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 Silver Impregnated Dressings to Reduce Wound Complications in Obese Patients at Cesarean Section (NCT01528696), a randomized phase 4 study. The primary outcome is Number of Patients Who Experience One or More Wound Complications.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01528696 |
| Phase | Phase 4 |
| Condition | Obesity, Complications; Caesarean Section, Wound |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 37 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Michigan |
| Results posted | Yes |
2. Clinical Question
Population
Obese patients undergoing cesarean section. The registry summary describes this group as being at high risk for wound complications and states that these complications occur in approximately 20% of patients. That figure is context from the summary, not an observed rate in this trial.
Intervention
Silverlon, a silver-impregnated dressing placed over the incision in the postoperative period.
Comparator
A standard island-type dressing after cesarean section.
Primary question
Whether the groups differed in the number of patients experiencing one or more wound complications within six weeks. The composite included cellulitis, wound dehiscence, seroma, hematoma, abscess, and fascial dehiscence, identified through wound evaluation using the medical record or patient report.
The intended comparison is clinically focused: it asks whether the dressing strategy is associated with fewer patients experiencing at least one complication in the specified postoperative period. Because the endpoint is a composite, an event in any one of its listed categories would count toward the primary outcome. The record does not report separate results for those categories or an overall result for the composite.
Recruitment was terminated when the study team could not gather outcome information by the intended survey or chart review. Consequently, the registry record does not report whether the groups differed on the primary question. It also does not support a conclusion about the comparative effect of the dressings.
3. Trial Design
The registry classifies NCT01528696 as a randomized, single-masked, parallel-group phase 4 trial. The two interventions were Silverlon and a standard dressing. In the Silverlon arm, obese patients undergoing cesarean section were to receive a silver-impregnated dressing; in the standard arm, they were to receive a standard island-type dressing. The record does not identify who was masked, describe the allocation procedure beyond stating that assignment was randomized, or report further details of the study protocol.
Enrollment was 37. The trial began in 2012-02, and the primary completion date was 2013-01. Its status is terminated. The registry explains that recruitment stopped because the team could not gather outcome data through the intended survey or chart review, and that further attempts at data gathering were stopped. This reason is important when interpreting the absence of results: the record does not present an analyzed comparison of the assigned groups.
The primary endpoint was the number of patients with one or more wound complications within six weeks. The registry also lists febrile morbidity and patient report of pain severity and control as secondary outcomes. It records three outcome measures overall, but reports no analyses. The record does not describe the planned statistical test, any adjustment factors, a sample-size justification, interim analyses, or an analysis population. Those details are not reported in the registry record.
The randomized parallel design would ordinarily support a comparison between groups, provided outcomes were collected and analyzed according to an appropriate plan. Random assignment by itself does not establish the treatment contrast: the relevant outcome information is needed to estimate that contrast. Here, the record states that outcome data could not be gathered, so the design description cannot be treated as evidence of an effect.
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 | Standard Dressing | Silverlon |
|---|---|---|
| STARTED | 18 | 19 |
| Hospital Stay (2-5 Days) | 18 | 19 |
| COMPLETED | 0 | 0 |
| NOT COMPLETED | 18 | 19 |
Reasons for not completing this period:
| Reason | Standard Dressing | Silverlon |
|---|---|---|
| See detailed description | 18 | 19 |
Analysis population for the primary outcome, as defined in the registry: For logistical reasons, we were unable to gather outcome data either by the intended survey or by chart review. When it became clear that we would be unable to complete the study, recruitment was terminated and further attempts at data gathering were stopped. Therefore no outcome data could be analyzed.
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.
| Characteristic | Unit | Standard Dressing | Silverlon | Total |
|---|---|---|---|---|
| Participants analysed | 18 | 19 | 37 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 18 | 19 | 37 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Female | Participants | 18 | 19 | 37 |
| Sex: Female, Male: Male | Participants | 0 | 0 | 0 |
| Region of Enrollment: United States | participants | 18 | 19 | 37 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Patients Who Experience One or More Wound Complications, measured over 6 weeks.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint counts patients who experience one or more wound complications within six weeks of cesarean section. The registry defines the composite as cellulitis, wound dehiscence, seroma, hematoma, abscess, or fascial dehiscence, based on wound evaluation found in the medical record or reported by the patient. The unit of interest is therefore the patient with at least one listed complication, rather than the total number of individual events.
A composite endpoint can capture several clinically relevant types of complication in one outcome. It may be useful when the study question concerns a broad category of wound problems rather than a single diagnosis. However, the combined result would not, by itself, show which component contributed events or whether the components behaved similarly. The registry does not report component-specific outcomes.
The six-week timeframe specifies the period in which complications were to be counted. That definition makes the intended outcome more concrete, but it does not resolve the central limitation: the registry says that the study team could not obtain outcome data by the intended survey or chart review. Thus, no primary endpoint result is reported. The endpoint's definition should not be mistaken for an observed finding, and the registry record cannot establish a comparison between the dressing groups for this outcome.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The key interpretive fact is the absence of primary outcome data. The registry describes a randomized comparison of Silverlon with a standard dressing, but it also states that wound outcome information could not be collected through the intended survey or chart review. Recruitment was then terminated and further data-gathering attempts stopped. Without those outcomes, there is no reported estimate of the difference between groups, no confidence interval for that difference, and no reported statistical test of the primary question.
This is not a result showing that the groups were the same. It is also not evidence that either dressing reduced or increased wound complications. A comparison requires observed outcomes from the groups, together with a defined analysis. In their absence, the direction and magnitude of any difference are unknown from the registry record. The absence of an effect estimate also means that its precision cannot be assessed.
The listed enrollment is 37, but enrollment alone does not reveal how many participants had a wound complication. The adverse-event figures are separate registry entries and should not be substituted for the primary endpoint: serious adverse events and other adverse events are not the same measure as the composite wound-complication outcome. Likewise, the record's count of three outcome measures does not mean that results are available for those measures.
Statistical uncertainty is commonly expressed with a confidence interval, which describes a range of values compatible with the data and the analysis assumptions. Here, no primary effect estimate or interval is reported, so there is no interval to interpret. A p-value is also not reported for the primary outcome. This is not a case in which a non-significant result can be read as evidence of no difference; the record lacks the outcome comparison needed for such a test.
The registry reports no analyses. It does not give a statistical plan, identify analysis populations, or report how missing outcomes would have been handled. Those omissions limit assessment of the intended inferential approach, but they do not change the basic interpretation: the available registry record does not report an analyzed primary outcome. The results should therefore be described as unavailable, rather than as a positive, negative, or null finding.
9. Statistical Methods Explained
The trial is described as randomized and parallel-group. In general, random assignment is intended to make treatment groups comparable at the point of assignment, on average, and a parallel design follows groups assigned to different interventions. These design features do not guarantee that a valid comparison can be made: outcomes must also be measured, recorded, and analyzed. The registry reports that the intended outcome data were not obtained, so the randomized design does not yield a reported treatment-effect estimate in this record.
The registry labels masking as single, but does not say which people were masked or how masking was maintained. That information is not reported in the registry record. The record also does not describe the randomization method, allocation concealment, or any procedures for ensuring that participants in each arm were followed similarly. These are protocol details, not details that can be inferred from the design labels alone.
The primary outcome is binary at the patient level: each patient either met the composite definition of one or more wound complications within six weeks, or did not. A statistical comparison would generally need the number with the outcome and the number assessed in each arm, along with a chosen measure of effect and method of inference. Those primary outcome counts and analyses are not reported. No relative or absolute effect estimate, confidence interval, or p-value for the primary endpoint is available in the registry record.
A confidence interval is a general statistical way to convey the uncertainty around an estimate. Its width depends on information in the data and on the method used. Since the registry does not report a primary estimate or outcome counts, there is no primary confidence interval to interpret. The absence of an interval is not equivalent to a narrow interval around no effect; it means that the record does not provide the estimate-and-uncertainty pair.
The record lists febrile morbidity and patient report of pain severity and control as secondary outcomes. It does not report results for these measures or specify their scales, time points, or analysis methods. There are three outcome measures listed overall, but the registry reports zero analyses. These entries identify intended or registered outcomes; they do not establish that the outcomes were collected or analyzed.
Over-dispersion is a general issue for count outcomes when observed variability exceeds what a chosen probability model assumes. It can make standard errors too small if the model does not accommodate the extra variability. That concept is not directly applicable to the registry's stated primary endpoint in its patient-level form, and no model or dispersion assessment is reported. It would be inappropriate to attribute any particular modeling choice to this trial.
The registry includes a description of planning illustrations based on a stated fraction of an observed effect, using a two-sided significance level of 0.05, equal allocation, and a normal approximation. It also distinguishes participant-per-arm planning illustrations from total-event planning for time-to-event outcomes. Such illustrations are planning exercises, not observed power. The record does not report the trial's own sample-size justification or its design assumptions. Because the primary outcome data are unavailable, no observed effect for this endpoint can be interpreted from the registry record, and the illustrations cannot supply that missing trial result.
There is no reported interim analysis or stopping rule. The record does say recruitment was terminated when outcome collection proved infeasible and further attempts to gather data stopped. That is the stated reason for termination; it should not be recast as a decision based on an efficacy or safety analysis, because no such analysis is reported.
In general, a complete statistical report would describe the analysis population, how missing observations were handled, the effect measure, the inferential method, and uncertainty around the estimate. The registry does not report these elements for the primary outcome. Their absence prevents a detailed audit of the intended analysis, while the unavailable outcome data prevent a numerical assessment of the treatment comparison itself.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists febrile morbidity and patient report of pain severity and control as secondary outcomes, in addition to the primary wound-complication endpoint. It does not report analyses for these outcomes. A multiplicity adjustment or strategy for interpreting multiple outcome tests is not reported in the registry record. As no outcome analyses are presented, there are no reported tests whose multiplicity handling can be evaluated.
The primary outcome description states that the team was unable to gather outcome data by the intended survey or chart review. When that limitation became clear, recruitment was terminated and further data-gathering attempts were stopped. This is more consequential than a report of partial follow-up: the registry does not provide the outcome counts needed for the planned primary comparison. The reasons for unavailable participant-level outcomes beyond the logistical difficulty described are not reported.
The registry does not report how missing outcomes were defined or handled, whether any participants had partial outcome information, or whether sensitivity analyses were considered. It does not identify an intention-to-treat, per-protocol, or other analysis population. These details are not reported in the registry record, so no claim can be made about the actual analysis population or how missingness might have affected an estimate.
Missing outcome data can limit both the validity and precision of a trial comparison. In general, the consequences depend on how much information is missing and why it is missing, among other factors. Here, the record does not provide enough outcome information to characterize those consequences numerically. The defensible interpretation is that primary and secondary outcome results are unavailable in the registry, not that missing data were handled in a particular way.
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 |
|---|---|---|---|
| Standard Dressing | 0 | 18 | 0.0% |
| Silverlon | 0 | 19 | 0.0% |
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 |
|---|---|
| Standard Dressing | 0 of 18 |
| Silverlon | 0 of 19 |
The adverse-event record lists zero serious adverse events among 18 participants at risk in the standard-dressing group and zero among 19 participants at risk in the Silverlon group. It also lists zero other adverse events among 18 participants at risk in the standard group and zero among 19 at risk in the Silverlon group. No serious adverse-event terms are listed. The death figures are not reported in the registry record.
These are the adverse-event figures recorded for the groups; they are not the primary wound-complication results. The serious adverse-event and other-adverse-event categories should not be interpreted as interchangeable with the composite endpoint of cellulitis, wound dehiscence, seroma, hematoma, abscess, or fascial dehiscence. The record does not report how the adverse-event entries were collected or whether they capture every wound complication.
Zero recorded events does not establish that no event occurred in the underlying study population. In particular, the registry separately states that the team could not gather the intended outcome data. The adverse-event entries therefore should be read as registry-reported counts with their listed numbers at risk, not as evidence that either dressing has a particular safety profile or as a comparison establishing a difference between groups.
12. What the Result Does, and Does Not, Mean
The record documents an attempt to compare Silverlon with a standard island-type dressing among obese patients undergoing cesarean section. It describes random assignment, a parallel-group design, a six-week composite wound-complication endpoint, and two secondary outcomes. It also records enrollment of 37 and a terminated status. These details establish the intended study question and the trial's administrative and design context.
What the record does not establish is whether the groups differed in wound complications, febrile morbidity, or patient-reported pain severity and control. The stated difficulty collecting outcome data led to termination of recruitment and further data gathering. Without outcome results, there is no basis in the registry record for estimating the direction, size, or precision of a treatment contrast. The findings cannot be characterized as showing benefit, harm, equivalence, or no difference.
The posted adverse-event counts are limited information about the reported adverse-event categories, not substitutes for the unreported primary outcome. Nor does enrollment of 37 resolve the uncertainty: the number enrolled is not a measure of how many experienced the primary endpoint. The absence of a reported effect estimate and confidence interval means that statistical precision cannot be judged.
This distinction matters when reading trial records. A trial can have a defined clinical question and a randomized design while still not providing analyzable evidence for that question. Here, the registry supports a description of the intended comparison and the reason the results are unavailable. It does not support a clinical conclusion about the relative outcomes of the two dressings.
13. Why This Trial Matters Statistically
This trial is statistically instructive because it separates the presence of a randomized design from the availability of evidence about an outcome. Randomization can support a fair comparison when the assigned groups have outcome data, but it cannot replace measurement and analysis. In this record, the primary endpoint is defined in detail, yet the registry reports that the intended data could not be gathered. That leaves the central comparison unanswered.
The case also illustrates why a missing result must not be interpreted as a null result. A null estimate with adequate precision would be a quantitative finding; an unavailable estimate is not. Since there is no reported effect estimate, confidence interval, or primary-outcome test, readers cannot assess either the direction of a possible difference or how precisely it might have been measured.
Composite endpoints require careful reading as well. The registered primary outcome combines several types of wound complication, each of which would count toward a patient experiencing one or more complications. Even if an overall composite result were reported, component results would help readers understand what drove it. The registry does not provide either form of outcome result, underscoring the difference between defining an endpoint and observing it.
Finally, the trial record emphasizes the value of transparent reporting about feasibility and missing outcomes. It states why recruitment ended and why results could not be collected, while leaving the statistical analysis details unreported. This allows readers to distinguish a study that found no difference from one that does not report an analyzable comparison. That distinction is essential for sound statistical interpretation.
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 principal limitation is that the registry reports no primary outcome data. The stated endpoint required information from wound evaluation in the medical record or patient report, but the study team could not complete the intended survey or chart review. Recruitment was terminated and further data gathering stopped. Consequently, the primary endpoint cannot be compared between arms using the registry record.
The same lack of reported results applies to the listed secondary outcomes, febrile morbidity and patient report of pain severity and control. Their measurement details and findings are not reported. The registry records three outcome measures but no analyses, so there is no reported outcome estimate or analysis population to assess.
Statistical planning and analysis details are limited. A sample-size justification, planned test, effect measure, handling of missing outcome data, multiplicity strategy, and interim analysis plan are not reported in the registry record. The masking label is single, but who was masked is not specified. The randomization method and allocation concealment details are also not reported.
The adverse-event record includes zero serious and zero other adverse events for the listed group denominators, but deaths are not reported. Those entries do not answer the primary wound-complication question and do not remedy the lack of outcome collection. Overall, the record is informative about the intended design and the reason results are unavailable, but it does not provide the clinical outcome evidence needed to estimate a treatment effect.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Silver Impregnated Dressings to Reduce Wound Complications in Obese Patients at Cesarean Section — NCT01528696.
- Registry record last updated 2017-04-04; status last verified 2017-02.
- Results first posted 2017-04-04.
- 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
NCT01528696 is a randomized, single-masked, parallel-group phase 4 trial sponsored by the University of Michigan. It compared Silverlon, a silver-impregnated dressing, with a standard island-type dressing in obese patients undergoing cesarean section. Enrollment was 37. The trial began in 2012-02, had a primary completion date of 2013-01, and is listed as terminated.
The primary endpoint was one or more wound complications within six weeks. Secondary outcomes were febrile morbidity and patient report of pain severity and control. The registry states that outcome data could not be gathered by the intended survey or chart review, after which recruitment and further data-gathering attempts stopped. It reports no analyses. Adverse-event entries list zero serious and zero other adverse events in each group; deaths are not reported. The record does not report a comparative result for the primary or secondary outcomes.