DSAP Treatment Comparison: 2% Lovastatin/ 2% Cholesterol vs 2% Lovastatin Alone: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for DSAP Treatment Comparison: 2% Lovastatin/ 2% Cholesterol vs 2% Lovastatin Alone (NCT04359823), a randomized phase 1 study. The primary outcome is Measurement of Treatment Efficacy Determined by DSAP-GASI Score (Disseminated Actinic Porokeratosis General Assessment Severity Index).

2. Clinical Question

3. Trial Design

This was a Phase 1, randomized, single-blinded, parallel-group study. The registry lists an enrollment of 31 and identifies actinic porokeratosis as the condition. The sponsor was the Medical University of South Carolina. The study is recorded as completed, with a start date of 2020-08-24 and primary completion date of 2021-04-23.

The two groups received topical ointments containing 2% lovastatin, with cholesterol added in the combination group. Both arm descriptions specify application to lesions with occlusion twice daily for 12 weeks. The registry summary describes virtual follow-up and photographs to document progress. For the primary assessment, the record describes standardized patient-documented photographs, with repeat photography if image quality or standardization was inadequate. It says lesions were graded by 2 blinded physicians before and after treatment.

Random allocation and a parallel-group structure support a between-group treatment comparison in principle. Single blinding means the record reports some masking, but it does not identify who was blinded; that detail is not reported in the registry record. The method used to generate or conceal the allocation is also not reported in the registry record. The registry lists 31 enrolled, while primary outcome summaries are posted for 12 participants in each group. The record does not provide a complete account of participant flow or explain the difference between enrollment and the primary summaries.

The study includes a primary outcome and a set of secondary outcomes covering quality of life, lesion appearance, color and size, treatment-associated pain and itch, and application frequency in relation to severity assessment. The registry record does not report a sample-size justification, a statistical analysis plan, or a planned interim analysis. Those details should not be inferred from the posted results.

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: Treatment efficacy was based on investigator-standardized patient-documented photographs. Repeat photo documentation was obtained if image quality was inadequate or angle, lighting or location was not standardized to prior photos. Thirty-one subjects enrolled in the study, of which 24 provided clear pictures across all four visits (i.e. \~77%) and were considered in the efficacy analysis.

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 Measurement of Treatment Efficacy Determined by DSAP-GASI Score (Disseminated Actinic Porokeratosis General Assessment Severity Index), measured over 12 weeks.

The primary endpoint is recorded at 12 weeks and is labeled as the percent decrease in mean DSAP-GASI score. The registry describes DSAP-GASI as an exploratory clinical measure modified from a validated psoriasis index. It scores plaque/rim elevation, scaling, and color, using categories from 0= clear through 4=severe. The record says lesions were assessed before and after treatment by 2 blinded physicians.

A score based on lesion features is intended to summarize clinical appearance in a structured way rather than relying only on an unstructured impression. Comparing a participant's assessment before and after treatment can describe change over the treatment period. The registry also says that standardized patient-documented photographs informed the efficacy assessment and that repeat photographs were obtained if image quality or standardization was inadequate.

There is an important wording distinction in the record: the endpoint title and unit refer to a percent decrease in mean DSAP-GASI score, whereas the description calls the primary endpoint percentage of lesion clearance. The relationship between those labels is not explained further in the registry record. The posted group summaries are 50.0% and 51.4%, but a measure of spread, confidence interval, or direct test for the primary comparison is not reported. Therefore, the summaries describe the recorded endpoint but do not establish how precisely the groups differ.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods determine what a comparison estimates and how much uncertainty remains around it. For this study, the primary outcome is a continuous-style summary expressed as a percent decrease in mean DSAP-GASI score, while several posted secondary outcomes are participant counts for categorical changes. These outcome types require different summaries and inferential methods. The registry record does not report the sponsor's statistical analysis plan, so the methods below explain how to interpret the posted statistics rather than assert which procedures were planned or used.

What does a group summary tell us?

A group summary describes the recorded outcome for participants included in that group. The primary summaries are 50.0% and 51.4%, each based on 12 participants. A small numerical separation between group summaries does not, by itself, show whether the underlying treatment effects are similar or different. That assessment depends on variability, uncertainty, and a prespecified approach to comparison. No spread measure, confidence interval, or primary p-value is reported in the registry record.

A confidence interval expresses a range of values compatible with the data under a statistical model and quantifies uncertainty in an estimate. A narrow interval indicates greater precision than a wide interval. For the primary comparison, no interval is reported, so the precision cannot be assessed directly. It is not appropriate to create one from the posted summaries alone when the necessary information about variability and analysis is absent.

How should the binary comparisons be read?

For a binary outcome, a risk difference compares the proportion with the event in one group with the proportion in the other. A confidence interval around that difference reflects uncertainty in the estimate. When an interval includes zero, the data are compatible with no difference as well as with differences in either direction at the confidence level used. The posted secondary comparisons include risk differences and intervals. Their uncertainty is substantial, and the unadjusted p-values should not be read as a complete account of evidence, especially given the number of outcomes considered.

Risk ratios and odds ratios are other ways to express binary contrasts. They use different scales from risk differences, so their numerical values do not have the same interpretation. A ratio near the null value is compatible with little or no relative difference, while interval width indicates precision. The registry's recalculated secondary comparisons include ratio summaries, but these are simple unadjusted recalculations from posted counts, not sponsor-reported analyses. The registry record lists no sponsor-reported secondary analyses.

Why does the analysis population matter?

An analysis population specifies which randomized or enrolled participants contribute to each result and how missing outcomes are handled. This can affect interpretation because participants with available photographs or assessments may differ from those without them. The registry record lists 31 enrolled and reports primary summaries based on 12 participants in each group. It also begins to state that 24 provided clear, but the outcome description is incomplete. A full participant flow, analysis-population definition, and missing-data method are not reported in the registry record.

What do the sample-size illustrations mean?

The sample-size figures are planning illustrations computed from observed secondary effects. The record states assumptions of a two-sided significance level of 0.05, equal allocation, and a normal approximation, with calculations for specified fractions of the observed effect. Such calculations answer a hypothetical planning question: what group size would be indicated under those assumptions if a future study sought to detect an effect of that chosen size? They are not observed power, do not describe the achieved power of this study, and do not establish that the trial's own design was based on those calculations. The trial's sample-size justification is not reported in the registry record.

For count outcomes, over-dispersion is a general concern when variability exceeds what a simple count model assumes. If present, it can make standard errors too small and confidence intervals too narrow unless the analysis allows for the extra variability. This is a general statistical consideration, not a claim about this trial: the primary endpoint is a score-based percentage summary, and the registry record does not report a count-model analysis or an over-dispersion assessment.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists several secondary outcomes in addition to the primary endpoint. It does not report how many hypotheses were planned for formal testing, whether testing was hierarchical, or whether any correction for multiple comparisons was used. A multiplicity strategy matters because examining multiple outcomes can increase the chance of at least one apparently unusual result even when no true effect is present. The posted unadjusted secondary comparisons should therefore be treated as exploratory, not as definitive evidence.

Missing-data handling is also not reported in the registry record. The study enrolled 31, while the primary summaries are based on 12 participants in each group. The endpoint description begins to state that 24 provided clear, but it ends before specifying what was provided or completing the account. The record does not explain why primary summaries are available for those group sizes, whether participants without usable assessments were excluded, or whether any imputation or sensitivity analysis was used. No reason for missingness should be assumed.

The analysis population is not defined in the registry record. It is therefore unclear whether the primary results include all randomized participants, only participants with evaluable photographs, or another analysis set. The record also does not provide a full flow from enrollment to outcome assessment, or a description of adherence to the twice-daily application schedule. These omissions make it difficult to judge whether the posted summaries represent all enrolled participants or a subset with available assessments.

The record lists no sponsor-reported analyses. It does not report the statistical plan, a sample-size justification, or an interim analysis. The available information is sufficient to describe the posted outcomes and the recalculated comparisons, but not to reconstruct the complete planned analysis or determine how missing observations and multiple outcomes were handled.

11. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The serious adverse event figures report zero events in each group: the combination group lists 0 among 17 at risk, and the lovastatin-alone group lists 0 among 14 at risk. Both groups also list zero deaths. The registry record therefore reports no serious adverse events or deaths in these safety summaries.

For other adverse events, the combination group lists 3 among 17 at risk, while the lovastatin-alone group lists 0 among 14 at risk. These counts are descriptive. They do not, by themselves, establish a causal difference between treatments, and the registry record does not provide a statistical comparison or confidence interval for these figures.

Safety summaries need to be interpreted in light of the number of participants observed, the completeness of reporting, and the duration of follow-up. The registry describes a 12-week treatment period, but does not provide detailed event terms for the non-serious events in the posted summary. Zero reported serious events does not show that serious events are impossible, and the counts alone cannot characterize risks beyond the study's recorded follow-up and reporting.

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

The posted results describe a randomized comparison of two topical formulations: lovastatin with cholesterol and lovastatin alone. At 12 weeks, the primary summaries are 50.0% and 51.4%, respectively, each based on 12 participants. These values are close as descriptive summaries. However, the registry record does not report a direct primary comparison, confidence interval, or p-value, so the precision and statistical uncertainty of the contrast are not established.

The endpoint itself has a wording ambiguity. It is titled as a percent decrease in mean DSAP-GASI score, while its description refers to percentage of lesion clearance. The record describes a score of plaque/rim elevation, scaling, and color, with grades from clear to severe, but it does not explain how the two endpoint descriptions align. The exact interpretation of the reported percentages is therefore limited by the registry's description.

The secondary outcomes add descriptive information on symptoms and lesion-related assessments, but the posted secondary comparisons are unadjusted and some are imprecise. The registry record does not report a multiplicity plan, analysis populations, or missing-data methods. That leaves uncertainty about how to interpret the secondary findings and how representative the primary summaries are of all enrolled participants.

These results do not establish that either formulation is superior, equivalent, or ineffective. A close pair of group summaries is not proof of equivalence; such a conclusion would require an appropriate design and analysis with a prespecified equivalence margin, neither of which is reported in the registry record. Likewise, a lack of a reported primary p-value is not evidence that the treatments have no difference. The available record supports a cautious descriptive reading, not a definitive treatment conclusion.

13. Why This Trial Matters Statistically

This study illustrates why a numerical endpoint summary and an inferential comparison are not interchangeable. The primary group values, 50.0% and 51.4%, are easy to compare descriptively, but without a measure of variability or an uncertainty interval, the reader cannot tell how precisely they estimate the outcomes in the groups. A direct comparison estimate would also clarify the direction and scale of the contrast.

The trial also highlights the importance of a clear endpoint definition. A percent decrease in mean DSAP-GASI score and percentage of lesion clearance may not communicate the same measurement unless the relationship is specified. The record gives a structured description of the score and its grading, but does not reconcile the distinct wording. That kind of ambiguity affects interpretation before any statistical test is considered.

Finally, the difference between enrollment and the group sizes used for the primary summaries makes participant flow and missing-data reporting important. The record does not explain the analysis population or how incomplete assessments were handled. Secondary outcomes and planning illustrations can be informative, but they do not fill those gaps. The statistical lesson is that transparent reporting of estimands, analysis populations, uncertainty, and multiplicity is essential for readers to distinguish descriptive patterns from reliable comparative evidence.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

Several limitations are specific to the information recorded for this trial. First, the primary endpoint's description is not fully consistent: its title and unit refer to percent decrease in mean DSAP-GASI score, while the explanatory text calls it percentage of lesion clearance. The registry record does not state how those descriptions relate or give enough detail to reconstruct the calculation.

Second, the primary results are reported without a measure of spread or a confidence interval, and there is no primary comparison estimate or p-value. The group summaries therefore cannot be used to judge the precision of the treatment contrast. The registry also does not report the statistical analysis plan, the sample-size justification, or any interim analysis.

Third, participant flow and analysis populations are unclear. The record lists 31 enrolled and primary summaries for 12 participants per group, and its outcome description ends after beginning to state that 24 provided clear. It does not complete that account or report how incomplete photographs or outcomes were handled. Although the record describes repeat photographs when quality or standardization was inadequate, it does not say how many were repeated or how any remaining unusable assessments affected analysis.

Finally, the secondary outcomes are multiple and no multiplicity plan is reported. The recalculated comparisons are unadjusted, and their planning illustrations depend on observed effects rather than a reported prospective design justification. The single-blind label is given, but the identity of the blinded party is not. These limitations concern what the registry record reports; they do not establish that any unreported procedure was or was not performed.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: DSAP Treatment Comparison: 2% Lovastatin/ 2% Cholesterol vs 2% Lovastatin Alone — NCT04359823.
• Registry record last updated 2023-12-07; status last verified 2023-02.
• Results first posted 2023-12-07.
• 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.

18. Record Summary

NCT04359823 is a completed Phase 1 randomized, single-blinded, parallel-group study sponsored by the Medical University of South Carolina. It compared topical 2% lovastatin with topical 2% lovastatin plus 2% cholesterol for actinic porokeratosis. The registry lists enrollment of 31 and a treatment period of 12 weeks.

The primary outcome was described using DSAP-GASI, a score of plaque/rim elevation, scaling, and color. The posted percent-decrease summaries are 50.0% for the combination group and 51.4% for lovastatin alone, with 12 participants in each group. The registry record does not report a primary comparison estimate or uncertainty interval. It lists secondary outcomes concerning quality of life, lesion characteristics, pain, itch, and application frequency. Analysis populations, missing-data handling, multiplicity methods, and the statistical analysis plan are not reported in the registry record.