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 Scar Appearance After Postoperative Hydrocolloid Dressing Versus Standard Petrolatum Ointment (NCT05618912), a randomized na study. The primary outcome is Cosmetic Outcome.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05618912 |
| Phase | NA |
| Condition | Scar, Skin Scarring, Skin Cancer |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 146 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Indiana University |
| Results posted | Yes |
2. Clinical Question
Population
Patients having a sutured surgical wound. The registry lists scar and skin-wound conditions and reports enrollment of 146 participants. The primary-outcome description notes that the 7-day responses came from fewer participants than were originally assigned to each arm because some did not respond.
Intervention
A hydrocolloid dressing applied over the sutured wound and left in place for 7 days.
Comparator
Petrolatum jelly and bandaging, with the dressing re-applied daily during the same period.
Primary question
How did patients and surgeons assess cosmetic scar appearance at 7 days after surgery, using the modified visual analogue scar scale? Numerical primary-outcome results are not reported in the registry record.
The practical contrast is between a dressing intended to remain in place during the initial postoperative period and a petrolatum dressing that requires daily re-application. The registry describes randomized allocation and a double-masked, parallel design. It also says patients and dermatologic surgeons were to complete surveys at 7 days, 30 days, and 90 days after surgery. The listed primary endpoint is the 7-day cosmetic outcome; the record does not provide numerical findings for the later survey times.
This question concerns assessments of scar appearance, not a direct measure of wound healing or a comparison of long-term scar appearance. The registry lists complications as a secondary outcome, but does not report numerical results for that outcome in the information available. Accordingly, the posted record supports describing the trial question and planned comparison, but not determining which dressing produced higher cosmetic scores or whether any difference was precisely estimated.
3. Trial Design
The registry describes a randomized, double-masked, parallel-group controlled trial sponsored by Indiana University. The listed enrollment is 146, and the status is completed. The record gives a start date of 2022-10-17 and a primary completion date of 2023-10-16. These registry entries describe the trial’s administrative record; they do not establish how many participants contributed data to each outcome.
After the wound was closed with sutures, participants were assigned to hydrocolloid dressing or petrolatum jelly dressing. The hydrocolloid dressing was to remain in place for 7 days. In the comparator arm, petrolatum jelly and bandaging were to be re-applied daily during this period. Patients and dermatologic surgeons were described as completing surveys at 7 days, 30 days, and 90 days after surgery. The record labels the study double-masked but does not explain which people were masked or how masking was maintained with the two visibly different dressing routines.
The primary outcome is a mean cosmetic-outcome score at 7 days, assessed by patients and surgeons with a modified visual analogue scar scale. The scale ranges from 1, described as the worst possible scar appearance, to 10, described as the best possible scar appearance. The record also lists number of participants with complications as a secondary outcome. It identifies 4 outcome measures, but does not report the numerical primary results or the methods used to combine, compare, or analyze assessments. It lists 0 analyses. Details such as the allocation procedure beyond use of a randomization generator, the sample-size justification, and the full statistical plan 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.
Overall Study
| Stage | Hydrocolloid Dressing Arm | Petrolatum Jelly Dressing Arm |
|---|---|---|
| STARTED | 72 | 74 |
| COMPLETED | 58 | 55 |
| NOT COMPLETED | 14 | 19 |
Reasons for not completing this period:
| Reason | Hydrocolloid Dressing Arm | Petrolatum Jelly Dressing Arm |
|---|---|---|
| Lost to Follow-up | 14 | 19 |
Analysis population for the primary outcome, as defined in the registry: The above numbers reflect the number of patients who responded at 7-day postoperative followup and is smaller than the original number of participants in each arm due to lack of response by some participants
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 | Hydrocolloid Dressing Arm | Petrolatum Jelly Dressing Arm | Total |
|---|---|---|---|---|
| Participants analysed | 72 | 74 | 146 | |
| Age, Continuous | years | 63.8 (SD 11.5) | 61.3 (SD 13.5) | 61.9 (SD 12.9) |
| Sex: Female, Male: Female | Participants | 40 | 45 | 85 |
| Sex: Female, Male: Male | Participants | 32 | 29 | 61 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): White | Participants | 72 | 73 | 145 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 1 | 1 |
6. Primary Endpoint
The registry lists the primary outcome as Cosmetic Outcome, measured over 7 days.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Error |
| Unit | score on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is cosmetic outcome at 7 days after surgery. It uses a modified visual analogue scar scale, with scores ranging from 1 for the worst possible scar appearance to 10 for the best possible scar appearance. The registry describes the measure as a score and specifies that the reported summary is a mean with standard error. Patients and surgeons assessed cosmetic appearance; the record does not give separate numerical results for each assessor or explain whether their assessments were combined.
A mean provides a summary of the scores in a group, while the standard error describes uncertainty around an estimated mean. Neither summary, on its own, gives the full distribution of scores or shows how much individual assessments varied. To judge a contrast between dressings, readers would need the group results and a clearly defined between-group estimate, preferably with an interval expressing its precision. Those numerical primary-outcome results are not reported in the registry record.
Cosmetic assessment is relevant to the stated question because the trial compares dressing strategies with scar appearance as its primary outcome. The 7-day time point captures an early postoperative assessment. It should not be treated as evidence about later scar appearance: although surveys at 30 days and 90 days are described, numerical results at those times are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a randomized comparison and describes the cosmetic outcome the trial intended to assess. However, the available record does not report the group means, standard errors, or a between-group estimate for the primary outcome. It therefore does not establish the direction or magnitude of the observed cosmetic-score contrast at 7 days. It also gives no confidence interval or p-value for that contrast. Without these results, neither the precision of the comparison nor whether the observed data are compatible with a range of potentially relevant effects can be assessed.
The outcome description says that the 7-day responses came from fewer participants than were originally in each arm because some participants did not respond. The record does not give the number responding in either arm. This matters because missing responses reduce the information available and can affect interpretation if people who respond differ from people who do not. The registry does not report an analysis of missingness or describe how absent scores were handled.
Enrollment is listed as 146. For the safety information, the registry lists 72 participants at risk in the hydrocolloid arm and 74 in the petrolatum arm. Those safety counts should not be mistaken for the number contributing primary-outcome responses: the primary-outcome description explicitly says response counts were smaller than the original number in each arm, and does not provide the arm-specific response totals.
The registry lists 4 outcome measures and 0 analyses. It does not report whether the primary comparison used an unadjusted or adjusted model, how patient and surgeon assessments were handled, or whether any analysis accounted for the parallel randomized design beyond comparing the assigned arms. No multiplicity strategy is reported. The absence of a reported analysis means that a formal statistical conclusion about the primary contrast cannot be drawn from the registry record.
Overall, the record supports a description of the trial’s design, intervention routines, endpoint, and some safety counts. It does not supply the numerical outcome evidence needed to quantify the cosmetic comparison. The appropriate reading is therefore limited: the trial asked a specific randomized question, but the posted registry information does not show what the measured scores were or how uncertain any difference may have been. This is not evidence that the arms had identical results; it is an absence of reported primary-outcome results in the registry record.
9. Statistical Methods Explained
The registry describes a randomized, double-masked, parallel-group study. In a randomized trial, assignment is intended to make the groups comparable on average at the outset, including with respect to characteristics that were not measured. Randomization does not guarantee that groups will be identical, particularly in a trial of finite size, and it does not by itself address missing outcome data or measurement limitations. The registry says a randomization generator was used, but the sequence-generation details and allocation-concealment procedures are not reported in the registry record.
What does a mean score summarize?
The primary outcome is described as a mean score on a scale from 1 to 10. A mean summarizes the group’s scores in a single value, which can make the average assessment easier to compare across arms. But the mean does not show whether scores were tightly clustered or widely spread, whether the distribution was uneven, or whether a small number of scores strongly influenced the average. The registry does not provide the individual-level data or a distributional summary needed to inspect those features.
The record identifies standard error as the dispersion measure accompanying the mean. Standard error describes the sampling uncertainty of an estimated mean; it is not the same as the spread of individual scores. A confidence interval uses an estimate and its uncertainty to show a range of values reasonably compatible with the data under the analysis assumptions. No confidence interval for the primary outcome is reported in the registry record. A standard error for each arm, even if available, would not by itself describe the uncertainty in the between-arm contrast unless the comparison and its uncertainty were also reported.
Why is the between-arm estimate important?
For a randomized comparison, the central quantity is typically the estimated difference between the groups on the primary outcome, together with an interval expressing its precision. Group means can help readers understand the observed scores, but the contrast directly addresses how the groups differed. A p-value, when reported, addresses compatibility with a specified null hypothesis under a statistical model; it does not state the size or clinical importance of an effect. The registry record reports no numerical group means, between-arm estimate, confidence interval, or p-value for the primary endpoint. As a result, none of these features can be interpreted for this trial from the posted registry information.
How should missing responses be considered?
The primary-outcome description says that the number responding at 7 days was smaller than the original number in each arm because of nonresponse. In general, missing outcome data matter because the observed respondents may not represent all randomized participants. If response is related to scar appearance, treatment assignment, or other factors, an analysis limited to respondents may not estimate the same contrast as an analysis of all assigned participants. This is a general statistical concern, not a claim about why participants in this trial did not respond. The reasons for nonresponse, response counts by arm, assumptions about missingness, and any methods for handling missing scores are not reported in the registry record.
What does over-dispersion mean in general?
Over-dispersion is a general issue for outcomes whose observed variability is greater than a statistical model expects. When a model assumes less variability than the data contain, standard errors can be too small and intervals too narrow, making results appear more precise than they are. The relevance of over-dispersion depends on the outcome and model. The primary endpoint is described as a mean score, but the registry does not identify the model used to analyze it or report diagnostics. It would therefore be inappropriate to assert that over-dispersion occurred or that a particular correction was required.
What can be said about sample-size planning?
The registry record does not report the trial’s sample-size justification or a target effect used in its design. A planning illustration based on an observed effect, when available, is not the same as the trial’s original design justification and does not measure the probability that this completed trial detected an effect. Sample-size calculations are planning exercises that depend on assumptions about the effect, variability, significance level, allocation, and analysis. The record describes an illustrative approach using a two-sided significance level of 0.05, equal allocation, and a normal approximation, but does not report numerical planning results in the available information. Any such illustration should be read as a hypothetical planning aid, not as observed power or evidence that the trial was adequately or inadequately sized.
What remains unknown about the analysis?
The record lists 0 analyses. It does not specify the exact analysis population, whether participants were analyzed according to randomized assignment, how assessments from patients and surgeons were treated, or whether covariates were included. It also does not describe a model for the repeated survey time points. These details are important because analytic choices affect the estimate and its uncertainty. In their absence, the registry’s design and endpoint descriptions can be explained, but the analysis cannot be reconstructed or independently evaluated from the posted information.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 4 outcome measures, describes surveys at 7 days, 30 days, and 90 days, and names complications as a secondary outcome. It identifies the 7-day cosmetic score as the primary endpoint. Considering several outcomes, time points, or assessors can raise multiplicity concerns: the more comparisons examined, the greater the chance that at least one result appears statistically unusual even when there is no underlying effect. This is a general statistical issue, not evidence that a particular adjustment was or was not used in this trial.
The registry record does not report a multiplicity strategy, a hierarchy for secondary outcomes, or which comparisons were prespecified for formal testing. It also does not report numerical results for the later cosmetic assessments or the complications outcome. The number of listed outcomes alone cannot establish how many statistical tests were conducted; the record lists 0 analyses.
Missing data are also relevant to interpretation. The primary-outcome description states that the 7-day response count was smaller than the original number in each arm because some participants did not respond. The arm-specific response counts, reasons for nonresponse, and method for handling missing scores are not reported in the registry record. Without those details, it is not possible to assess whether the reported respondents were representative of the randomized groups or how missingness may have affected the estimates.
The registry does not report the analysis population or whether the analysis followed randomized assignment. It also does not state how patient and surgeon assessments were combined or analyzed separately. These omissions limit assessment of both the primary comparison and the role of additional outcomes. They do not prove that the trial lacked a prespecified plan; they mean that the relevant plan and analysis details are not reported in the registry record.
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 |
|---|---|---|---|
| Hydrocolloid Dressing Arm | 0 | 72 | 0.0% |
| Petrolatum Jelly Dressing Arm | 0 | 74 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Hydrocolloid Dressing Arm | 0 of 72 |
| Petrolatum Jelly Dressing Arm | 0 of 74 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Hydrocolloid Dressing Arm | 60 of 72 |
| Petrolatum Jelly Dressing Arm | 40 of 74 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Hydrocolloid Dressing Arm | Petrolatum Jelly Dressing Arm |
|---|---|---|---|
| Itching | Skin and subcutaneous tissue disorders | 29 of 72 | 28 of 74 |
| Surgical site pain | Skin and subcutaneous tissue disorders | 14 of 72 | 7 of 74 |
| Post-op bleeding | Skin and subcutaneous tissue disorders | 13 of 72 | 5 of 74 |
| Wound dehiscence | Skin and subcutaneous tissue disorders | 4 of 72 | 0 of 74 |
| Required antibiotics | Skin and subcutaneous tissue disorders | 0 of 72 | 0 of 74 |
The registry lists 72 participants at risk in the hydrocolloid dressing arm and 74 in the petrolatum jelly dressing arm for the adverse-event summary. It reports 0 serious adverse events in each arm and 0 deaths in each arm. It also lists 60 participants with other adverse events in the hydrocolloid arm and 40 in the petrolatum arm.
These figures describe the registry’s reported counts; they do not by themselves show the kinds, severity, timing, or duration of the other adverse events. The record does not provide those details in the information available. Nor does it report an adjusted comparison or uncertainty interval for the safety counts. A zero count of serious adverse events in the registry is not proof that the risk is absent; it means that none were recorded in the listed groups during the reported accounting. The figures should not be used to infer a treatment effect on safety without fuller event definitions, follow-up information, and an appropriate comparison.
The safety denominators also should not be assumed to be the primary-outcome response counts. The primary endpoint description separately states that some participants did not respond at 7 days and that the response population was smaller than the original number in each arm. The arm-specific number contributing cosmetic scores is not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The trial addresses a clear comparison: a hydrocolloid dressing left in place for 7 days versus daily petrolatum jelly dressing after a sutured wound. The registry describes randomization, a double-masked parallel design, and a primary assessment of cosmetic appearance at 7 days. It also records follow-up surveys at 30 days and 90 days. These details define the research question and the intended timing of assessments.
They do not establish the observed cosmetic outcomes. The numerical scores for the primary endpoint, their standard errors, and a between-arm estimate are not reported in the registry record. Consequently, the record does not show which arm had a higher average score, the size of any contrast, or the precision of an estimate. It also does not report numerical results for the later cosmetic assessments. A missing result should not be read as proof of no difference, nor as proof of a difference.
The registry reports 0 serious adverse events and 0 deaths in each arm, alongside other adverse-event counts. Those counts are descriptive and do not, on their own, establish comparative safety. The record’s primary-outcome description also notes nonresponse at 7 days, but does not give arm-specific response totals or explain how missing scores were handled. These points limit interpretation of the outcomes and the completeness of the evidence available in the registry.
The status is completed and enrollment is listed as 146, but completion of a trial does not ensure that results are fully reported in a registry. The posted information allows readers to understand what was planned and to identify important reporting gaps. It does not support a conclusion about the comparative cosmetic effects of the dressing strategies, the precision of that comparison, or the results at later time points.
13. Why This Trial Matters Statistically
This trial is statistically interesting because it compares two distinct postoperative dressing routines while defining a patient- and surgeon-assessed cosmetic outcome. The randomized design is intended to support a fair comparison between assigned strategies. The endpoint is a scored assessment rather than a simple event count, so interpretation depends on the scale, the way assessments were summarized, and the uncertainty around the group contrast.
The registry also makes clear why enrollment alone is not enough to judge the evidence. Although enrollment is listed as 146, the primary-outcome description says that fewer participants responded at 7 days than were originally in each arm. Without the arm-specific response totals, the means, and the analysis details, readers cannot tell how much information contributed to the primary comparison or how precisely it was estimated.
Another statistical issue is the presence of several outcomes and survey time points. The record identifies 4 outcome measures and 0 analyses, but does not describe a multiplicity plan or the analysis of later assessments. A clear prespecified approach helps readers distinguish the primary question from additional exploratory comparisons. Its absence from the registry record limits the ability to assess how results would have been interpreted across outcomes.
Finally, the safety counts illustrate the distinction between a descriptive record and a comparative statistical conclusion. Counts of serious events and other adverse events are useful to report, but they require context about event definitions, follow-up, and uncertainty before they can support a comparative interpretation. The key statistical contribution of a complete record would be a transparent account of the primary estimate, its precision, missing responses, and analysis choices. Those results are not reported in the registry record.
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 main limitation for interpreting this trial from the registry record is that numerical results for the primary cosmetic outcome are not reported. There are no arm-specific means, standard errors, or between-arm estimate in the available information. Without those quantities, the observed contrast and its precision cannot be assessed. The record also does not give numerical results for the 30-day or 90-day cosmetic assessments.
The primary-outcome description acknowledges that some participants did not respond at 7 days and that the number responding was smaller than the original number in each arm. It does not report the number of respondents by arm, the reasons for nonresponse, or how missing scores were treated. This prevents assessment of the extent and possible consequences of missing outcome data.
The record describes the trial as double-masked, but does not say who was masked or how masking was maintained. Because the two dressing routines differ, those implementation details would help readers evaluate how assessments may have been influenced. The record also does not explain whether patient and surgeon scores were analyzed separately or combined.
Although the registry lists 4 outcome measures and a secondary complications outcome, it does not report the statistical analysis plan, multiplicity handling, analysis population, or numerical results for complications. It lists 0 analyses. The sample-size justification and the exact method used for the primary comparison are not reported in the registry record. These gaps restrict independent evaluation of the analysis and prevent a conclusion about the comparative cosmetic outcome based on the posted information.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Scar Appearance After Postoperative Hydrocolloid Dressing Versus Standard Petrolatum Ointment — NCT05618912.
- Registry record last updated 2024-12-11; status last verified 2024-12.
- Results first posted 2024-12-11.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
The registry record describes a completed randomized, double-masked, parallel-group trial sponsored by Indiana University, with enrollment of 146. Participants were assigned to hydrocolloid dressing left in place for 7 days or petrolatum jelly dressing re-applied daily after wound closure with sutures. Surveys by patients and dermatologic surgeons were described at 7 days, 30 days, and 90 days after surgery.
The primary outcome is a 7-day cosmetic score on a scale from 1, worst possible scar appearance, to 10, best possible scar appearance, summarized as a mean with standard error. The record notes that some participants did not respond at 7 days, but does not give response totals by arm. It lists 4 outcome measures and 0 analyses. Numerical primary and later cosmetic results, analysis details, and the trial’s sample-size justification are not reported in the registry record. Safety listings include 0 serious adverse events and 0 deaths in each arm.