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 Clinical Evaluation of the Photoallergy Potential of Xenaderm Ointment (NCT00645164), a na phase 1 study. The primary outcome is Frequency Distribution of Skin Irritation Scores.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00645164 |
| Phase | Phase 1 |
| Condition | Healthy |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | Quadruple |
| Enrollment | 59 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Healthpoint |
| Results posted | Yes |
2. Clinical Question
Population
Healthy participants were enrolled. The registry record reports enrollment of 59 and says the primary endpoint analysis was based on participants who completed the study. The number who completed it is not reported in the registry record.
Intervention
The product under evaluation was Xenaderm ointment. The registry record also lists an ointment vehicle. It describes participants as serving as their own control, but does not report the detailed sequence or procedures for product application and light exposure.
Comparator
This is a single-group study, and allocation is listed as not applicable. The registry record cautions that the arms are not a like-for-like control comparison. The record therefore does not establish a randomized comparison of Xenaderm with vehicle.
Primary question
The study assessed the frequency distribution of skin irritation scores 48-hours post irradiation. Scores ranged from 0, meaning no reaction, to 7, meaning a large vesiculo-bullous reaction. Photoallergic reactions were characterized by scores of 3 or higher. The score counts themselves are not reported in the registry record.
3. Trial Design
The registry record describes a phase 1, completed, single-group study sponsored by Healthpoint. It lists 59 participants, all described as healthy. The recorded study start was 2008-03, and primary completion was 2008-05. The study title and brief description identify its purpose as evaluating whether exposure to light causes photoallergic skin reactions associated with Xenaderm ointment.
The listed interventions are Xenaderm, classified as a drug, and ointment vehicle, classified as other. The arm description says that a subject serves as their own control. This indicates a within-participant control concept, but the registry record does not report enough procedural detail to establish how the comparison was carried out, including the application sequence or the timing of the different exposures.
Masking is listed as quadruple, while allocation is listed as not applicable. The record does not identify the masked roles or explain how masking was implemented. It also explicitly cautions that this was not a randomized comparison and that the arms are not a like-for-like control comparison. The masking designation should therefore not be mistaken for evidence of random allocation or for proof that all sources of bias were controlled.
The primary endpoint was a frequency distribution of irritation scores assessed 48-hours post irradiation. The endpoint description says the analysis population consisted of participants who completed the study. The number of completers, participant flow, and reasons for any non-completion are not reported in the registry record. Although the study is marked completed, that status alone does not provide the missing endpoint results or analysis details.
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 | Xenaderm |
|---|---|
| STARTED | 59 |
| COMPLETED | 52 |
| NOT COMPLETED | 7 |
Reasons for not completing this period:
| Reason | Xenaderm |
|---|---|
| Lost to Follow-up | 2 |
| Withdrawal by Subject | 4 |
| Protocol Violation | 1 |
Analysis population for the primary outcome, as defined in the registry: Analysis was based on number of subjects who completed the study.
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 | Xenaderm |
|---|---|---|
| Participants analysed | 59 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 59 |
| Age, Categorical: >=65 years | Participants | 0 |
| Age Continuous | years | 38.8 (SD 12.1) |
| Sex: Female, Male: Female | Participants | 37 |
| Sex: Female, Male: Male | Participants | 22 |
| Region of Enrollment: United States | participants | 59 |
6. Primary Endpoint
The registry lists the primary outcome as Frequency Distribution of Skin Irritation Scores, measured over 48-hours post irradiation.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | Scores on a scale |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the frequency distribution of skin irritation scores measured 48-hours post irradiation. The scale uses whole-number scores from 0, indicating no reaction, to 7, indicating a large vesiculo-bullous reaction. The registry record characterizes photoallergic reactions as irritation scores of 3 or higher.
A frequency distribution describes how many observations fall at each score. It can show whether scores cluster at the no-reaction end of the scale or occur at higher levels, and it preserves more detail than reporting only whether a threshold was crossed. A threshold can also be useful when the study question concerns the occurrence of reactions meeting a prespecified description. These are general reasons to report both score distributions and a clinically defined threshold; the record does not report a separate threshold-based analysis.
The analysis population is described as participants who completed the study, but the number of participants in that population and the counts at each score are not reported in the registry record. Consequently, the endpoint definition is available, but the observed distribution and the number of participants scoring 3 or higher cannot be assessed from the recorded results.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes what the primary endpoint was intended to measure, but it does not report the endpoint counts or any statistical analyses. It names the outcome as the frequency distribution of skin irritation scores at 48-hours post irradiation and defines the scale and the score threshold used to characterize photoallergic reactions. Without the numbers at the individual scores, the observed pattern of irritation cannot be described.
No estimate of the frequency of scores at or above 3 is reported. There is also no reported comparison estimate, confidence interval, hypothesis test, or p-value. The record lists zero analyses. It is therefore not possible to quantify the observed reaction frequency, describe the precision of an estimate, or assess statistical evidence for a difference between exposures from the registry record.
The design information also limits what a comparison could mean. The study is listed as single-group, with allocation not applicable, and the arm description says that a subject serves as their own control. At the same time, the record warns that this is not a randomized comparison and that the arms are not a like-for-like control comparison. A within-participant design can, in general, control for stable characteristics of an individual, but valid interpretation still depends on the actual procedures, exposure sequence, measurement conditions, and handling of the paired observations. Those details are not reported in the registry record. The listed design should not be read as proof that a causal contrast between Xenaderm and vehicle was established.
The enrollment count is 59, whereas the primary endpoint description refers to people who completed the study. The number who completed the study is not reported. Without that count, the relation between enrollment and the endpoint analysis population is unclear. The record also does not state how missing scores, incomplete exposures, or other departures from the intended assessment were handled.
For safety, the record lists zero serious adverse events among 59 participants at risk and 25 other adverse events. The number at risk for the latter category is not reported. These are separate registry entries and should not be combined into a single rate or used to infer that all other safety outcomes were absent. Overall, the posted record supports a description of the study question, design labels, and selected safety counts, but not a conclusion about the observed primary endpoint pattern or its precision.
9. Statistical Methods Explained
What kind of endpoint is this? The primary outcome is a count distribution across ordered irritation-score categories. Each participant’s score is an integer on a scale from 0 to 7, with higher categories representing more pronounced irritation according to the scale description. This is not a continuous measurement with arbitrary decimal precision, nor is the endpoint itself described as a single mean score. Reporting counts at each category would preserve the shape of the response pattern. The registry record gives the endpoint definition but no category counts.
Why does the full distribution matter?
General statistical explanation: An ordinal scale has a natural order, but the distance between neighboring categories is not necessarily equal in a biological or practical sense. A mean score can therefore hide important features, such as whether most observations are at the bottom of the scale while a small number are at higher scores. A category-by-category frequency distribution makes that pattern visible. A threshold summary can answer a more focused question about scores meeting a defined criterion, but it discards distinctions among scores on the same side of the threshold. The registry record defines scores of 3 or higher as characterizing photoallergic reactions, but does not report category counts or a threshold count.
What would a comparison require?
General statistical explanation: When the same participant contributes observations under more than one condition, those observations are paired rather than independent. A suitable analysis should account for that pairing; treating the observations as unrelated can misrepresent the variability in a contrast. The registry record says that a subject serves as their own control, but does not report the detailed exposure sequence, the specific paired-data method, or any analysis results. It also identifies the study as single-group and warns that the arms are not a like-for-like control comparison. The available labels are not enough to reconstruct an appropriate comparative analysis.
Masking is recorded as quadruple. In general, masking can reduce the influence of expectations on treatment administration, assessment, or reporting, depending on who is masked and how. The record does not identify the masked roles or describe procedures used to maintain masking. Masking and randomization are distinct design features: masking does not establish random allocation. Allocation is listed as not applicable, and the record states that the study was not a randomized comparison.
What does the analysis population mean?
The endpoint description says the analysis was based on participants who completed the study. In general, restricting an analysis to completers can make the analyzed group differ from the enrolled group if completion is related to the outcome or to study procedures. Understanding that possibility requires knowing how many participants completed the study, why anyone did not complete it, and how incomplete observations were handled. Those details are not reported in the registry record. The enrollment count of 59 should not be treated as the number analyzed for the primary endpoint without confirmation.
What precision or significance can be assessed?
General statistical explanation: A confidence interval expresses the uncertainty around an estimated quantity under a specified statistical model. A narrow interval generally indicates greater precision than a wide interval, while neither interval width nor a p-value alone establishes the practical importance of a result. For an outcome recorded in categories, precision could be described for category frequencies or for a clearly defined contrast, provided the counts and analysis method are available. No confidence interval, test result, p-value, or endpoint count is reported in the registry record. Statistical significance and precision therefore cannot be evaluated from these entries.
The record lists one outcome measure and zero analyses. A defined outcome measure does not itself show that a result was calculated, and the registry record does not provide an analysis plan or explain whether additional analyses were performed but not recorded. No adjustment for multiple testing, interim analysis, or prespecified statistical model is reported.
How should the planning illustrations be understood?
The stated planning illustration uses a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It describes the effect to detect as a stated fraction of the observed effect. For time-to-event tables, the stated quantity is total events; for other outcomes, it is participants per arm. These are assumptions for planning illustrations, not a description of the study’s own design or an observed power calculation. Equal allocation between two arms does not match the registry’s single-group design label, so the illustration should not be treated as a retrospective assessment of this study’s power. The trial’s own sample-size justification is not reported in the registry record.
There are no recalculated estimates reported for interpretation. In general, a recalculation from summary statistics can differ from a sponsor’s analysis if it uses a different model, population, or adjustment. No sponsor analysis is listed in this record, so there is no posted analysis estimate to compare with a recalculation.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists one primary outcome measure and zero analyses. It does not report a statistical analysis plan, a testing hierarchy, or any correction for multiple comparisons. The presence of one listed endpoint does not establish that only one analysis was planned or performed; details about additional outcomes or exploratory analyses are not reported in the registry record.
Multiplicity refers generally to the increased chance of a false-positive finding when multiple hypotheses are tested. Whether and how that issue applies depends on the number of analyses, their relationships, and which results are treated as confirmatory. Since no analysis results or multiplicity approach are reported, the record does not support an assessment of this issue for the study.
The primary endpoint population is described as participants who completed the study. The number of completers is not reported, and the record does not describe missing-data methods, exclusions, or reasons for non-completion. It also does not report an intention-to-treat analysis or another named analysis population. These omissions make it impossible to establish exactly how many participants contributed to the primary endpoint or whether incomplete observations could have influenced the recorded findings.
The record states that the study is completed, but completion status does not supply the missing analysis details. The protocol, sample-size justification, interim analyses, and statistical plan are not reported in the registry record. No assumptions about those procedures can be verified from the available entries.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Xenaderm | 0 | 59 | 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 |
|---|---|
| Xenaderm | 25 of n/a |
Most frequent non-serious adverse event terms
| Event term | Organ system | Xenaderm |
|---|---|---|
| Tape reaction | Skin and subcutaneous tissue disorders | 17 of 59 |
| Itching at test site | General disorders | 8 of 59 |
| Headache | Nervous system disorders | 6 of 59 |
| Burning at test site | General disorders | 3 of 59 |
| Fever | General disorders | 3 of 59 |
The registry record lists 59 participants at risk for serious adverse events and zero participants affected in that category. It separately lists 25 other adverse events, but does not report the number at risk for that category. The record does not provide event descriptions for the other adverse events, and no serious adverse event terms are listed.
These entries should be read as separate safety counts. The 25 other adverse events are not a count of serious adverse events, and the missing denominator means their frequency among participants at risk cannot be determined from the record. The record also does not report the number of deaths; an unreported entry should not be interpreted as a zero count.
In general, a safety count describes what was recorded for a specified category and population. It does not, by itself, establish causation or provide a complete account of all possible events. The registry entries do not provide enough detail to characterize the nature, timing, or relationship of the other adverse events to the study interventions.
12. What the Result Does, and Does Not, Mean
The record documents a study designed to evaluate skin irritation scores after light exposure in healthy participants, with Xenaderm and ointment vehicle listed as interventions. It defines the primary score scale and identifies scores of 3 or higher as characterizing photoallergic reactions. It also reports enrollment of 59 and selected adverse-event counts. These details clarify the study question and some design features.
However, the registry record does not report the primary outcome frequencies. It therefore does not show how many participants had each score, how many had scores of 3 or higher, or how the observed scores were distributed. Without those data, the endpoint cannot be summarized quantitatively, and no estimate of its precision can be assessed. No statistical analysis results are listed.
The study’s single-group designation, the description of participants serving as their own control, and the warning that the arms are not a like-for-like control comparison all matter when interpreting any potential contrast. The registry record does not describe enough of the procedures or analysis to establish a comparative effect. Quadruple masking does not change the fact that allocation is listed as not applicable and that the record explicitly says the comparison was not randomized.
More generally, the absence of a posted endpoint result is not evidence that no reactions occurred, nor is it evidence of a particular reaction frequency. Likewise, zero serious adverse events in the listed group is a specific registry count, not a complete assessment of every safety outcome. The other adverse-event denominator and the death count are not reported.
The defensible conclusion is limited: the registry record specifies the intended score-based assessment and reports selected design and safety information, but it does not provide the primary endpoint results needed to characterize the study’s observed irritation-score pattern.
13. Why This Trial Matters Statistically
This study illustrates why a clear endpoint definition and an available endpoint result are both needed for statistical interpretation. The registry record specifies an ordered score scale, its observation time, and a threshold used to characterize photoallergic reactions. Those details explain what the investigators intended to measure. Without the score frequencies, however, readers cannot tell what pattern was observed or how often scores met the stated threshold.
The record also highlights the distinction between masking and allocation. Quadruple masking is listed, but allocation is not applicable, and the record describes a single-group study rather than a randomized comparison. A within-participant control can be a useful design concept in general, but the details of its implementation and the analysis of paired observations matter. In this case, those details are not reported, and the record cautions against treating the arms as a like-for-like comparison.
Another statistical lesson concerns analysis populations. The endpoint is described as based on participants who completed the study, while the record reports enrollment of 59. Because the number of completers and the handling of missing observations are not reported, the analysis denominator cannot be verified. Clear reporting of participant flow and analysis populations is important for interpreting both event counts and their uncertainty.
Finally, planning assumptions should not be confused with the study’s own design or with evidence generated by the observed data. The record’s planning illustration uses assumptions that include equal allocation between two arms, whereas the study is described as single-group. Such illustrations do not substitute for a reported sample-size justification, analysis plan, or endpoint result. This case shows how registry design labels, outcome definitions, and analysis results serve different purposes and should be interpreted separately.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The primary limitation for statistical interpretation is that the score distribution is not reported. Although the registry record describes the scale and the 48-hours post irradiation assessment, it gives no counts by score and no count of participants meeting the score threshold of 3 or higher. No primary analysis results are listed.
The endpoint population is described as participants who completed the study, but the number of completers is not reported. The record does not give participant flow, reasons for non-completion, or methods for handling missing scores. Thus, the endpoint denominator and the potential effect of incomplete observations cannot be assessed.
The design description is also limited. The study is listed as single-group, allocation is not applicable, and participants are described as serving as their own control. The record explicitly warns that the arms are not a like-for-like control comparison. It does not report the procedures needed to understand the paired exposures, their sequence, or how a comparison was analyzed. Masking is listed as quadruple, but the masked roles and implementation are not described.
The registry record does not report a statistical analysis plan, sample-size justification, interim analyses, or multiplicity procedures. It lists one outcome measure and zero analyses, which does not resolve whether other analyses were planned or conducted. The planning illustration is not a substitute for the study’s own design justification, particularly because its stated equal-allocation assumption differs from the single-group design label.
Safety reporting is incomplete for interpretation: the denominator for the 25 other adverse events and the death count are not reported, and the other-event descriptions are absent. These limitations do not change the recorded counts, but they constrain what can be concluded from them.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Clinical Evaluation of the Photoallergy Potential of Xenaderm Ointment — NCT00645164.
- Registry record last updated 2010-06-08; status last verified 2010-06.
- Results first posted 2009-04-06.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
The registry record describes a completed phase 1, single-group study sponsored by Healthpoint, with 59 healthy participants enrolled. It lists Xenaderm and ointment vehicle, describes participants as serving as their own control, and records quadruple masking. Allocation is listed as not applicable, and the record cautions that the arms are not a like-for-like control comparison.
The primary endpoint was the frequency distribution of skin irritation scores 48-hours post irradiation, on a whole-number scale from 0 to 7. Scores of 3 or higher were characterized as photoallergic reactions. The endpoint analysis was described as based on participants who completed the study, but the number of completers and the score distribution are not reported in the registry record. Zero serious adverse events among 59 at risk and 25 other adverse events are listed; the latter denominator is not reported. No statistical analyses are listed.