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 Efficacy of Silk - Like Bedding Fabric Pillow Case in the Treatment of Acne Vulgaris (NCT00767104), a randomized na study. The primary outcome is Total Lesion Count.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00767104 |
| Phase | NA |
| Condition | Acne Vulgaris |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 40 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Wake Forest University |
| Results posted | Yes |
2. Clinical Question
Population
Participants with acne vulgaris. The registry record reports enrollment of 40 participants and describes the primary outcome population as participants in each group.
Intervention
A standard-size pillowcase made from a silk-like fabric, used every night for 12 weeks. The record describes the fabric as woven from 100 percent synthetic yarns.
Comparator
A cotton pillowcase, also used every night for 12 weeks. The arm description identifies this as a placebo comparator and says it is made of 100% cotton.
Primary question
What was the mean number of papules, pustules and cysts at Week 12 in each group, and how precisely were those group means estimated?
The research question concerns the relationship between pillowcase assignment and acne lesion counts at the stated follow-up. The primary endpoint is the total count of papules, pustules and cysts at Week 12, reported as a mean for each group with a 95% confidence interval. The posted result gives group-specific estimates, rather than a treatment-effect estimate from a direct statistical comparison.
The registry record describes random allocation to the silk-like or cotton pillowcase. It also identifies the study as single-masked, but does not report who was masked. The primary comparison is therefore between the groups assigned to the two pillowcase conditions, as described in the record. The record also lists percentage reduction in total lesion count as a secondary outcome, but does not include numeric group results for that outcome in the information summarized in the posted results.
3. Trial Design
The registry record describes a randomized, single-masked, parallel-group study of pillowcases for acne vulgaris. Participants were assigned to a silk-like pillowcase or a cotton pillowcase. The reported enrollment is 40, with 20 participants in each arm in the primary outcome results. The study is marked completed. The record lists a start date of 2008-10 and primary completion in 2009-03.
The intervention description specifies nightly use for 12 weeks. The silk-like pillowcase is described as a standard-size case made from a light-weight plain-weave fabric woven of 100 percent synthetic yarns. The cotton comparator is described as a placebo pillowcase made of 100% cotton, also used nightly for 12 weeks. Although the intervention names and arm descriptions identify the comparison, the record does not explain the practical details of allocation concealment or who knew the assigned group.
A parallel design assigns participants to a group and compares outcomes across groups at the designated assessment. Randomization is intended, in general, to reduce systematic differences between groups at assignment. It does not guarantee that all characteristics are balanced in a study of this size, nor does the design description alone show how the randomization was carried out. Those details are not reported in the registry record.
The registry record gives the primary completion time and describes the primary outcome assessment at Week 12. It does not report details of visit schedules, adherence measurement, handling of pillowcase use outside the study instruction, or whether assessments were made by masked evaluators. These omissions limit the ability to reconstruct how the assigned conditions and outcome measurements were implemented.
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 | DermaTherapy Pillowcases | Control Pillowcase |
|---|---|---|
| STARTED | 20 | 20 |
| COMPLETED | 19 | 18 |
| NOT COMPLETED | 1 | 2 |
Reasons for not completing this period:
| Reason | DermaTherapy Pillowcases | Control Pillowcase |
|---|---|---|
| Lost to Follow-up | 1 | 2 |
Analysis population for the primary outcome, as defined in the registry: Number of participants in each group
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 | DermaTherapy Pillowcases | Control Pillowcase | Total |
|---|---|---|---|---|
| Participants analysed | 20 | 20 | 40 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 20 | 20 | 40 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Female | Participants | 15 | 15 | 30 |
| Sex: Female, Male: Male | Participants | 5 | 5 | 10 |
| Region of Enrollment: United States | participants | 20 | 20 | 40 |
6. Primary Endpoint
The registry lists the primary outcome as Total Lesion Count, measured over 12 weeks.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | lesions |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is total lesion count at Week 12. It is defined as the number of papules, pustules and cysts. The record identifies the measure as continuous and reports a mean for each group, with a 95% confidence interval. The endpoint population is described as the number of participants in each group.
A count of lesions gives a direct numerical description of the acne lesions included in the registry definition at the assessment time. Reporting a mean summarizes the group’s lesion counts in a single value, while the confidence interval conveys uncertainty around that estimated mean. The mean does not show how individual participants’ counts were distributed. In particular, it does not indicate whether most participants had counts near the mean or whether participants’ counts varied widely.
The endpoint is a Week 12 measure; it is not, by itself, a measure of change from baseline. The posted primary results do not include baseline group means or a baseline-adjusted estimate in the information summarized in the registry record. A secondary outcome is listed as percentage reduction in total lesion count, but a numeric estimate for that outcome is not included. The primary endpoint therefore supports a description of the reported group means at Week 12, not a conclusion about within-person change or a directly estimated difference between groups.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
At Week 12, the reported mean total lesion count was 36.6 in the experimental silk-like pillowcase group, with a 95% confidence interval from 22.9 to 50.3. In the control cotton pillowcase group, the reported mean was 30.7, with a 95% confidence interval from 18.7 to 42.6. These are group-specific summaries of papules, pustules and cysts, as defined by the registry record.
The confidence intervals indicate uncertainty in the estimated group means. They are not ranges containing every participant’s lesion count, and they do not show the spread of individual outcomes. The record reports the mean and confidence interval, but does not provide a standard deviation or other measure of participant-level variability in the primary outcome results. The intervals for the two group means overlap. Overlap alone is not a formal test of the difference between groups and does not establish whether a difference is statistically compatible with the data.
The posted results do not give a direct between-group estimate, confidence interval for a between-group contrast, or p-value for the primary endpoint. The registry record also lists zero analyses. Consequently, the group means should not be presented as an adjusted treatment effect or as the result of a formal comparison. The available data support describing the observed means and their reported precision, but do not quantify the uncertainty in the difference between assignments.
The observed mean in the silk-like group is 36.6 and the observed mean in the cotton group is 30.7. Those values describe the endpoint as posted; they do not establish why the groups’ estimates differ. Without a reported comparative analysis and further information about baseline measurements, missing observations and analysis populations, the group summaries do not resolve whether any apparent contrast reflects assignment, chance variation, or other features of the data and analysis.
The registry record lists percentage reduction in total lesion count as a secondary outcome, but does not give numeric estimates for it in the posted results. It is therefore not possible to use that listed outcome to clarify the primary endpoint pattern. Nor does the record report enough information to assess whether the primary outcome analysis adjusted for baseline lesion counts or other participant characteristics.
These results are best read as endpoint summaries at the stated follow-up, with substantial uncertainty around each group mean. They do not demonstrate a treatment effect, and they do not establish that the pillowcase conditions are equivalent. A direct comparison estimate with its uncertainty would be needed to quantify the contrast between assigned groups. The information in the registry record does not report such an estimate.
9. Statistical Methods Explained
The registry record identifies the primary outcome as a continuous measure summarized by a mean, with a 95% confidence interval for each group. It describes a randomized parallel-group design, but does not report the statistical methods used to analyze the primary endpoint. The explanations below describe general statistical concepts and how they relate to the form of the posted results; they do not imply that a particular method was used in this trial.
What does a confidence interval describe?
In general, a confidence interval is an estimate of the range of values reasonably compatible with the observed data under the method used to construct the interval. A 95% confidence interval is a procedure with a long-run coverage interpretation: across repeated uses under its assumptions, intervals constructed by that procedure would contain the target parameter at the stated rate. It is not a statement that a particular participant’s outcome lies in the interval, nor does it express the probability that the fixed mean is inside this particular interval.
For this trial, the reported intervals accompany the mean lesion count in each group. They describe uncertainty around those means, not uncertainty around a direct comparison. A confidence interval for a treatment contrast would address a different quantity: the difference between group means or another prespecified contrast. No such interval is reported in the registry record. The group-specific intervals should not be substituted for it.
Why does the mean need context?
In general, a mean condenses a set of measurements into a single summary. It can be useful for comparing groups, but it does not describe the shape of the outcome distribution, the presence of unusually high or low values, or how outcomes vary among participants. Count outcomes can be skewed or have variability that changes with the mean. Those properties may affect which analysis is appropriate and how well its uncertainty estimates perform. The registry record does not report the individual-level distribution, a standard deviation, or a model used to account for count-related features.
General methods for count outcomes can include models that represent the count distribution and its variance. Over-dispersion is a general concern when observed variability is greater than a model’s assumed variability; if not addressed, estimated uncertainty can be too small. This is a methodological consideration, not a finding about these trial data. The record does not report whether over-dispersion was assessed or whether a count model was used. The posted outcome is a mean with a confidence interval, and further details about how those summaries were calculated are not reported in the registry record.
What does randomization contribute?
In general, random assignment helps make treatment groups comparable in expectation by using a chance process to assign interventions. It does not ensure that the groups will be identical in every characteristic, especially in a trial with limited enrollment. Randomization also does not by itself remove bias from missing outcomes, departures from assigned treatment, outcome assessment, or selective reporting. The registry record identifies the allocation as randomized, but the method for sequence generation and allocation concealment is not reported.
The record describes the study as single-masked, but does not say which people were masked. Masking can, in general, reduce the opportunity for knowledge of assignment to influence behavior, assessment or analysis, depending on who is masked and how the outcome is obtained. Since the masked role and implementation are not reported, the label alone does not permit a fuller assessment of those protections.
What is missing from the comparative analysis?
A statistical analysis of the randomized comparison would ordinarily need to specify the target contrast, the analysis population, the handling of missing outcomes and the model or test used. These details are not reported in the registry record. No direct comparison estimate or p-value is included in the posted primary results. Without the comparison estimate and its uncertainty, the means cannot be used to quantify how precisely the groups differ.
General statistical significance testing is not a substitute for estimating effect size and precision. A p-value, if reported, would address compatibility of the data with a specified null model under assumptions; it would not describe the size or practical importance of an effect. No primary p-value is reported. Likewise, confidence intervals for each group mean do not provide a p-value for a group comparison.
How should planning illustrations be read?
In general, a sample-size illustration based on an observed effect is a planning exercise, not a summary of what the trial demonstrated. The planning assumptions recorded for this study specify a two-sided significance level of 0.05, equal allocation, a normal approximation, and a target effect expressed as a fraction of the observed effect. Such illustrations do not represent observed power, and they are not the trial’s own design justification. The registry record does not report the trial’s sample-size justification or statistical plan. No planning count is interpreted as an observed result.
Overall, the statistical information in the registry record consists of the group means and their 95% confidence intervals, alongside the trial’s design labels and enrollment information. The analysis model, comparison method, assumptions, and sensitivity analyses are not reported in the registry record. This distinction matters: descriptive summaries can characterize the posted endpoint, while inference about a between-group effect requires an explicitly reported comparative analysis.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists a primary endpoint of total lesion count at Week 12 and a secondary outcome of percentage reduction in total lesion count. It does not report a multiplicity strategy, such as how inference would be handled across outcomes or analyses. Without that information, the record does not establish whether any result was designated as confirmatory, whether adjustments were planned, or whether the reported outcomes represent all outcomes assessed.
There is no direct comparative analysis reported for the primary endpoint in the posted results. The record lists zero analyses. It does not describe an analysis population, such as whether all randomized participants were included regardless of adherence, or whether participants were analyzed according to a different rule. The primary endpoint population is described as the number of participants in each group, but this does not specify the analysis approach.
Missing-data handling is not reported in the registry record. The available summary does not say whether any Week 12 outcome values were missing, how missing values were handled, or whether any sensitivity analysis assessed the effect of missingness. The reported group sizes in the primary results should not be interpreted as proof that every randomized participant contributed a measured endpoint, since the record does not describe that relationship.
These reporting gaps limit assessment of the robustness and scope of the posted estimates. They do not establish that missing data or multiplicity problems occurred; they mean that the registry record does not report how those issues were addressed. The record also does not report interim analyses or a prespecified statistical plan.
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 |
|---|---|---|---|
| DermaTherapy Pillowcases | 0 | 20 | 0.0% |
| Control Pillowcase | 0 | 20 | 0.0% |
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 |
|---|---|
| DermaTherapy Pillowcases | 0 of 20 |
| Control Pillowcase | 0 of 20 |
The registry safety figures report 0 serious adverse events among 20 participants at risk in each of the two reported groups. They also report 0 other adverse events among 20 participants at risk in each group. These entries describe events captured in the registry record; they should not be read as proof that no harm occurred or that all possible events were assessed and recorded.
The safety group labels are DermaTherapy Pillowcases and Control Pillowcase, while the primary outcome arms are labeled Experimental Silk-like Pillowcases and Control Cotton Pillowcase. The record does not explain the difference in the experimental safety label. Caution is therefore appropriate when connecting the safety entries to the named primary outcome arms.
Deaths are marked as not reported in the registry record, rather than reported as zero. The registry record does not provide further details about adverse-event definitions, collection procedures, follow-up for safety, severity grading beyond the serious-event category, or attribution to the pillowcases. The event counts should be interpreted as limited posted safety information, not as a comprehensive estimate of risk.
12. What the Result Does, and Does Not, Mean
The posted results describe mean total lesion counts at Week 12 for participants assigned to the silk-like and cotton pillowcase groups. Each mean is accompanied by a 95% confidence interval, which conveys uncertainty around that group-specific estimate. The results provide a numerical snapshot of the measured endpoint in each group.
They do not provide a direct estimate of the difference between the groups. The registry record does not report a confidence interval or p-value for that contrast, or a primary analysis method. The group means alone therefore cannot establish the size or precision of a treatment effect. The difference between two reported means is not, by itself, an adjusted or formally tested comparison.
The results also do not establish that the two pillowcase conditions have equivalent outcomes. Equivalence requires a defined margin and an analysis designed to assess whether the uncertainty around a comparison falls within that margin. Neither an equivalence margin nor an equivalence analysis is reported in the registry record. Similarly, absence of a reported comparative test is not evidence that there is no difference.
The primary measure is a count at Week 12, not a reported baseline-to-follow-up change. The registry record does not provide baseline group values in the primary results, nor does it describe baseline adjustment. The secondary outcome of percentage reduction is listed, but numeric estimates for it are not included in the posted results. Therefore, the primary means should not be interpreted as evidence about within-person improvement.
General interpretation also depends on how participants were assessed, whether the assigned pillowcases were used as instructed, how missing outcome values were handled, and who was masked. The record does not report enough detail to assess these issues. The results do not support medical advice or a conclusion about whether one pillowcase should be used; they support only a cautious statistical description of the posted group summaries and their limits.
13. Why This Trial Matters Statistically
This trial is statistically notable for asking a focused question using a randomized parallel-group comparison and a concrete count outcome. The registry record identifies the assignment as randomized and reports mean lesion counts at a defined follow-up. Those features make the intended comparison understandable, while the reported confidence intervals indicate that uncertainty around group means is relevant to interpretation.
At the same time, the record illustrates why outcome summaries and comparative inference are not interchangeable. Separate means and confidence intervals describe each group, but they do not directly quantify the contrast that the trial question asks about. A comparative estimate with its uncertainty would make it possible to describe both the direction and precision of the observed contrast without relying on informal comparison of separate intervals.
The endpoint is a count, making distribution and variability important statistical considerations. General methods for count data may need to account for skewness or over-dispersion, but the record does not report the model used or how distributional assumptions were assessed. This underscores the value of reporting analysis methods alongside numerical results, particularly when only group means are available.
The registry record also highlights the distinction between planning and evidence. A sample-size illustration based on an observed effect is not observed power and does not explain the trial’s original design. The trial’s sample-size justification and statistical plan are not reported. Similarly, a completed status and an outcome estimate do not resolve questions about missing observations, analysis populations, multiplicity or masking.
For clinical researchers and biostatisticians, the central lesson is to separate what is measured, what is estimated, and what is formally compared. The record supplies group-level endpoint summaries, but limited analysis details. A transparent account of the contrast, its uncertainty, the handling of missing outcomes and the prespecified analysis would strengthen interpretation of this type of trial.
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 primary limitation for interpreting this trial is that the registry record reports group means and confidence intervals without a direct between-group estimate. It does not report a comparative confidence interval, p-value, or analysis method. As a result, the posted endpoint summaries do not quantify the precision of the contrast central to the randomized question.
The record describes the primary endpoint at Week 12 but does not report baseline lesion-count summaries in the information. It is therefore not possible to assess baseline comparability from the posted primary results or determine whether the endpoint analysis accounted for baseline counts. The listed secondary outcome, percentage reduction in total lesion count, has no numeric result in the posted information.
Additional design and analysis details are not reported in the registry record. These include the randomization procedure, allocation concealment, the identity of the masked party, the statistical model, the analysis population, missing-data handling and any sensitivity analyses. The record does not report a sample-size justification, multiplicity strategy, interim analyses or a prespecified statistical plan. Their absence from the record is a reporting limitation and does not prove that these procedures were absent from the conduct of the study.
The arm descriptions give nightly pillowcase use for 12 weeks, but the registry record does not report adherence, exposure measurement or the degree to which assigned use was maintained. Nor does it describe the outcome-assessment procedure. These missing details constrain assessment of how assignment translated into exposure and how lesion counts were obtained.
Safety reporting is also limited: the record gives adverse-event counts but does not provide definitions, collection methods or further follow-up details, and deaths are not reported. Finally, the experimental safety-group label differs from the experimental primary-outcome arm label, and that naming difference is not explained. These limitations call for restrained interpretation of both efficacy summaries and safety figures.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Efficacy of Silk - Like Bedding Fabric Pillow Case in the Treatment of Acne Vulgaris — NCT00767104.
- Registry record last updated 2018-09-11; status last verified 2018-08.
- Results first posted 2017-04-10.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
The registry record describes a completed randomized, single-masked, parallel-group study of pillowcases for acne vulgaris. It reports enrollment of 40, with 20 participants in each primary outcome group. The intervention was a silk-like pillowcase and the comparator was a cotton pillowcase, each described for nightly use over 12 weeks.
The primary endpoint was mean total lesion count at Week 12, defined as papules, pustules and cysts. The experimental group mean was 36.6, with a 95% confidence interval from 22.9 to 50.3; the control group mean was 30.7, with a 95% confidence interval from 18.7 to 42.6. No direct comparative estimate is reported in the registry record. Percentage reduction in total lesion count is listed as a secondary outcome, without numeric results in the posted information.
The safety entries report 0 serious and 0 other adverse events in each group, with deaths not reported. Details of the analysis method, missing-data handling, analysis population, multiplicity, and statistical plan are not reported in the registry record.