Performance, Safety and Efficacy of NPWT Device: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Performance, Safety and Efficacy of NPWT Device (NCT04102865), a non-randomized na study. The primary outcome is Negative Pressure Maintenance at Nominal 80 mmHg.

2. Clinical Question

3. Trial Design

NCT04102865 is listed as a prospective, multicentre study of a single-use negative-pressure wound therapy device. Its title describes assessment of performance, safety and efficacy. The registry classifies the study as non-randomized, unmasked and single-group, with enrollment of 90. Phase is listed as NA. The study status is completed; the recorded start date is 2019-07-12 and primary completion date is 2022-07-06.

The record describes abdominal and knee surgery types, each with the investigational single-use dressing. These are not randomized treatment arms and should not be interpreted as a device-versus-control comparison. The groups represent different surgery types, so differences between their outcomes could reflect differences in the procedures or participant mix rather than the device. A control condition is not reported in the registry record.

The primary endpoint is a continuous measure of device-recorded negative pressure. It is defined as the mean of pressure values recorded during treatment for the two surgery types, with a nominal target of 80 mmHg and a timeframe of 30 days post-op. The registry record names standard deviation as the dispersion measure and identifies the Full Analysis Set as enrolled participants with available data for the specified surgery type.

Secondary outcomes address surgical site infection, surgical site complications, visual inspection of skin, wound and skin visual analog scale assessments, knee range of motion, and pain during dressing wear and removal. Although the record lists 11 outcome measures, it lists 0 analyses. Numerical primary and secondary efficacy results are not reported in the registry record. The study design and endpoint definitions therefore describe what was intended to be assessed, but do not establish the observed level of device performance or clinical outcomes.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Full Analysis Set (FAS) population included enrolled participants with available data for the surgery type specified.

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: Full Analysis Set (FAS) population utilized. Participants with Intent-to-Treat (ITT) that included all enrolled in the study.

6. Primary Endpoint

The registry lists the primary outcome as Negative Pressure Maintenance at Nominal 80 mmHg, measured over 30 days post-op.

The primary endpoint is negative pressure maintenance at nominal 80 mmHg. It is a continuous measure: the registry defines it as the average of negative-pressure values recorded by the device over the treatment duration for abdominal and knee surgery types. The stated timeframe is 30 days post-op. The record specifies a mean and standard deviation as the summary measures.

This type of measure is used to describe whether the device readings, on average, were near the nominal pressure level during treatment. A mean gives a summary of the central level of the recorded values, while the standard deviation describes how spread out those values are around the mean. Neither alone shows the range of individual readings or the pattern over time. General statistical context: repeated pressure measurements may vary during treatment, so an average can conceal short-lived departures from the nominal level. The registry record does not describe any additional summaries of that variation.

The endpoint is a device-performance measure, not a direct measure of wound healing, infection prevention, pain or another clinical outcome. Those subjects appear among secondary outcomes, but their results are not reported in the registry record. Although the endpoint definition is available, the primary mean, standard deviation, sample count contributing to the estimate and any confidence interval are not reported. Thus, the record does not permit assessment of the observed pressure level or its precision.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a mean describe?

The primary endpoint is continuous and summarized as a mean: the average of pressure values recorded by the device during treatment. A mean is a compact description of the central level of a set of measurements. It does not show the individual readings, how they change over time, or whether values were consistently close to the nominal 80 mmHg. The registry record specifies standard deviation as the measure of dispersion, but does not report its value. General statistical context: standard deviation describes the spread of observations around their mean; it is not the uncertainty in the mean itself.

How does uncertainty differ from variability?

Variability concerns how dispersed participant-level or measurement-level observations are. Uncertainty concerns how precisely a statistic, such as a mean, has been estimated. A confidence interval is a general way to express uncertainty around an estimate: it gives a range of values compatible with the data and the method used, under its assumptions. It does not guarantee that the true value lies in the interval. The registry record does not report a confidence interval for the primary endpoint, so the precision of the estimate cannot be evaluated. The record also does not describe whether pressure observations were summarized within participants before forming a group-level estimate.

Why does the analysis population matter?

The primary endpoint population is described as the Full Analysis Set, including enrolled participants with available data for the surgery type specified. That definition makes data availability part of inclusion in the endpoint summary. If participants without available measurements differ systematically from those with measurements, the observed-data summary may not represent all enrolled participants. General statistical context: missing data can affect both the estimated mean and its uncertainty, depending on why data are missing and how the analysis handles them. The registry record does not report the amount or reasons for missing primary endpoint data, or any imputation or sensitivity analysis.

What can the surgery-type groups establish?

The record is classified as non-randomized and single-group, with abdominal and knee surgery types. These categories do not create a randomized treatment-control contrast. General statistical context: random allocation can help balance measured and unmeasured characteristics between treatment groups, while non-randomized comparisons may be confounded by differences in who receives each intervention or by the context of care. Here, the record specifically cautions that the surgery-type groups are not a like-for-like control comparison. Therefore, a difference between them would not by itself identify a device effect. The record does not report an adjusted comparison model or a comparator group.

What do the planning assumptions mean?

The sample-size assumptions describe an illustration using a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect to detect stated as a fraction of the observed effect. For time-to-event calculations, the stated convention is total events using Schoenfeld; other calculations are expressed as participants per arm. These are planning conventions, not a description of this study’s observed analysis. The study is single-group and its abdominal and knee categories are not like-for-like control arms, so those assumptions should not be mistaken for its actual design. Planning sample sizes are illustrations, not observed power. The registry record does not report a protocol-based sample-size justification or the numerical observed effect needed to interpret such illustrations.

Why does over-dispersion matter?

General statistical context: over-dispersion occurs when data vary more than a statistical model assumes. If a model underestimates variation, its standard errors can be too small and confidence intervals too narrow, making results appear more precise than they are. For a continuous pressure measure, the choice of summary and model should reflect the data structure and variability. The registry record identifies a mean and standard deviation but does not report a model, distributional assessment, repeated-measure approach or adjustment for over-dispersion. No particular modeling choice can therefore be inferred.

What can be concluded from the listed analyses?

The registry lists 11 outcome measures but 0 analyses. It does not report inferential tests, p-values, confidence intervals, adjusted estimates or a statistical analysis plan. General statistical context: a p-value, when reported, measures how compatible data are with a specified null model; it does not measure the probability that a treatment works or the size or clinical importance of an effect. Since no primary numerical result or inferential analysis is reported, those interpretations cannot be made for this study from the registry record. The result definitions and safety counts should be read descriptively, not as evidence of a tested comparative effect.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Abdominal", "Knee")
n   <- c(58, 18)
m   <- c(-71.5, -56)
sp  <- c(25.1, 28.2)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Abdominal  58  -71.500  25.100  -78.100  -64.900
CARM  Knee  18  -56.000  28.200  -70.024  -41.976

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists 11 outcome measures, including the primary pressure-maintenance endpoint and secondary measures covering surgical site infection, surgical site complications, skin condition, wound and skin visual analog scale assessment, knee range of motion, and pain during dressing wear and removal. It lists 0 analyses. The record does not report a multiplicity adjustment, a hierarchy among secondary outcomes, or a statistical plan specifying which comparisons would be confirmatory. When many outcomes are assessed, general statistical context is that the chance of at least one apparently unusual result can increase if each is tested independently. Without a reported analysis plan or results, it is not possible to determine how multiplicity was handled.

The Full Analysis Set is defined as enrolled participants with available data for the surgery type specified. The registry record does not report the number with available primary-endpoint data, the extent or reasons for missing observations, or how missingness was addressed. It does not report whether participants were excluded from any endpoint analysis or whether sensitivity analyses assessed the effect of missing data. General statistical context: conclusions based only on available data can be affected if availability is related to the outcome or participant characteristics.

The record provides endpoint definitions and adverse-event entries but no numerical efficacy analyses for the primary or secondary outcomes. It also does not report a statistical analysis plan, interim analyses, or an approach to multiplicity. These omissions limit assessment of how prespecified analyses, missing observations and multiple endpoints may have influenced interpretation.

12. 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.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: anastomic leak (5.9%), dizziness (4.5%), deep vein thrombosis (4.5%), application site vesicles (4.5%), dysponea (4.5%).

Safety entries are separated by surgery type. For the abdominal group, the record lists 68 at risk for serious adverse events and 19 affected; for other adverse events it lists 68 at risk and 45 affected. For the knee group, it lists 22 at risk for serious adverse events and 1 affected; for other adverse events it lists 22 at risk and 19 affected. Deaths are recorded as 0 for each group. These are descriptive counts, not a randomized comparison of treatments.

The registry also lists serious adverse-event terms and percentages: Anastomic leak, 5.9%; Dizziness, 4.5%; Deep vein thrombosis, 4.5%; Application site vesicles, 4.5%; Dysponea, 4.5%; and Postoperative wound infection, 2.9%. The record does not state the denominator basis for these percentages in the safety summary, nor does it establish that listed terms are mutually exclusive. They should not be added together or treated as an overall event rate.

General statistical context: affected-participant counts describe the recorded safety experience, but do not establish that the device caused an event or that risk differs from another treatment. The non-randomized, single-group design has no like-for-like control comparison, and the registry record does not provide an adjusted safety analysis. These entries therefore describe reported events without supporting a comparative causal conclusion.

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

The registry record establishes that this completed study was designed to assess performance, safety and efficacy of an investigational single-use negative-pressure wound therapy device. Its primary measure is average device-recorded pressure during treatment, referenced to a nominal 80 mmHg and assessed at 30 days post-op. The record also identifies secondary clinical and skin assessments and reports safety counts for abdominal and knee surgery types.

It does not report the primary mean, standard deviation, confidence interval or numerical results for the secondary outcomes. As a result, the observed pressure level, variability and precision cannot be assessed from the registry record. The record’s endpoint definition is not itself an outcome finding. Similarly, the presence of secondary outcome names does not show whether infections, complications, skin changes, pain or range-of-motion outcomes occurred at any particular level.

The design does not support a like-for-like treatment comparison: allocation is non-randomized, the study is single-group, and abdominal and knee groups are surgery types rather than randomized control arms. The available safety counts are descriptive; they do not establish comparative risk or causation. No medical conclusion about an individual’s care follows from these registry entries.

The sample-size assumptions describe planning illustrations based on the observed effect, with a stated normal approximation and equal allocation between two arms. Such illustrations are not observed power and do not replace reported outcome estimates. Because the registry record does not report the numerical primary result or a statistical analysis, it cannot support an inference about the magnitude or precision of the primary endpoint. What it does support is a description of the study’s intended measures, design, analysis population definition and recorded adverse-event counts.

14. Why This Trial Matters Statistically

This trial is statistically instructive because it distinguishes a device-performance endpoint from clinical outcomes. The primary measure summarizes pressure recorded by the device, whereas secondary outcomes address infection, surgical site complications, skin condition, pain and knee range of motion. These measure different aspects of the study and should not be treated as interchangeable evidence. A device-level average alone would not describe every pressure reading or establish a clinical effect.

The design also highlights the importance of identifying the actual comparison. Abdominal and knee surgery types are not randomized treatment and control groups. Their outcomes cannot be interpreted as a controlled estimate of the effect of the device. Non-randomized studies can provide useful descriptive information, but causal interpretation requires careful attention to comparability and confounding; the registry record does not report an adjusted comparative analysis.

Another important issue is the gap between endpoint definition and result reporting. The registry specifies a mean and standard deviation and defines the Full Analysis Set, yet does not report the numerical primary result, its precision, or the number contributing data. Without those elements, readers cannot assess the central estimate, variability or uncertainty. Listing numerous outcomes without reported analyses also makes multiplicity and analysis-selection questions difficult to evaluate.

Finally, the safety counts illustrate why event summaries need context. Counts separated by surgery type are descriptive, and the design offers no randomized control group for estimating comparative risk. The registry record is therefore most informative about what was intended to be measured and how the study was organized; it is limited as a source for judging observed efficacy or comparative safety.

15. 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 contains substantial design and outcome-reporting limitations for statistical interpretation. It identifies a completed, non-randomized, single-group study but does not report the numerical primary endpoint result, standard deviation, confidence interval or the number of participants contributing pressure measurements. Although enrollment is listed as 90, the record does not give the endpoint-specific available-data counts. This prevents assessment of the estimate’s precision and the extent to which missing measurements may matter.

Abdominal and knee are different surgery types, not randomized comparator groups. Any contrast between them would not isolate a device effect, and the registry record reports no control group or adjusted comparative analysis. The record also does not report participant characteristics, details of missingness, or whether those with available measurements differed from other enrolled participants. These omissions limit assessment of representativeness and potential selection effects.

The registry lists 11 outcome measures but 0 analyses. It does not report a statistical analysis plan, multiplicity procedure, inferential tests or numerical secondary outcomes. Therefore, the role of each outcome in the analysis and the possibility of selective emphasis cannot be assessed. The record does not describe interim analyses or a protocol-based sample-size justification.

Safety information is descriptive and lacks a like-for-like control comparison. The percentage denominator basis for listed serious adverse-event terms is not stated in the record. Together, these limitations mean that the registry entries characterize study design and recorded safety counts but do not support precise estimates of device performance or comparative clinical outcomes.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Performance, Safety and Efficacy of NPWT Device — NCT04102865.
• Registry record last updated 2024-12-11; status last verified 2022-12.
• Results first posted 2024-11-21.
• 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.

19. Record Summary

NCT04102865 is a completed prospective, multicentre, non-randomized, unmasked, single-group study of an investigational single-use negative-pressure wound therapy device. Enrollment is listed as 90. The study concerns abdominal and knee surgery types and wound healing and prevention.

The primary endpoint is mean device-recorded negative pressure, with standard deviation, at a nominal 80 mmHg and a timeframe of 30 days post-op. The Full Analysis Set is described as enrolled participants with available data for the surgery type specified. The record lists secondary outcomes for infection, complications, skin condition, visual analog scale assessments, knee range of motion and pain during wear and removal.

The registry lists 11 outcome measures and 0 analyses. It does not report numerical primary or secondary efficacy results. Safety counts are reported separately for abdominal and knee groups, with 0 deaths recorded for each. The groups are surgery types, not like-for-like control arms, so the recorded design does not support a randomized comparative interpretation.