Efficacy and Safety Study With Visonac Photodynamic Therapy (PDT): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Efficacy and Safety Study With Visonac Photodynamic Therapy (PDT) (NCT00933543), a randomized phase 2 study. The primary outcome is Proportion of Patients With Success According to the Dichotomized IGA Scale Based on Facial Assessments 12 Weeks After the First Treatment. Success is Defined as an Improvement of at Least 2 Grades From the Baseline Score..

2. Clinical Question

The clinical question concerns a binary definition of success rather than the average change in a continuous acne measure. Each participant either met the stated IGA improvement threshold or did not. The comparison therefore concerns the proportions meeting that threshold in the Visonac and vehicle groups.

The registry record identifies the condition as acne vulgaris and describes the trial as involving patients with moderate to severe disease. It does not report the precise eligibility criteria or the baseline characteristics of participants. The intervention and comparator both included photodynamic therapy, so the randomized contrast is between Visonac cream and vehicle cream in the setting of the stated light treatment. The registry record does not report enough detail to determine other differences in treatment procedures or participant care.

3. Trial Design

The registry record identifies this as a phase 2, randomized, parallel-group trial with 107 participants enrolled. Its official title describes a prospective, randomized, stratified, placebo-controlled, multicenter study; the record does not report the participating centers or the details of any stratification. The record classifies masking as quadruple, while the official title describes the study as double blinded. Further information about who was masked and how masking was maintained is not reported in the registry record.

Participants were assigned to Visonac cream with photodynamic therapy or vehicle cream with photodynamic therapy. The listed arm sizes are 54 and 53. Both arm descriptions specify a light dose of 37 J/cm2. The trial summary describes use of Aktilite CL512 and red light, and says the cream was used without occlusion. The number and timing of treatments beyond the primary endpoint’s reference to the first treatment are not reported in the registry record.

The primary endpoint was assessed 12 weeks after the first treatment. The record also lists secondary outcomes on facial inflammatory, non-inflammatory, and total lesion counts, including changes from baseline and threshold-based outcomes. The registry lists the trial as completed. Its recorded start is 2009-08 and primary completion is 2010-03. The original protocol, sample-size justification, detailed allocation procedures, and trial-specific statistical analysis plan are not reported in the registry record. The observed enrollment should therefore be distinguished from any planned enrollment target, which is not reported.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: ITT

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 Proportion of Patients With Success According to the Dichotomized IGA Scale Based on Facial Assessments 12 Weeks After the First Treatment. Success is Defined as an Improvement of at Least 2 Grades From the Baseline Score., measured over 12 weeks after the first treatment.

The primary endpoint is the proportion of participants with success on a dichotomized IGA scale, based on facial assessments 12 weeks after the first treatment. Success is defined as improvement of at least 2 grades from baseline. The registry identifies the analysis population as ITT, and the outcome is expressed as a percentage of participants.

This endpoint reduces an ordinal assessment to a binary outcome: a participant either meets the improvement threshold or does not. That makes the result interpretable as the frequency of participants reaching a specified level of change, rather than as an average score change. The threshold is part of the outcome definition; it does not describe every possible change in IGA or the magnitude of improvement among participants who meet it.

General statistical note: dichotomizing an ordered measure can make a chosen threshold easy to communicate, but it discards distinctions within each category. Participants with different changes can be counted together if they fall on the same side of the threshold. The threshold-based result therefore answers a narrower question than a full analysis of the underlying scale would answer.

The registry record does not report the IGA category definitions, the baseline distribution of scores, or how missing endpoint assessments were handled. Those details matter for understanding how the binary outcome was constructed and which participants contributed to the analysis.

7. Results Posted in the Registry

• Visonac Cream With PDT: 9.3% (5/54) versus 1.9% (1/53) on control; risk difference 7.4 percentage points (95% CI -1.2 to 15.9), risk ratio 4.91 (0.59–40.61); unadjusted two-proportion z-test p = 0.097.

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.

Percent Change From Baseline in Facial Inflammatory (Nodules, Papules, and Pustules)Lesion Count

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Visonac Cream With PDT: mean -35.40 versus -20.30 on control; difference -15.10 (95% CI -28.38 to -1.82), standardized effect d = -0.43; z-test p = 0.026.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Visonac Cream With PDT than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Percent Change From Baseline in Facial Non Inflammatory Lesion Count

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Visonac Cream With PDT: mean -25.30 versus -15.80 on control; difference -9.50 (95% CI -26.03 to 7.03), standardized effect d = -0.22; z-test p = 0.260.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Visonac Cream With PDT and the control. The interval gives the range of effects that remain compatible with the data.

Percent Change From Baseline in Facial Total Lesion Count

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Visonac Cream With PDT: mean -29.50 versus -18.00 on control; difference -11.50 (95% CI -23.72 to 0.72), standardized effect d = -0.36; z-test p = 0.065.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Visonac Cream With PDT and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary outcomes cover inflammatory, non-inflammatory, and total facial lesion counts, along with threshold-based outcomes involving lesion reductions. For the continuous outcomes at the stated six-week follow-up, the arm means indicate reductions from baseline in both groups, and the Visonac group’s mean changes are more negative than the vehicle group’s for the three listed lesion-count measures. The estimated between-group differences are not equally precise across outcomes: one posted unadjusted interval excludes zero, while the other two include zero.

This overall pattern is compatible with differences in the direction of the primary result, but the secondary outcomes measure different things and are assessed at a different time. The primary outcome is a threshold-based IGA success proportion at 12 weeks; the posted continuous secondary outcomes are mean changes in lesion counts at six weeks. Their estimates cannot be treated as direct confirmation or contradiction of the primary endpoint.

The registry record lists 23 secondary outcome measures as posted and describes 26 outcome measures overall. It does not report a multiplicity adjustment or a prespecified hierarchy for interpreting the secondary analyses. General statistical note: examining many outcomes increases the chance that some results will appear notable by chance, even when no underlying differences exist. Unadjusted secondary p-values therefore carry less weight than a primary analysis specified in advance, particularly when the analysis plan and outcome hierarchy are not available in the registry record.

The secondary results are best treated as additional descriptive evidence rather than a set of independent confirmations. The record does not report enough information to assess whether all planned secondary outcomes are represented, how missing observations were handled for each measure, or whether the displayed analyses were prespecified.

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

• Percent Change From Baseline in Facial Inflammatory (Nodules, Papules, and Pustules)Lesion Count
• Percent Change From Baseline in Facial Inflammatory (Nodules, Papules, and Pustules)Lesion Count
• Percent Change From Baseline in Facial Non Inflammatory Lesion Count
• Percent Change From Baseline in Facial Non Inflammatory Lesion Count
• Percent Change From Baseline in Facial Total Lesion Count
• Percent Change From Baseline in Facial Total Lesion Count
• Proportion of Patients With a Reduction of at Least 50% From Baseline in Facial Non-inflammatory Lesion Count
• Proportion of Patients With a Reduction of at Least 50% From Baseline in Facial Inflammatory Lesion Count From Baseline

9. Statistical Interpretation

10. Statistical Methods Explained

What does the primary outcome count?

The primary outcome is binary: success means an improvement of at least 2 grades from baseline on the dichotomized IGA scale at the stated facial assessment time. The arm-level percentages are the observed proportions of participants meeting this definition. General statistical note: a binary outcome can be compared using several measures, including a difference in proportions and an odds ratio. These measures use the same outcome counts but express the contrast on different scales, so their numerical values are not interchangeable.

What is the reported comparison?

The registry reports a Cochran-Mantel-Haenszel analysis with an odds ratio of 6.43, a 95% confidence interval from 0.65 to 63.18, and p = 0.070. The record’s official title describes the trial as stratified, but the registry does not report the strata or enough detail to reconstruct the analysis. General statistical note: the Cochran-Mantel-Haenszel method can combine evidence across strata while accounting for the stratification in the comparison. The result should be interpreted as the analysis reported in the record, not as an unstratified odds ratio reconstructed from the overall counts.

The posted results also permit a simple unadjusted recalculation of the risk difference. That estimate is 0.074, with a 95% confidence interval from -0.012 to 0.159 and p = 0.097. It compares the overall observed proportions without the reported stratified method. Because the estimand and method differ, the unadjusted recalculation and sponsor-reported odds ratio answer related but not identical statistical questions.

How should the p-values be read?

General statistical note: a p-value measures how unusual data at least as incompatible with a specified null model would be, if that model and the analysis assumptions were correct. It is not the probability that the null hypothesis is true, nor does it measure the probability that the result will replicate. A p-value also does not describe the size or practical importance of a difference. The registry reports p-values for the primary comparison and lists no trial-specific decision threshold or multiplicity procedure in the posted record.

The p-value for the sponsor-reported analysis and the one for the unadjusted recalculation differ because the analyses use different effect measures and methods. Neither should be considered in isolation from the confidence interval and observed event proportions. General statistical note: confidence intervals communicate a range of estimates compatible with the data and model at the stated confidence level; they are not guarantees that the true effect lies within the particular interval.

What do the secondary continuous outcomes measure?

The posted secondary outcomes include mean percent change from baseline in inflammatory, non-inflammatory, and total facial lesion counts at the stated follow-up. The registry gives a mean and standard deviation for each arm. The listed recalculations compare arm means using an unadjusted mean difference and give confidence intervals and unadjusted p-values. General statistical note: the standard deviation describes variability among individual observations, whereas the standard error describes uncertainty in an estimated mean. A mean difference is expressed in the outcome’s units; it is not a percentage of participants meeting a threshold.

The registry does not report adjusted models for these secondary outcomes. The posted recalculations are simple comparisons based on summary statistics and should not be mistaken for a full reconstruction of the trial’s analysis plan. Details such as covariate adjustment, transformations, and missing-data methods are not reported in the registry record.

Why does over-dispersion matter in general?

General statistical note: over-dispersion occurs when the variability in count or binary data is greater than a statistical model assumes. If a model understates variability, its standard errors can be too small and its confidence intervals too narrow. The registry does not report an over-dispersion assessment or a model for the primary binary outcome, so no conclusion about over-dispersion in this trial can be drawn from the posted record.

What can be reconstructed?

The simple recalculations use posted arm summaries and are explicitly unadjusted. They are useful for understanding the observed contrast on common scales, but they do not reveal unreported design or analysis choices. The registry record does not report the original statistical plan, interim analyses, exact stratification factors, missing-data procedures, or the rationale for the selected analysis methods. General statistical note: statistical methods are most informative when their assumptions, target population, and handling of incomplete observations are specified alongside the estimates.

11. Confidence Intervals and Precision

The primary arm-level estimates are 9.26% and 1.89%. Their posted 95% confidence intervals extend from 1.53 to 16.99 for the Visonac group and from 0.0 to 5.55 for the vehicle group. These intervals show that the observed percentages are estimated with limited precision; the small number of successes leaves room for a wide range of plausible underlying proportions.

The sponsor-reported odds ratio is 6.43, with a 95% confidence interval from 0.65 to 63.18. The interval is broad and includes values on either side of 1. That width signals that the odds contrast is not estimated precisely. The simple unadjusted risk-difference recalculation is 0.074, with a 95% confidence interval from -0.012 to 0.159. This interval includes zero and spans both negative and positive differences, illustrating uncertainty on the difference scale.

General statistical note: a confidence interval reflects both the observed data and the assumptions of the method used to construct it. A broad interval means the estimate is compatible with a wider range of values; it does not mean that all values in the interval are equally likely. Overlap between arm-specific intervals is not a substitute for a direct interval for the treatment contrast. The direct comparison and its own uncertainty are the more relevant quantities for evaluating the contrast.

The trial enrolled 107 participants, with 54 and 53 listed in the primary arms. In this setting, the limited number of participants and threshold successes contributes to uncertainty. The registry record does not report whether the confidence intervals account for all design features, including any stratification, beyond the named reported analysis. Precision should therefore be considered together with the method and the incompletely reported analysis details.

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 this trial’s binary and continuous outcomes; they are not total event counts. Total-event figures apply to time-to-event planning, and these posted outcomes are not time-to-event outcomes. The planning illustration uses a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. It considers the stated fractions of the observed effect: 100%, 75%, and 50% of the observed effect. The trial’s own original design assumptions and sample-size justification are not reported in the registry record.

The 80% power column gives the estimated number of participants per arm under the planning assumptions for a design with an 80% chance of detecting the specified effect if that effect is the true one and the assumptions hold. The 90% power column gives the corresponding planning number for a design with a 90% chance under those assumptions. These are planning quantities, not guarantees of a result and not evidence about the probability that a treatment effect exists.

Smaller effects require more participants to detect under otherwise similar assumptions, which is why planning for 75% or 50% of an observed effect produces larger per-arm figures than planning for the full observed effect. Observed effects can be unstable, especially in a small study, so these illustrations should not be treated as definitive targets for a future study. This is not observed power: the calculations are prospective planning illustrations based on the observed effect and stated assumptions, not a measure of the probability that the completed trial detected an effect.

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 = 0.019; treatment proportion p₁ = 0.093; average p̄ = 0.056.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.3244 = 0.6359.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.3202 = 0.2695.
4. n = (0.6359 + 0.2695)² / (0.0737)² = 150.8, rounded up to 151 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 <- 0.0188679245283019                          # control proportion
p1 <- 0.0925925925925926                          # 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(933543)
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 = 151 (80% power), 202 (90% power)
 75% of observed effect: n per arm = 227 (80% power), 303 (90% power)
 50% of observed effect: n per arm = 414 (80% power), 554 (90% power)
power.prop.test: 150.8 
Simulated power at n = 151 per arm: 0.839 (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. Analyses Reported by the Sponsor

The registry reports the sponsor’s primary comparison as a Cochran-Mantel-Haenszel odds ratio of 6.43, with a 95% confidence interval from 0.65 to 63.18 and p = 0.070. This is the trial’s posted analysis. It is distinct from the simple recalculation based on the overall counts, which estimates an unadjusted risk difference of 0.074, with a 95% confidence interval from -0.012 to 0.159 and p = 0.097.

The two analyses use different effect measures: an odds ratio in the reported analysis and a risk difference in the recalculation. The reported method is also stratified, while the recalculation is unadjusted. Their numerical estimates and p-values therefore should not be compared as though they were alternate calculations of exactly the same quantity using the same method.

The registry record does not describe the strata, the full analysis plan, or other details needed to independently reproduce the reported method. The recalculation is a transparent summary-statistic comparison, not a correction to the sponsor’s analysis. The reported interval is wide, so the sponsor’s estimate is imprecise; the unadjusted result likewise has uncertainty spanning zero. Because the record does not flag a discrepancy between the posted analysis and the recalculation, neither estimate is presented as superseding the other. The reported analysis remains the trial’s own analysis, while the recalculation offers a separate view on the risk-difference scale.

15. Multiplicity, Missing Data and Analysis Populations

The registry record identifies a primary endpoint and lists numerous secondary outcomes, but it does not report how multiplicity was handled. In particular, the record does not state whether the sponsor adjusted significance thresholds or confidence intervals for multiple outcomes, whether a hierarchy governed testing, or whether some secondary analyses were exploratory. Without those details, the secondary p-values should be read as unadjusted evidence and not as a family of results with a known overall error rate.

The primary outcome is identified as an ITT analysis, but the registry record does not explain how the analysis population was operationalized. It does not report the number of participants with missing primary assessments, how missing outcomes were classified or imputed, or whether all randomized participants were included in the analysis. The registry’s arm sizes and outcome-specific analysis sizes may differ for some secondary measures, but the reasons for those differences are not reported.

The record does not report the original statistical analysis plan, protocol deviations, interim analyses, stopping rules, or the trial’s planned sample-size justification. It also does not provide details about stratification factors or how the reported Cochran-Mantel-Haenszel analysis used them. These absences limit assessment of whether the posted analyses follow the original plan and how robust they are to alternative analytic choices.

General statistical note: multiplicity and missing-data procedures can affect uncertainty and interpretation. Multiple tests can increase the chance of chance findings, while the handling of missing observations can affect the analyzed population and estimate. These are not reasons to presume bias in the posted results; they are areas where the registry record does not supply enough detail to assess the analysis fully.

16. 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 2.8% reporting threshold.

Most frequent non-serious adverse event terms

The posted adverse-event figures list zero serious adverse events among 54 participants in the Visonac cream with PDT group and zero among 53 participants in the vehicle cream with PDT group. No serious adverse-event terms are listed. These are counts in the registry record for the groups and participants at risk; they do not establish that serious events could not occur.

Other adverse events are listed for 46 of 54 participants in the Visonac group and 32 of 53 participants in the vehicle group. These counts do not, by themselves, describe severity, timing, duration, relatedness to treatment, or whether participants experienced more than one event. The registry record does not report those details in the posted safety summary.

Deaths are not reported in the registry record. The observed safety counts should be read as descriptive information from this trial, not as a complete characterization of risk or a comparison adjusted for differences in follow-up. The registry record does not provide further detail about safety definitions, ascertainment procedures, or the duration of safety follow-up.

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

The primary result describes the observed proportion of participants who met a defined IGA improvement threshold 12 weeks after the first treatment. The Visonac arm had a higher observed success proportion than the vehicle arm, but the estimated contrast is imprecise. The reported odds-ratio interval is wide and includes 1, and the unadjusted risk-difference interval includes zero. These uncertainty measures indicate that the posted data do not tightly determine the size of the difference.

The result does not establish what would happen in every patient with acne vulgaris, nor does it give a complete account of changes in lesion counts, longer-term outcomes, or safety. It concerns a specific phase 2 trial, a specific treatment comparison in which both groups received PDT, and a particular binary endpoint at a stated follow-up. The registry record describes patients from 9 to 35 years old, but detailed eligibility and baseline characteristics are not reported.

General statistical note: statistical evidence and clinical importance are different questions. A point estimate describes the observed contrast, while its uncertainty describes the range of values compatible with the data and method. Judging importance also depends on the outcome, threshold, population, and context, which are not fully characterized by a p-value or odds ratio.

The posted results do not show whether the outcome definitions, analyses, and missing-data procedures followed the original plan, because the protocol and full statistical plan are not reported in the registry record. Nor do these results determine whether a similar estimate would be seen in another population or setting. They are one trial’s reported findings, with limited precision and incomplete methodological detail.

18. Why This Trial Matters Statistically

This trial is statistically instructive because it illustrates how the same binary outcome can be reported using different effect measures. The sponsor’s reported analysis is a stratified odds ratio, while a simple recalculation from the posted event counts gives a risk difference. Both describe a contrast between the randomized groups, but they answer the comparison on different scales and use different methods. Clear labeling of the estimand and analysis method is essential for meaningful interpretation.

The primary endpoint also shows why point estimates should be read with their confidence intervals. The observed success proportions differ, but the comparison is uncertain: the reported odds-ratio interval is broad, and the unadjusted risk-difference interval spans zero. A single estimate cannot convey that lack of precision. The outcome is based on a threshold, so it also highlights how a binary definition can simplify communication while concealing variation within the underlying assessment.

Finally, the record illustrates the importance of reporting methods alongside outcomes. Information about stratification, multiplicity, missing data, and the original sample-size justification is not reported in the registry record. Without those details, readers can describe the posted estimates but have limited ability to evaluate the full analysis plan or the relationship between planned and reported analyses. These statistical considerations are relevant when interpreting both the primary result and the collection of secondary findings.

19. 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.
• Participant counts were reconstructed from posted percentages and arm sizes, so small rounding differences are possible.

The primary comparison is based on 107 enrolled participants, and the posted arm sizes are 54 and 53. The number of primary successes is small, which contributes to the wide confidence interval for the reported odds ratio. The estimates therefore leave substantial uncertainty about the underlying contrast.

The registry record does not report the detailed eligibility criteria, participant baseline characteristics, study locations, or the specific stratification factors. Although the official title describes the trial as stratified and multicenter, those details are not available in the posted record. The record also does not explain the difference between the title’s double-blinded wording and its quadruple masking classification.

The registry does not report the full protocol, original statistical analysis plan, sample-size justification, interim analyses, missing-data methods, or multiplicity strategy. These omissions limit assessment of the prespecification of analyses and the handling of incomplete observations. The primary population is labeled ITT, but the record does not define how that population was formed or describe which participants were excluded from individual analyses.

The primary endpoint is a dichotomized IGA assessment at one follow-up point. The record does not provide the scale’s category definitions or the baseline score distribution. The secondary outcomes use different measures and follow-up timing, and the registry does not report enough information to establish their analysis hierarchy. The safety summary gives event counts but not event details, treatment relatedness, or duration of safety follow-up. These limitations concern what can be learned from the registry record; they do not establish that the unreported methods were inadequate.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Efficacy and Safety Study With Visonac Photodynamic Therapy (PDT) — NCT00933543.
• Registry record last updated 2013-12-11; status last verified 2013-11.
• Results first posted 2013-11-15.
• 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.

23. Record Summary

The registry record describes a completed phase 2 randomized, parallel-group, placebo-controlled study of Visonac cream with photodynamic therapy for acne vulgaris. It lists 107 participants and compares Visonac cream with vehicle cream, with PDT in both arms and a stated light dose of 37 J/cm2.

The primary outcome is the proportion meeting an improvement threshold of at least 2 grades on the dichotomized IGA scale 12 weeks after the first treatment. The posted arm proportions are 9.26% and 1.89%. The sponsor-reported Cochran-Mantel-Haenszel odds ratio is 6.43, with a 95% confidence interval from 0.65 to 63.18 and p = 0.070. A separate unadjusted recalculation gives a risk difference of 0.074, with a 95% confidence interval from -0.012 to 0.159 and p = 0.097.

The registry lists secondary lesion-count outcomes and adverse-event counts. Details about the original analysis plan, missing-data handling, multiplicity, and sample-size justification are not reported in the registry record.