Adipose Tissue Extract and Platelet-rich Plasma Use for Wound Healing: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Adipose Tissue Extract and Platelet-rich Plasma Use for Wound Healing (NCT02799290), a non-randomized phase 2 study. The primary outcome is Wound Re-epithelization.

2. Clinical Question

3. Trial Design

This was a phase 2, non-randomized, parallel study sponsored by Tampere University. The registry reports that the study began in 2015-06, had primary completion in 2016-05, and is completed. Enrollment was 24. The record lists three groups: no intervention, adipose tissue extract application, and platelet-rich plasma gel application. Although ATE and PRP are identified as interventions, the listed control group received no intervention.

Non-randomized allocation is a central design feature. Without random assignment, differences between groups may reflect not only the assigned treatment but also differences in participant or wound characteristics, care, or other factors. The registry record does not describe how group assignment occurred or provide baseline information that would help assess comparability. It therefore does not support treating the groups as a like-for-like controlled comparison.

The design is described as parallel, meaning the study has separate groups rather than a stated crossover in which participants receive multiple treatments in sequence. The record also describes masking as single, but does not identify who was masked or specify what information was concealed. The meaning and practical implementation of masking therefore cannot be assessed from the registry record.

The stated primary endpoint was assessed through observational digital photography using specialized custom-made software. The registry says the outcome was measured as a whole per group, using a group mean and standard deviation, and not as participant-level healing. The outcome timeframe was 30 days. Secondary outcomes listed were scar properties, oxygenated hemoglobin, and melanin concentration in the wound. Numerical results, analysis methods, and detailed timing for those secondary measures 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

Analysis population for the primary outcome, as defined in the registry: Measured as a whole per group as mean and standard deviation of group and not participant healing.

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: Wound healing characteristics of donor sites in time

6. Primary Endpoint

The registry lists the primary outcome as Wound Re-epithelization, measured over 30 days.

Wound re-epithelialization was the primary endpoint. Re-epithelialization refers generally to restoration of an epithelial covering over a wound. In this study, the endpoint was expressed in days and assessed over a 30-day timeframe. The registry describes observational digital photography analyzed with specialized custom-made software.

As a general statistical consideration, a time-based measure can represent how quickly a healing milestone is reached. Its interpretation depends on a clear definition of the milestone, consistent observation, and a suitable way to handle cases where the milestone is not observed within the measurement period. The registry record does not provide further detail about the operational definition, image-assessment procedures, or handling of observations without a recorded healing time.

The record specifies that the endpoint was measured for each group as a whole, reporting a group mean and standard deviation rather than participant-level healing. This matters because a group-level summary does not show how outcomes varied across participants or donor sites, and it limits the kinds of participant-level comparisons that can be interpreted. The registry record does not report the group means, standard deviations, or a statistical comparison. Consequently, the direction, size, and precision of any difference in re-epithelialization cannot be described from the registry information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods help translate observed measurements into estimates and show how much uncertainty surrounds those estimates. In this study, however, the registry record does not report an analysis plan or numerical analyses. The concepts below explain how such methods generally relate to the stated design and endpoint; they do not describe analyses known to have been performed.

What does a group mean describe?

A mean is a measure of the center of a set of observations. For wound re-epithelialization measured in days, a group mean would summarize the average recorded duration for that group under the definition used in the study. A standard deviation describes how dispersed observations are around the mean. It is not the same as a confidence interval: the standard deviation describes variation in observations, whereas a confidence interval describes uncertainty in an estimated quantity.

The registry describes the primary measure as a whole-group mean and standard deviation, not participant-level healing. That distinction limits what can be inferred. A group summary cannot show the individual outcome distribution, identify influential observations, or establish whether the outcome was recorded consistently across participants. The registry record does not report the numerical means or standard deviations, nor does it explain the underlying aggregation in further detail.

Why does the allocation method matter?

In a randomized study, allocation by chance is intended to balance measured and unmeasured characteristics across groups on average. This study was non-randomized. General statistical reasoning therefore requires attention to possible confounding: a factor associated with both group assignment and healing may contribute to a group difference. Relevant factors might include baseline wound characteristics or care practices, but their measurement and role in this study are not reported in the registry record. No adjustment approach is reported.

The registry lists three arms, including a no-intervention control, and explicitly cautions that the arms are not a like-for-like control comparison. This is important when interpreting any apparent contrast. A statistical adjustment can address some measured differences under appropriate assumptions, but it cannot automatically remove bias from unmeasured or poorly measured factors. The registry record does not describe whether any adjusted comparisons were planned or conducted.

What would an uncertainty interval add?

A confidence interval is a statistical range around an estimate that reflects sampling uncertainty under a specified method and its assumptions. It helps readers assess the precision of an estimated contrast, rather than focusing only on a point estimate. A wide interval indicates that a range of effects remains compatible with the data and method; a narrow interval indicates a more precise estimate. The registry record reports neither an interval nor a primary-outcome estimate, so precision cannot be assessed.

A p-value is another statistical quantity, usually used to assess how compatible the data are with a null hypothesis under a specified model. It does not measure the size or clinical importance of an effect, and it does not replace an interval. No p-value or test result is reported in the registry record. Without a stated analysis method, even a numerical p-value would be difficult to interpret fully.

How should planning calculations be read?

The record describes a sample-size planning illustration based on the observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustration is described as considering a stated fraction of the observed effect. For non-time-to-event outcomes, such planning figures are expressed as participants per arm; time-to-event planning figures are described as a total number of events. These are planning illustrations, not observed trial results and not observed power.

As a general concept, a planning calculation estimates the amount of information a future study might need under assumed conditions. Its output depends on the effect used, variability, significance level, allocation, and statistical model. The registry record does not report the numerical planning outputs, and it does not establish that the planning assumptions were part of this trial's original design. They should not be interpreted as evidence that the completed study had a particular probability of detecting an effect.

Why can group summaries be inadequate for a days-based outcome?

A time-to-event analysis is one general approach for outcomes defined by time until an event. It can account for participants whose event time is not observed during follow-up, if the relevant observation and censoring information is available. The registry describes the primary outcome in days but does not report a time-to-event analysis or specify how observations not reaching the endpoint within the timeframe were handled. It would be inappropriate to assume that such an analysis was used.

Other possible approaches depend on how the endpoint was operationalized and how observations were collected. For example, a model for a continuous outcome would require assumptions about the outcome distribution and errors. The registry record does not identify a model, test, or assumptions. The reported group-level measurement also means that participant-level modeling cannot be inferred from the description.

What does over-dispersion mean in general?

For count outcomes, over-dispersion means that the observed variability exceeds what a chosen model, such as a simple Poisson model, would expect. A model that ignores substantial over-dispersion can produce uncertainty estimates that are too small. This concept is not directly a reported feature of the primary endpoint, which is described in days, and the registry does not report a count-based analysis. It is relevant only as a general example of why model assumptions matter.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary outcome, wound re-epithelialization, and secondary outcomes of scar properties, oxygenated hemoglobin, and melanin concentration in the wound. It reports four outcome measures, but does not give results for the secondary measures or explain how they were defined, timed, or analyzed. A list of outcomes alone does not establish which comparisons were made or how conclusions would account for multiple testing.

As a general statistical issue, testing several outcomes or contrasts can increase the chance of finding at least one apparently notable result by chance. Researchers may address this through a prespecified hierarchy, adjustment procedures, or careful distinction between confirmatory and exploratory analyses. The registry record does not report whether multiplicity was addressed, which outcomes or comparisons were prioritized in analysis, or whether any adjustment was planned.

Missing-data handling is also not reported in the registry record. There is no description of missing endpoint observations, exclusions, imputation, or sensitivity analyses. Because the primary measure is described as group-level rather than participant-level, the record also does not clarify how incomplete or unavailable measurements contributed to the group summaries.

Analysis populations are not reported. The registry does not specify whether analyses included all enrolled participants, only those with usable measurements, or another defined group. It also reports no statistical analyses. These absences limit assessment of selection, missingness, and the relationship between planned outcomes and reported results; they should not be filled by assuming standard methods were used.

11. Safety Results

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

Deaths

Other (non-serious) adverse events

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

The registry lists safety counts separately for the control, ATE, and PRP gel groups. For the control group, 24 were at risk for serious adverse events and 0 were affected; 24 were at risk for other adverse events and 0 were affected, with 0 deaths. For ATE, 13 were at risk for serious adverse events and 0 were affected; 13 were at risk for other adverse events and 0 were affected, with 0 deaths. For PRP gel, 11 were at risk for serious adverse events and 0 were affected; 11 were at risk for other adverse events and 0 were affected, with 0 deaths.

These figures describe the events recorded in the registry, not a guarantee that no harm occurred. Zero recorded events can be compatible with uncertainty about uncommon events, and the counts do not establish comparative safety. Interpretation also depends on how events were defined, collected, and followed. Those details are not reported in the registry record. The group counts should be read as safety reporting, not as evidence that the interventions are risk-free.

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

The registry record establishes that a completed phase 2 study examined ATE and PRP gel in relation to split-thickness donor-site wound healing, alongside a no-intervention control. It identifies wound re-epithelialization in days as the primary endpoint and lists secondary measures related to scar properties and wound characteristics. The study's non-randomized parallel design and the group-level description of the primary measure are important context for interpreting any results.

The record does not report numerical primary or secondary outcome results, estimates of between-group differences, uncertainty intervals, or p-values. It therefore does not show whether one group had faster or slower recorded re-epithelialization, nor how large or precise a difference might have been. No conclusion about the comparative outcome can be drawn from the registry information alone.

Even with outcome estimates, non-randomized allocation would call for caution about causal interpretation. Groups may differ in ways that affect healing, and the registry does not describe assignment procedures, baseline characteristics, or statistical adjustment. The group-level nature of the endpoint further limits individual-level interpretation and the assessment of variation among participants.

The safety record reports zero serious adverse events, other adverse events, and deaths in each listed group. Those reported counts do not establish the absence of risk, particularly without detailed event definitions and collection methods. The study record is informative about the questions and outcomes registered, but it does not provide enough results or methods to establish the magnitude, precision, or causal meaning of treatment differences.

13. Why This Trial Matters Statistically

This study is statistically notable because its central outcome is described as a group-level measure rather than participant-level healing. The registry says re-epithelialization was summarized as a mean and standard deviation for each group. That choice affects the information available for estimating variability, comparing groups, and understanding how individual healing experiences differ. Readers should not interpret a group summary as if it were a collection of participant-level results.

The non-randomized allocation is another important feature. It highlights the difference between observing outcomes in treatment groups and estimating a causal effect. In general, randomization helps make groups comparable in expectation; without it, differences in group composition may remain an alternative explanation for outcome differences. The registry itself cautions that the arms are not a like-for-like control comparison, and does not report adjustment or baseline information.

The endpoint description also raises general questions about measurement. Digital photography and specialized software were used, but the record does not give operational criteria, assessor details, or procedures for handling uncertain images or incomplete observations. These features matter because consistency of measurement can affect both the estimated group mean and its uncertainty.

Finally, the absence of posted analysis results is itself consequential. A registered study purpose and outcome definitions do not reveal the magnitude or precision of outcomes. The record supports a clear account of the design and its limitations, but not a statistical conclusion about comparative healing. This distinction is useful when reading clinical-trial registries: design information and results information answer different questions.

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 registry record leaves several trial-specific details unreported. It does not describe the non-randomized allocation procedure, explain who was masked under the single-masking designation, or provide baseline characteristics. These omissions make it difficult to assess group comparability and the possibility of confounding.

The primary endpoint is described as a whole-group measure, not participant-level healing. The record does not explain how the group-level mean and standard deviation were derived, whether observations were independent, or how repeated measurements or multiple donor sites were handled. The endpoint's operational definition and the procedure for assessing digital photographs are also not reported in detail.

Although the endpoint timeframe is 30 days, the registry does not report how incomplete follow-up or a healing milestone not observed within that timeframe was handled. Missing-data methods, analysis populations, statistical models, and multiplicity procedures are not reported. The registry also does not provide the primary or secondary outcome results, so effect magnitude and precision cannot be evaluated.

The safety figures report zero events in the listed categories, but event definitions, ascertainment procedures, and details of follow-up are not reported. The registry's planning illustration is not the trial's own design justification and does not provide evidence of observed power. Together, these limitations restrict both statistical interpretation and the strength of any causal conclusions that could be drawn from the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Adipose Tissue Extract and Platelet-rich Plasma Use for Wound Healing — NCT02799290.
• Registry record last updated 2021-01-07; status last verified 2020-12.
• Results first posted 2021-01-07.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

NCT02799290 is a completed phase 2, non-randomized, parallel study sponsored by Tampere University. The registry reports enrollment of 24 and lists a no-intervention control, adipose tissue extract application, and platelet-rich plasma gel application. The study began in 2015-06 and reached primary completion in 2016-05.

The primary endpoint was wound re-epithelialization in days over a 30-day timeframe, assessed through digital photography and specialized software. The registry describes group-level means and standard deviations rather than participant-level healing. Secondary outcomes were scar properties, oxygenated hemoglobin, and melanin concentration in the wound.

Numerical outcome results, analysis methods, missing-data procedures, and analysis populations are not reported in the registry record. The safety record lists zero serious adverse events, other adverse events, and deaths in each group. Non-randomized allocation and the group-level endpoint limit interpretation of comparative effects.