Comparison of Two Botulinum Toxins Type A on Forehead Wrinkles: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparison of Two Botulinum Toxins Type A on Forehead Wrinkles (NCT01014871), a randomized phase 2 study. The primary outcome is Severity of the Forehead Wrinkles by the Evaluator at Maximum Contraction and at Rest Using the Forehead Wrinkles Severity Scale (0 to 3) at Each Study Visit and for Each Side of the Forehead.

2. Clinical Question

The design asks about a relative difference between products under a split-face arrangement. Each subject received both products, one on each side, and random allocation determined which product went on which side. This makes the subject a natural basis for comparing the treated sides, while reducing the influence of characteristics shared by both sides of the same person.

The endpoint is repeated: the registry describes assessments from baseline through Month 5, including early visits and later follow-up. It also distinguishes ratings at rest from ratings at maximum contraction. Those conditions and visits define several related comparisons, rather than one self-evident summary. The registry record does not identify a single time point or condition as the sole comparison for interpreting treatment differences.

The clinical question is therefore about the pattern of measured severity over time and across the two forehead sides. The posted registry record does not report numerical primary-outcome results or an inferential comparison. It is not possible from that record to describe the size, direction, or precision of a difference between Azzalure and Vistabel.

3. Trial Design

This was a randomized, single-centre, controlled, evaluator-blinded, bilateral split-face comparison study. The study is listed as phase 2 and completed. Enrollment was 30. The registry lists a start in 2009-07 and primary completion in 2010-04.

At baseline, one botulinum toxin type A was injected into one forehead side and the other product into the opposite side. Side allocation was randomized. The interventions are named Azzalure and Vistabel. The design is identified as a single-group model, which is consistent with an intra-individual comparison: both products are used within a participant rather than assigned to separate parallel groups. The registry describes evaluator blinding, but further details about who was masked and how masking was maintained are not reported in the registry record.

In a split-face design, each participant contributes observations under both treatments. That feature can make the comparison less affected by characteristics common to both sides, but it also means that the observations from the two sides are linked. An analysis should account for that pairing; treating the sides as if they came from unrelated people would not reflect the study structure. The registry record does not describe the statistical method used for the primary comparison.

Wrinkle severity was assessed at baseline, Days 1, 2, 3, 7, 10, 14, and 30, and Months 4 and 5. Evaluations were specified at rest and at maximum contraction, separately for each forehead side. The registry identifies a continuous outcome expressed as a mean with standard deviation, and names the Intention To Treat population for the primary outcome.

Although the study is marked completed, completion alone does not establish what the results were or how the primary comparison was conducted. Numerical primary-outcome results, analysis details, and a sample-size justification are not reported in the registry record. The description identifies the design and measurement schedule, but it does not give enough information to reconstruct a treatment-effect 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.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Intention To Treat

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 Severity of the Forehead Wrinkles by the Evaluator at Maximum Contraction and at Rest Using the Forehead Wrinkles Severity Scale (0 to 3) at Each Study Visit and for Each Side of the Forehead, measured over 5 months : Baseline, Days 1, 2, 3, 7, 10, 14, 30, Months 4 and 5.

The primary endpoint is evaluator-assessed forehead wrinkle severity, measured with the Forehead Wrinkles Severity Scale, which runs from 0 to 3. Ratings are specified at rest and at maximum contraction, for each forehead side and at each listed visit from baseline through Month 5. The registry describes the outcome as a mean with standard deviation and identifies the Intention To Treat population.

A severity scale turns an evaluator's assessment into an ordered score that can be tracked over time. Repeated measurements can describe whether observed severity changes after treatment and whether the pattern differs between the two treated sides. Assessing at rest and at maximum contraction captures the endpoint under two stated conditions; the registry does not explain how those conditions are combined, if at all, for a single summary.

Using the same participant for both products offers a within-person comparison. In general, this can control for participant characteristics shared across the forehead, while the side-level difference remains the focus. Because the two ratings belong to the same participant, their statistical dependence is relevant when estimating uncertainty.

The outcome description specifies what was measured, but the registry record does not report the observed means, standard deviations, treatment contrasts, or confidence intervals. Nor does it identify one visit and assessment condition as the definitive primary contrast. Thus, the endpoint is clearly described, but its numerical findings and their precision cannot be evaluated from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical structure follows from the way the study was organized: two products were applied to different sides of the same participant, the side assignment was randomized, and the same evaluator-assessed outcome was repeated over visits. The registry identifies the primary measure as a continuous outcome summarized by a mean and standard deviation. It does not report the model, test, or estimation procedure used.

Why does the split-face structure matter?

In general, paired observations are analyzed with their relationship intact. Ratings from the two sides of one participant are likely to share influences, such as the participant's overall characteristics and the assessment setting. A comparison based on each participant's side-to-side contrast can account for that shared context. An analysis that treated all side-specific ratings as independent would ignore the design and could misstate uncertainty.

Pairing does not guarantee a more precise estimate in every circumstance. The gain depends on how strongly the paired measurements are associated and on the variation in their differences. Those features are not reported in the registry record. The record also does not specify whether the analysis used participant-level contrasts, a repeated-measures model, or another method suited to the paired design.

What do a mean and standard deviation describe?

In general, a mean describes the average observed score within the group or condition being summarized. A standard deviation describes how dispersed individual observations are around that mean. These summaries are not themselves a comparison between products. To estimate a treatment difference, an analysis must compare the two sides while respecting the paired observations and the relevant assessment time and condition.

A mean-based summary can be useful for describing a continuous endpoint, but the scale has a bounded range from 0 to 3. Interpretation should therefore remain tied to the outcome's scoring system and the observed distribution. The registry record does not provide distributions or summaries that would allow assessment of whether a mean alone adequately represents the observations.

How should repeated visits be handled?

Repeated observations from one participant are correlated in general: measurements closer together or taken from the same person cannot automatically be treated as unrelated. A repeated-measures analysis can model that dependence, while a prespecified visit-specific comparison may focus on a particular assessment. The registry record lists baseline and multiple post-baseline visits through Month 5, as well as ratings at rest and at maximum contraction. It does not state how time, assessment condition, or their combination entered the primary analysis.

Baseline measurement can help describe starting severity and can be used in analysis, but the registry record does not state whether the comparison used change from baseline, post-baseline scores adjusted for baseline, or another approach. No model assumptions, covariates, or handling of correlation are reported. These choices affect the estimand and its uncertainty, so they cannot be inferred from the outcome description alone.

What does a confidence interval add?

Generally, a confidence interval accompanies an estimate to show its statistical uncertainty. It is not a guarantee that the true value lies within the interval, and it does not determine clinical importance on its own. The interval's interpretation depends on the analysis and assumptions. No primary treatment estimate or confidence interval is reported in the registry record, so neither uncertainty nor compatibility with different effect sizes can be assessed.

What can be inferred from the record?

The random assignment of products to forehead sides is stated, and the evaluator is described as blinded. Randomization helps protect the comparison from systematic side-allocation choices, while evaluator blinding can reduce bias in scoring. Those safeguards do not disclose the analysis or demonstrate that every potential bias was avoided. Details about sequence generation, allocation concealment, blinding procedures, and protocol adherence are not reported in the registry record.

The registry lists no analyses and does not present a reduced primary comparison. It is therefore not possible to reproduce or verify an inferential result. General principles can explain what an appropriate paired, repeated-measures analysis would need to consider, but they do not identify the method actually used in this study. No recalculated treatment effect or planning illustration can be interpreted as an observed primary result from the registry information.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome includes more than one assessment condition and multiple visits. In general, examining many time points or related outcomes can increase the chance of finding an apparently notable result by chance if one is selected after looking at the data. A prespecified primary contrast, or an explicit multiplicity strategy, helps clarify how a family of comparisons is interpreted. Neither a primary visit-and-condition contrast nor a multiplicity procedure is reported in the registry record.

The registry identifies the primary population as Intention To Treat. That label indicates the intended analysis population, but it does not by itself explain how participants with missing measurements were handled, whether all randomized participants contributed to every analysis, or how deviations from assigned side treatment were treated. The number and pattern of missing outcome observations, imputation methods, and sensitivity analyses are not reported in the registry record.

For repeated measurements, missingness can affect which participants contribute to each visit and may influence estimates if the absence of a rating is related to the outcome. In general, analysts describe the extent of missingness and state the assumptions behind any method used to address it. The registry record does not give this information, so the robustness of any primary result to incomplete follow-up cannot be assessed.

The registry does not list an analysis or a numerical primary result. It also does not report a statistical analysis plan, interim analyses, or a sample-size justification. These omissions prevent assessment of whether the displayed or intended comparisons followed prespecified choices. They should not be filled in by assuming conventional methods or procedures.

11. 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 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports zero serious adverse events among 30 participants at risk for Azzalure and zero among 30 at risk for Vistabel. It separately reports other adverse events affecting 15 participants in the Azzalure group and 18 in the Vistabel group, with 30 at risk in each group. Death counts are not reported in the registry record.

These figures are reported for the two product groups in a split-face study. Since each participant received both products, the groups should not be read as separate parallel cohorts. The record does not specify whether an individual experiencing an event could be counted in both product groups, how events were assigned to a side, or the observation period used for these counts. The counts therefore should not be combined or treated as a direct estimate of comparative risk.

Serious adverse events and other adverse events are distinct registry categories. A count of zero serious events is a statement about the reported category during the recorded observation, not proof that a risk is absent. The registry does not provide event descriptions, severity grading for other events, exposure-adjusted rates, or a statistical comparison. These safety counts do not establish a causal difference between products and do not replace the unreported primary efficacy analysis.

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

The study is designed to compare two botulinum toxin type A products within the same participant, using randomized assignment of product to forehead side and evaluator-assessed wrinkle severity. Its primary endpoint is described in detail: scores at rest and at maximum contraction, at repeated visits through Month 5, with the outcome summarized as a mean and standard deviation in the Intention To Treat population.

What the registry record does not provide is equally important. It contains no numerical primary-outcome results, treatment contrast, uncertainty interval, or inferential test. The record therefore does not show whether the observed scores favored either product, whether any difference was large or small, or how precisely a difference was estimated. A completed status and a stated outcome do not supply those missing findings.

In general, statistical significance and clinical importance are different questions. A small estimated difference can be precise, while a larger estimate can be uncertain; clinical relevance also depends on the meaning of the scale and the judgment applied to a change. Without an estimate, interval, and interpretive context, neither issue can be resolved. The scale range alone does not establish what change would matter to participants or evaluators.

The split-face design can support an efficient within-person comparison, but it does not establish that products are equivalent or interchangeable. Equivalence requires an appropriate design, a defined margin, and an analysis that evaluates whether uncertainty excludes differences beyond that margin. Such details and results are not reported in the registry record.

The safety counts describe reported adverse-event categories, but they cannot determine comparative safety in the absence of event detail and analysis. Overall, the record supports a description of the study question, design, measurement schedule, and reported event counts. It does not support a conclusion that either product produced better wrinkle-severity outcomes or a conclusion that their outcomes were the same.

13. Why This Trial Matters Statistically

This trial is statistically notable for using a split-face design. Instead of assigning separate participants to each product, it applied both products within each participant and randomized which side received each one. This design makes the comparison intrinsically paired and places emphasis on the analysis of within-participant differences.

That structure illustrates why trial design and statistical analysis must align. The two sides share a participant, but they are not identical experimental units in every respect. An analysis that accounts for the pairing can use the study's structure; one that ignores it may misrepresent the uncertainty. The registry record identifies the paired design but does not report how the primary analysis handled that dependence.

The outcome also highlights a common challenge in clinical trials: repeated assessments can create a family of related questions. Here, severity is assessed at rest and at maximum contraction, across visits extending from baseline to Month 5. Without a clearly identified principal contrast and reported approach to multiple comparisons, a reader cannot know which result would carry the primary inferential emphasis.

Finally, this record distinguishes trial registration from a full account of trial findings. It documents the intended comparison and endpoint, and gives limited adverse-event counts, but provides no numerical primary outcome analysis. Statistical interpretation requires both a design and the results needed to quantify an effect and its uncertainty. The distinction is important: a well-described question is not itself an answer to that question.

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 principal limitation for interpretation is that the registry record does not report numerical results for the primary endpoint. The repeated wrinkle-severity ratings are described, but there are no means, standard deviations, contrasts, or uncertainty intervals to assess. No primary analysis is listed. Accordingly, the comparative outcome cannot be independently evaluated from the registry record.

The endpoint covers multiple visits and two assessment conditions, yet the record does not identify one visit-condition combination as the main treatment contrast. It does not describe how the repeated observations were modeled, whether baseline was incorporated analytically, or how multiplicity was handled. These missing details limit interpretation even if a numerical result were available elsewhere.

The study is described as evaluator-blinded, but the registry does not explain who else was masked, how masking was maintained, or whether evaluators could distinguish sides or products. Details about allocation concealment, treatment administration, adherence, and protocol deviations are also not reported in the registry record.

The primary population is labeled Intention To Treat, but procedures for missing outcome data are not stated. The registry provides no participant flow, visit-level completeness, or sensitivity analysis. It is therefore not possible to judge how missing assessments may have affected estimates.

Enrollment was 30, but the record does not report a sample-size justification. It also lacks outcome variability and within-participant association information needed to understand the precision that this design could deliver. Finally, the single-centre setting may constrain how broadly findings would apply, but participant characteristics beyond the stated wrinkle severity are not reported. These limitations leave both the result and its wider applicability uncertain.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Comparison of Two Botulinum Toxins Type A on Forehead Wrinkles — NCT01014871.
• Registry record last updated 2021-02-18; status last verified 2012-04.
• Results first posted 2012-04-05.
• 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.

18. Record Summary

The registry record describes a completed phase 2, randomized, single-centre, evaluator-blinded split-face comparison of Azzalure and Vistabel in subjects with moderate to severe forehead wrinkles. Enrollment was 30. Each product was assigned to one forehead side, with side allocation randomized.

The primary outcome is evaluator-assessed wrinkle severity at rest and at maximum contraction, measured with the Forehead Wrinkles Severity Scale from 0 to 3 across visits through Month 5. The primary population is identified as Intention To Treat. The registry reports zero serious adverse events in each product group and other adverse events affecting 15 participants in the Azzalure group and 18 in the Vistabel group.

Numerical primary-outcome results, a treatment comparison, analysis methods, missing-data procedures, and multiplicity handling are not reported in the registry record. The design and measurement schedule are described, but the record does not establish the direction, size, or precision of comparative wrinkle-severity outcomes.