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 Evaluation of Opticell Ag on Split-Thickness Skin Graft Donor Sites in Adult Subjects (NCT02642679), a na na study. The primary outcome is Pain.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02642679 |
| Phase | NA |
| Condition | Split-thickness Skin Graft Donor Sites |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 19 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Brigham and Women's Hospital |
| Results posted | Yes |
2. Clinical Question
Population
Adults with split-thickness skin graft donor sites. The registry record lists an enrollment of 19 participants.
Intervention
Opticell Ag, a chitosan-based dressing, covered with a transparent occlusive dressing and gauze pads. The dressing arrangement is described as allowing controlled leakage through perforations in the occlusive layer.
Comparator
There is no separate comparator group. The registry describes a single-group case series, with no randomized allocation.
Primary question
The primary outcome is pain measured using a visual analog scale during up to 14 days of dressing use. The registry record does not report numerical pain results or a comparison with another dressing or usual care.
The study was intended to evaluate management of split-thickness skin graft donor site wounds using Opticell Ag. Its primary question is descriptive: what pain measurements were recorded during the dressing-use period among the participants treated with this dressing? Pain was assessed at several points, including postoperative day 1, before a dressing change on days 5-7, and before and after dressing removal on days 10-14.
Because only one group is described, the record does not support a randomized, between-treatment comparison. The clinical question therefore differs from whether Opticell Ag performs better than another dressing. Nor does the registry record report numerical measurements that would allow the average pain level or its variation to be described. Wound Healing Quality is listed as a secondary outcome, but its numerical results are not reported in the registry record.
3. Trial Design
This was a prospective, single-center case series of adults with split-thickness skin graft donor sites. The registry lists Brigham and Women's Hospital as the sponsor, an enrollment of 19, and a completed study. The recorded start is 2016-01 and the primary completion is 2016-10. The phase is listed as NA.
The study has a single-group model and evaluates the device Opticell Ag. No allocation to different groups is listed, and masking is recorded as none. The intervention description specifies Opticell Ag covered by a transparent occlusive dressing (Tegaderm) with evenly distributed perforations, allowing controlled leakage into cotton gauze pads placed over the dressing combination.
These design features matter for interpretation. A case series can describe observations among participants treated in the study, but without a distinct comparator group it cannot separate changes associated with the dressing from changes that might occur over time or from other influences. The record does not describe randomization or a controlled comparison. It also does not report a protocol-level explanation of how participants were selected beyond the adult donor-site population, or whether the enrolled participants all contributed data to each outcome.
The registry lists three outcome measures and three analyses, but detailed numerical results and analysis descriptions are not reported in the registry record. The stated purpose is to evaluate management of donor-site wounds using Opticell Ag. The record does not report a sample-size justification, detailed statistical analysis plan, or interim analyses.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Before assignment: Enrolled participants were excluded from the study prior to experimental dressing application if they were found unable to comply with necessary wound care/follow up, or if their surgeon requested they no longer be enrolled.
Overall Study
| Stage | Opticell Ag |
|---|---|
| STARTED | 19 |
| COMPLETED | 16 |
| NOT COMPLETED | 3 |
Reasons for not completing this period:
| Reason | Opticell Ag |
|---|---|
| Withdrawal by Subject | 1 |
| Physician Decision | 1 |
| Physician Decision | 1 |
Analysis population for the primary outcome, as defined in the registry: Pain was evaluated on postoperative day 1, before the dressing was changed on days 5-7, and before and after dressing removal on days 10-14 using the Visual Analog Scale (VAS). The patient was asked to mark his/her pain level on the line between the two endpoints.
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.
Population: Subjects undergoing split-thickness autografting by the burn or plastic surgery services at the Brigham and Women's Hospital.
| Characteristic | Unit | Opticell Ag |
|---|---|---|
| Participants analysed | 19 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 16 |
| Age, Categorical: >=65 years | Participants | 3 |
| Sex: Female, Male: Female | Participants | 7 |
| Sex: Female, Male: Male | Participants | 12 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 4 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 15 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 3 |
| Race (NIH/OMB): White | Participants | 15 |
| Race (NIH/OMB): More than one race | Participants | 1 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Region of Enrollment: United States | Participants | 19 |
| Allergies to chitosan/shellfish | Participants | 0 |
| Reason for split-thickness skin graft: Burn | Participants | 16 |
| Reason for split-thickness skin graft: Soft tissue defect | Participants | 3 |
| Donor site area | square centimeters | 196.9 (17.5 to 440) |
| Dermatome setting | inches | 0.0122 (0.011 to 0.014) |
6. Primary Endpoint
The registry lists the primary outcome as Pain, measured over Assessed up to 14 days of use.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | units on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is pain reported by the participant using a visual analog scale (VAS). The record describes the scale as a horizontal line 10 centimeters (100 mm) long, with 0 for no pain at one end and 10 for the worst pain imaginable at the other. A participant marks the point on the line that represents their pain intensity. The endpoint is characterized as a continuous measure, summarized by a mean and standard deviation.
Pain was assessed on postoperative day 1, before the dressing was changed on days 5-7, and before and after dressing removal on days 10-14. The stated timeframe is up to 14 days of use. Repeated assessments can describe pain at different stages of dressing use and removal, but they do not constitute independent groups: measurements from the same participant are related.
In general, a VAS is used to capture a person's reported intensity along a continuum rather than forcing the response into a small set of categories. A mean can describe the central level of the recorded scores, while a standard deviation describes their spread among observations. The numerical mean, standard deviation, participant count contributing at each assessment, and any estimates of change are not reported in the registry record. As a result, the endpoint definition is available, but its observed distribution and course cannot be assessed from the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes a completed single-group case series with an enrollment of 19 and pain as the primary outcome. It specifies how pain was assessed and when assessments were planned, but does not report numerical pain results. In particular, the record does not give a mean, standard deviation, confidence interval, p-value, or participant count with usable pain measurements at each assessment. The numerical direction, size, and precision of any observed pain pattern therefore cannot be characterized from the record.
The absence of an outcome estimate is not evidence that pain was absent, unchanged, low, or high. It means that the registry record does not provide the measurements needed to reach those descriptions. The listed outcome and analysis counts do not substitute for result values. Wound Healing Quality is listed as a secondary outcome, while its results are not reported in the registry record.
The single-group structure also limits what could be concluded even if descriptive pain measurements were available. A sequence of scores could describe what was observed among participants receiving Opticell Ag, but without a separate comparison group it would not establish how the same participants would have fared with another dressing or without the intervention. Differences over time can reflect multiple influences; the record does not provide a controlled design to distinguish them.
Precision is also not assessable without numerical estimates and their uncertainty. In general, a confidence interval gives a range of values compatible with an estimate under the assumptions of the analysis. A narrow interval indicates greater statistical precision than a wide one, but neither precision nor clinical importance can be judged without the estimate, interval, and context. No such pain estimate or interval is reported in the registry record.
The registry lists an enrollment of 19, but that figure alone does not establish how many participants contributed to each pain assessment or whether any measurements were missing. Enrollment should not be treated as the analysis count for every time point. The record also does not state whether the three listed analyses were descriptive or inferential, how repeated measurements were handled, or how missing measurements were treated. Therefore, the posted information supports a description of the study's aim and measurement schedule, but not a quantitative conclusion about observed pain or wound healing.
9. Statistical Methods Explained
What does a mean and standard deviation describe?
The primary outcome is a continuous pain score, and the registry identifies the mean and standard deviation as its summary measures. In general, a mean is the arithmetic average of recorded scores. It describes the center of the observations, but does not show whether individual scores were clustered near that center or spread widely around it. The standard deviation describes that spread in the same units as the score.
A mean and standard deviation can be useful for a roughly symmetric distribution, but they do not reveal the full shape of the data. A skewed distribution, outlying scores, or distinct subgroups can be obscured by those two summaries. For repeated pain measurements, useful interpretation also depends on how many participants contributed at each assessment and whether the reported summary refers to participants, observations, or another unit of analysis. Those details and the actual pain summaries are not reported in the registry record.
How should repeated measurements be understood?
The planned assessments occur at multiple stages: postoperative day 1, before a dressing change on days 5-7, and before and after dressing removal on days 10-14. In general, repeated measurements from one participant are correlated because they come from the same person. Treating each recorded score as if it came from an unrelated participant can understate uncertainty and distort statistical tests. A repeated-measures analysis can account for the within-participant relationship, but different methods rely on different assumptions.
The registry record does not report the method used to analyze repeated measurements, whether a change-from-baseline measure was defined, or whether the timing of assessments was handled as categorical or continuous. It also does not provide numerical results for any assessment. Thus, the schedule can be described, but the analysis of the sequence and its precision cannot be reconstructed.
What would an uncertainty estimate add?
In general, a confidence interval communicates uncertainty around an estimated quantity. For a mean, it indicates a range of values that are compatible with the observed data and the analysis assumptions. It is not a range containing a specified proportion of individual participants' scores. A standard deviation describes individual-level spread; a confidence interval around a mean describes uncertainty about the mean. These quantities answer different questions.
A p-value, when used, describes how unusual data at least as inconsistent with a null hypothesis would be under that hypothesis and the model assumptions. It does not measure the magnitude or importance of an effect. Confidence intervals and p-values are not reported for the primary outcome in the registry record, and the null hypothesis or inferential procedure is not reported. No conclusion about statistical significance can be drawn from the information recorded.
What do planning assumptions mean?
In general, a sample-size calculation estimates how many observations a design would need to detect a chosen effect under stated assumptions. Such planning illustrations are not observed results and are not observed power. The assumptions recorded for the planning illustration are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the target effect is a stated fraction of the observed effect. For time-to-event calculations, the stated quantity is total events, while other illustrations use participants per arm.
Those assumptions describe a hypothetical two-arm planning setup, whereas this study is recorded as a single-group case series. The planning assumptions should therefore not be read as the actual design or as evidence that the study had a particular probability of detecting an effect. The registry record does not report a trial-specific sample-size justification, and the numerical planning outputs are not stated in the record. The observed effect needed for such a calculation is also not reported in the registry record.
Why does over-dispersion matter, and does it apply?
In general, over-dispersion occurs when count data vary more than a statistical model assumes. If ignored, uncertainty can be understated and inference can be misleading. It is especially relevant to some count outcomes, not a direct description of a continuous VAS score. The primary endpoint is a continuous measure, and the registry record does not identify a count model or report a method that would require an over-dispersion assessment.
More broadly, the registry does not state the distributional checks, model assumptions, covariate adjustments, handling of repeated observations, or missing-data methods used. These are not details that can be inferred from the fact that the outcome is continuous or from the listed analysis count. The methods recorded are sufficient to identify the intended measurement and its stated summary type, but not to reproduce the statistical analysis or evaluate its assumptions.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists three outcome measures and three analyses, but the outcomes and analysis details beyond the named primary pain endpoint and the secondary outcome Wound Healing Quality are not described in sufficient detail to assess the full testing plan. The record does not state whether the analyses were prespecified, which outcomes or time points were considered primary for inference, or whether any adjustment for multiple testing was used.
Multiplicity arises when several outcomes, time points, or statistical tests are examined. In general, testing many hypotheses can increase the chance of finding at least one apparently unusual result by chance. Strategies such as identifying a primary hypothesis in advance or adjusting inference can address different aspects of this issue. The registry record does not report which strategy, if any, was used. Since numerical estimates and tests are not reported, multiplicity cannot be evaluated from the posted results.
Missing-data handling is also not reported in the registry record. The enrollment of 19 does not establish the number of observed scores at each scheduled pain assessment. The record does not state whether participants missed assessments, withdrew, had incomplete measurements, or were excluded from particular analyses. It also does not describe imputation or other methods for handling incomplete observations. In general, missingness can affect both the estimate and its uncertainty, depending on why observations are absent and how the analysis handles them.
The analysis population is not reported in the registry record. It is therefore unclear whether results, if any, were intended to include all enrolled participants or only those with particular follow-up data. These gaps do not demonstrate that an analysis was inappropriate; they mean that key details needed to assess its scope and robustness are not recorded.
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 |
|---|---|---|---|
| Opticell Ag | 0 | 19 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Opticell Ag | 0 of 19 |
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 |
|---|---|
| Opticell Ag | 0 of 19 |
The registry reports 0 serious adverse events among 19 participants at risk in the Opticell Ag group. It also reports 0 other adverse events among 19 at risk and 0 deaths. No serious adverse event terms are listed.
These figures describe the events entered in the registry record for this group; they do not establish that every participant experienced no symptom or event of any kind. The record does not provide event definitions, event-collection procedures, follow-up completeness, or a detailed account of non-serious events beyond the reported count. It also does not describe a comparator group, so these figures cannot be used to compare event frequencies between treatments.
In general, a zero count in a study group is an observed count, not proof that an event cannot occur. Interpretation depends on the number of participants followed, duration and completeness of observation, and how events were defined and collected. The registry lists 19 at risk, but does not report more detailed safety follow-up information. The reported figures should therefore be read as the registry's recorded counts, not as a guarantee about safety or an estimate of comparative risk.
12. What the Result Does, and Does Not, Mean
The record establishes that Opticell Ag was evaluated in a prospective, single-center case series involving adults with split-thickness skin graft donor sites, with an enrollment of 19. It also identifies the pain scale, the assessment schedule, and Wound Healing Quality as a secondary outcome. These details describe the study's focus and measurement approach.
The record does not establish the observed level or course of pain. Numerical results for pain are not reported in the registry record, nor are numerical results for Wound Healing Quality. Without those data, no estimate of average pain, spread of scores, change across assessments, or precision can be described. The registry record also does not report a comparison with another dressing or a control group.
Even if descriptive results were available, the single-group case-series design would not provide a randomized estimate of how outcomes differ between Opticell Ag and an alternative. Changes observed over time cannot by themselves be attributed to the dressing, because other factors may also influence pain or wound healing. The record does not support a claim that the dressing improves or worsens either outcome.
The safety entries report 0 serious adverse events, 0 other adverse events, and 0 deaths among 19 at risk in the Opticell Ag group. Those registry counts are relevant descriptions of reported events, but the record does not provide the detailed follow-up and ascertainment information needed to interpret them as evidence about all possible events or comparative safety.
Overall, the registry record supports an account of the study design, intended outcomes, assessment schedule, and recorded safety counts. It does not supply the outcome estimates needed for a quantitative assessment of pain or wound healing, or a controlled treatment comparison.
13. Why This Trial Matters Statistically
This study is statistically informative as an example of why design and reporting determine which questions can be answered. A prospective case series can collect structured measurements at planned stages of care. Here, pain was specified as a continuous participant-reported outcome, and the assessment schedule included several stages of dressing use and removal. That structure is useful for describing what was measured.
At the same time, a single-group design answers a narrower question than a controlled comparison. It can describe outcomes observed in the treated group if those results are reported, but it cannot isolate a treatment contrast against another dressing. The lack of a comparator is not repaired by an analysis of repeated measurements within the group: within-person change and between-treatment difference are distinct statistical questions.
Reporting the numerical endpoint results is essential for assessing both magnitude and uncertainty. A named endpoint and measurement schedule do not reveal the average score, variation, completeness of follow-up, or precision. In this registry record, the numerical pain results and numerical wound-healing results are not reported, so readers cannot assess the observed distributions or their uncertainty.
The safety counts also illustrate why denominators and context matter. The record reports 0 serious adverse events among 19 at risk, but does not provide detailed event collection or follow-up information. A count is an important descriptive fact, not a complete characterization of risk.
The record therefore highlights a general statistical distinction: study purpose, observed data, and causal interpretation are not interchangeable. A clear account of methods and outcome values is needed to understand what was observed, while a comparator and an appropriate design are needed to support treatment comparisons.
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 most direct limitation of the available record is that it does not report numerical results for the primary pain endpoint. Mean scores, standard deviations, uncertainty estimates, and participant counts at each assessment are not reported in the registry record. Numerical results for the secondary outcome Wound Healing Quality are also not reported in the registry record.
The study is described as a single-center, prospective case series with one group and no masking. No separate control group or randomized allocation is reported. Consequently, the design does not provide a like-for-like treatment comparison, and observations over time would not alone distinguish the dressing's contribution from other influences.
The enrollment is 19, but the number contributing data to each outcome or time point is not reported in the registry record. Completeness of follow-up and handling of missing measurements are also not reported. The record does not describe the analysis population, statistical model, adjustments, or how the repeated pain assessments were analyzed.
Although three outcome measures and three analyses are listed, the record does not describe the full set of outcomes and tests, the multiplicity strategy, or whether the analyses were prespecified. A trial-specific sample-size justification is not reported in the registry record. The planning illustration's assumptions are not a substitute for a study-specific justification, and its two-arm assumptions do not describe the recorded single-group design.
Finally, the registry's safety counts lack detailed information about event definitions and ascertainment. These limitations concern what can be assessed from the record; they do not establish that unreported procedures or data were absent from the study itself.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Evaluation of Opticell Ag on Split-Thickness Skin Graft Donor Sites in Adult Subjects — NCT02642679.
- Registry record last updated 2017-12-08; status last verified 2017-11.
- Results first posted 2017-12-08.
- 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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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, prospective, single-center case series evaluating Opticell Ag on split-thickness skin graft donor sites in adults. It lists Brigham and Women's Hospital as sponsor, enrollment of 19, a start of 2016-01, and primary completion in 2016-10. The study is recorded as single-group, with allocation listed as NA and masking as none.
Pain is the primary outcome, measured by VAS at assessments extending up to 14 days of use. Wound Healing Quality is listed as a secondary outcome. The numerical results for these outcomes, the detailed statistical methods, missing-data handling, and analysis populations are not reported in the registry record.
The Opticell Ag group has 0 serious adverse events, 0 other adverse events, and 0 deaths recorded among 19 at risk. No separate comparator group is described, so the record does not provide a controlled treatment comparison.