Efficacy/Safety/Subject Satisfaction/Duration of Response of Clobetasol Propionate Spray vs Ointment in Plaque Psoriasis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Efficacy/Safety/Subject Satisfaction/Duration of Response of Clobetasol Propionate Spray vs Ointment in Plaque Psoriasis (NCT00733954), a randomized phase 4 study. The primary outcome is Number of Participants Who Are Clear/Almost Clear of Plaque Psoriasis From Baseline to End of Treatment Based on the Overall Disease Severity (ODS) Scale.

2. Clinical Question

3. Trial Design

NCT00733954 was a Phase 4, randomized, parallel-group trial of clobetasol propionate spray and clobetasol propionate ointment in plaque psoriasis. The registry record lists the trial as completed, with Galderma R&D as sponsor. The recorded start was 2007-08 and primary completion was 2008-04. Enrollment was 250. Masking is listed as none, so this was an unmasked comparison.

Participants were randomized to one of two treatment schedules. The spray group used clobetasol propionate spray 0.05% for 4 weeks, and the ointment group used clobetasol propionate ointment 0.05% for 2 weeks. Each group had a 2-week follow-up after treatment. The registry record therefore describes an assessment schedule with different treatment durations between arms, rather than equal-duration treatment courses.

The primary endpoint is reported for an intent-to-treat population using last observation carried forward. The primary timeframe is stated as baseline and Week 2 and baseline and Week 4; the description specifies end of treatment as Week 4 for spray and Week 2 for ointment. The primary results include 124 participants in the spray group and 125 in the ointment group. Those arm-specific denominators are the relevant numbers for interpreting the posted outcome counts; enrollment and outcome denominators need not be identical.

The trial also lists secondary outcomes on disease severity and signs of psoriasis, including erythema, scaling, and plaque elevation, at treatment and follow-up assessments. The registry record lists 19 outcome measures, and 18 secondary outcomes are posted. No statistical analysis details beyond the information described with the outcomes are reported in the registry record. In particular, the original sample-size justification, planned analysis procedures, and any interim analyses 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.

Before assignment: The specified wash-out period up to baseline was 14 days (topical steroid containing medication and/or UVB treatment, Dovonex, anthralin and/or tar); and 4 weeks (systemic corticosteroids, biologics and/or PUVA treatment).

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Intent-to-treat (ITT), Last observation carried forward (LOCF)

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants Who Are Clear/Almost Clear of Plaque Psoriasis From Baseline to End of Treatment Based on the Overall Disease Severity (ODS) Scale, measured over Baseline and Week 2 and Baseline and Week 4.

The primary endpoint counts participants classified as clear or almost clear on the Overall Disease Severity scale at the end of treatment. The scale has five ordered categories: Clear/Almost Clear, Mild, Moderate, Severe, and Very Severe. Clear/Almost Clear is the best category, while Severe/Very Severe is the worst. The endpoint reduces the scale to whether each participant reached either of the two most favorable categories or did not.

This kind of endpoint is binary at the participant level: each participant either meets the clear/almost-clear criterion or does not. Reporting a count makes the outcome directly interpretable as the number meeting that criterion among the participants in each group. It does not show how far participants who remained outside those categories moved along the scale, and it should not be read as a complete summary of every change in disease severity.

Using a clearly defined category can make a clinical outcome easier to understand and compare between groups. The primary question is whether the proportion of participants reaching the threshold differed between the randomized groups. The registry record reports the endpoint for the intent-to-treat population with last observation carried forward. Since the treatment periods differed, the comparison concerns outcomes at each group’s own end of treatment, not outcomes after the same number of treatment weeks.

7. Results Posted in the Registry

• Clobetasol Propionate Ointment: 35.2% (44/125) versus 50.0% (62/124) on control; risk difference -14.8 percentage points (95% CI -26.9 to -2.7), risk ratio 0.70 (0.52–0.95); unadjusted two-proportion z-test p = 0.018.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Number of Participants Who Are Clear/Almost Clear of Plaque Psoriasis From Baseline to After Two Weeks of Treatment Based on the Overall Disease Severity (ODS) Scale

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Clobetasol Propionate Ointment: 35.2% (44/125) versus 31.5% (39/124) on control; risk difference 3.7 percentage points (95% CI -8.0 to 15.4), risk ratio 1.12 (0.79–1.59); unadjusted two-proportion z-test p = 0.530.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Clobetasol Propionate Ointment and the control. The interval gives the range of effects that remain compatible with the data.

Number of Participants Who Are Clear/Almost Clear of Plaque Psoriasis From Baseline to 2 Weeks Post Treatment Based on the Overall Disease Severity (ODS) Scale

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Clobetasol Propionate Ointment: 26.4% (33/125) versus 40.3% (50/124) on control; risk difference -13.9 percentage points (95% CI -25.5 to -2.3), risk ratio 0.65 (0.46–0.94); unadjusted two-proportion z-test p = 0.020.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically lower for Clobetasol Propionate Ointment than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Number of Participants With Decrease in Signs of Psoriasis (Erythema) From Baseline to After Two Weeks of Treatment

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Clobetasol Propionate Ointment: 26.4% (33/125) versus 23.4% (29/124) on control; risk difference 3.0 percentage points (95% CI -7.7 to 13.7), risk ratio 1.13 (0.73–1.74); unadjusted two-proportion z-test p = 0.583.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Clobetasol Propionate Ointment and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes broaden the assessment beyond the primary end-of-treatment threshold. They cover clear/almost-clear status at other timepoints and decreases in particular signs of psoriasis, including erythema, scaling, and plaque elevation. The posted results therefore address both the persistence of a severity classification over follow-up and changes in individual signs. Together, these outcomes can help describe whether patterns differ by the time of assessment or by the feature being evaluated.

The overall pattern should be considered alongside, not as a replacement for, the primary comparison. Some secondary estimates are directionally consistent with the primary contrast, while others are close to no difference and their confidence intervals include zero. This mixed pattern is one reason to avoid treating any single secondary result as a definitive confirmation or contradiction of the primary finding. The secondary outcomes also use different assessment times, so contrasts do not all represent the same point in the treatment and follow-up schedule.

Unadjusted secondary results carry less weight because the registry record lists multiple outcomes and timepoints but does not report a multiplicity procedure. General explanation: when many statistical tests are conducted, the chance of at least one apparently unusual result can increase even if no real group difference exists. Adjustment methods or a prespecified hierarchy can help manage that issue, but whether such a plan existed or was applied is not reported in the registry record. The registry record lists no reported analyses for the posted secondary outcomes.

Secondary findings are therefore most useful as context and as potential grounds for further investigation. They should be read with their estimates and confidence intervals, the timing of each measurement, and the absence of reported multiplicity handling in mind. Their presence does not establish a consistent effect across every sign, timepoint, or outcome, and their results do not alter the definition of the primary endpoint.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Number of Participants Who Are Clear/Almost Clear of Plaque Psoriasis From Baseline to After Two Weeks of Treatment Based on the Overall Disease Severity (ODS) Scale
• Number of Participants Who Are Clear/Almost Clear of Plaque Psoriasis From Baseline to 2 Weeks Post Treatment Based on the Overall Disease Severity (ODS) Scale
• Number of Participants With Decrease in Signs of Psoriasis (Erythema) From Baseline to After Two Weeks of Treatment
• Number of Participants With Decrease in Signs of Psoriasis (Scaling) From Baseline to After Two Weeks of Treatment
• Number of Participants With Decrease in Signs of Psoriasis (Plaque Elevation) From Baseline to After Two Weeks of Treatment
• Number of Participants With Decrease in Signs of Psoriasis (Erythema) From Baseline to End of Treatment
• Number of Participants With Decrease in Signs of Psoriasis (Scaling) From Baseline to End of Treatment
• Number of Participants With Decrease in Signs of Psoriasis (Plaque Elevation) From Baseline to End of Treatment

9. Statistical Interpretation

10. Statistical Methods Explained

What does the primary outcome count?

The primary outcome is binary because it divides participants into those rated Clear/Almost Clear and those not rated in either of those categories. Each participant contributes to one category in the outcome count. This is different from analyzing all five severity categories separately or calculating a mean score change. General explanation: a binary endpoint simplifies the question to whether a prespecified threshold was reached, but that simplicity can leave out information about changes that do not cross the threshold.

What does a risk difference express?

The risk difference is the difference between the groups’ proportions meeting the endpoint. The posted comparison is expressed as ointment relative to spray. Its estimate is -0.148. A negative value indicates a lower observed proportion in the ointment group under that contrast’s direction. The risk difference is an absolute comparison on the proportion scale, rather than a relative ratio. General explanation: an absolute difference is often useful for communicating how separated two group proportions are, while a ratio describes their relative relationship. The registry record also includes relative measures, but interpretation centers on the posted risk difference and its confidence interval.

How should the p-value be read?

The primary unadjusted p-value is 0.018. General explanation: a p-value describes how compatible the observed data are with a specified null hypothesis under the assumptions of the statistical procedure. It is not the probability that the null hypothesis is true, nor does it quantify the clinical importance of the result. The particular test or model used to obtain the posted p-value is not reported in the registry record. Because the value is unadjusted, it should not be treated as if it accounts for testing multiple endpoints or comparisons.

What role does randomization play?

The allocation is listed as randomized, with a parallel-group model. General explanation: random allocation is intended to make treatment groups comparable on average at the start of a trial, including for factors that may not be measured. It does not guarantee that groups are identical, and it does not remove the need to consider outcome measurement, missing data, or analysis choices. Masking is listed as none. That means the trial is described as unmasked; the registry record does not provide further detail about who knew each participant’s assignment or how outcome ratings were conducted.

What does intent-to-treat with last observation carried forward mean?

The primary population is described as intent-to-treat, with last observation carried forward. General explanation: intent-to-treat analysis generally aims to retain participants in the groups to which they were randomized, preserving the randomized comparison. Last observation carried forward is a missing-data procedure in which the last observed outcome is used in place of a later missing value. This method can affect estimates if the carried-forward value does not represent the participant’s unobserved later status. The registry record does not report how many primary outcome observations were missing, why observations were missing, or whether other missing-data approaches were used.

What is not specified about the analysis?

The registry record posts arm counts, a risk difference, a confidence interval, and an unadjusted p-value. The exact statistical test or model, any covariate adjustment, and the handling of the ordinal scale before it was reduced to the clear/almost-clear endpoint are not reported in the registry record. The original sample-size justification and any planned interim analyses are also not reported in the registry record. These details matter because they define how data are translated into statistical evidence and how much confidence to place in assumptions behind the reported estimates.

Why can over-dispersion matter in general?

Over-dispersion is a general statistical issue in which observed variability is greater than expected under a model’s assumptions. It is not a reported feature of this binary primary outcome, and the registry record does not state that an over-dispersion adjustment was used. In general, if an analysis assumes less variability than the data contain, standard errors may be too small and confidence intervals may be too narrow. Whether that concern applies depends on the outcome and statistical model; no such model details are reported for this comparison.

How should the secondary results fit with the primary result?

Secondary outcomes include clear/almost-clear status at other timepoints and changes in individual signs of psoriasis. These can add context about timing and different dimensions of disease severity, but they do not replace the primary endpoint. General explanation: each additional outcome or timepoint creates another opportunity to observe a result that differs by chance. Unless a statistical plan specifies how those tests are handled, unadjusted secondary p-values should be viewed as exploratory rather than as independent confirmation. The registry record lists no reported analyses for the posted secondary outcomes.

11. Confidence Intervals and Precision

The primary risk difference is -0.148, with a 95% confidence interval from -0.270 to -0.026. The interval gives a range of effect estimates compatible with the data under the statistical method used to construct it. General explanation: a confidence interval is not a guarantee that the true value lies within the particular interval, but a method that produces intervals at the stated confidence level will cover the true value at that rate over repeated use under its assumptions.

The interval is entirely below zero, consistent with the direction of the posted point estimate for ointment relative to spray. Its span also indicates that the data do not pinpoint a single effect size. The interval ranges from a more negative difference to a difference closer to zero, so the point estimate should be read alongside the full range rather than alone. The registry record does not report the exact method used to calculate this interval.

The numbers of participants contributing to the primary outcome are 124 in the spray group and 125 in the ointment group. These denominators provide context for the uncertainty around a binary comparison: counts from finite groups do not establish the exact population proportions. The confidence interval reflects statistical uncertainty under its assumptions, but it does not incorporate every possible source of uncertainty, such as bias from unmasked assessment, limitations in the endpoint definition, or uncertainty about missing-data handling.

The interval does not resolve whether the observed contrast would be similar under equal treatment durations, since the primary endpoint was measured at Week 4 for spray and Week 2 for ointment. Nor does it describe the results for outcomes not included in the primary comparison. Statistical precision should therefore be considered together with the trial’s assessment schedule and the analysis details that are not reported in the registry record.

12. 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.

The planning figures are participants per arm for the binary outcomes in this trial. They are not total event counts. The registry record’s planning illustration uses a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. It uses the stated fraction of the observed effect as the effect to detect. The original trial’s design assumptions and sample-size justification are not reported in the registry record; these calculations are planning illustrations based on the observed results, not a reconstruction of the trial’s original design.

For the primary outcome, planning for 100% of the observed effect gives 175 participants per arm for 80% power and 233 participants per arm for 90% power. Planning for 75% of the observed effect gives 314 participants per arm for 80% power and 420 participants per arm for 90% power. Planning for 50% of the observed effect gives 712 participants per arm for 80% power and 953 participants per arm for 90% power.

General explanation: the 80% and 90% columns describe the planned probability of detecting the chosen effect at the stated significance level if the assumptions hold and the effect is real. The higher power target requires a larger planned sample for the same effect. The rows use progressively smaller fractions of the observed effect; smaller effects are harder to detect and require more participants. These planning estimates are not observed power. They do not show the probability that the trial’s result is correct, and they do not change the uncertainty in the completed trial’s observed estimate.

The figures depend on the observed effect used as a planning reference. Because that reference comes from the trial’s result, the values should be treated as illustrations for future planning rather than as evidence that the completed trial was adequately or inadequately designed. The outcome-specific assumptions and the trial’s own design rationale are not reported in the registry record.

13. 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 z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.500; treatment proportion p₁ = 0.352; average p̄ = 0.426.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6993 = 1.3706.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6914 = 0.5819.
4. n = (1.3706 + 0.5819)² / (-0.1480)² = 174.1, rounded up to 175 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
p0 <- 0.5                          # control proportion
p1 <- 0.352                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^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 (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(733954)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 175 (80% power), 233 (90% power)
 75% of observed effect: n per arm = 314 (80% power), 420 (90% power)
 50% of observed effect: n per arm = 712 (80% power), 953 (90% power)
power.prop.test: 174.1 
Simulated power at n = 175 per arm: 0.797 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-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.

14. Multiplicity, Missing Data and Analysis Populations

The registry record lists 19 outcome measures and 18 posted secondary outcomes, alongside the primary outcome. Testing multiple outcomes, timepoints, or contrasts raises a multiplicity issue: the more tests performed, the more likely it is that at least one result will appear statistically notable by chance. General explanation: multiplicity can be addressed through approaches such as a prespecified primary endpoint, a testing hierarchy, or statistical adjustment, depending on the trial’s objectives and analysis plan.

The primary comparison has an unadjusted p-value of 0.018. The registry record does not report whether the primary p-value was adjusted for any other analyses, whether a formal multiplicity procedure was planned, or which outcomes were designated as confirmatory beyond the primary label. The secondary outcomes also include unadjusted comparisons, and their reported analyses are not listed. Whether these outcomes were analyzed under a prespecified hierarchy or considered exploratory is not reported in the registry record.

The primary population is described as intent-to-treat with last observation carried forward. The registry record does not report the extent or pattern of missing primary or secondary data, reasons for missingness, or sensitivity analyses using alternative assumptions. General explanation: missing-data procedures rely on assumptions about what unobserved outcomes might have been. Carrying forward the last observation can be problematic if a participant’s condition would likely change after that last measurement, but the direction and impact cannot be determined without further information.

The registry record does not report the original sample-size justification, an analysis plan, interim analyses, the exact test or model used for the primary comparison, or covariate adjustment details. These are important elements for assessing how the study was planned and how much flexibility existed in the analysis. Their absence from the registry record does not demonstrate that no such procedures existed; it means the record does not describe them.

The results should consequently be read as posted outcome summaries with limited documentation of multiplicity and missing-data handling. The primary endpoint remains the clearest focal comparison, while secondary results offer context but not an independently adjusted set of confirmatory tests.

15. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

For serious adverse events, the registry record lists 0 affected participants among 122 at risk in the spray group and 0 among 123 at risk in the ointment group. For other adverse events, it likewise lists 0 affected participants among 122 at risk in the spray group and 0 among 123 at risk in the ointment group. The serious adverse event terms list is empty.

These figures describe what was recorded for the specified safety categories and the listed at-risk groups. The safety denominators differ from the primary efficacy denominators, which are 124 and 125. The registry record does not report deaths; the death entries are not populated with a numerical count. It also does not provide additional details about event definitions, collection methods, duration of safety follow-up, or whether all adverse events were included in the posted categories.

Zero recorded events in these groups should not be interpreted as proof that an event is impossible or that the formulations have no safety risks. General explanation: a trial’s safety counts describe observed events in its participants and follow-up period, while rare or later events may not be captured in a particular study. The registry figures should be read narrowly as event counts recorded for these categories.

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

The primary results show that more participants in the spray group than in the ointment group were counted as clear or almost clear at the end of their respective treatment periods. The posted contrast is an absolute risk difference, and its confidence interval is entirely on the negative side when expressed as ointment relative to spray. This is a statistical description of the observed data, not a general recommendation about treatment.

The comparison is tied to a specific study population, a particular disease-severity classification, and an assessment schedule in which the spray was used for 4 weeks and the ointment for 2 weeks. The primary outcome was assessed at the end of each group’s treatment period. It therefore does not isolate the effect of formulation under equal treatment durations, and the posted results do not establish what would happen under other schedules or in other populations.

The endpoint captures reaching Clear/Almost Clear, not the full distribution across all severity categories or every possible change in signs of psoriasis. A participant who improved but did not reach the threshold is not counted as a primary endpoint success. The primary count also does not describe individual responses or guarantee that all participants in a group had similar outcomes.

The posted p-value is unadjusted, and the registry record does not report how multiplicity was handled across the many outcomes. Nor does the record detail the exact primary statistical test, the original sample-size rationale, or missing-data sensitivity analyses. These omissions do not erase the posted estimates, but they limit how comprehensively the findings can be evaluated.

In practical interpretation, the primary result is one piece of evidence about a defined threshold at particular assessment times. It should be considered with the confidence interval, study design, outcome definition, secondary results, safety reporting, and analysis details that are not reported in the registry record. It does not by itself establish broad or lasting effects beyond the trial’s measured outcomes.

17. Why This Trial Matters Statistically

This trial illustrates why the endpoint and its timing are central to a statistical comparison. The primary outcome is a threshold classification, while the treatment arms have different treatment durations and therefore different end-of-treatment assessment weeks. A group contrast can be calculated precisely from the posted counts, but its interpretation depends on what was measured and when it was measured.

It also shows why absolute effects and uncertainty should be read together. The risk difference describes the direction and size of the group contrast on the proportion scale, while its confidence interval communicates a range of compatible values. A p-value alone would not show that range or convey the assessment-schedule difference.

The trial’s secondary outcomes demonstrate a familiar challenge in clinical research: many related outcomes and timepoints can provide useful context, yet unadjusted statistical results across them are not equivalent to a single confirmatory test. Without reported multiplicity procedures, readers should distinguish the primary comparison from secondary patterns and avoid over-weighting isolated results.

Finally, the planning illustrations demonstrate how sample requirements depend on the effect targeted and the power goal. Smaller targeted effects require larger participant counts under the stated planning assumptions. Those illustrations are separate from the original trial design, whose sample-size justification is not reported in the registry record. Keeping planning calculations distinct from completed-trial precision prevents the common error of treating a retrospective planning calculation as observed power.

18. 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.

A key trial-specific limitation is the unequal treatment duration: the spray group received treatment for 4 weeks and the ointment group for 2 weeks. The primary endpoint was measured at each group’s end of treatment, at Week 4 and Week 2 respectively. The primary comparison therefore combines formulation with a difference in treatment exposure and assessment timing; it is not an equal-duration comparison.

Masking is listed as none. Because the primary endpoint involves a severity rating, lack of masking may be relevant to outcome assessment, although the registry record does not state who performed the ratings or what safeguards were used. The record also does not report details of allocation concealment or baseline balance between groups.

The primary outcome dichotomizes an ordered scale at Clear/Almost Clear. That makes the endpoint straightforward to count, but it does not show the distribution across the remaining categories or distinguish participants with different degrees of improvement who did not meet the threshold. The posted secondary measures add some context but do not resolve every limitation of the primary summary.

There is limited reporting of analysis details. The exact test or model, original sample-size justification, any interim analyses, multiplicity strategy, and missing-data sensitivity analyses are not reported in the registry record. Last observation carried forward is specified for the primary population, but the amount and pattern of missing data are not reported. Safety event counts are posted, but details about ascertainment and follow-up are not reported.

These limitations affect interpretation of the strength and scope of the findings. They do not change the posted counts or estimates, but they counsel against extending the result beyond the stated population, endpoint, and schedule.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Efficacy/Safety/Subject Satisfaction/Duration of Response of Clobetasol Propionate Spray vs Ointment in Plaque Psoriasis — NCT00733954.
• Registry record last updated 2022-08-23; status last verified 2014-04.
• Results first posted 2009-08-20.
• 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.

22. Record Summary

NCT00733954 is a completed Phase 4 randomized parallel-group trial sponsored by Galderma R&D. It enrolled participants with plaque psoriasis and compared clobetasol propionate spray 0.05% with clobetasol propionate ointment 0.05%. The recorded start was 2007-08, primary completion was 2008-04, and enrollment was 250. Masking is listed as none.

The spray schedule was 4 weeks of treatment followed by 2 weeks of follow-up; the ointment schedule was 2 weeks of treatment followed by 2 weeks of follow-up. The primary endpoint counted participants rated clear or almost clear at end of treatment. The primary outcome population was intent-to-treat with last observation carried forward.

The posted primary counts were 62 of 124 for spray and 44 of 125 for ointment. The risk difference for ointment relative to spray was -0.148, with a 95% confidence interval from -0.270 to -0.026 and an unadjusted p-value of 0.018. The registry record also lists secondary outcomes and safety counts, but several details of the statistical plan and analysis are not reported in the registry record.