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 Investigation of Two Different Wound Dressings (NCT02904200), a randomized na study. The primary outcome is Changes on Peri-Wound Skin.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02904200 |
| Phase | NA |
| Condition | Wounds and Injuries |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 2 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Molnlycke Health Care AB |
| Results posted | Yes |
2. Clinical Question
Population
The investigation enrolled people with wounds and injuries. The registry record reports that 2 subjects were included and 1 completed follow-up; the other subject withdrew consent. Further eligibility details and participant characteristics are not reported in the registry record.
Intervention
One study intervention was a sterile soft silicon adhesive dressing. The registry record describes the investigation as involving the Avance NPWT System and comparing two different fixations. Additional details about how the dressing was applied are not reported in the registry record.
Comparator
The comparator was a sterile acrylic adhesive dressing. The study was randomized, open, controlled, and parallel. The registry record does not report the randomization procedure or whether allocation was concealed.
Primary question
The intended primary question was whether periwound skin scores changed from baseline to termination when using the two dressings. The primary endpoint was intended to be the change in a five-item score, assessed at baseline and later visits. Because the baseline score was not evaluable for the subject who completed follow-up, the endpoint could not be calculated as intended. The registry record presents the primary outcome at day 12 instead. It reports no statistical evaluation and gives no numerical day-12 scores or treatment comparison.
3. Trial Design
This was a randomized, open, controlled pilot investigation with a parallel-group model. It compared a sterile soft silicon adhesive dressing with a sterile acrylic adhesive dressing during treatment with the Avance NPWT System. The registry record lists no masking. The study was sponsored by Molnlycke Health Care AB and was marked terminated. The recorded start was 2016-10, and primary completion was 2017-05.
The registry record reports enrollment of 2 subjects. It states that 1 completed follow-up and the other withdrew consent. No statistical evaluation was performed because only 2 subjects were included and only 1 completed follow-up. These registry entries sharply limit what can be learned about variation in outcomes or differences between dressings. The record does not provide a numerical account of how participants were assigned between the two interventions, so no group-specific outcome comparison can be reconstructed from the information reported.
The intended primary outcome was change in periwound skin score from baseline to termination. The record states that the baseline score for the subject who completed follow-up was not evaluable because of missing values. Consequently, the primary endpoint could not be calculated as intended, and the primary outcome is presented at day 12. Pain around dressing removal was a secondary objective, with a VAS Scale (0-100mm) listed as a secondary outcome. Numerical results for that outcome are not reported in the registry record.
Details such as the randomization method, allocation concealment, recruitment procedures, eligibility criteria, and prespecified statistical analysis plan are not reported in the registry record. The pilot designation alone does not establish the study’s intended role or explain the reason it was terminated.
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 | Avance® Film With Safetac® | Avance® Transparent Film |
|---|---|---|
| STARTED | 2 | 0 |
| COMPLETED | 1 | 0 |
| NOT COMPLETED | 1 | 0 |
Reasons for not completing this period:
| Reason | Avance® Film With Safetac® | Avance® Transparent Film |
|---|---|---|
| Withdrawal by Subject | 1 | 0 |
Analysis population for the primary outcome, as defined in the registry: No statistical evaluation was performed because only 2 subjects were included into the study and 1 completed follow up (other subject withdrew consent). Due to missing values for the one subject that completed follow up, the primary outcome is presented at 12 days.
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: The clinical investigation was prematurely closed due to very slow recruitment. Only two subjects were enrolled. Only one went through all visits. No conclusion can be made from the report. No statistical evaluation was performed because only 2 subjects were included into the study.
| Characteristic | Unit | Avance® Film With Safetac® |
|---|---|---|
| Participants analysed | 2 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 2 |
| Age, Categorical: >=65 years | Participants | 0 |
| Sex: Female, Male: Female | Participants | 1 |
| Sex: Female, Male: Male | Participants | 1 |
| Race and Ethnicity Not Collected | Participants | — |
| Region of Enrollment: Sweden | participants | 2 |
| Baseline Pain | score on a scale | 1.5 (SD 1.5) |
6. Primary Endpoint
The registry lists the primary outcome as Changes on Peri-Wound Skin, measured over Visit 4 last visit (day 12).
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | score on a scale |
| Endpoint classification | not reduced to a single comparison |
The intended primary endpoint was change in the sum of five periwound skin scores from baseline to termination. The five assessed features were Redness/Irritation, Flaky, Maceration, Blistering, and Skin tears. Each feature was scored from 0 to 3, with higher scores representing more severe findings; the sum ranged from 0 to 15, and higher total scores indicated a worse outcome. The planned visits were baseline, day 4, day 7, and the last visit at day 12.
In general, a combined score can give a structured way to track several related features using a consistent measure. A baseline-to-follow-up change is intended to describe how that measure moves over time, rather than only describing its value at one visit. Interpretation depends on having evaluable measurements at both time points and on understanding the meaning of the scale.
Here, the registry record says the baseline score was not evaluable because of missing values for the subject who completed follow-up. The change endpoint therefore could not be calculated as intended. The record presents the primary outcome at day 12 instead, but does not report the numerical score. It is thus not possible to describe the observed score level or a change from baseline using the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The central statistical fact is that the registry record reports no statistical evaluation. It explains that only 2 subjects were included and 1 completed follow-up. It also states that missing baseline values for the follow-up completer prevented calculation of the intended primary endpoint. The registry record therefore does not provide a treatment-effect estimate, an uncertainty interval, or a test of a difference between the dressings.
The primary outcome is described as a day-12 score, but no numerical score is reported. Without the posted values, it is not possible to characterize the skin findings at that visit, compare them across dressings, or assess the size and direction of any observed difference. The record’s description of the scale establishes that higher values indicate a worse outcome; it does not establish what the participants’ scores were.
The intended analysis was based on change from baseline to termination. Change scores require evaluable measurements at both the starting and ending time points. When a baseline value is missing, that participant’s change cannot be obtained from the described measurements. Substituting a day-12 value changes the quantity being described: a single follow-up score is not the same as a baseline-to-follow-up change. The registry record does not report a replacement analysis that compares groups using day-12 values.
In general, a confidence interval expresses uncertainty around an estimate under the assumptions of the statistical method. No confidence interval is reported for the primary outcome, and with no numerical primary comparison in the registry record, its precision cannot be assessed. A p-value would address compatibility between data and a specified statistical model or null hypothesis; no primary-outcome p-value is reported. Neither the absence of a reported p-value nor the lack of an evaluable endpoint establishes that the dressings are equivalent.
The secondary objective concerned pain before, during, and after dressing removal from baseline to termination. The record lists a VAS Scale (0-100mm), but does not report pain values, a comparison, or an analysis. Therefore, the registry record does not allow an assessment of the magnitude or uncertainty of any pain difference.
The posted safety figures describe events in a group labeled Avance® Film With Safetac®. They report 0 serious adverse events among 2 at risk, 1 other adverse event among 2 at risk, and 0 deaths. These counts are descriptive. They do not supply comparative estimates between the silicon and acrylic dressing groups, and the registry record does not list serious adverse event terms. The safety counts should not be treated as evidence of a comparative risk difference.
Overall, the record documents the study question and the obstacle to the intended primary analysis, but does not give numerical efficacy results. The data reported are too limited to support a reliable estimate of comparative performance or precision.
9. Statistical Methods Explained
The registry record identifies a randomized, open, controlled, parallel investigation, but reports no statistical evaluation. General statistical concepts can clarify what the intended endpoint would have represented and what conclusions the available record can support; they cannot replace the missing outcome values.
What does a change score represent?
In general, a change score is calculated from an outcome measured at follow-up and the same outcome measured at baseline. It describes movement on the scale over time. A comparison of change between groups then asks whether that movement differs by assigned intervention. This approach depends on having usable measurements at both times and on the scale being applied consistently.
The intended endpoint was the change in a summed periwound skin score, using five separately scored features. Each feature used a 0-to-3 scoring range, and the total score ranged from 0 to 15; higher totals indicated a worse outcome. The record says the baseline score was not evaluable for the subject who completed follow-up because of missing values. It consequently presents the primary outcome at day 12 rather than as the intended baseline-to-termination change. Since no numerical day-12 score is reported, the endpoint cannot be independently described or compared from the registry record.
Why does the number of observations matter?
In general, an estimate based on very few observations is sensitive to the outcomes of the individuals observed. A small study also provides little information about the distribution of scores or the amount of natural variation. Randomization can help make groups comparable in expectation, but it does not guarantee balance in a very small realized sample. Here, the record reports enrollment of 2 subjects and follow-up completion by 1. It states that no statistical evaluation was performed. The record does not report group-specific outcome counts or estimates, so it is not possible to assess balance or quantify variability.
For a comparison to be informative, the analysis needs an outcome definition, observations for each intervention, and a stated method for estimating the difference and its uncertainty. The registry record does not report an analysis of the primary endpoint or a numerical comparison. No particular test, model, adjustment, or estimation method should be inferred from the randomized design alone.
How should uncertainty be understood?
In general, a confidence interval gives a range of values compatible with the observed data under a specified method and its assumptions. A narrow interval can indicate greater precision, while a wide interval indicates less precision. A p-value is a different summary: it describes how unusual data at least as inconsistent with a null hypothesis would be under a statistical model, if that model and hypothesis were correct. Neither measure by itself conveys clinical importance. The registry record reports no primary-outcome confidence interval or p-value, and gives no numerical primary comparison from which either could be interpreted.
With a bounded score, analysts may also consider whether a chosen statistical model represents the scale and its distribution adequately. In general, over-dispersion occurs when count-like data vary more than an assumed model allows, which can make standard errors and tests unreliable if ignored. That general issue does not establish that over-dispersion was relevant to this score, and the registry record reports no fitted model, distributional assessment, or adjustment. No model choice can be attributed to the investigators from the information reported.
What do planning illustrations tell readers?
In general, sample-size planning asks how many participants per arm would be needed to detect a specified effect under stated assumptions. The registry’s planning description specifies a two-sided significance level of 0.05, equal allocation, and a normal approximation, with effects expressed as fractions of an observed effect. It also distinguishes total-event planning for time-to-event outcomes from participants-per-arm planning for other outcomes. These are planning assumptions, not observed trial results, and a planning calculation based on an observed effect is not observed power. Numerical planning estimates are not reported in the registry record, and the record does not state that these assumptions formed the study’s original design plan.
Planning illustrations cannot repair the missing baseline measurement or create a comparative estimate from an outcome that was not statistically evaluated. The record does not report a sample-size justification, and the reason for the enrollment and termination history is not described. Those omissions should remain distinct from general statistical principles.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists the periwound skin score as the primary outcome and a VAS Scale (0-100mm) as a secondary outcome. It describes pain before, during, and after dressing removal as a secondary objective. No multiplicity strategy is reported in the registry record. In general, when multiple outcomes or time points are tested, the chance of at least one apparently notable result can increase; prespecified methods may be used to address that issue. The record does not establish whether such methods were planned or used.
Missing data affect the primary endpoint directly. The record says the baseline score was not evaluable because of missing values for the one subject who completed follow-up. The intended change from baseline to termination could not therefore be calculated as planned, and the outcome is presented at day 12. The other subject withdrew consent. The reasons for the missing baseline values and the withdrawal are not reported beyond these descriptions, and no method for handling missing data is reported.
The registry record states that no statistical evaluation was performed because only 2 subjects were included and 1 completed follow-up. It does not report an analysis population, such as whether analyses were intended to follow assignment regardless of adherence, or how participants with incomplete data would be handled. No imputation procedure, sensitivity analysis, or alternative primary analysis is reported. These details are important because choices about incomplete observations can affect which participants contribute to an estimate and how uncertain that estimate is.
Without a reported analysis population, missing-data method, or numerical group comparison, readers cannot determine how the intended analysis would have treated the incomplete records. The record does not support conclusions about the robustness of results to missingness, and it provides no multiplicity-adjusted or unadjusted primary-outcome analysis.
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 |
|---|---|---|---|
| Avance® Film With Safetac® | 0 | 2 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Avance® Film With Safetac® | 0 of 2 |
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 |
|---|---|
| Avance® Film With Safetac® | 1 of 2 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Avance® Film With Safetac® |
|---|---|---|
| Blisters | Skin and subcutaneous tissue disorders | 1 of 2 |
The registry record reports safety counts for a group labeled Avance® Film With Safetac®. For serious adverse events, 0 affected participants are reported among 2 at risk. For other adverse events, 1 affected participant is reported among 2 at risk. The death count is 0. No serious adverse event terms are listed.
These are descriptive counts, not estimates of a comparative safety effect. The record does not provide event details for the other adverse event, its timing, severity, or relationship to an intervention. It also does not provide a comparison of these safety counts between the silicon and acrylic dressing interventions. The relationship between the safety-group label and the two intervention labels is not specified in the registry record, so the group should not be assigned to either dressing by assumption.
In general, a count of participants affected is different from a count of all events, since one participant can potentially experience more than one event. The record does not clarify whether the reported figures count participants or individual events beyond the labels used for affected participants. With the small enrollment and incomplete follow-up described in the record, these counts provide limited descriptive information and should not be read as a precise estimate of safety differences.
12. What the Result Does, and Does Not, Mean
The registry record supports a narrow description: this was a randomized, open, controlled pilot comparing two adhesive wound dressings, and the intended primary endpoint was a change in periwound skin score. The record states that only 2 subjects were included, 1 completed follow-up, and no statistical evaluation was performed. Missing baseline values for the follow-up completer meant the intended change endpoint could not be calculated. The primary outcome is described at day 12, but its numerical value is not reported.
These registry entries do not establish whether one dressing produced better or worse skin scores. No group-specific scores, treatment-effect estimate, or uncertainty interval is reported. The record therefore cannot show the magnitude, direction, or precision of a comparative effect. A day-12 outcome in one participant is also not interchangeable with a comparison of baseline-to-termination changes across two groups.
The same caution applies to pain. A VAS Scale (0-100mm) is listed, but no pain results or statistical comparison are reported. The safety counts provide a limited descriptive record but do not establish a difference in risk between dressings. In general, absence of a statistically evaluated result is not evidence that two interventions have the same effect, nor is it evidence that either has a particular effect.
The findings should not be extrapolated beyond the people and observations recorded. The registry does not report enough participant or outcome detail to assess whether the study population represented a broader clinical population. Its terminated status is recorded, but the reason for termination is not reported. The record also does not explain the original sample-size rationale or provide a statistical analysis plan.
Accordingly, the result is best understood as an incomplete and non-evaluable primary comparison in a very small pilot investigation. It documents the intended question and why the planned endpoint was unavailable, rather than establishing a comparative conclusion about the dressings.
13. Why This Trial Matters Statistically
This investigation illustrates why endpoint planning and endpoint availability are distinct. The intended primary measure was a baseline-to-termination change in a structured skin score. The registry record says the baseline value was not evaluable for the subject who completed follow-up, so the intended change could not be calculated. Presenting a follow-up score at day 12 does not restore the missing baseline information; it describes a different quantity.
The record also demonstrates the limits of inference when only a very small number of participants are enrolled and follow-up is incomplete. Random allocation is a design feature, not a guarantee that a small study will yield a stable or precise treatment comparison. The registry explicitly reports that no statistical evaluation was performed. Without numerical results for each intervention, readers cannot judge the size of any difference or its uncertainty.
In general, a pilot study can be useful for learning about feasibility, outcome measurement, and study procedures. Whether those were the goals of this investigation, and what conclusions were drawn about them, are not reported in the registry record. Its pilot designation should not be mistaken for evidence that the comparative endpoint was estimated reliably.
The study is also a useful reminder that reporting an outcome scale is not the same as reporting outcome data. The score range and interpretation are described, but the day-12 score is not. Similarly, listing a pain scale does not provide evidence about pain, and descriptive safety counts do not establish comparative risk. Transparent interpretation depends on distinguishing planned measures, recorded observations, and statistical conclusions rather than treating them as interchangeable.
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 immediate limitation is the unavailable primary change endpoint. The registry record states that missing values made the baseline score unevaluable for the subject who completed follow-up, so the intended baseline-to-termination comparison could not be calculated. Although the primary outcome is presented at day 12, no numerical score is reported. As a result, readers cannot assess the observed periwound skin outcome or compare it between interventions.
The record reports enrollment of 2 subjects and follow-up completion by 1, with the other subject withdrawing consent. It also states that no statistical evaluation was performed. These circumstances prevent estimation of a reliable treatment difference and leave little information about outcome variability. The registry record does not report group-specific enrollment or outcome values, so allocation balance and any descriptive contrast cannot be assessed.
Important design and analysis details are absent: the randomization procedure, allocation concealment, eligibility criteria, participant characteristics, missing-data handling, analysis population, and statistical analysis plan are not reported in the registry record. The reason for termination and the rationale for the enrollment target are also not reported. These omissions make it difficult to judge design execution or the intended interpretation of the results.
The secondary pain outcome is listed without numerical results or an analysis. Safety information is limited to the reported counts and does not include serious event terms or a comparative account by dressing. The relationship of the safety-group label to the two intervention labels is not specified. Together, these limitations mean the record offers no basis for a precise comparative conclusion on skin outcomes, pain, or safety.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Clinical Investigation of Two Different Wound Dressings — NCT02904200.
- Registry record last updated 2021-04-01; status last verified 2020-09.
- Results first posted 2021-04-01.
- 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
NCT02904200 is a terminated, randomized, open, controlled, parallel pilot investigation comparing sterile soft silicon and sterile acrylic adhesive dressings during treatment with the Avance NPWT System. The recorded start was 2016-10, and primary completion was 2017-05. The registry record reports enrollment of 2 subjects; 1 completed follow-up and the other withdrew consent.
The intended primary outcome was change in a five-feature periwound skin score from baseline to termination. Missing baseline values for the follow-up completer prevented calculation of that endpoint as intended, so the primary outcome is presented at day 12. No numerical primary result or statistical evaluation is reported. Pain was a secondary objective, with a VAS Scale (0-100mm) listed, but no numerical pain result is reported. The safety record lists 0 serious adverse events, 1 other adverse event, and 0 deaths in the recorded group. The reason for termination and further statistical analysis details are not reported in the registry record.