Benzac 5% Gel in Combination With Cosmetic Products in Acne Vulgaris: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Benzac 5% Gel in Combination With Cosmetic Products in Acne Vulgaris (NCT02589405), a na phase 4 study. The primary outcome is Number of Participants Satisfied and Very Satisfied With Regimen.

2. Clinical Question

The study’s stated aim was to evaluate the complete regimen in patients with acne. Its primary outcome focused on participants’ satisfaction with the regimen rather than a direct comparison of the regimen with another treatment or control. That distinction matters: satisfaction is a patient-reported assessment, and a single-group result would describe responses among the people assessed, not establish how responses would have differed under another regimen.

The outcome description specifies that the population includes only participants who answered the satisfaction question. It also notes that this explains a discrepancy with the total number of participants. However, the registry record does not report the number who answered or the number satisfied or very satisfied. The result therefore cannot be interpreted as a response rate, and the extent to which nonresponse affects interpretation cannot be assessed from the record.

3. Trial Design

This is a completed phase 4 study of a three-part regimen for acne vulgaris, sponsored by Galderma R&D. The registry lists an enrollment of 50. The recorded study start is 2015-08, and primary completion is listed as 2016-01. The registry status is COMPLETED.

The treatment group is described as receiving Benzac® 5% Gel once daily, Dermotivin® Soft Liquid soap twice daily, and Cetaphil® Dermacontrol Moisturizer SPF30 once daily. The interventions are classified as a drug and two other interventions. The study model is SINGLE GROUP; allocation is NA, and masking is NONE. The registry record therefore describes an unmasked study without a separate comparison group, rather than a randomized, blinded comparison.

The primary outcome is the number of participants satisfied and very satisfied with the regimen at 12 weeks. Its stated population consists only of those who answered the question. The record says this accounts for a discrepancy with total enrollment, but does not provide the number of respondents or an outcome count. It lists one outcome measure and no analysis entries. The absence of an analysis entry does not establish whether analyses were conducted outside the registry; it means those analyses are not reported in the registry record.

Because there is no comparator group, the study design can describe participant responses during use of the regimen but cannot estimate a between-group treatment effect. The record does not report random assignment, a control condition, or masking. Further details about the protocol, recruitment, eligibility criteria, or the conduct of outcome assessment are 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.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Only Data Observed: All subjects that answered this question (which explains the discrepancy with the total number of participants) -

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: Intent-to-Treat population

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants Satisfied and Very Satisfied With Regimen, measured over 12 weeks.

The primary endpoint is the number of participants who reported being satisfied or very satisfied with the three-part regimen. It is recorded as a participant count, with a timeframe of 12 weeks. The outcome description limits the population to people who answered the satisfaction question, rather than necessarily all enrolled participants.

Patient satisfaction can capture an aspect of treatment experience that clinical measures alone may not represent. As a general statistical point, a count of satisfied respondents is easiest to interpret when its denominator—the number of people who provided an answer—is also known. A proportion can describe the share of respondents who selected the specified responses, but that proportion cannot be calculated without both the count and the respondent denominator.

Neither the satisfaction count nor the number of respondents is reported in the registry record. The endpoint therefore identifies what the study intended to measure, but does not permit a numerical conclusion about satisfaction. The record also does not report the wording or response options for the question, or how unanswered questions were handled beyond specifying that the analysis population includes only answerers.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies a count outcome: the number of participants satisfied or very satisfied with the regimen. It does not report an analysis method, an estimate, an uncertainty interval, or a test result for that outcome. The explanations below describe general statistical concepts; they are not a claim that any particular method was used in this study.

What does a participant count tell us?

A count describes how many people in a defined group meet an outcome definition. For this endpoint, the relevant group is participants who answered the satisfaction question. A count alone does not indicate what share of that group had the specified responses. To interpret a share, the denominator must be the number of respondents assessed for the question. Here, neither the count nor the respondent denominator is reported in the registry record.

Counts also depend on clear outcome definitions. The registry title and description identify the combined categories “satisfied” and “very satisfied,” but the response wording, other response categories, and assessment procedure are not reported in the registry record. Those details can affect how consistently an outcome is understood and recorded.

Why does the study design matter?

A single-group study observes participants receiving a regimen without a separate comparator group. In general, a summary from such a study can describe the observed group, but it does not directly estimate how outcomes would differ under another treatment or no treatment. That is because the unobserved comparison outcome is not available in the design. The record lists allocation as NA and masking as NONE, and it does not describe a control group.

In a randomized comparison, random assignment can support a between-group contrast by making the groups comparable on average, subject to the study’s conduct and analysis. That principle does not apply as a group comparison in this single-group record. An unmasked design can also leave participant-reported outcomes open to expectations or knowledge of treatment. These are general considerations; the registry record does not report how expectations affected responses.

What would an uncertainty interval add?

In general, a confidence interval expresses the statistical uncertainty around an estimate under a specified method and assumptions. For a respondent proportion, the interval would depend on the number meeting the outcome and the total number assessed. It could help distinguish a relatively precise estimate from one with substantial uncertainty. No confidence interval or endpoint estimate is reported in the registry record, and the needed respondent count and denominator are not reported. No numerical interval can therefore be interpreted.

A confidence interval would not correct limitations in the design or measurement. Even a precise estimate among respondents would describe that respondent group; it would not create a comparison group or resolve potential bias from missing answers. Statistical precision and the strength of a causal conclusion are different issues.

What does the planning description mean?

The registry’s sample-size assumptions describe a planning illustration based on an observed effect, not the trial’s own design. That illustration specifies a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. This is a hypothetical planning framework and should not be mistaken for the actual single-group study design. The registry record does not report the trial’s sample-size justification or a protocol-based sample-size calculation.

The planning description does not supply a numerical planning estimate in the record details, and no observed primary effect is reported from which to assess such an illustration. Planning calculations are not observed power. In general, they describe the sample size that would be needed under stated assumptions; they do not show the probability that this completed study detected an effect, nor do they establish that an effect exists.

The record does not report an interim-analysis plan, a statistical analysis plan, model specifications, or a method for calculating uncertainty. It also does not report adjusted analyses. Those omissions mean that readers cannot determine whether any unreported analysis accounted for additional factors or used a particular inferential method. It would be inappropriate to infer those methods from the endpoint type or the planning description.

Why might over-dispersion matter in other settings?

As a general concept, over-dispersion arises when observed variation in count data exceeds what a chosen statistical model expects. If present, a model that assumes too little variation can produce uncertainty estimates that are too narrow. Whether over-dispersion is relevant depends on the outcome structure and model. The primary outcome in this record is a participant count, but no model or dispersion parameter is reported, so there is no basis to say that over-dispersion was assessed or affected the analysis.

The key methodological distinction is between a defined outcome and a reported analysis of that outcome. This record supplies the former—the satisfaction question and its assessment timeframe—but does not report the numerical result or its statistical uncertainty. General statistical methods can explain what such information would mean, but cannot fill in the missing result.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Treatment Regimen")
n      <- c(48)
events <- c(42)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Treatment Regimen  48  42  87.5  74.8  95.3  75.3  94.1  75.2  94.1

11. Multiplicity, Missing Data and Analysis Populations

Multiplicity concerns the risk of misleading findings when several outcomes, comparisons, or analyses are examined. The registry record lists one outcome measure and no analysis entries. It does not report whether additional analyses or outcomes were planned or examined outside the registry, whether any adjustment for multiple testing was planned, or whether the primary outcome was selected from a larger set. These details are not reported in the registry record, so the extent of any multiplicity cannot be assessed.

The outcome population includes only people who answered the satisfaction question. The record notes that this explains a discrepancy with the total number of participants, but it does not state how many answered or how unanswered responses were handled in any analysis. Restricting an outcome summary to respondents can be appropriate for describing their answers, but it leaves uncertainty about how those responses relate to people without recorded answers. If response is related to satisfaction, a respondent-only summary may not represent all enrolled participants. Whether that occurred cannot be determined from the record.

The record does not report an intention-to-treat analysis, a per-protocol analysis, or another named analysis population. It also does not report imputation, sensitivity analyses for missing data, or reasons for nonresponse. These methods and details are therefore not reported in the registry record. The absence of an analysis entry should not be interpreted as proof that no analysis occurred; it indicates that the registry record does not document one.

No statistical analysis plan or interim-analysis information is reported in the registry record. As a result, readers cannot assess whether outcome definitions, analysis populations, or missing-data procedures were specified before results were examined.

12. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 2% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: hypersensitivity (2.0%), dyspnoea exertional (2.0%).

For the three-part treatment regimen, the registry lists 50 at risk for serious adverse events and an affected count of 1. It also lists 50 at risk for other adverse events and an affected count of 13. The recorded deaths count is 0. These are the safety figures entered in the registry record; they are not comparative estimates because no separate control group is reported.

The serious-event terms listed are Hypersensitivity at 2.0% and Dyspnoea exertional at 2.0%. The record identifies these as top serious terms. It does not provide further details about timing, duration, severity, relatedness to the regimen, or whether events resolved. The terms should therefore be read as recorded safety classifications, not as evidence about cause.

In general, serious adverse events and other adverse events are distinct categories in safety reporting. A count in either category does not by itself establish that the regimen caused an event. Nor does the number of recorded events describe the full clinical context or allow comparison with another regimen. The registry record does not report a comparative safety analysis or additional detail that would support broader conclusions.

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

The record establishes that a completed phase 4, single-group study evaluated a regimen consisting of Benzac® 5% Gel, Dermotivin® Soft Liquid soap, and Cetaphil® Dermacontrol Moisturizer SPF30. Its primary question concerned the number of respondents who were satisfied or very satisfied after 12 weeks. The record also provides safety counts for the regimen.

It does not report the numerical satisfaction result or the respondent denominator. As a result, it does not show how many respondents selected either satisfaction category, what proportion they represented, or how precise such an estimate might be. The outcome’s stated aim should not be treated as an outcome finding.

Even if the primary count were available, the single-group, unmasked design would describe observations in the treated group rather than establish a comparative effect. Without a separate comparator, the record cannot show how satisfaction or safety would have differed under another regimen. This is a limitation of what the design can answer, not a conclusion about the participants’ actual experiences.

The safety entries document recorded counts and serious-event terms, but they do not establish causation or provide a comparative safety estimate. The registry record does not report the clinical details needed to interpret individual events, nor does it report an analysis linking safety outcomes to the regimen.

In statistical terms, this record is informative about the study’s question, intervention, design, and some safety reporting, but incomplete for evaluating its primary endpoint. Any conclusion should remain within those boundaries. The record does not support a statement that the regimen did or did not improve acne, nor a numerical statement about participant satisfaction.

14. Why This Trial Matters Statistically

This study illustrates why the endpoint, analysis population, and design need to be read together. The primary outcome is a participant-reported satisfaction count, but it applies only to respondents. Since the registry record does not report either the count or the number answering, readers cannot calculate or assess a respondent-level estimate. That missing denominator is especially important when an outcome is explicitly limited to those who answered.

The record also illustrates the difference between documenting an intervention and estimating its comparative effect. It describes a combined regimen and a single-group design, with no separate comparator. A finding from that design would be descriptive of the observed group; it could not directly quantify a difference against an alternative. This distinction prevents a treatment aim from being mistaken for evidence of comparative benefit.

Another statistical lesson is that a planning framework is not the same as the completed study’s analysis. The registry’s planning description refers to a hypothetical two-arm calculation, while the recorded study model is single-group. Such planning assumptions do not change the actual design, and planning illustrations are not observed power. The record does not provide a trial-specific sample-size justification or primary-outcome analysis.

Finally, safety counts and a satisfaction outcome answer different questions. Safety entries can be reported even when the primary efficacy or experience outcome is unavailable, but they do not substitute for it. Together, these features make transparent reporting of denominators, analysis methods, and outcome estimates important for interpreting a clinical trial record.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The central limitation for interpreting the primary outcome is that its numerical result is not reported in the registry record. The record also does not report the number of respondents, although it states that only answerers were included and that this explains a discrepancy with total enrollment. Without these values, satisfaction cannot be quantified, and the potential effect of unanswered questions cannot be assessed.

The single-group, unmasked design has no separate comparator. It therefore cannot provide a direct between-group estimate, and participant-reported satisfaction may be sensitive to expectations in an unmasked setting. These are design considerations; the record does not report that expectations affected answers.

The intervention combines a drug with two cosmetic products. The record does not describe separate groups or analyses that would distinguish the contributions of the individual components. It also does not report the detailed outcome question, response options, eligibility criteria, or the procedures used to collect responses. Those details are not reported in the registry record.

The registry lists no analysis entries and does not report a statistical analysis plan, a sample-size justification, missing-data methods, or confidence intervals for the primary endpoint. The status is COMPLETED, but completion alone does not supply those missing results or methods. The safety record gives counts and serious-event terms without further clinical detail or a comparator. These limitations restrict interpretation to the documented design, endpoint definition, and recorded safety information.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Benzac 5% Gel in Combination With Cosmetic Products in Acne Vulgaris — NCT02589405.
• Registry record last updated 2021-02-18; status last verified 2018-09.
• Results first posted 2019-02-11.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

NCT02589405 is a completed phase 4, single-group study sponsored by Galderma R&D. It evaluated Benzac® 5% Gel once daily with Dermotivin® Soft Liquid soap twice daily and Cetaphil® Dermacontrol Moisturizer SPF30 once daily in acne vulgaris. Enrollment is listed as 50; the recorded study start is 2015-08 and primary completion is 2016-01.

The primary outcome was the number of participants satisfied or very satisfied with the regimen at 12 weeks, among those who answered the question. The registry record does not report the outcome count or respondent denominator, and it lists no analysis entries. Safety figures include a serious-event affected count of 1, an other-adverse-event affected count of 13, and deaths of 0. With no separate comparator group, the record describes a single-group evaluation rather than a comparative treatment estimate.