraction of the observed effect. Such calculations do not represent observed power, and they do not show the trial’s original design justification. The actual sample-size rationale is not reported in the registry record. Numerical planning results are not reported in the registry record.

The registry record lists 16 analyses overall, but does not describe the complete statistical plan, how the analyses were selected, or how multiplicity was handled. In general, conducting multiple tests can increase the chance of at least one false-positive finding if results are interpreted without an appropriate strategy. The record does not state whether any adjustment or hierarchical testing approach was planned. The primary result should therefore be interpreted as the reported primary comparison, without inferring a multiplicity procedure that is not documented.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("N-Acetylcysteine (NAC)", "Placebo")
n   <- c(8, 13)
m   <- c(-3.3, -3.1)
sp  <- c(9.3, 12.7)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  N-Acetylcysteine (NAC)  8  -3.300  9.300  -11.075  4.475
CARM  Placebo  13  -3.100  12.700  -10.775  4.575

11. Analyses Reported by the Sponsor

The sponsor’s reported primary analysis is a Wilcoxon (Mann-Whitney) comparison between the NAC and placebo groups, with p = 0.9. The posted group summaries are mean changes of -3.3 for NAC and -3.1 for placebo, with standard deviations of 9.3 and 12.7, respectively. The registry record identifies 8 participants in the NAC completer analysis and 13 in the placebo analysis.

The sponsor’s p-value comes from the reported rank-based analysis. It is not calculated from the difference between the posted means, and it should not be described as a test of that mean difference. A separate unadjusted recalculation of the sponsor’s analysis is not reported in the registry record, nor is a confidence interval for the treatment contrast. Consequently, there is no reported recalculated estimate to compare directly with the sponsor’s analysis.

The discrepancy indicator is false, so the registry record does not flag a disagreement between a sponsor result and a recalculated result. The sponsor’s reported analysis remains the available inferential result for the primary endpoint. Its p-value offers limited information without an effect estimate and precision interval: it does not quantify the size of a possible difference and does not demonstrate equivalence.

The descriptive means can still be read as group-level changes, but they do not replace the sponsor’s stated statistical comparison. A reader should keep the descriptive summaries, the rank-based p-value, and the absent confidence interval distinct when assessing what the primary result does and does not show.

12. Multiplicity, Missing Data and Analysis Populations

The registry record lists a primary outcome of PANESS motor-function change and four secondary outcomes: ADHD symptoms reported through parent/teacher surveys; motor-cortex inhibition/excitation measures expressed as ratios; motor-cortex measures expressed in milliseconds; and MRI-based brain-tissue microstructural properties. It also lists 5 outcome measures and 16 analyses overall. Numerical results for the secondary outcomes are not reported in the registry record.

Multiple outcomes and analyses raise a general multiplicity question. When many hypotheses are tested, the chance of obtaining at least one apparently positive result can increase if each is judged separately without adjustment. Statistical plans may address this in different ways, such as defining one primary hypothesis, specifying a testing hierarchy, or adjusting significance thresholds. Which approach, if any, was planned for this study is not reported in the registry record. The record does not identify how the 16 analyses relate to each other or how their results were prioritized.

The primary analysis population requires attention as well. The registry says two NAC participants were withdrawn after randomization and before receiving drug and were not analyzed. Two additional NAC participants withdrew during treatment before the week-8 primary assessment. The reported completer analysis includes 8 NAC participants and 13 placebo participants. The registry record does not report a full intention-to-treat analysis, a per-protocol definition, or a sensitivity analysis for missing primary outcomes.

In general, excluding participants after randomization can affect the comparability created by random assignment, depending on why they were excluded and how their outcomes differ from those observed. Missing outcomes can also affect the estimate if the probability of missingness is related to outcomes or treatment. The registry record does not provide enough information to determine whether such effects occurred. Reasons for the withdrawals, imputation methods, and assumptions about missing data are not reported in the registry record.

The record describes assessments at baseline, follow-up, and post-treatment, but it does not give a detailed analysis plan for repeated measurements or identify whether all available measurements contributed to the primary comparison. The handling of any other missing measurements is not reported in the registry record. These gaps limit assessment of how robust the primary result is to analysis-population choices and missing-data assumptions.

13. 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 reports serious adverse events for 0 of 12 participants at risk in the NAC group and 0 of 13 participants at risk in the placebo group. It reports no deaths in either group. No serious adverse-event terms are listed. These are the posted serious-event counts for the groups, not evidence that the possibility of serious harm has been ruled out.

The registry also reports other adverse events affecting 4 of 12 participants at risk in the NAC group and 5 of 13 participants at risk in the placebo group. The presence of an event in these summaries does not by itself establish that the event was caused by the assigned treatment. The record does not provide the event terms or additional detail in the adverse-event information, so the nature, severity, timing, and relationship to treatment cannot be assessed from these counts alone.

In general, zero reported serious events in a trial of this size should be interpreted as an observation from the participants monitored, not as proof that an event cannot occur. Safety interpretation depends on the duration and completeness of follow-up, how events were defined and collected, and the precision of estimates. The registry record does not provide a confidence interval for the serious-event comparison or enough detail to assess the completeness of event ascertainment. The reported 8-week treatment period is not a substitute for information about the duration of safety follow-up.

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

The primary outcome results describe change in PANESS scores from baseline to the end of 8 weeks. The mean change was -3.3 units in the NAC group and -3.1 units in the placebo group. The sponsor’s reported Wilcoxon (Mann-Whitney) comparison had p = 0.9. On a scale where higher scores correspond to greater symptom severity, the negative group means indicate lower average scores at the endpoint than at baseline in each analyzed group. The reported comparison does not indicate evidence of a between-group difference under that test.

That result does not establish that NAC and placebo are equivalent. Equivalence requires a prespecified range of differences considered unimportant and an analysis that evaluates that range. Such a margin is not reported in the registry record. A high p-value is not proof of no effect, and it does not quantify the largest effect still compatible with the observations. A confidence interval for the group contrast is not reported, so the precision of the comparison is unclear.

The result also does not show whether NAC affects ADHD symptoms, motor-cortex measures, or MRI-based brain-tissue properties. Those are listed secondary outcomes, but their numerical findings are not reported in the registry record. Nor does the primary outcome alone answer every broader question about learning, behavior, or safety. The results are tied to the PANESS measure and its stated week-8 assessment.

The analysis included 8 participants in the NAC group and 13 in the placebo group, following withdrawals in the NAC group. Because the registry does not report a full analysis plan, missing-data methods, or sensitivity analyses, the effect of these analysis choices cannot be assessed. The group standard deviations also show that individual change scores varied, but the summaries do not describe individual trajectories.

In general, a trial result is most informative when the estimated difference, its uncertainty, the analysis population, and the outcome’s clinical interpretation are considered together. The posted result supplies a sponsor p-value and group summaries but not a confidence interval or a clinically important-change threshold. It therefore supports a cautious description of the observed comparison, rather than a categorical claim about efficacy, equivalence, or the absence of an effect.

15. Why This Trial Matters Statistically

This trial illustrates why a p-value should not stand alone as the account of a clinical comparison. The posted primary result combines a rank-based test with descriptive means and standard deviations. The test addresses the relative ordering of observations across groups, while the summaries describe average change and variability. Keeping those roles distinct helps avoid treating the p-value as an effect estimate or treating the mean summaries as the reported test statistic.

It also shows why effect estimates and confidence intervals matter. A p-value of 0.9 does not tell readers how large a difference might be compatible with the data. Without an interval for the treatment contrast, the precision of the comparison is difficult to judge. A non-significant result cannot on its own distinguish a very small effect from an imprecisely estimated effect.

The analysis population is another important part of interpretation. The trial randomized 12 participants to NAC, but the primary completer analysis included 8 in that group; the placebo analysis included 13. The record reports withdrawals in the NAC group but does not fully describe missing-data methods or sensitivity analyses. A clear account of which participants contributed to each analysis and how missing outcomes were handled is essential to understanding a randomized comparison.

Finally, multiple outcomes and analyses make a prespecified statistical plan important. The registry lists 16 analyses overall, but does not report how multiplicity was handled or how the analyses were prioritized. The primary endpoint can be interpreted as the stated main comparison, but the broader pattern of results cannot be assessed from the numerical information reported. These are general lessons in transparent statistical reporting, illustrated by the information available for this trial.

16. 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 comparison has no reported confidence interval for the between-group effect. This limits assessment of precision and of which effect sizes remain compatible with the data. The registry record also gives no threshold for a clinically important PANESS change, so the clinical relevance of a particular score difference cannot be evaluated using a stated criterion.

The reported primary analysis is a completer analysis. The record says that two NAC participants were withdrawn after randomization but before receiving drug and were not analyzed, and that two more withdrew before the week-8 primary assessment. The registry does not describe the withdrawal reasons, the missing outcomes, an intention-to-treat analysis, or sensitivity analyses. The consequences of these exclusions therefore cannot be established from the record.

The sponsor’s reported test is Wilcoxon (Mann-Whitney), but the record does not give individual outcome distributions or detailed assumptions. The available means and standard deviations are useful summaries, yet they cannot show the full distribution or individual response patterns. A recalculated comparison and its uncertainty are not reported in the registry record.

Four secondary outcomes are listed, but numerical results are not reported in the registry record. The record lists 16 analyses overall without a detailed account of the statistical plan or any multiplicity strategy. This makes it difficult to understand the full set of planned and reported comparisons or to assess how selective reporting may have been addressed.

The registry metadata lists quadruple masking, while the trial description calls the study double-blind; the record does not explain the terminology. The study is described as single-center, and the primary assessment is at the end of an 8-week treatment period. The registry record does not report longer-term primary-outcome results. These details limit what can be concluded about broader settings or outcomes beyond the stated assessment.

17. Related Tutorials

18. Related Statistical Calculators

19. Sources

• ClinicalTrials.gov: Antioxidant Therapy With N-acetylcysteine for Children With Neurofibromatosis Type 1 — NCT04481048.
• Registry record last updated 2026-06-05; status last verified 2026-05.
• Results first posted 2026-06-05.
• 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.

20. Record Summary

NCT04481048 is a completed, randomized, parallel-group Phase II trial of NAC versus placebo in children with NF1. The registry lists enrollment of 25 and a study start date of 2021-02-23, with primary completion on 2024-06-25. The primary endpoint was change from baseline in PANESS motor-function scores at the end of 8 weeks.

The primary completer analysis included 8 participants in the NAC group and 13 in the placebo group. Mean changes were -3.3 and -3.1 units, with standard deviations of 9.3 and 12.7, respectively. The sponsor reported a Wilcoxon (Mann-Whitney) comparison with p = 0.9. A confidence interval for the comparison is not reported in the registry record.

The record lists four secondary outcomes and 16 analyses overall, but numerical secondary results and details of the statistical plan are not reported in the registry record. Serious adverse events and deaths were reported as 0 in each group; other adverse events affected 4 of 12 participants at risk in the NAC group and 5 of 13 in the placebo group.