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 A Study of Different Use Regimens Using Two Acne Treatments (NCT00907257), a randomized phase 4 study. The primary outcome is Change From Baseline in Total Facial Acne Lesion Count.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00907257 |
| Phase | Phase 4 |
| Condition | Acne Vulgaris |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 247 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Bausch Health Americas, Inc. |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned people with acne vulgaris. The primary endpoint was analyzed in the Per Protocol Population, defined in the registry record as ITT subjects who completed 12 weeks of treatment and evaluations without major protocol deviations. The registry record lists an enrollment of 247, but the endpoint analysis includes the reported arm sizes of 109 and 112. Those figures describe different parts of the record; the primary result applies to the specified analysis population.
Intervention
The “Same Time of Day” regimen used 5% benzoyl peroxide wash and 0.04% tretinoin gel at the same time of day. The registry summary describes the question as whether using both acne products in the morning was as safe and efficacious as splitting their use between morning and evening. The exact timing within the day for the same-time regimen is not further specified in the registry record.
Comparator
The “Different Times of Day” regimen used 5% benzoyl peroxide wash in the morning and 0.04% tretinoin gel in the evening. The contrast is therefore between schedules for the same two named products, rather than between the presence and absence of either product. The record identifies randomized allocation and a parallel-group design.
Primary question
The primary question was how the two schedules compared on change from baseline in total facial acne lesion count from baseline to Week 12. Total count includes non-inflammatory and inflammatory lesions, plus nodules or cysts. Change was calculated as the value after baseline minus the baseline value, so negative values indicate improvement. The posted least-squares mean changes were 39.74 for the same-time regimen and 40.02 for the different-times regimen; the reported mean difference was 0.28. These estimates describe the endpoint in the stated analysis population and do not, by themselves, establish that the schedules are equivalent.
3. Trial Design
The registry record identifies this as a completed Phase 4, randomized, single-masked, parallel-group study of two use regimens for benzoyl peroxide wash and tretinoin gel. Enrollment is listed as 247. The study began in 2009-02, and primary completion is listed as 2009-09. The condition was acne vulgaris. The sponsor is Bausch Health Americas, Inc.
The two arms differed in timing. In the Same Time of Day arm, 5% benzoyl peroxide wash and 0.04% tretinoin gel were used at the same time of day. In the Different Times of Day arm, the wash was used in the morning and the gel in the evening. The record’s brief summary frames the study as assessing whether using both products in the morning was as safe and efficacious as using one in the morning and one in the evening. The detailed timing for the same-time regimen is not reported in the registry record.
The primary outcome was change from baseline in total facial acne lesion count at Week 12. Its analysis population was the Per Protocol Population: ITT subjects who completed the 12 weeks of treatment and evaluations with no major protocol deviations. The reported arm sizes for this endpoint are 109 for Same Time of Day and 112 for Different Times of Day. They should not be read as the enrollment count; they refer to the endpoint analysis population.
The record also lists secondary outcomes concerning changes in inflammatory and non-inflammatory lesion counts and their totals, and measurement of success. Detailed numerical results for those outcomes are not reported in the registry record. The original sample-size rationale, randomization details, masking procedures, and statistical analysis plan are also 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 | Same Time of Day | Different Times of Day |
|---|---|---|
| STARTED | 123 | 124 |
| COMPLETED | 110 | 112 |
| NOT COMPLETED | 13 | 12 |
Reasons for not completing this period:
| Reason | Same Time of Day | Different Times of Day |
|---|---|---|
| Adverse Event | 0 | 4 |
| Protocol Violation | 1 | 2 |
| Lost to Follow-up | 3 | 3 |
| Withdrawal by Subject | 1 | 2 |
| Per IRB-Subject became vulnerable | 1 | 0 |
| Moved | 1 | 0 |
| Personal Reasons | 6 | 1 |
Analysis population for the primary outcome, as defined in the registry: Per Protocol Population, which includes all Intention to Treat (ITT) subjects who completed the 12 weeks of treatment and evaluations with no major protocol deviations.
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 | Same Time of Day | Different Times of Day | Total |
|---|---|---|---|---|
| Participants analysed | 123 | 124 | 247 | |
| Age Continuous | years | 18.5 (SD 6.86) | 18.6 (SD 6.94) | 18.5 (SD 6.89) |
| Sex: Female, Male: Female | Participants | 60 | 66 | 126 |
| Sex: Female, Male: Male | Participants | 63 | 58 | 121 |
| Region of Enrollment: United States | participants | 123 | 124 | 247 |
| Fitzpatrick Score: I | Participants | 8 | 5 | 13 |
| Fitzpatrick Score: II | Participants | 31 | 29 | 60 |
| Fitzpatrick Score: III | Participants | 44 | 52 | 96 |
| Fitzpatrick Score: IV | Participants | 24 | 22 | 46 |
| Fitzpatrick Score: V | Participants | 8 | 12 | 20 |
| Fitzpatrick Score: VI | Participants | 8 | 4 | 12 |
6. Primary Endpoint
The registry lists the primary outcome as Change From Baseline in Total Facial Acne Lesion Count, measured over Baseline to Week 12.
| Element | Registry entry |
|---|---|
| Result type | Least Squares Mean |
| Measure of spread | Standard Error |
| Unit | Lesions |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is change from baseline in total facial acne lesion count, measured from baseline to Week 12. Total count combines non-inflammatory lesions, inflammatory lesions, and nodules or cysts. The registry defines change as the post-baseline value minus the baseline value; accordingly, negative change indicates improvement, while positive change indicates an increase in the count relative to baseline. The posted least-squares mean changes are positive: 39.74 in the Same Time of Day arm and 40.02 in the Different Times of Day arm.
Lesion count is a continuous measure: it can take a range of numerical values, and its average change can be compared between randomized groups. Summarizing the outcome as a total gives one overall measure across the listed lesion types, while the secondary outcomes separately address inflammatory and non-inflammatory counts and measurement of success. The total endpoint is relevant to the stated comparison because it captures change in overall facial lesion burden during the treatment period; it does not describe every individual lesion type or every aspect of treatment experience.
The reported estimates are least-squares means, with standard errors of 1.64 and 1.62. The exact statistical model and any covariates used to obtain those estimates are not reported in the registry record. The stated analysis population also matters: the result is for participants meeting the registry’s per-protocol definition, not necessarily every randomized participant.
7. Results Posted in the Registry
- Different Times of Day: mean 40.02 versus 39.74 on control; difference 0.28 (95% CI -4.24 to 4.80), standardized effect d = 0.02; z-test p = 0.903.
Mean difference: Different Times of Day
95% CI: -4.24 to 4.80
Recalculated from the posted summary statistics
8. Statistical Interpretation
The reported least-squares mean change in total facial lesion count was 39.74 for Same Time of Day and 40.02 for Different Times of Day. Under the registry’s definition, negative values indicate improvement; both posted means are positive. The reported mean difference, calculated in the comparison as Different Times of Day relative to Same Time of Day, is 0.28. The posted unadjusted p-value is 0.903.
The reported interval for the mean difference extends from -4.238 to 4.798. It includes zero, so the estimates are compatible with no mean difference as well as with differences in either direction across the range of that interval. This does not establish that the schedules are identical or equivalent. An absence of a statistically clear difference is not the same as demonstrating that any difference is small enough to be unimportant. The registry record does not report an equivalence or non-inferiority margin.
The comparison is based on the per-protocol population described in the record: ITT subjects who completed 12 weeks of treatment and evaluations without major protocol deviations. This population definition can affect how broadly the estimates apply to all randomized participants. The record does not explain how many participants were excluded from the per-protocol population, why any exclusions occurred, or how missing endpoint observations were handled.
The reported standardized effect is d = 0.016, with a pooled standard deviation of 17.13; the standard deviation is identified as approximate. These are descriptive, recalculated comparison statistics, not additional outcomes observed separately from the lesion-count data. The small standardized estimate is consistent with the close posted group means, but it does not resolve questions about the precision of the estimate, the relevance of a possible difference, or the consequences of the per-protocol analysis.
The registry record supplies no detailed model specification, covariate list, multiplicity procedure, or original sample-size justification. The p-value is unadjusted. It should therefore be read as the reported unadjusted result for this comparison, not as a complete account of all planned analyses. The record lists secondary outcomes, but their numerical results are not reported in the registry record. Overall, the posted primary comparison gives an estimate near zero relative to the reported lesion-count variability, with an interval that allows differences in both directions. It does not establish equivalence, and it does not by itself answer every safety or efficacy question raised by the study summary.
9. Statistical Methods Explained
The primary measure is continuous: it is a numerical change in total lesion count. A group mean summarizes the average change among participants in the analyzed group. The registry reports least-squares means, a statistical term commonly used for means estimated from a model. General explanation: a model can account for specified design factors or covariates when estimating group means, but the exact model, covariates, and handling of repeated measurements are not reported in the registry record. The posted values should therefore be interpreted as the reported least-squares means, without assuming which adjustments were made.
What does the mean difference represent?
The reported mean difference is 0.28, with the comparison expressed as Different Times of Day relative to Same Time of Day. It summarizes the contrast between the two reported mean changes on the lesion-count scale. Because the endpoint is defined as the post-baseline count minus the baseline count, a positive mean change indicates an increase from baseline. The direction of the contrast is distinct from the direction of improvement: the difference compares the two group averages, while the sign of each group’s change describes its movement relative to baseline.
A mean difference is an estimate, not a guarantee that every participant experienced a change of that size. Individual responses can vary around a group average. The registry reports standard errors of 1.64 and 1.62 for the two least-squares means. General explanation: a standard error describes the estimated sampling uncertainty in a statistic, such as a mean; it is not the spread of individual participant outcomes. The posted pooled standard deviation is 17.13 and is marked approximate. It describes variability on the lesion-count scale, whereas the standard error concerns uncertainty in the estimated means.
How should the p-value be read?
The posted unadjusted p-value is 0.903. General explanation: a p-value describes how compatible the observed data are with a specified null model, under the assumptions of the analysis; it is not the probability that the null hypothesis is true, nor a measure of clinical importance. The registry record does not state the full null-testing procedure or a prespecified threshold for this endpoint. The value is reported as unadjusted, and the record does not report whether any multiplicity adjustment was planned or performed.
A large p-value does not prove that two regimens have the same effect. A study can fail to provide clear evidence of a difference while still leaving uncertainty about the size or direction of a possible difference. To demonstrate equivalence, investigators generally need a prespecified margin defining what differences count as acceptably small, together with an analysis designed to test that question. Such a margin and an equivalence analysis are not reported in the registry record.
What does the standardized effect add?
The reported standardized effect is d = 0.016. General explanation: a standardized effect expresses a group contrast in relation to a measure of variability, allowing its scale to be compared with the observed spread. It does not replace the original-unit mean difference. Here, the pooled standard deviation used for the calculation is identified as approximate, and the standardized value is a recalculated, unadjusted statistic from posted summary data. It should not be mistaken for a separately reported sponsor analysis or for a validated threshold of clinical importance.
The primary estimates are reported for the Per Protocol Population. The record defines this as ITT subjects who completed the 12 weeks of treatment and evaluations with no major protocol deviations. General explanation: restricting an analysis to participants who meet protocol-completion criteria can change the population represented by the estimate, because participants without complete follow-up or with major deviations may not be included. The registry record does not provide the number or reasons for exclusions, nor does it report a complementary all-randomized analysis for this endpoint.
Why does variation matter?
Participant-level lesion counts can vary, even when group averages are close. General explanation: greater variability makes a group contrast harder to estimate precisely, while lower variability can make estimates more precise, all else being equal. The standard error and interval convey uncertainty about the estimated group contrast; the pooled standard deviation gives a separate sense of the observed scale of variation. These quantities answer different questions and should not be treated as interchangeable. No new calculation from the posted values is needed to see that the interval for the mean difference spans both negative and positive values.
The underlying model, assumptions checks, handling of influential observations, missing-data procedures, and any sensitivity analyses are not reported in the registry record. The registry also does not report interim analyses or the original design’s statistical plan. These omissions limit how fully an outside reader can assess robustness. The primary result remains interpretable as the posted comparison of least-squares mean change, but the record does not establish the analytic details that produced it beyond the endpoint definition, analysis population, estimates, standard errors, and comparison statistics.
10. Confidence Intervals and Precision
The reported mean difference is 0.28, and its interval runs from -4.238 to 4.798. The interval includes zero and extends to both negative and positive values. In practical terms, the estimate alone is not precise enough to rule out differences in either direction within the reported range. The confidence level for this interval is not reported in the registry record, so it should not be assigned a level that the record does not state.
General explanation: a confidence interval gives a range of values compatible with the data and the assumptions of the statistical method. Its width reflects uncertainty in the estimated contrast; it is not a range containing a specified proportion of individual participant outcomes. An interval that includes zero does not show that the true difference is exactly zero. It indicates that zero is among the values compatible with this reported interval.
The standard errors for the arm estimates are 1.64 and 1.62. The record does not report the interval method, model details, or whether the comparison interval incorporates any adjustment. The posted p-value is unadjusted. Those details matter when assessing how the interval and test relate to one another.
The result is not an equivalence finding. Equivalence requires a defined margin and an analysis demonstrating that the interval is sufficiently contained within that margin; no such margin is reported in the registry record. The observed mean difference and interval describe uncertainty for the primary comparison, but they do not establish whether a difference would be clinically important. That threshold is also not reported in the registry record.
11. Planning a Similar Trial: Sample Size
This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.
| Effect to detect | Participants per arm, 80% power | Participants per arm, 90% power |
|---|---|---|
| 100% of the observed effect | 58,778 | 78,687 |
| 75% of the observed effect | 104,494 | 139,887 |
| 50% of the observed effect | 235,110 | 314,746 |
The planning figures are participants per arm, not total events. Each entry describes a planning illustration based on a stated fraction of the observed effect. The assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. For the rows using 100%, 75%, and 50% of the observed effect, the calculation asks how many participants per arm would be needed to detect that fraction under those assumptions. The original trial’s design assumptions and sample-size justification are not reported in the registry record.
The 80% power column represents a planning target for the probability of detecting the specified effect under the calculation’s assumptions; the 90% power column uses a higher target probability. These are design targets, not probabilities that the observed result is correct. The listed values rise as the assumed effect becomes smaller: planning to detect a smaller effect requires more participants per arm, all else held to the stated assumptions. The curve should be read in the same planning context, as a representation of how the required sample size changes with the effect being targeted.
For illustration, planning for 100% of the observed effect gives 58,778 participants per arm for 80% power and 78,687 for 90% power. Planning for 75% gives 104,494 and 139,887 participants per arm, respectively; planning for 50% gives 235,110 and 314,746. These unusually large illustrations follow from using the very small observed difference as the target effect. They are recalculations for planning, not the trial’s enrollment target or a description of the original design. This is not observed power.
12. How the Sample Size Is Derived
Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z1−α/2 = 1.960) and the desired power (z1−β = 0.842 for 80% and 1.282 for 90%).
Formula
n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.
Worked calculation for this trial
- Observed difference Δ = 0.280; pooled standard deviation σ = 17.133.
- n = 2 × (1.96 + 0.842)2 × 17.1332 / 0.2802 = 58,777.5, rounded up to 58,778 participants per arm for 80% power.
The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).
R code
alpha <- 0.05
z_a <- qnorm(1 - alpha / 2) # two-sided
delta <- 0.280000000000001 # observed difference in means
sigma <- 17.1334424245412 # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))
# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")
# Simulation: exact two-sample t-test using simulated means and variances
set.seed(907257)
n <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n)) # difference in sample means
s2 <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1)) # pooled sample variance
tstat <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))
Output from running the code
100% of observed effect: n per arm = 58,778 (80% power), 78,687 (90% power)
75% of observed effect: n per arm = 104,494 (80% power), 139,887 (90% power)
50% of observed effect: n per arm = 235,110 (80% power), 314,746 (90% power)
power.t.test: 58778.4
Simulated power at n = 58,778 per arm: 0.799 (20000 replicates)The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.
13. Multiplicity, Missing Data and Analysis Populations
The registry record lists the primary outcome as change from baseline in total facial acne lesion count and lists two secondary outcomes: change in inflammatory and non-inflammatory lesion counts and their totals, and measurement of success. The primary result is accompanied by an unadjusted p-value. The numerical results for the secondary outcomes are not reported in the registry record, and no multiplicity procedure is reported.
General explanation: when several outcomes or comparisons are tested, the chance of finding at least one apparently notable result can increase if each test is treated independently. A prespecified multiplicity procedure can address that issue, but the appropriate interpretation depends on the planned testing strategy. The registry record does not report whether these outcomes were tested under a hierarchy, adjusted together, or treated as separate analyses. The posted unadjusted p-value should therefore not be described as multiplicity-adjusted evidence.
The primary analysis population is specified as the Per Protocol Population, consisting of ITT subjects who completed 12 weeks of treatment and evaluations without major protocol deviations. The registry record does not report an analysis of all randomized participants for the primary endpoint, the number or reasons for any exclusions, or how missing observations were handled. It also does not report imputation, a missing-data sensitivity analysis, or a strategy for participants who discontinued treatment or assessments.
These omissions matter because the population included in an analysis and the handling of unavailable measurements can affect the estimate and its uncertainty. The registry does not report the original statistical analysis plan, interim analyses, or the full outcome-testing plan. It is therefore not possible from the record to determine which analyses were prespecified, how any departures were handled, or how the secondary results would alter interpretation of the primary comparison.
14. 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 |
|---|---|---|---|
| Same Time of Day | 3 | 123 | 2.4% |
| Different Times of Day | 0 | 124 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Same Time of Day | 0 of 123 |
| Different Times of Day | 0 of 124 |
Most frequent serious adverse event terms
| Event term | Organ system | Same Time of Day | Different Times of Day |
|---|---|---|---|
| Cardiac Arrhythmia | Cardiac disorders | 1 of 123 | 0 of 124 |
| Viral Myocarditis | Cardiac disorders | 1 of 123 | 0 of 124 |
| Ovarian Cyst | Reproductive system and breast disorders | 1 of 123 | 0 of 124 |
Serious events with the highest arm-level rate: cardiac arrhythmia (0.8%), viral myocarditis (0.8%), ovarian cyst (0.8%).
The registry reports serious adverse event figures for both arms. In Same Time of Day, 3 serious adverse events are marked as related among 123 participants at risk; in Different Times of Day, 0 are marked as related among 124 participants at risk. The other serious-event counts are 0 in each arm, with the same respective at-risk group sizes. The registry lists Cardiac Arrhythmia, Viral Myocarditis, and Ovarian Cyst among the top serious-event terms, each at 0.8%.
These figures describe reported serious events and should not be treated as a complete account of all adverse experiences. The record does not give the event-term breakdown by arm, the timing or duration of events, or additional context for the listed terms. Death counts are not reported in the registry record. The figures alone do not establish that a regimen caused or prevented an event, and they do not answer broader safety questions beyond the reported categories and counts.
15. What the Result Does, and Does Not, Mean
The primary comparison estimates the difference between the two schedules in change from baseline in total facial acne lesion count at Week 12, for the specified per-protocol population. The least-squares mean changes are 39.74 for Same Time of Day and 40.02 for Different Times of Day. The mean difference is 0.28, and the reported interval ranges from -4.238 to 4.798. The unadjusted p-value is 0.903. Together, these figures describe an estimated contrast close to zero relative to the uncertainty in that contrast, while leaving room for differences in either direction.
The result does not establish that the schedules are equivalent. The registry record does not report an equivalence margin or a non-inferiority framework. Nor does this comparison prove that either schedule is beneficial or ineffective. The posted endpoint is a change in lesion count, and its definition makes negative values indicative of improvement. The reported group mean changes are positive, but the record alone does not establish why those values occurred or support a causal explanation beyond the randomized comparison.
The finding is also limited to the stated outcome and time frame. It does not provide the numerical secondary-outcome results, a complete account of individual responses, or evidence about outcomes beyond baseline to Week 12. The per-protocol analysis population may not represent all randomized participants, and the registry does not describe missing-data handling or a complementary all-randomized primary analysis.
The reported serious adverse event figures offer a limited view of safety reporting: three related serious events in the Same Time of Day group and none in the Different Times of Day group, alongside zero other serious events in both groups. The record does not provide enough detail to infer a causal safety difference. A sound reading is therefore specific: the registry posts a close primary group contrast with an interval spanning both directions, along with limited serious adverse event counts. It does not settle equivalence, clinical importance, or broader safety questions.
16. Why This Trial Matters Statistically
This trial illustrates why a comparison should be read through its estimate and uncertainty rather than through a single p-value. The posted mean difference is 0.28, while the interval from -4.238 to 4.798 includes zero and values in both directions. The p-value of 0.903 is unadjusted. These statistics address the observed comparison, but they do not demonstrate that the schedules are the same or that a possible difference is unimportant.
It also shows why endpoint definitions and analysis populations matter. The primary outcome is change in a total that includes non-inflammatory and inflammatory lesions, plus nodules or cysts. The registry defines the change as the later count minus baseline, so negative values indicate improvement. The result applies to a per-protocol population with completion and deviation criteria, rather than automatically applying to every randomized participant. Without additional information on exclusions and missing observations, the reach of the estimate is difficult to assess fully.
The planning illustration provides another statistical lesson: required sample size depends strongly on the effect being targeted. Because the observed contrast is small, planning to detect a smaller fraction of that effect yields very large per-arm figures under the stated assumptions. Those are prospective planning calculations, not evidence about the probability that the observed result is true, and not the trial’s original design rationale.
Finally, registry results should be interpreted in light of what is not documented. The record does not report the full statistical plan, multiplicity handling, secondary numerical results, or an equivalence framework. Recognizing those gaps keeps conclusions proportional to the posted evidence and separates a near-zero point estimate from a definitive claim of sameness.
17. 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 posted primary result is restricted to the Per Protocol Population, defined as ITT subjects who completed 12 weeks of treatment and evaluations without major protocol deviations. The registry record does not report the number or reasons for any exclusions from that population, or whether a primary analysis including all randomized participants was conducted. This limits assessment of how selection into the analysis may affect interpretation.
The registry does not report the method used to handle missing endpoint observations, any imputation, or sensitivity analyses. It also does not give the detailed statistical model or covariates used for the least-squares means, the interval method, or the original statistical analysis plan. The confidence level of the reported interval is not stated. The p-value is unadjusted, while multiplicity handling is not reported.
The primary outcome is measured from baseline to Week 12. Results for the listed secondary outcomes are not reported in the registry record, and the record does not provide a numerical account of other time points. It also does not report an equivalence margin or a clinically important difference threshold, so the primary comparison cannot establish whether any difference is acceptable or meaningful.
The safety information is limited to the posted serious adverse event counts and terms. The term-by-arm breakdown, event timing, and death counts are not reported in the registry record. The original sample-size justification and design assumptions are also not reported; the posted planning illustrations use the observed effect and should not be treated as the trial’s design rationale.
18. Related Tutorials
19. Related Statistical Calculators
20. Sources
- ClinicalTrials.gov: A Study of Different Use Regimens Using Two Acne Treatments — NCT00907257.
- Registry record last updated 2012-02-15; status last verified 2012-02.
- Results first posted 2011-01-21.
- 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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21. Record Summary
The completed Phase 4 study NCT00907257 randomized participants with acne vulgaris to two schedules for using 5% benzoyl peroxide wash and 0.04% tretinoin gel. It used a single-masked, parallel-group design. The primary outcome was change from baseline in total facial acne lesion count from baseline to Week 12, analyzed in the stated Per Protocol Population.
The posted least-squares mean changes were 39.74 for Same Time of Day and 40.02 for Different Times of Day. The reported mean difference was 0.28, with an interval from -4.238 to 4.798 and an unadjusted p-value of 0.903. The interval includes zero and extends in both directions; the comparison does not establish equivalence. The record lists two secondary outcomes, but their numerical results and several details of the analysis plan are not reported in the registry record.