A Clinical Trial to Evaluate the Efficacy of Two Acne Treatments: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Clinical Trial to Evaluate the Efficacy of Two Acne Treatments (NCT02755545), a randomized phase 4 study. The primary outcome is Percent Change From Baseline in Total Lesions at Week 12.

2. Clinical Question

The study summary describes 24 weeks of use, whereas the listed primary endpoint is measured at week 12. The question addressed is therefore specifically about the registered week-12 endpoint, not a conclusion about the entire period of use. The page can describe the design, outcome definition, and available safety counts, but the efficacy comparison itself is not reported in the registry record.

3. Trial Design

This was a phase 4, randomized, double-masked, parallel-group, multicenter clinical trial sponsored by Galderma R&D. The registry record lists 127 enrolled participants and a completed status. It describes two active topical treatment arms: adapalene, applied once daily, and salicylic acid, applied 1 to 3 times daily. It does not report the allocation ratio, the locations of the study centers, or additional details about how randomization and masking were implemented.

The study summary describes adult men and women with mild to moderate facial acne, including at least 5 inflammatory lesions and 10 - 100 non-inflammatory lesions. The stated purpose was to evaluate the two treatments over 24 weeks of use. The primary endpoint listed in the registry record, however, concerns percent change from baseline in total lesions at week 12. This distinction matters when interpreting the scope of the posted endpoint: it is a measurement at a specified time point, not a summary of all outcomes across the full period of use.

The record lists 127 enrolled participants and says 117 were included in the efficacy analysis. It does not state why the analysis population was smaller, whether participants were excluded before or after randomization, or how the analysis population was defined. It also lists one outcome measure but no analyses. Thus, the record supplies design and outcome descriptions without the arm-level efficacy estimates or inferential results needed to evaluate the primary comparison.

The registry record does not report the planned sample-size justification, a detailed statistical analysis plan, or whether interim analyses were planned. Any sample-size figures elsewhere on the page should be read as planning illustrations based on the observed effect, not as the trial's original design calculations and not as observed power.

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: A total of 127 were enrolled, but only 117 were included in the efficacy 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.

6. Primary Endpoint

The registry lists the primary outcome as Percent Change From Baseline in Total Lesions at Week 12, measured over Baseline and 12 weeks.

The primary endpoint is titled percent change from baseline in total lesions at week 12. It uses lesion counts recorded by an investigator or designee at baseline and week 12. The count combines inflammatory lesions, defined as papules and pustules, with non-inflammatory lesions, defined as open and closed comedones. Counts were recorded across the forehead, left cheek, chin, and right cheek, with the total across those four areas included in the endpoint description.

A change in total lesion count is a continuous measure: it can reflect the extent to which a participant's recorded lesion burden changes rather than classifying participants only as improved or not improved. Expressing change as a percent of baseline is intended to place change in relation to the participant's starting count. In general, that can help describe change across participants whose baseline counts differ. The registry record does not give the actual endpoint values, the method used to handle baseline values in the calculation, or a definition of the direction and sign convention used for the reported change.

The endpoint is clinically interpretable as a summary of several types and locations of facial lesions, but that summary can conceal variation among lesion types or facial areas. The registry description says the lesion types and locations were also analyzed separately. Those multiple categories make it important to distinguish the stated primary endpoint from other possible summaries. The posted record does not provide numerical results for the endpoint or the separate categories, so the measure's definition is available but its observed magnitude and precision are not.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes the primary endpoint as a mean of a continuous measure: percent change from baseline in total lesion count at week 12. A mean summarizes the central tendency of measured changes across participants. The listed dispersion measure is the standard deviation, which describes variation among individual observations around the mean. It is not the same as the uncertainty in an estimated mean or in a between-group contrast. In general, a confidence interval conveys uncertainty about an estimate, while a standard deviation describes variability in the underlying observations.

The outcome description specifies that investigators or designees counted open comedones, closed comedones, papules, and pustules on the face. It groups papules and pustules as inflammatory lesions, and open and closed comedones as non-inflammatory lesions. Counts were recorded in four facial areas and as a total across those areas. This definition makes clear what was counted, but the record does not provide the numerical observations or the calculation details behind the reported percent change. It also does not report a model, adjustment variables, or the exact statistical test used for the primary comparison.

In general, a comparison of two randomized groups can be expressed as a difference in their mean outcomes. An estimate alone is not enough to judge precision: a confidence interval helps show the range of values compatible with the data and the analysis assumptions. A p-value, when reported, addresses compatibility with a specified null hypothesis under a statistical model; it does not describe the size or clinical importance of an effect. No such comparison estimate, confidence interval, or p-value is reported in this registry record.

The registry identifies the trial as randomized and parallel-group. Randomization is generally intended to make treatment groups comparable in expectation, but its interpretation depends on implementation and on how participants are included in the analysis. The registry record does not report the allocation ratio, sequence-generation method, concealment details, or a full analysis plan. Double masking indicates that the study is recorded as double-masked, but the record does not identify which roles were masked or describe how masking was maintained.

The endpoint includes measurements from more than one lesion type and facial location, while its title singles out total lesions at week 12. In general, testing many outcomes, categories, locations, or time points can increase the chance of finding an apparently notable result by chance if the analysis does not address multiplicity. A prespecified primary endpoint can help focus interpretation, but details of any multiplicity strategy are not reported in the registry record. The record also notes multiple categories or time points and does not reduce them to one comparison. Without results and a stated analysis plan, readers cannot establish which comparisons were tested or how any multiplicity was handled.

The standard deviation is relevant because participant outcomes may vary considerably. In general, when continuous data show more variability than a model assumes, standard errors and tests based on that model can be misleading. This is often described as over-dispersion in contexts where a model expects less variability than the data exhibit. The record does not provide the outcome data, model, or diagnostics needed to assess whether over-dispersion arose or how it was addressed. It would therefore be inappropriate to infer a particular distribution or modeling strategy from the endpoint description alone.

The record states that 127 participants were enrolled and 117 were included in the efficacy analysis. In general, analysis populations can be defined in different ways, such as including all randomized participants according to assigned group or restricting analysis to participants with available measurements. The registry record does not state which approach was used, whether assignment was analyzed as randomized, or why the efficacy analysis included fewer participants than were enrolled. It also does not describe missing-data assumptions, imputation, or sensitivity analyses.

The sample-size section is a planning illustration based on the observed effect, using a two-sided significance level of 0.05, equal allocation, and a normal approximation. In general, such calculations estimate the number of participants per arm needed to detect an assumed effect under specified assumptions. Rows for smaller fractions of an observed effect represent planning for a smaller target effect, not additional observed trial comparisons. These figures are not observed power and should not be interpreted as the original protocol's sample-size justification. The registry record does not report that justification or explain whether its original planning used the same assumptions.

Because the posted record lists no analyses, none of the general methods above can be confirmed as the methods actually used for the primary endpoint. They describe how to understand common statistical ideas, not an assertion that this trial used a particular test, model, adjustment, or missing-data procedure.

10. Multiplicity, Missing Data and Analysis Populations

The endpoint description covers total lesions and also describes separate lesion types and facial locations. The registry record notes that the primary outcome has several categories or time points and has not been reduced to one comparison. When several outcomes, subgroups, or time points are examined, multiplicity can make an isolated result harder to interpret unless the analysis plan specifies which comparison is primary and how other tests are handled. The record does not report a multiplicity adjustment, hierarchy of tests, or detailed prespecification of the analyses. It also lists no analyses, so readers cannot see which categories or time points produced results.

The record gives an enrolled count of 127 and says 117 were included in the efficacy analysis. It does not explain the difference, define the efficacy population, or state whether participants were analyzed according to randomized assignment. Those details matter because excluding participants or measurements can affect the comparability created by randomization. The reason for the difference in counts is not reported in the registry record.

Handling of missing outcome data is not reported in the registry record. The record does not say how many week-12 measurements were missing, why any measurements were missing, whether values were imputed, or whether sensitivity analyses examined alternative assumptions. Without this information and the numerical endpoint results, it is not possible to assess the potential impact of missing data or determine the robustness of the efficacy findings. These are reporting gaps; they do not establish that a particular method was or was not used.

11. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 3% reporting threshold.

Most frequent non-serious adverse event terms

The registry lists serious adverse events separately for the two treatment groups. For adapalene, 62 participants were at risk and 0 serious adverse events were recorded. For salicylic acid, 65 participants were at risk and 0 serious adverse events were recorded. Deaths were recorded as 0 in both groups. These are counts as presented in the registry; they do not by themselves establish that the treatments have equivalent safety profiles.

For other adverse events, the record lists 2 events among 62 participants at risk in the adapalene group and 0 among 65 at risk in the salicylic acid group. The registry record does not provide event terms, severity, timing, duration, or details about whether events led to treatment discontinuation. It also does not report a statistical comparison of these counts. The groups' recorded counts should therefore be read descriptively, with the limited detail in the record kept in view.

A zero count in a registry table means no event was recorded in that category for the listed group; it does not demonstrate that no risk exists. These safety figures are not a complete assessment of every possible adverse effect, and the posted record does not provide the detail needed to interpret individual events or compare risks precisely.

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

This record establishes that a randomized, double-masked, parallel-group study compared topical adapalene with topical salicylic acid in adults with mild to moderate facial acne. It identifies a primary endpoint based on percent change from baseline in total facial lesions at week 12 and describes the lesion-counting procedure. It also reports enrollment, the smaller efficacy-analysis count, and limited adverse-event counts. These are useful features of the trial record, but they do not constitute a posted efficacy result.

The registry record does not report the mean endpoint value in either group, the between-group estimate, or a measure of its precision. Accordingly, it cannot show from the posted information whether the average change differed between groups, the direction of any difference, or how uncertain an estimate might be. The absence of these results is not evidence of no difference and is not evidence that either treatment had a particular effect.

The record also does not provide enough detail to evaluate how participants with missing or incomplete outcome data were handled, how the efficacy population was defined, or whether the multiple lesion categories and locations were addressed in a prespecified way. No original sample-size justification or detailed statistical plan is reported. A planning illustration based on an observed effect, if viewed elsewhere on the page, is not evidence of observed power and does not fill those reporting gaps.

The serious adverse-event and death counts are zero in both arms, while the other adverse-event count is 2 in the adapalene arm and 0 in the salicylic acid arm. These sparse descriptive counts do not establish equivalence or provide a complete comparative safety assessment. Taken together, the posted record supports a description of the trial's question, design, outcome definition, and recorded safety counts. It does not support a conclusion about comparative efficacy or a definitive treatment recommendation.

13. Why This Trial Matters Statistically

This trial illustrates the difference between a clearly described endpoint and a reported analysis. The registry gives a specific primary measure—percent change from baseline in total lesions at week 12—and explains which lesion types and facial areas contributed to the count. That detail helps readers understand what the investigators intended to measure. But without arm-level results and an analysis, the endpoint description alone cannot answer the treatment comparison.

It also highlights the importance of separating the target population from the analyzed population. The record reports 127 enrolled participants and 117 included in the efficacy analysis, without explaining the difference. Transparent reporting of analysis-population definitions and participant flow helps readers judge whether the comparison reflects the randomized groups and how incomplete observations may affect interpretation.

The outcome structure raises a further statistical issue: the endpoint description includes several lesion categories and locations, while the registered primary title focuses on total lesions at a particular time point. Multiple outcomes or time points require clear reporting of which analysis is primary and how other analyses are interpreted. The registry record does not describe those analysis details or provide results for the categories.

Finally, the record shows why safety counts need context. Counts of serious and other adverse events can be informative, but event descriptions, follow-up details, and comparative analyses are needed for a fuller interpretation. This trial is therefore statistically instructive not because the registry establishes a treatment result, but because it shows what can and cannot be learned when design and outcome definitions are available while the efficacy analysis is not.

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 interpreting efficacy is that the registry record does not report numerical results for the primary endpoint or an analysis comparing the treatment arms. Although the endpoint and measurement process are described, readers cannot assess the size, direction, or precision of an efficacy difference from this record.

The registry reports 127 enrolled participants and 117 included in the efficacy analysis but does not explain how the analysis population was defined or why these counts differ. It does not report participant flow by arm, reasons for exclusion, the amount or pattern of missing week-12 data, or the method used to handle missing observations. These omissions prevent assessment of possible selection and missing-data effects.

The outcome description includes total lesions as well as separate lesion categories and facial locations. The record does not report results for these categories, which comparisons were considered primary beyond the listed endpoint, or whether multiplicity was addressed. It also does not report the analysis model, adjustment variables, confidence intervals, p-values, or a detailed statistical plan.

The safety information is limited to counts. The record does not provide event names or descriptions for the other adverse events, their severity or timing, or a statistical comparison. It also does not report the original sample-size justification. These limitations are specific to the information available in the registry record and should not be taken as proof that unreported procedures or assessments were not carried out.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Clinical Trial to Evaluate the Efficacy of Two Acne Treatments — NCT02755545.
• Registry record last updated 2023-12-28; status last verified 2023-12.
• Results first posted 2023-12-28.
• 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 4, randomized, double-masked, parallel-group, multicenter trial sponsored by Galderma R&D. It enrolled 127 adults with mild to moderate facial acne to compare topical adapalene, applied once daily, with topical salicylic acid, applied 1 to 3 times daily. The study summary describes 24 weeks of use.

The listed primary endpoint is percent change from baseline in total lesions at week 12, based on counts of inflammatory and non-inflammatory lesions across four facial areas. The record says 117 participants were included in the efficacy analysis, but does not explain the difference from the enrolled count. It lists no analyses and does not report arm-level efficacy results or a statistical comparison.

No serious adverse events or deaths were recorded in either group. Other adverse-event counts were 2 for adapalene and 0 for salicylic acid. Event details and comparative safety analyses are not reported in the registry record.