Comparison of Surgical Procedures to Reduce Urinary Stress Incontinence: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparison of Surgical Procedures to Reduce Urinary Stress Incontinence (NCT00064662), a randomized phase 2, phase 3 study. The primary outcome is 24 Month Cumulative Success Rate Computed From Kaplan Meier Time-to-event Analysis (Reported as Percent Success)..

2. Clinical Question

The trial addressed a direct comparison between two surgical approaches used for predominantly stress urinary incontinence. Its stated primary aim was to compare treatment success. Secondary aims included quality of life, sexual function, satisfaction with treatment outcomes, complications, and the need for further treatment after surgery. These aims describe the questions the trial was intended to address, but the registry record does not include posted secondary results.

The primary endpoint combined several indicators rather than relying on a single symptom measure. Success required no self-reported incontinence symptoms on the MESA questionnaire, <15g in pad weight during a 24 hr pad test, no incontinence episodes on a 3-day voiding diary, no leakage on a provocative stress test at a standardized bladder volume, and no retreatment for urinary incontinence. The comparison therefore concerns the composite definition as a whole, not each component considered separately.

The registry identifies a two-year timeframe for the primary endpoint. It also describes planned follow-up as a minimum of two years and up to four years. The primary result should be read as the reported two-year estimate, rather than as a summary of outcomes across the entire possible follow-up period.

3. Trial Design

The registry describes a randomized, parallel-group clinical trial with no masking. It lists phase 2 and phase 3 and an enrollment of 655. The study status is completed. The listed start date is 2002-02, and primary completion is recorded as 2006-06. The sponsor is Carelon Research.

Participants were assigned to one of two surgical procedures: Burch Modified Tanagho, described as Burch colposuspension, or Autologous Fascia Sling, described as a pubovaginal sling using autologous rectus fascia. The posted primary analysis includes 329 participants in the Burch group and 326 in the Sling group. The registry states that all participants randomized were included in the time-to-event analysis. It does not give further details about how allocation was generated or concealed.

Because the trial was unmasked, participants and clinical staff were not described as blinded to the assigned procedure. The record does not report whether outcome assessors or analysts were masked. Masking can affect how subjective outcomes are collected or interpreted, while objective measurements may be less directly influenced; the composite endpoint includes both reported symptoms and measured or observed criteria. The available record does not say whether specific safeguards were used for those assessments.

The registry’s brief description anticipated follow-up for a minimum of two years and up to four years. The primary endpoint is specified at two years. The recorded enrollment and randomized group sizes describe the trial population, but do not by themselves reveal the number with complete follow-up at the endpoint or how censoring was handled. Those details are not reported in the registry record.

The protocol’s sample-size justification, planned statistical methods beyond the reported analysis, and any interim monitoring arrangements are not reported in the registry record. The presence of phase labels does not supply those missing design details. The registry lists two outcome measures, but the posted results summarized for this trial include the primary endpoint and no posted secondary results.

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: All participants randomized were included in time to event analysis.

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 24 Month Cumulative Success Rate Computed From Kaplan Meier Time-to-event Analysis (Reported as Percent Success)., measured over Two years.

The primary endpoint was the 24 Month Cumulative Success Rate computed from Kaplan-Meier time-to-event analysis and reported as percent success. Success was a composite: participants had to report no incontinence symptoms on the MESA questionnaire, have <15g of pad weight during a 24 hr pad test, report no incontinence episodes on a 3-day voiding diary, have no leakage on a provocative stress test at a standardized bladder volume, and have no retreatment for urinary incontinence. Retreatment could include anti-incontinence surgery, tightening of a sling, collagen injections, medication, behavioral treatment, or devices specifically used to treat stress urinary incontinence.

Using a composite can represent several clinically relevant dimensions of outcome in one endpoint. It can capture symptoms, measured leakage, observed leakage during testing, and subsequent treatment rather than focusing on only one type of evidence. A participant must meet all stated criteria to satisfy this definition of success, so the overall estimate does not show which component most often determined success or failure. Separate results for the individual components are not reported in the registry record.

In general, Kaplan-Meier methods estimate outcomes over time while accounting for participants whose event status is not observed through the full follow-up period, under assumptions about censoring. The registry calls the measure a cumulative success rate, but does not describe the event coding, censoring rules, or handling of missing component measurements. The reported value is therefore best interpreted according to the registry’s endpoint label and definition, with those methodological details left uncertain.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a Kaplan-Meier estimate represent?

In general, Kaplan-Meier analysis estimates the pattern of an outcome over time, rather than treating every participant as if their follow-up ended at the same moment. It can incorporate information from participants who are observed for different lengths of time, including those whose later outcome status is unknown, by censoring their observation at the last point when they are known to be under observation. The interpretation depends on the event definition and on assumptions about how censoring relates to the outcome.

The registry describes the primary measure as a cumulative success rate computed from Kaplan-Meier time-to-event analysis and gives a two-year estimate for each group. It also states that all randomized participants were included in the time-to-event analysis. However, it does not report the event coding, the rule for censoring, the number censored, or the amount of follow-up contributing to each estimate. The registry label and estimates can be reported, but the missing analytic details make it difficult to reconstruct the method fully.

What is the log-rank test assessing?

In general, a log-rank test compares time-to-event experience between groups across the follow-up period. Unlike a test that considers only an endpoint at one fixed time, it uses the ordering and timing of events over observed follow-up. Its result is commonly expressed as a p-value. Here, the registry reports p = 0.01 for the comparison of Burch and Sling.

A p-value is not the probability that the null hypothesis is true, nor is it a measure of the size of a difference. It summarizes how incompatible the observed test result is with the null hypothesis, under the test’s assumptions. Interpretation also depends on what was designated in advance as the primary comparison and whether other analyses were considered; those details are not reported in the registry record.

How should the confidence intervals be read?

In general, a confidence interval communicates uncertainty in an estimate under the method used to calculate it. The registry reports a 95% confidence interval of 32% to 44% for Burch and 41% to 53% for Sling. These intervals accompany the group-specific cumulative success estimates. They are not intervals for the difference between groups, and they do not establish the size or precision of a direct contrast.

The registry does not report a confidence interval for a comparative effect measure. The log-rank p-value supplies a test result, but it does not replace an effect estimate with its uncertainty interval. In general, statistical interpretation is clearer when both the estimated contrast and its uncertainty are available, alongside the test result.

Why does the composite definition matter?

A composite endpoint combines several criteria into a single outcome. In this trial, success incorporated a questionnaire, pad weight, voiding diary, provocative stress test, and absence of retreatment. In general, composites can broaden the outcome represented and may capture multiple aspects of a condition. At the same time, the overall result can be influenced by whichever component occurs most often or is most affected by treatment. Without results for each component, the overall estimate cannot show their separate contributions.

The criteria also differ in how they are obtained. Some depend on participant reports, while others depend on a measurement, a clinical test, or whether additional treatment occurred. An unmasked trial may be relevant when outcomes include reported symptoms or decisions about subsequent care. The registry does not report whether outcome assessors were masked or how retreatment decisions were standardized, so the extent of any influence cannot be determined from this record.

What does over-dispersion mean in general?

Over-dispersion is a general statistical issue in which observed variability is greater than a model assumes. It can make standard errors too small and confidence intervals too narrow if the model does not account for the extra variability. It is not reported as a feature of this analysis, and the registry does not describe a model that would allow an assessment of over-dispersion. It should not be presumed to apply to this time-to-event comparison.

The record also does not give enough information to assess proportional hazards, which is an assumption used by some time-to-event models, or to determine whether such a model was used. A log-rank test does not itself report a hazard ratio. No hazard ratio or model-based effect estimate is posted for this endpoint.

What can be inferred from the reported analysis?

The reported estimates describe the cumulative success results at two years, and the log-rank test compares time-to-event patterns. The randomized parallel design supports a comparison of the assigned groups, but a complete evaluation also requires details about allocation, follow-up, censoring, missing outcomes, and prespecified analyses. These details are not reported in the registry record. No numerical result should be constructed from the group estimates beyond what the registry reports.

In general, planning sample sizes are not observed power. A sample-size illustration based on an observed effect is a hypothetical planning exercise, not evidence that the trial had a particular probability of detecting an effect. The registry record does not report the trial’s own sample-size justification or sufficient planning details to assess its original power calculation.

10. Analyses Reported by the Sponsor

The registry reports the sponsor’s two-group analysis as a log-rank test with p = 0.01. It also reports the two-year cumulative success estimates and their group-specific 95% confidence intervals: 38% for Burch, with an interval from 32% to 44%, and 47% for Sling, with an interval from 41% to 53%.

No separate unadjusted recalculation of a two-arm effect estimate is reported for this endpoint in the registry record. The record indicates that a two-arm comparison value is missing or not estimable for this count-other endpoint. Accordingly, there is no recalculated comparison to set against the sponsor’s log-rank analysis. The registry does not flag a discrepancy between sponsor and recalculated results.

The sponsor’s reported analysis is the available inferential comparison. It should not be replaced by a calculation based on the separate group percentages, since those percentages are Kaplan-Meier estimates from time-to-event analysis and are not sufficient to reproduce a log-rank test. The p-value does not supply a comparative effect size or an uncertainty interval for the contrast. Details of the sponsor’s full analysis plan, including any adjustment or additional analyses, are not reported in the registry record.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures, while the posted results summarized for this trial include the primary endpoint and no posted secondary results. The trial description names secondary aims involving quality of life, sexual function, satisfaction with treatment outcomes, complications, and the need for other treatment after surgery. Their results are not reported in the registry record. The record does not identify how many comparisons were planned for each aim or whether they were part of a formal testing hierarchy.

Multiplicity arises when researchers conduct several statistical tests or examine several outcomes. In general, testing many hypotheses can increase the chance that at least one result appears statistically significant by chance. Researchers may address this through a prespecified hierarchy, adjustment procedures, or a distinction between confirmatory and exploratory analyses. The registry does not report whether any such approach was planned or used. The log-rank p-value should therefore be understood as the reported result for the primary comparison, without assuming that it was adjusted for other outcomes or analyses.

The primary endpoint itself is composite, with multiple criteria that contribute to the definition of success. The overall result does not identify the component-specific outcomes, and results for the individual criteria are not reported in the registry record. The record also does not report whether additional subgroup or sensitivity analyses were undertaken. Their existence, number, and results cannot be inferred from the posted primary analysis.

The record states that all randomized participants were included in the time-to-event analysis. It does not describe missing questionnaire, pad-test, diary, or stress-test data; how incomplete composite assessments were classified; or how participants with incomplete follow-up were handled. It also does not report the number censored or reasons for censoring. In general, time-to-event methods can accommodate differing observation times, but their interpretation depends on how censoring and missing outcomes arise and are handled.

The record does not identify an interim-analysis plan, stopping rule, or monitoring procedure. It also does not give the protocol’s sample-size rationale or a detailed statistical analysis plan. These omissions prevent assessment of the original multiplicity strategy, missing-data plan, and analysis-population definitions. The stated analysis population is all randomized participants, but further details about deviations from assigned procedures or exclusions are not reported in the registry record.

12. Safety Results

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

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: genitourinary (8.9%), wound complication requiring surgical intervention (3.6%), bleeding (0.9%), pelvic pain (0.6%), gastrointestinal (0.3%).

The registry reports serious adverse events for 32 of 329 participants at risk in the Burch group and 42 of 326 participants at risk in the Sling group. It also reports other adverse events affecting 156 participants at risk in the Burch group and 206 participants at risk in the Sling group. These are posted counts, not a complete account of the nature, timing, severity, or duration of each event. No adjusted safety comparison or uncertainty interval is reported.

The listed serious adverse-event terms include Genitourinary at 8.9%, Wound complication requiring surgical intervention at 3.6%, Bleeding at 0.9%, Pelvic pain at 0.6%, Gastrointestinal at 0.3%, and Respiratory distress requiring intubation at 0.3%. The record does not specify the denominator or group attribution for these term percentages, so they should not be treated as arm-specific rates. Event categories may also overlap unless otherwise stated; the registry does not explain overlap in these data.

Death counts are not reported in the registry record. The adverse-event counts alone do not establish that one procedure caused more harm than the other. Differences in follow-up, event definitions, reporting, and participant exposure can matter when interpreting safety data, and the registry does not provide enough detail to assess those factors fully. The counts describe reported events in this trial and should be read separately from the primary success comparison.

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

The result describes a randomized comparison of two procedures in women with predominantly stress urinary incontinence. At two years, the cumulative success estimate was 38% for Burch and 47% for Sling, using a definition that required participants to meet all listed symptom, measurement, test, and retreatment criteria. The log-rank analysis reported p = 0.01. Together, these figures describe the posted primary outcome and its time-to-event comparison.

They do not show the results for each part of the composite, nor do they provide a direct effect estimate with a confidence interval. The separate confidence intervals quantify uncertainty around the group-specific estimates, not around a difference between procedures. The p-value indicates the result of the reported test under its assumptions; it does not state the clinical importance of the comparison or the probability that a particular participant will meet the success definition.

The registry’s findings are limited to the reported population, endpoint, follow-up, and analysis. They do not establish results for the secondary aims because those results are not posted. The primary endpoint is specifically a composite of criteria, so the result should not be rephrased as a result for symptoms alone, leakage alone, or avoidance of further treatment alone. The posted figures also do not characterize outcomes over the full possible follow-up of up to four years.

The randomized design is relevant to the comparison, but important analysis and conduct details are not reported in the registry record. These include allocation procedures, detailed follow-up and censoring information, missing-data handling, outcome-assessor masking, and the prespecified statistical plan. These gaps do not negate the reported estimates, but they limit independent assessment of how they were obtained and how broadly they should be interpreted.

In general, statistical evidence should be considered alongside endpoint meaning, precision, study conduct, and the relevance of the trial population. The record supports describing the two-year estimates and the reported log-rank result. It does not support a broader claim about every outcome of interest, the separate components of success, or outcomes beyond the reported analysis.

14. Why This Trial Matters Statistically

This trial is statistically notable because it directly randomized participants between two surgical procedures and reported a time-to-event analysis for a composite success outcome. Randomization is intended to make groups comparable at assignment, while a parallel design follows the assigned groups separately. The record reports the group sizes and states that all randomized participants were included in the time-to-event analysis.

The endpoint illustrates how clinical trials can combine several dimensions of outcome. Questionnaire responses, pad weight, diary reports, provocative testing, and retreatment were all part of the success definition. That breadth may make the endpoint more representative of overall treatment success than a single measure, but it also makes interpretation dependent on the composite’s full set of criteria. Component-specific results would help explain what the overall estimate represents; they are not reported in the registry record.

The analysis also illustrates the distinction between a time-to-event test and a fixed-time estimate. The log-rank p-value evaluates group patterns over time, while the reported two-year cumulative success percentages give group estimates at a specified time. Neither alone provides a direct contrast with an uncertainty interval. Recognizing which statistical quantity answers which question prevents a test result from being mistaken for an effect size.

Finally, the record demonstrates why reporting completeness matters. The primary result is available, but secondary results and important analytic details are not. Readers can describe what was posted without assuming details about missing data, multiplicity, censoring, sample-size justification, or interim monitoring. That separation between reported evidence and unreported methods is central to careful interpretation of registry results.

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 gives limited detail about participant eligibility and baseline characteristics beyond the description of women with predominantly stress urinary incontinence. The results therefore cannot be assessed across participant subgroups from the information reported. The allocation method and concealment procedures are not reported in the registry record, and the record identifies no masking. Whether outcome assessors or analysts were masked is also not reported.

The primary endpoint combines several kinds of evidence. The record does not provide component-specific results, so it is not possible to determine which criteria contributed most to the group estimates. The definitions and procedures for collecting questionnaire, pad-test, diary, and stress-test data are not described in detail. The handling of incomplete component data and missing visits is not reported.

Although the registry states that all randomized participants were included in the time-to-event analysis, it does not report censoring counts, censoring reasons, event coding, or the method used to handle participants without complete follow-up. The trial description anticipates follow-up for a minimum of two years and up to four years, while the primary endpoint is reported at two years. The posted result does not characterize the full potential follow-up period.

The registry reports a log-rank p-value and group-specific confidence intervals, but no direct comparative effect estimate with an uncertainty interval. The statistical analysis plan, sample-size justification, interim analyses, and multiplicity strategy are not reported in the registry record. Results for secondary aims are not posted, and death counts are not reported. These limits make the available record useful for describing the primary posted estimates, but insufficient for a full reconstruction of trial conduct and analysis.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Comparison of Surgical Procedures to Reduce Urinary Stress Incontinence — NCT00064662.
• Registry record last updated 2013-05-10; status last verified 2013-05.
• Results first posted 2012-09-28.
• 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

NCT00064662 is a completed randomized, unmasked, parallel-group trial comparing Burch colposuspension with a pubovaginal sling using autologous rectus fascia in women with predominantly stress urinary incontinence. The registry lists phase 2 and phase 3, enrollment of 655, a start date of 2002-02, and primary completion at 2006-06. Follow-up was described as a minimum of two years and up to four years.

The primary endpoint was a two-year Kaplan-Meier cumulative success estimate based on a composite of symptom, pad-test, voiding-diary, stress-test, and retreatment criteria. The estimates were 38% for Burch, with a 95% confidence interval from 32% to 44%, and 47% for Sling, with a 95% confidence interval from 41% to 53%. The reported log-rank p-value was 0.01. The registry states that all randomized participants were included in the time-to-event analysis.

Secondary results are not posted in the registry record. The record does not report the detailed statistical plan, sample-size justification, interim analyses, censoring rules, missing-data procedures, or a comparative effect estimate with its confidence interval.