Blinded, Randomized Study Evaluating Aurstat Versus Control in the Treatment of Atopic Dermatitis Associated Pruritus: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Blinded, Randomized Study Evaluating Aurstat Versus Control in the Treatment of Atopic Dermatitis Associated Pruritus (NCT01905631), a randomized phase 2 study. The primary outcome is Reduction of Itching in AD.

2. Clinical Question

3. Trial Design

This was a phase 2 randomized study comparing Aurstat Anti-Itch Hydrogel with an untreated control over three days. The registry lists double masking. The treatment instructions were to apply Aurstat twice daily or as needed for up to three days; control participants were instructed to apply nothing for the same period. Participants in both groups were asked to keep a diary of adverse events or other events.

The registry records total enrollment of 30. The posted outcome summaries list 20 participants in the Aurstat group and 10 in the untreated control group. The primary outcome description concerns people aged 12–75 years diagnosed with atopic dermatitis, and the brief description characterizes the condition as mild to moderate. The registry's study-model classification says “single group,” while its arm descriptions and posted results list two groups. That difference in the design information is not explained in the registry record.

The study is marked completed. Its recorded start was 2013-07 and primary completion was 2013-09. There is one posted outcome measure and no posted secondary outcome measures. The registry record does not report the original sample-size justification, detailed allocation procedures, or the trial's statistical analysis plan. The posted sample-size figures are planning illustrations based on the observed effect, not the trial's original design assumptions.

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.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Itch score

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 Reduction of Itching in AD, measured over 3-days.

The primary outcome is titled “Reduction of Itching in AD” and is recorded as a mean score on a scale, with standard deviation as the measure of spread. The timeframe is 3-days. The description identifies a visual analog assessment: participants indicated their itching along a line 154 mm long. A mark at 0 mm means no itching, while 154 mm means the most itching. Thus, lower positions on the stated scale correspond to less reported itching.

A visual analog scale is used to turn a subjective experience into a continuous numerical measure. This permits summaries such as group means and standard deviations, and allows a mean difference between groups to be estimated. It does not remove the subjective nature of the assessment: the score remains a participant's report of itching. The registry brief also mentions subject assessment, investigator global assessment, and photographs for tolerability, but only one outcome measure is posted, and its primary description concerns itching.

The record does not say whether the arm values represent final scores, change from baseline, or another summary of scores during the three-day period. It also does not report baseline scores or a fuller scoring schedule. This limits what can be inferred about how the mean difference maps to change in itching over time.

7. Results Posted in the Registry

• Treatment Group (Aurstat): mean 1.55 versus 1.70 on control; difference -0.15 (95% CI -0.62 to 0.32), standardized effect d = -0.20; z-test p = 0.531.

8. Statistical Interpretation

9. Statistical Methods Explained

The posted outcome is continuous, and the registry describes its summary as a mean with standard deviation. A mean represents the arithmetic average of the scores in a group. A standard deviation describes how dispersed individual scores are around that average: a larger standard deviation indicates greater observed spread. General statistical interpretation of these summaries depends on how scores were collected, whether the distributions are suitable for the chosen analysis, and whether all groups were measured comparably. The registry record does not provide score-level data or distributional diagnostics.

What does the mean difference describe?

The reported contrast is Aurstat minus untreated control, with an estimate of -0.15. A negative estimate means that the posted average score is lower in the Aurstat group than in the control group. This direction is consistent with less itching on the described scale, where the low end represents no itching. The contrast is an unadjusted comparison; the registry does not describe covariate adjustment or a baseline-adjusted model. It also does not say whether the values represent final scores or change from baseline, so the estimate should not be relabeled as a change-score effect.

A group contrast is a summary, not a description of every participant's response. Participants can have scores above or below their group average, and the standard deviations show that scores vary within each group. The mean difference does not indicate how many participants improved, how much individual scores changed, or whether any specific participant experienced a particular result. Those details are not reported in the registry record.

How should the p value be read?

The unadjusted p value is 0.531. In general, a p value measures how unusual data at least as incompatible with a specified null hypothesis would be if that hypothesis and the statistical model were correct. It is not the probability that the null hypothesis is true, and it is not a measure of the size or clinical importance of an effect. A larger p value does not prove that the groups are the same. In this study, the p value should be considered together with the estimated mean difference and its interval, the group sizes, and the missing details about the outcome and analysis.

The registry record does not state the trial's prespecified significance threshold or the complete test specification. The sample-size planning assumptions separately list a two-sided significance level of 0.05 for planning illustrations; that does not establish that the same threshold or procedure governed the trial's own analysis. No detailed statistical analysis plan is reported.

What does an interval add?

A confidence interval is a range of values compatible with the data under a stated method and confidence level. In general, narrower intervals indicate greater precision, while wider intervals reflect greater uncertainty. The posted interval for the mean difference includes zero and extends in both directions. That feature means the result does not narrowly identify the direction of the group contrast. The confidence level and construction method for this interval are not reported in the registry record, so those details cannot be assessed.

Interpretation of a continuous outcome can be affected by skewness, outliers, or unequal variability between groups. General methods may use robust procedures or models appropriate to the data when those features matter. The record gives group means and standard deviations but no individual scores, diagnostics, or description of such methods. It is therefore not possible to determine whether the assumptions behind the reported comparison were checked or whether an alternative analysis was considered.

Why do variation and missing scores matter?

Over-dispersion, in general, means that observed variability is greater than a model assumes. If a method understates variability, its uncertainty estimates can be too small; if variability is modeled appropriately, the resulting interval better reflects the observed spread. The present outcome is continuous, and the registry reports standard deviations rather than a count model, so over-dispersion in its count-data sense is not the central issue. Still, the unequal observed spreads make it relevant to ask how variability was handled. The registry does not describe a variance assumption or an analysis robust to unequal spread.

Missing outcome data can also change the analysis population and potentially affect a group comparison, depending on why scores are missing and how they are handled. The registry record does not report the number of missing primary outcome values, reasons for missingness, imputation procedures, or sensitivity analyses. Nor does it define whether the posted results use all randomized participants or another population. These gaps prevent a full evaluation of missing-data bias.

There is one posted outcome measure and no posted secondary outcome measures, but the registry does not report a complete protocol or analysis plan. The trial's approach to interim analyses, multiplicity, outcome selection, and analysis populations is not reported in the registry record. The unadjusted p value and interval can therefore be read as the posted summary comparison, without assuming that other analysis choices were prespecified or that unreported analyses were conducted.

10. Confidence Intervals and Precision

The mean-difference estimate is -0.15, with a reported interval whose lower limit is negative and whose upper limit is positive. The interval includes zero. In general, an interval communicates the range of effects that remain compatible with the data under the method used; its width communicates precision. Here, the interval spans values favoring either group, so the direction and size of the underlying group difference are not determined precisely by the posted data.

The group means are 1.55 for Aurstat and 1.7 for untreated control, with standard deviations of 0.826 and 0.483, respectively. The outcome summaries are based on 20 and 10 participants. With small groups and visible variation in scores, the observed group means may be sensitive to individual values. That is a general concern when interpreting means from small samples, not a claim that a particular participant drove this result.

The confidence level and method used to construct the interval are not reported in the registry record. The interval endpoints are therefore best treated as the posted uncertainty bounds, without assigning a confidence level or assuming a specific model. The registry also does not explain whether the outcome values are final scores or changes from baseline, and that ambiguity affects the substantive meaning of the estimate. The interval expresses statistical uncertainty around the reported contrast; it does not capture all uncertainty arising from incomplete outcome definitions, missing-data handling, or the study's design and reporting limitations.

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.

The planning figures are participants per arm, not total events. The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect used for each illustration is a stated fraction of the observed effect. The original trial's own sample-size assumptions and justification are not reported in the registry record.

For 100% of the observed effect, the illustration gives 376 participants per arm for 80% power and 503 participants per arm for 90% power. For 75% of the observed effect, it gives 668 participants per arm for 80% power and 894 participants per arm for 90% power. For 50% of the observed effect, it gives 1,502 participants per arm for 80% power and 2,010 participants per arm for 90% power.

In plain terms, the 80% power column gives the illustrative number in each arm for a design with an 80% chance of detecting the specified effect under the listed assumptions, if the assumed effect and model are correct. The 90% column gives the corresponding number for a design with a 90% chance. Higher power generally requires more participants under otherwise matching assumptions. The examples also show that smaller effects need more participants: when planning for a smaller fraction of the observed effect, the listed per-arm numbers increase.

These are planning illustrations based on the observed effect, not observed power for the completed trial. They do not show that the trial had a particular probability of success, and they should not be read as the original enrollment target. The registry record does not report that target's justification or assumptions.

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 z_1−α/2 = 1.960) and the desired power (z_1−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

1. Observed difference Δ = -0.150; pooled standard deviation σ = 0.733.
2. n = 2 × (1.96 + 0.842)² × 0.733² / -0.150² = 375.3, rounded up to 376 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 <- -0.15                      # observed difference in means
sigma <- 0.733456713105825                     # 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(1905631)
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 = 376 (80% power), 503 (90% power)
 75% of observed effect: n per arm = 668 (80% power), 894 (90% power)
 50% of observed effect: n per arm = 1,502 (80% power), 2,010 (90% power)
power.t.test: 376.3 
Simulated power at n = 376 per arm: 0.802 (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 one primary outcome measure and no posted secondary outcome measures. This limited outcome listing does not establish that the full protocol contained no additional outcomes or that only one analysis was planned. A complete protocol and statistical analysis plan are not reported in the registry record, so the planned approach to multiplicity cannot be assessed.

Multiplicity arises when several outcomes, time points, groups, or statistical tests are considered. In general, testing many hypotheses can increase the chance of a chance finding if results are interpreted without accounting for the testing strategy. The available record does not describe whether there were multiple planned time points, subgroup analyses, or other comparisons, nor whether any multiplicity adjustment was planned. The single posted primary outcome should therefore be distinguished from a complete account of all analyses.

Missing-data information is also limited. The registry does not report how many primary outcome scores were missing, why any scores were absent, or how missing observations were handled. It does not identify whether results follow an intention-to-treat population, a per-protocol population, or another analysis population. Without those details, it is not possible to know which participants contributed to the outcome summaries or to assess how exclusions or missing measurements might influence the comparison.

The record does not report interim analyses, stopping rules, or a prespecified analysis plan. Their absence from the record should not be interpreted as evidence that they were or were not part of the conduct of the trial. The unadjusted p value is a posted comparison, but its relationship to any broader testing strategy is unknown. These reporting gaps limit judgments about selective analysis and the reliability of inferential claims beyond the summary data shown.

14. Safety Results

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

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 records serious adverse events in 0 of 10 participants in the untreated control group and 0 of 20 participants in the Aurstat group. These figures describe the counts recorded among the participants at risk in each group. They do not mean that the chance of a serious event is zero, particularly in a study of this size and duration. The registry lists no serious adverse event terms.

The record separately lists other adverse events in 0 of 10 control participants and 1 of 20 Aurstat participants. The event description is not reported in the registry record. These counts should not be combined with the serious adverse event figures: they are reported as a separate category.

Deaths are not reported in the registry record. The study lasted three days, so these safety counts concern a short observation period as recorded, and they cannot describe longer-term events. The figures are descriptive; the registry does not provide a comparative safety analysis or enough detail to assess event severity, timing, or relatedness.

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

The posted result is a comparison of mean itching scores over a three-day timeframe in a randomized study of Aurstat and untreated control. The Aurstat group had a mean score of 1.55, compared with 1.7 in the control group, and the reported mean difference was -0.15. The direction of the estimate corresponds to a lower score in the Aurstat group on the described scale. The unadjusted p value is 0.531, and the interval for the difference includes zero and extends in both directions.

These data do not precisely identify the direction or size of a group difference. They also do not establish that the groups are equivalent. The observed summary is based on 20 Aurstat participants and 10 control participants, and the registry does not clarify whether the posted scores are endpoint values or changes from baseline. The results cannot be translated into a number of participants who improved, an individual response, or a clinical threshold because those details are not reported.

The registry's entry describes randomization and double masking, but its study-model field says single group even though two arms are listed. It does not report the full allocation process, analysis populations, missing-data methods, confidence level, or statistical analysis plan. Those uncertainties should be considered alongside the numerical comparison.

Accordingly, the record supports a cautious description of the posted score summaries and their uncertainty, rather than a broad conclusion about efficacy or safety. The sample-size illustrations are planning calculations, not evidence about the completed trial's power. The adverse-event counts are descriptive and limited to the short trial period. No medical conclusion or recommendation follows from these registry data alone.

16. Why This Trial Matters Statistically

This trial illustrates why a numerical estimate and its uncertainty should be read together. The mean-difference estimate is negative, but the reported interval includes zero and stretches toward values favoring either group. The p value, meanwhile, is a measure tied to a statistical test and its assumptions, not a direct statement about the probability that the treatment has an effect. Reading all three together discourages treating one number as a definitive verdict.

It also demonstrates the importance of clear outcome definitions. The registry explains the visual analog scale's endpoints, but the reported arm values are not clearly identified as final scores or changes from baseline. Without that distinction, even a correctly reported contrast is harder to connect to the clinical question of reduction in itching. For clinical researchers, specifying measurement timing and the estimand—the quantity a comparison is intended to describe—is central to interpretable results.

The design and reporting fields also matter. Randomization and double masking are recorded, while the study-model classification says single group despite two listed arms. The record does not resolve that inconsistency or describe the statistical analysis plan, missing-data approach, or analysis population. These omissions show why registry results are useful for transparency but may not replace a full protocol and results report.

Finally, the small group sizes and short timeframe place the findings in context. The planning illustrations demonstrate how assumptions about the effect size influence a future study's participant requirements, but they are not observed power and are not the original design rationale. The safety counts also need context: no serious events are listed, but a small, short study cannot settle questions about uncommon or longer-term events.

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.

Several limitations are specific to the registry record. The primary outcome is described as reduction of itching, but it is not clear whether the posted group means represent final visual analog scores, changes from baseline, or another summary. Baseline values and the exact measurement schedule are not reported. Consequently, the posted mean difference cannot be interpreted with confidence as a change attributable to treatment over time.

The measurement description gives a 154 mm line, but the group summaries are listed as scores on a scale without a clear unit or explanation of how the line measurements became the posted values. The interval's confidence level and construction method are not stated. These omissions limit reproducibility and make it difficult to compare this estimate with other score summaries.

The registry lists randomized, double-masked allocation and two arms, but its model classification says single group. The record does not explain this inconsistency or provide details of sequence generation, concealment, or how masking was maintained. It also does not report the original sample-size justification, the planned analysis population, handling of missing outcomes, or the full analysis plan. There is no posted secondary outcome measure, but the registry entry alone does not establish what may have appeared in a complete protocol.

Enrollment was 30, with 10 participants in control and 20 in treatment. The small groups limit precision, and the recorded timeframe is only three days. The adverse-event entry does not describe the one other event in the treatment group; deaths are not reported in the registry record. Longer-term tolerability and outcomes are not addressed by these short-term summaries.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Blinded, Randomized Study Evaluating Aurstat Versus Control in the Treatment of Atopic Dermatitis Associated Pruritus — NCT01905631.
• Registry record last updated 2022-10-24; status last verified 2022-10.
• Results first posted 2022-10-24.
• 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.

21. Record Summary

This completed phase 2 study compared Aurstat Anti-Itch Hydrogel with untreated control in a randomized, double-masked, three-day trial. The registry records enrollment of 30, with 20 participants in the treatment group and 10 in control. The primary outcome was itching assessed with a visual analog scale; one outcome measure is posted and no secondary outcome measures are posted.

The mean score was 1.55 for Aurstat and 1.7 for control, with a reported mean difference of -0.15, an unadjusted p value of 0.531, and an interval that includes zero. The record does not clarify whether the scores are final values or changes from baseline. Serious adverse events were recorded in 0 of 20 treatment participants and 0 of 10 control participants; one other adverse event was recorded in the treatment group. The statistical plan, missing-data handling, and analysis populations are not reported in the registry record.