A Study Comparing V.A.C. Negative Pressure Wound Therapy (NPWT) to Moist Wound Therapy (MWT) in the Treatment of Diabetic Foot Amputation Wounds: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study Comparing V.A.C. Negative Pressure Wound Therapy (NPWT) to Moist Wound Therapy (MWT) in the Treatment of Diabetic Foot Amputation Wounds (NCT00837096), a randomized na study. The primary outcome is Number of Participants With 100% Wound Closure.

2. Clinical Question

3. Trial Design

The registry describes a prospective, randomized, multicenter, parallel study comparing V.A.C. negative pressure wound therapy with moist wound therapy for diabetic foot amputation wounds. The allocation is recorded as randomized, the model as parallel, and masking as none. Phase is listed as NA. Enrollment is recorded as 19, and the study status is terminated.

The registry lists 10.0 participants in the V.A.C. Therapy arm and 9.0 in the MWT arm. The outcome timeframe is Day 84. The study began in 2007-06, and primary completion is recorded as 2008-04. These entries describe the registry record; they do not establish when each participant entered treatment or how long an individual was followed.

The registry record does not report the randomization method, allocation concealment, reasons for termination, or whether recruitment stopped early. It also does not report detailed eligibility criteria, sites, treatment adherence, or a protocol for handling treatment changes. The stated objective included examining healing, quality of life, and utilization costs, but no secondary outcomes are posted. The record lists one outcome measure and zero analyses. Thus, the available statistical interpretation is limited to the posted primary outcome counts and the safety summaries.

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:

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.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With 100% Wound Closure, measured over Day 84.

The primary endpoint is the number of participants with 100% wound closure at Day 84. It is a binary measure: the outcome records whether the specified closure criterion was met by that time. The V.A.C. Therapy arm has a posted value of 1.0 among 10.0 participants; the MWT arm has a posted value of 0.0 among 9.0 participants.

Complete wound closure is an interpretable healing outcome because it represents reaching a defined state rather than a change on a continuous scale. In general, a binary endpoint can be summarized by counting participants who meet the criterion in each group. However, interpretation depends on how the endpoint is defined, how the assessment is made, and how missing assessments are handled. The registry record does not give further operational details for the 100% closure criterion, the assessment process, or missing outcome data.

The endpoint is anchored to Day 84, but the record does not explain whether this was the only assessment time or how outcomes before or after that day were treated. The observed counts alone do not describe uncertainty around a treatment contrast. The registry record explicitly states that a two-arm comparison for this binary endpoint is missing or not estimable, so no inferential comparison is available from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies a randomized, parallel-group comparison and a binary primary endpoint. Randomization is intended, in general, to make treatment groups comparable in expectation with respect to measured and unmeasured characteristics. It does not guarantee balance in a small study, and it does not by itself resolve missing outcomes or define the analysis population. The registry record does not report the randomization sequence method, allocation concealment, or the planned analysis approach.

For a binary endpoint, the basic descriptive information is the number of participants meeting the criterion and the group denominator. Here, the posted outcome values are 1.0 for V.A.C. Therapy and 0.0 for MWT, with group sizes of 10.0 and 9.0. A comparative analysis could express the relationship between group risks using a chosen measure, but the choice of measure and method matters, especially when event counts are very small or a group has no observed events. No measure of comparative effect is reported in the registry record, and it explicitly identifies the two-arm binary comparison as missing or not estimable.

In general, statistical inference for binary outcomes may use methods based on large-sample approximations or methods designed for sparse data. Large-sample methods rely on approximations that may be unreliable with limited information. Exact approaches can avoid some approximation assumptions but still produce uncertainty, and their conclusions depend on the specified method and estimand. This is general statistical context only: the registry record does not name a test, model, estimation method, or estimand beyond the endpoint description.

A confidence interval and a hypothesis test answer related but different questions. In general, an interval describes uncertainty around an estimated effect, while a test evaluates compatibility with a specified null hypothesis under its assumptions. Neither is posted for the primary comparison. A p-value would not measure the size or clinical importance of an effect, and the absence of a reported p-value is not evidence of equivalence. No equivalence or non-inferiority framework is reported.

Adjustment for baseline covariates can sometimes improve precision or account for prespecified prognostic factors. It requires a defined model and adequate information, and it should be planned rather than selected after inspecting results. No adjusted analysis, baseline covariates, or prespecified statistical model is reported in the registry record. The number of analyses listed is zero, so there is no sponsor-reported inferential result to interpret alongside the counts.

The registry includes a planning-illustration assumption based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. Such calculations are planning illustrations, not observed power and not evidence about the chance that the treatment effect is real. The record does not report the trial's own sample-size justification. Because the binary comparison is marked missing or not estimable, a planning illustration should not be mistaken for a validated estimate of a future trial requirement or for a result of this study.

Multiplicity concerns arise when researchers test multiple outcomes, timepoints, subgroups, or treatment contrasts. In general, conducting many tests can raise the chance of at least one apparently unusual result unless the analysis plan addresses that issue. The registry lists one outcome measure and no secondary outcomes, but the record does not describe the full planned analysis set or any multiplicity procedure. It is therefore not possible to determine from the registry whether the posted endpoint was the only outcome considered in the study.

Finally, the reliability of a binary endpoint depends on consistent measurement and complete follow-up. General methods may specify how participants with missing assessments are handled, whether outcomes are analyzed by randomized assignment, and whether other populations are examined. Those details are not reported in the registry record. Without them, the raw counts cannot be interpreted as a fully specified intention-to-treat, per-protocol, or other analysis.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("V.A.C. Therapy", "Moist Wound Therapy (MWT)")
n      <- c(10, 9)
events <- c(1, 0)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  V.A.C. Therapy  10  1  10.0  0.3  44.5  1.8  40.4  2.3  41.3
ARM  Moist Wound Therapy (MWT)  9  0  0.0  0.0  33.6  -0.0  29.9  0.3  30.8

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure, the number of participants with 100% wound closure at Day 84, and zero secondary outcomes. It does not report a multiplicity strategy or clarify whether additional outcomes, timepoints, subgroup analyses, or interim analyses were planned or examined. In general, multiplicity matters when several statistical questions are tested because the chance of at least one apparently notable result can increase. The record does not support a conclusion about how that issue was handled.

Missing-data procedures are not reported. The registry gives group sizes and outcome values, but does not state whether every participant had an endpoint assessment, whether any participants withdrew, or how missing Day 84 status was classified. Therefore, the posted group sizes cannot be assumed to equal the number included in the endpoint analysis.

The analysis population is also not reported. Although the study is described as randomized, the record does not say whether the primary analysis followed randomized assignment, excluded participants, or used another population. No imputation method, sensitivity analysis, or handling of treatment changes is described. These omissions limit the ability to assess bias from missing outcomes or departures from the assigned treatment. They also prevent reconstructing an analysis that would supply an official comparative estimate.

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 5% reporting threshold.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: cellulitis (20.0%), osteomyelitis (11.1%), patient fell at home, transported to er by ems (11.1%), influenza (11.1%), biliary pancreatitis (10.0%).

The registry reports serious adverse events for 5 of 10 participants at risk in the V.A.C. Therapy group and 3 of 9 participants at risk in the MWT group. Other adverse events are recorded as 0 in each group, and deaths are recorded as 0 in each group. These figures are safety summaries, separate from the wound-closure endpoint.

The serious-event terms listed include Cellulitis (20.0%), Osteomyelitis (11.1%), Patient fell at home, transported to ER by EMS (11.1%), Influenza (11.1%), Biliary pancreatitis (10.0%), and Infected fracture hematoma (10.0%). The registry does not explain the basis for each listed percentage or whether terms represent participants, events, or another reporting convention. The terms should therefore be read as registry entries, not combined into a total.

In general, an adverse-event count does not establish that an event was caused by treatment. The record does not provide event timing, relatedness assessments, severity details beyond the serious-event category, or comparative safety analyses. With the information posted, the figures describe reported safety counts and do not establish a causal treatment difference.

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

The result describes a limited set of observations: at Day 84, the registry records 1.0 participant with 100% wound closure in the V.A.C. Therapy arm and 0.0 in the MWT arm. The record does not provide an estimable two-arm comparison, an uncertainty interval, or a reported statistical test. The observed counts can be stated, but they cannot by themselves establish a reliable treatment contrast.

These results do not show that either treatment works or fails, and they do not establish that the treatments are equivalent. A lack of an estimable comparison is not the same as a finding of no difference. It means the registry record does not provide the statistical result needed to quantify and assess a between-group contrast. The small group counts also make it particularly important not to overread a pattern based on very few observed outcome events.

The endpoint is complete wound closure at a specified time, but the registry gives limited detail about the definition and assessment process. It does not report missing outcome handling, analysis population, or a statistical plan. Those gaps affect how confidently the counts can be connected to the randomized comparison.

The record also reports serious adverse events in both groups, but does not establish whether they were related to treatment or provide a formal comparative safety analysis. Taken together, the posted findings are descriptive rather than conclusive. They should be understood as the outcome and safety information recorded for a terminated study, not as a general estimate of treatment effects in other populations or settings.

14. Why This Trial Matters Statistically

This trial illustrates why a randomized design and a posted outcome count are not enough to support a comparative conclusion. Randomization describes how treatment assignment was intended to occur, but interpretation also requires a clearly reported analysis, uncertainty around the estimated contrast, and information about who contributed outcome data. The registry records the design and raw primary outcome counts but does not provide an estimable binary comparison.

It also demonstrates the importance of distinguishing descriptive results from inferential results. A count can tell readers what the registry records in each arm, while an inferential analysis addresses how uncertain a contrast is and what assumptions support it. Here, the outcome is sparse, and the record explicitly marks the comparison as missing or not estimable. The descriptive pattern should not be mistaken for a precise estimate.

The study's terminated status, the absence of posted secondary outcomes, and the lack of reported analysis details further constrain what can be learned. Reasons for termination and the handling of missing data are not reported. This matters statistically because study completion and outcome availability can affect which participants contribute to the observed results.

The case therefore reinforces a general principle: readers need more than a treatment label and a numerical outcome count to judge a clinical comparison. Clear definitions, analysis populations, missing-data procedures, and uncertainty estimates are essential parts of an interpretable statistical record.

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 is incomplete for several features that would ordinarily help contextualize a randomized trial. It does not report detailed eligibility criteria, participant baseline characteristics, site-level information, allocation concealment, or the randomization method. It also does not report why the study was terminated. Without those details, it is difficult to assess who the findings may represent and how the trial was conducted.

The primary endpoint description identifies 100% wound closure at Day 84, but does not provide a detailed definition of closure or the assessment procedures. Missing-data handling and the analysis population are not reported, so it is unclear whether the posted group sizes correspond to all randomized participants or to participants with an observed endpoint.

The registry lists zero analyses and says that a two-arm comparison for the binary endpoint is missing or not estimable. There is no reported confidence interval, p-value, adjusted result, or statistical model. The record also gives no sample-size justification for the trial itself and no multiplicity plan. These are limitations of the statistical record; they do not establish what analyses may have been conducted outside it.

Safety information is likewise limited. The registry gives serious-event counts and a list of terms with percentages, but does not explain the percentage basis, event timing, or relationship to treatment. These summaries cannot support a detailed causal safety comparison. The terminated status and sparse posted outcome should therefore be kept in view when interpreting the descriptive results.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Study Comparing V.A.C. Negative Pressure Wound Therapy (NPWT) to Moist Wound Therapy (MWT) in the Treatment of Diabetic Foot Amputation Wounds — NCT00837096.
• Registry record last updated 2024-10-16; status last verified 2024-10.
• Results first posted 2018-12-19.
• 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

The registry describes a prospective, randomized, multicenter, parallel study of V.A.C. Therapy versus moist wound therapy for diabetic foot amputation wounds. Masking is listed as none, phase as NA, enrollment as 19, and status as terminated. The study began in 2007-06, with primary completion recorded as 2008-04.

The primary endpoint was the number of participants with 100% wound closure at Day 84. The posted values are 1.0 among 10.0 participants in the V.A.C. Therapy arm and 0.0 among 9.0 in the MWT arm. The registry reports that a two-arm comparison for this binary endpoint is missing or not estimable and lists zero analyses. No secondary outcomes are posted.

Serious adverse events are recorded for 5 of 10 participants at risk in the V.A.C. group and 3 of 9 in the MWT group. The registry does not provide the analysis details needed for a comparative efficacy or safety conclusion.