This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Effect of Samples on Acne Treatment With Epiduo® Gel (NCT01504204), a randomized phase 4 study. The primary outcome is Adherence to Study Medication.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01504204 |
| Phase | Phase 4 |
| Condition | Acne Vulgaris |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 20 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Wake Forest University |
| Results posted | Yes |
2. Clinical Question
Population
Patients with mild to moderate acne were the intended study population. The registry record identifies acne vulgaris as the condition and describes the study population as primarily female and identifying as Caucasian. The age description gives a median and ranges of subject ages as 19 years; further details about the population are not reported in the registry record.
Intervention
One group received adapalene plus benzoyl peroxide from a sample tube and a demonstration of how to use it at the first visit. This combines access to sample medication with application instruction, so the study contrast concerns that package rather than either component on its own.
Comparator
The comparison group received adapalene plus benzoyl peroxide from a standard tube, without a sample or a demonstration of proper use. Both groups therefore received the same named active medication combination, while the sample and demonstration differed between groups.
Primary question
The primary question was whether medication adherence, measured as the percentage of prescribed doses taken, differed between the group receiving a sample and demonstration and the group receiving only the standard tube. Adherence was measured electronically with a Medication Event Monitoring System cap from baseline to 6 weeks. The record also names changes in Acne Global Assessment and acne lesion count as secondary outcomes, but their numerical results are not reported in the registry record.
3. Trial Design
This completed Phase 4 study is recorded as randomized, unmasked, and parallel-group. It enrolled 20 participants, and its stated purpose was to compare adherence and treatment efficacy when patients with mild to moderate acne received a medication sample and instructions on proper application in addition to their stock-size tube, versus a stock-size tube alone. The sponsor was Wake Forest University. The recorded start was 2011-12, and primary completion was 2012-11.
The intervention group received adapalene plus benzoyl peroxide from a sample tube, along with a demonstration of how to use it at the first visit. The comparison group received adapalene plus benzoyl peroxide from a standard tube without a sample or demonstration. Because sample access and demonstration were bundled together, a difference between groups would not, by itself, distinguish the effect of the sample from the effect of instruction.
The primary outcome was adherence to study medication, defined as the percentage of prescribed doses taken and measured electronically with a Medication Event Monitoring System cap. Its timeframe was baseline to 6 weeks. The record identifies change in Acne Global Assessment and change in Acne Lesion Count as secondary outcomes. It does not report numerical findings for those secondary outcomes.
For the primary outcome, the posted group summaries list n=9.0 for each group. The safety figures list 10 participants at risk in each group, while the overall enrollment is 20. These are different denominators attached to different record entries; the reasons for the differences are not reported in the registry record. The masking field is none, so participants and study staff were not recorded as masked. Details of allocation concealment, the randomization sequence, and other implementation procedures 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
| Stage | Medication With Sample and Demonstration | Medication Without Samples |
|---|---|---|
| STARTED | 10 | 10 |
| COMPLETED | 9 | 9 |
| NOT COMPLETED | 1 | 1 |
Reasons for not completing this period:
| Reason | Medication With Sample and Demonstration | Medication Without Samples |
|---|---|---|
| Lost to Follow-up | 1 | 1 |
Analysis population for the primary outcome, as defined in the registry: the median and ranges of subject ages for the sample and no sample group were 19 years, primarily female identifying as Caucasian.
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.
| Characteristic | Unit | Medication With Sample and Demonstration | Medication Without Samples | Total |
|---|---|---|---|---|
| Participants analysed | 9 | 9 | 18 | |
| Age, Customized: Age | years | 19 (13 to 31) | 19 (13 to 29) | 19 (13 to 31) |
| Sex: Female, Male: Female | Participants | 8 | 6 | 14 |
| Sex: Female, Male: Male | Participants | 1 | 3 | 4 |
| Race/Ethnicity, Customized: Race(Caucasian) | Participants | 5 | 6 | 11 |
| Race/Ethnicity, Customized: Ethnicity(Non-Hispanic) | Participants | 8 | 9 | 17 |
| Region of Enrollment: United States | Participants | 9 | 9 | 18 |
6. Primary Endpoint
The registry lists the primary outcome as Adherence to Study Medication, measured over Baseline to 6 weeks.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Standard Deviation |
| Unit | percentage of doses |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint measures adherence to the assigned study medication as the percentage of prescribed doses taken from baseline to 6 weeks. The record says adherence was assessed electronically using a Medication Event Monitoring System cap. Such monitoring records medication-container openings and offers a way to measure medication-taking behavior over time, rather than relying only on a participant’s retrospective account. In general, a container-opening record is a measure used to assess adherence; it does not by itself establish that a dose was applied as instructed.
The outcome is reported as a median, with standard deviation identified as the dispersion measure. The posted summaries give 86.0 for the sample-and-demonstration group and 71.0 for the group without samples. Their reported dispersion values are 2.2 and 0.34, respectively. These are group summaries, not a reported estimate of the difference between groups. The registry record does not provide a confidence interval, a p-value, or an inferential analysis for the primary comparison.
Adherence is relevant to interpreting a treatment study because medication use can affect the amount of exposure participants receive. Here, the endpoint addresses whether the groups differed in recorded medication-taking behavior during the stated period. The endpoint does not directly establish a change in acne severity. Although the registry record also names changes in Acne Global Assessment and acne lesion count, those outcomes cannot be interpreted from numerical results that are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary-outcome summaries are medians of 86.0 for medication with a sample and demonstration and 71.0 for medication without samples. The registry record lists n=9.0 in each group. Dispersion is identified as standard deviation, with values of 2.2 and 0.34, respectively. These figures describe the recorded group summaries; they do not supply an estimate of uncertainty around a between-group effect.
No p-value, confidence interval, adjusted estimate, or other inferential result for the primary comparison is reported in the registry record. Therefore, the summaries alone do not establish whether a difference between groups is compatible with chance variation, nor do they quantify the precision of a group contrast. No recalculated comparison is presented. The registry record does not include a sponsor analysis for this endpoint that could be used to assess an inferential conclusion.
Interpretation also requires attention to what was randomized. One group received both a sample and an application demonstration, while the other received neither. Even if a formal comparison were available, the design contrast would address this combined package, not the independent contribution of sample medication or demonstration. The record does not report a design that separates those components.
The summary parameter is a median, while dispersion is labeled as standard deviation. In general, a median describes the central position of ordered observations, whereas standard deviation describes spread around a mean. Without additional information about the outcome distribution and analysis, the pairing does not support reconstructing a confidence interval or a standard error for the median. No such reconstruction should be treated as a substitute for a prespecified or sponsor-reported analysis.
The overall enrollment is 20, while the primary-outcome summaries list n=9.0 in each group and the safety entries list 10 at risk per group. These counts should not be conflated: the record does not explain why the denominators differ or how missing outcome observations were handled. In particular, the posted record does not establish whether the primary summaries include all randomized participants, only participants with observed adherence data, or another analysis population.
The secondary outcomes are change in Acne Global Assessment and change in Acne Lesion Count. Their numerical results and comparative analyses are not reported in the registry record. Consequently, the posted adherence summaries cannot answer whether acne assessments or lesion counts changed, or whether any such changes differed between groups. The study’s stated efficacy purpose is not accompanied by usable numerical results for these outcomes in the record.
9. Statistical Methods Explained
Randomization assigns participants to study groups using a chance-based process. In general, this can help balance measured and unmeasured characteristics across groups, although it does not guarantee balance in a small study. The registry record identifies the allocation as randomized and the model as parallel. It does not report the randomization sequence, allocation concealment, blocking or stratification, or other details of how assignment was implemented. Those details therefore cannot be used to judge how the assignment process operated.
What does the parallel-group comparison represent?
In a parallel design, participants are assigned to a group and outcomes are compared across groups. Here, the recorded contrast is medication with a sample and demonstration versus medication without samples or a demonstration. Both groups are described as receiving adapalene plus benzoyl peroxide. Since the sample and instruction occur together in one group, the comparison cannot identify their separate effects. That distinction is important when translating a group contrast into a claim about a particular part of the intervention.
The masking field is recorded as none. In general, masking can reduce the chance that knowledge of group assignment affects participant behavior, care, or outcome assessment. Because adherence is behavioral and the group procedures are visibly different, unmasked assignment may be relevant to interpretation. The registry record does not describe any masking of outcome assessors or other steps intended to limit awareness of assignment, so such steps should not be assumed.
How should the primary summary be read?
The primary outcome is expressed as a percentage of prescribed doses taken and summarized by the median. A median is the middle value after observations are ordered; it is less sensitive than a mean to especially high or low observations. The record identifies standard deviation as the dispersion measure. In general, standard deviation describes the spread of observations around their mean. A median and standard deviation summarize different features of a distribution, so the pair alone does not provide a complete description of the data or a direct estimate of uncertainty for a median.
The posted medians are 86.0 and 71.0, and the corresponding recorded dispersion values are 2.2 and 0.34. The group sample sizes for these summaries are n=9.0 and n=9.0. These values should be read as descriptive summaries, not as a reported treatment-effect estimate. The registry record gives no confidence interval or p-value for a between-group comparison. A confidence interval, in general, expresses a range of values compatible with a statistical procedure and its assumptions; without one, the precision of a contrast cannot be read from the group medians alone.
What can electronic adherence monitoring tell us?
The Medication Event Monitoring System cap was used to measure the percentage of prescribed doses taken. In general, electronic container monitoring provides a timestamped record of openings, which can support measurement of medication-taking patterns. A recorded opening is not necessarily proof that medication was applied, that the prescribed amount was used, or that it was used correctly. The registry record does not provide further details on how device records were translated into the adherence endpoint, how unreadable or missing records were treated, or whether monitoring could have changed participant behavior.
How should the analysis and planning information be understood?
The registry record lists no analyses for the outcomes. It therefore does not report the statistical model, comparison test, adjustment factors, or primary inferential procedure. It also does not report whether the primary analysis followed intention-to-treat, per-protocol, or another analysis-population principle. No adjusted or recalculated comparison is available to describe. The record does not provide an explanation of sample-size justification or interim analyses.
In general, sample-size planning estimates how many participants may be needed to detect an effect under stated assumptions; it is not a measure of the probability that an observed result is true. The record describes planning illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation; the target effect is stated as a fraction of the observed effect. Such illustrations are planning calculations, not observed power, and the registry record does not report a trial design justification based on them. Since no actual planning values are included in the record, they cannot be discussed as specific sample-size targets.
In general, statistical precision depends on the amount of information in the data, the outcome’s variability, and the method used for analysis. Small outcome groups can make estimates sensitive to individual observations, but the record does not support a new precision calculation. The appropriate reading is therefore limited to the posted descriptive summaries and to the absence of reported inferential results.
10. Multiplicity, Missing Data and Analysis Populations
The registry record names a primary adherence outcome and two secondary outcomes: change in Acne Global Assessment and change in Acne Lesion Count. It does not report a statistical plan describing how multiple outcomes were handled, whether any multiplicity adjustment was planned, or which outcome would govern a confirmatory conclusion. Without that information and without reported secondary outcome analyses, the scope of any formal claims cannot be assessed.
Missing-data methods are not reported in the registry record. The overall enrollment is 20, while the primary outcome summaries list n=9.0 in each group and the safety summaries list 10 at risk per group. The record does not explain these denominator differences, identify the reasons for unavailable primary-outcome measurements, or state whether missing observations were excluded, imputed, or handled by another method. It also does not state whether the adherence summaries include every randomized participant.
The analysis populations are not reported in the registry record. In particular, there is no statement identifying an intention-to-treat population, a per-protocol population, or another defined set of participants for the primary analysis. This limits assessment of whether the results reflect assigned groups or a subset selected by data availability or protocol adherence.
The registry record does not report a primary-outcome comparison test, confidence interval, p-value, or adjusted analysis. It lists the two secondary outcomes, but their numerical results and analyses are not reported. Thus, neither multiplicity control nor the effects of missing data can be evaluated from the posted record. These omissions do not show how the study team handled these issues; they mean the handling is not reported in the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Medication With Sample and Demonstration | 0 | 10 | 0.0% |
| Medication Without Samples | 0 | 10 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Medication With Sample and Demonstration | 0 of 10 |
| Medication Without Samples | 0 of 10 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Medication With Sample and Demonstration | 6 of 10 |
| Medication Without Samples | 6 of 10 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Medication With Sample and Demonstration | Medication Without Samples |
|---|---|---|---|
| Dryness | Skin and subcutaneous tissue disorders | 3 of 10 | 3 of 10 |
| itching | Skin and subcutaneous tissue disorders | 3 of 10 | 2 of 10 |
| redness | Skin and subcutaneous tissue disorders | 0 of 10 | 1 of 10 |
The safety entries list 10 participants at risk in each group. Serious adverse events are recorded for 0 participants in the medication-with-sample-and-demonstration group and 0 in the medication-without-samples group. Deaths are recorded as 0 in each group. Other adverse events are recorded for 6 participants in each group. The registry record lists no top serious adverse-event terms.
These counts describe the entries in the registry record during the safety reporting period, which is not specified in the available information. A zero count means no serious adverse events were recorded among those listed as at risk; it does not establish that the risk of a serious event is absent. In general, safety counts from a study are interpreted in light of the number observed, the observation period, and how events were collected and defined. The registry record does not provide further detail on those procedures or on event severity for the other adverse events.
The safety denominators differ from the n=9.0 listed for each primary-outcome summary. The reason is not reported in the registry record, so the denominators should be kept tied to their respective outcomes rather than treated as interchangeable.
12. What the Result Does, and Does Not, Mean
The posted results establish that the registry record contains descriptive summaries of adherence for the two groups. The median is 86.0 for medication with a sample and demonstration and 71.0 for medication without samples. The record also reports dispersion values of 2.2 and 0.34, respectively, and lists n=9.0 for each primary-outcome group. These summaries describe the observed records; they are not a reported estimate of the between-group effect.
The record does not report a confidence interval or a p-value for the primary comparison. Accordingly, it does not quantify the uncertainty around a difference between groups or provide a formal basis for deciding whether a comparison is statistically distinguishable from chance variation. The posted summaries alone do not establish that the sample-and-demonstration package changed adherence, and they do not establish that it did not.
The study contrast also combines two elements: sample medication and a demonstration of application. The comparison cannot identify which element, if either, accounts for a difference in recorded adherence. Because the registry record does not report numerical findings for the named acne-assessment and lesion-count outcomes, the adherence summaries do not answer the stated efficacy question about acne outcomes.
More broadly, a group summary does not describe every participant’s experience or establish the performance of an intervention in populations beyond the study. The record gives overall enrollment of 20, but does not explain why the primary and safety entries have different denominators. It also does not report missing-data methods or defined analysis populations. Those gaps limit how broadly the summaries can be interpreted.
The appropriate conclusion is narrow: the registry record reports medians and dispersion for electronically measured adherence, along with safety counts, but does not report an inferential comparison or numerical secondary outcome results. It therefore supports a description of the posted data, not a definitive conclusion about treatment efficacy or a causal explanation for any difference in the group summaries.
13. Why This Trial Matters Statistically
This trial is statistically informative as an example of how a behavioral endpoint can be central to a medication study. The primary outcome was adherence measured electronically as the percentage of prescribed doses taken. That endpoint addresses medication-taking behavior, which is distinct from clinical outcome measures such as the named changes in Acne Global Assessment and acne lesion count. Keeping those outcome types separate prevents an adherence summary from being mistaken for evidence about acne severity.
The design also illustrates the importance of defining the treatment contrast precisely. The randomized groups differed in both access to a sample tube and receiving a demonstration. A comparison of the groups therefore concerns the combined package. It cannot, without additional design features or analyses, separate the influence of sample medication from the influence of instruction.
Statistical interpretation depends not only on the observed summaries but also on uncertainty, analysis methods, and the population analyzed. The record gives group medians and dispersion but no confidence interval, p-value, or inferential model. It also does not describe missing-data handling or analysis populations, while outcome and safety denominators differ. These details matter because they determine how much confidence can be placed in a comparison and to whom it applies.
The record names secondary clinical outcomes but does not report their numerical results. That distinction highlights why outcome registration and outcome reporting are separate parts of the evidence record: listing an outcome indicates that it was named, but does not reveal its findings. A careful statistical reading therefore stays with what is reported and does not infer unreported efficacy results from adherence or safety summaries.
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 registry record does not report an inferential analysis of the primary adherence comparison. There is no confidence interval, p-value, comparison estimate, or stated statistical model. The reported medians and standard deviations therefore provide limited information about uncertainty and do not establish the statistical interpretation of a group contrast.
The primary outcome summaries list n=9.0 in each group, whereas the safety entries list 10 participants at risk per group, and the overall enrollment is 20. Reasons for the different denominators are not reported in the registry record. Neither missing-data procedures nor the analysis populations are described. It is consequently unclear which participants contributed to each outcome summary.
The trial was unmasked, and the intervention group received both a sample and an application demonstration. The record does not report procedures that would separate the effect of these components or describe whether outcome assessment was masked. Since the primary endpoint concerns adherence behavior, awareness of group assignment could be relevant, but the record does not quantify or assess that possibility.
The registry record names change in Acne Global Assessment and change in Acne Lesion Count as secondary outcomes, but numerical results for them are not reported. The outcome reporting therefore does not permit interpretation of the stated acne-efficacy outcomes. The record also does not report multiplicity procedures, a sample-size justification, or an interim-analysis plan. These omissions limit assessment of the statistical planning and the scope of any intended conclusions.
The record describes the population as primarily female and identifying as Caucasian, but provides limited additional population detail. It does not report enough information to assess how representative the enrolled participants were of other people with acne or how broadly findings might apply. The overall enrollment and short stated adherence timeframe also define the scope of the available observations, without establishing longer-term adherence or outcomes.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Effect of Samples on Acne Treatment With Epiduo® Gel — NCT01504204.
- Registry record last updated 2018-09-12; status last verified 2018-08.
- Results first posted 2018-01-23.
- 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.
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18. Record Summary
The registry record describes a completed, randomized, unmasked, parallel-group Phase 4 study sponsored by Wake Forest University. It enrolled 20 participants and compared adapalene plus benzoyl peroxide provided with a sample and application demonstration against medication from a standard tube without a sample or demonstration. The recorded start was 2011-12, and primary completion was 2012-11.
The primary outcome was the percentage of prescribed doses taken from baseline to 6 weeks, measured with a Medication Event Monitoring System cap. The posted medians are 86.0 and 71.0, with dispersion values of 2.2 and 0.34; each group summary lists n=9.0. No inferential comparison is reported. The record names changes in Acne Global Assessment and acne lesion count as secondary outcomes, but does not report their numerical results.
Safety entries list 0 serious adverse events and 0 deaths in each group, with 6 participants recorded as affected by other adverse events in each group. The safety denominator is 10 at risk per group. Reasons for the different outcome denominators, missing-data methods, analysis populations, and multiplicity procedures are not reported in the registry record.