Post Market Study Of Single Incision Sling Versus Transobturator Sling for Stress Urinary Incontinence: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Post Market Study Of Single Incision Sling Versus Transobturator Sling for Stress Urinary Incontinence (NCT01784588), a non-randomized na study. The primary outcome is Number of Subjects Meeting Definition of Treatment Success at 36 Months, by a Composite of Objective and Subjective Measures.

2. Clinical Question

This is a comparative clinical question, but the non-randomized allocation means the comparison is observational rather than a randomized estimate of a device effect. A group difference, if reported, would need to be interpreted in light of possible differences in who received each system and how care was delivered. The registry record does not describe adjustment for such differences. It also does not report the primary endpoint results, uncertainty intervals, or a statistical test for the comparison. Consequently, the definition of the question is clear, but its answer cannot be established from the registry record alone.

3. Trial Design

The registry record describes a prospective, non-randomized, parallel-cohort, multicenter study comparing the Solyx Single Incision Sling System with the Obtryx II Sling System. Enrollment is reported as 281, and the study status is completed. The recorded start is 2013-06, and primary completion is recorded as 2018-01-17. The listed phase is NA. These descriptors identify the study structure; they do not establish that the groups were comparable at baseline.

In a parallel-cohort design, participants are followed in the group associated with the device they receive rather than crossing between devices. Here, allocation was not randomized and masking was none. The registry record does not report how the device choice was made, whether clinicians or participants had preferences, or whether any allocation procedure sought to balance prognostic characteristics. Those details matter because they can influence which participants enter each cohort and can complicate interpretation of a group comparison.

The stated purpose was to compare the treatment device with the other sling system for stress urinary incontinence, with safety information and patient outcomes collected for three years and evaluated. The primary outcome is described at 36 months. The registry record does not report how many participants completed follow-up at that time, whether follow-up differed between groups, or how missing outcome measurements were handled.

The primary endpoint is a participant count meeting a composite success definition. The registry record lists one outcome measure and two analyses, but does not describe the analysis methods or the populations used for those analyses. It also does not report a randomization scheme, masking procedures, or a statistical analysis plan. These omissions limit assessment of how the planned comparison was carried out and whether the reported analysis, if available elsewhere, followed prespecified methods.

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

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 Subjects Meeting Definition of Treatment Success at 36 Months, by a Composite of Objective and Subjective Measures, measured over Data presented is for 36 months.

The primary endpoint is the number of participants meeting the definition of treatment success at 36 months. Success requires both an objective and a subjective component. The objective component is no direct observation of urine loss during cough provocation, with the protocol-required bladder-fill procedure. The subjective component is improvement on the Patient Global Impression of Improvement (PGI-I), defined as a response of “A little better,” “Much better,” or “Very much better.”

Combining these criteria makes the endpoint more demanding than relying on either test result or self-report alone. The objective measure captures urine loss under a specified provocation, while the PGI-I captures the participant’s overall perception of change relative to baseline. The combination can therefore represent success across two different kinds of evidence. It also means a participant must satisfy both components to count as a success under this definition.

Composite endpoints can be useful when a condition has more than one clinically relevant aspect, but their interpretation depends on the component rules. The endpoint does not indicate which component determined an individual outcome unless component results are reported separately. The registry record does not report the component-specific results or the number meeting the composite definition in either group. It therefore permits explanation of how success was defined, but not estimation of how often it occurred or comparison of success between the devices.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies the primary outcome as a count of participants meeting a binary success definition. A participant either meets the stated criteria or does not. The underlying clinical measurements are combined into the composite rule: a negative cough stress test under the specified procedure and a qualifying improvement response on the PGI-I. The registry record does not report the resulting success counts or the statistical model used to compare them.

What does a group comparison estimate?

In general, a comparison of binary outcomes may describe the difference in the proportions meeting the endpoint, a relative measure, or an adjusted association. These measures answer related but distinct questions. An absolute difference describes how far apart the observed group proportions are; a relative measure expresses one group’s outcome in relation to the other. An adjusted estimate attempts to account for selected participant characteristics. The registry record does not report which measure or model was used for the primary comparison, so none can be attributed to this study from the available record.

General statistical explanation: estimates should be read together with their uncertainty intervals. An interval reflects the sampling uncertainty under the analysis assumptions and indicates how precisely the effect has been estimated. It is not a guarantee that the true effect lies inside the interval, and it does not account automatically for bias from non-random allocation, missing data, or measurement choices. No primary-outcome interval is reported in the registry record.

Why does non-randomized allocation matter?

Random allocation is one way to balance measured and unmeasured prognostic factors between groups in expectation. In this study, allocation was non-randomized, so the device groups may differ before treatment. For example, treatment choice could be associated with clinical features, provider preference, or other factors, but the registry record does not report whether any of these occurred. They should be treated as possible sources of confounding, not as documented features of this study.

General statistical explanation: regression adjustment, weighting, matching, or stratification can address measured differences when appropriate data and assumptions are available. Such methods cannot guarantee removal of confounding, especially from factors that were not measured or were measured poorly. The registry record does not report whether any adjustment method was used, which covariates were considered, or whether balance was assessed. Accordingly, an adjusted causal interpretation cannot be evaluated from this record.

How should a binary composite be understood?

The composite endpoint requires both components to meet their respective criteria. This rule can provide a concise summary, but it can conceal differences in the components. One group could have a different pattern of objective test results and participant-reported improvement while producing a similar composite count. Conversely, a composite contrast does not show which component accounts for a difference. Separate component results would help interpret this issue, but they are not reported in the registry record.

Binary outcomes also discard detail within categories. The PGI-I has ordered response categories, but the success definition groups the qualifying improvement responses together and treats other responses as not meeting the subjective criterion. The endpoint therefore answers the prespecified threshold question rather than describing the full distribution of reported change. The registry record does not report analyses of the individual PGI-I categories.

What can planning calculations tell readers?

General statistical explanation: a sample-size calculation describes the amount of information a future study might need under stated assumptions about the target effect, significance level, allocation, and analysis. It is a planning exercise, not evidence that an observed result is precise or that a study had a particular probability of detecting an effect after completion. The registry’s planning assumptions describe an illustration based on a fraction of an observed effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation. The registry record does not report the resulting planning values in the information available for this analysis. Such illustrations should not be treated as observed power, and they do not replace the study’s actual outcome estimates and uncertainty intervals.

For binary outcomes, the precision of a group estimate depends on the number of participants with usable outcome data and on the frequency of the outcome. The enrollment figure alone does not establish the analyzed denominator at 36 months. The registry record does not report the number assessed for the primary endpoint in each group, the handling of incomplete follow-up, or the analysis population. Thus, the available information is insufficient to reproduce or evaluate the primary statistical comparison.

Finally, a statistically detectable contrast and a clinically important contrast are not interchangeable. Statistical inference concerns the data relative to a model and its assumptions; clinical importance requires interpretation of the effect’s magnitude and relevance. The registry record does not report a threshold for a clinically important difference. With neither the primary effect estimate nor its uncertainty reported, the statistical and clinical importance of the comparison cannot be assessed.

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("Solyx Single Incision Sling System", "Obtryx II Sling System")
n      <- c(104, 108)
events <- c(94, 96)
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  Solyx Single Incision Sling System  104  94  90.4  83.0  95.3  83.2  94.7  83.2  94.7
ARM  Obtryx II Sling System  108  96  88.9  81.4  94.1  81.6  93.5  81.6  93.5

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary outcome measure and two analyses, but does not report what the two analyses were, whether they addressed separate groups or estimands, or which result was designated primary for inference. It also does not report a multiplicity adjustment or a hierarchy of hypotheses. When several outcomes or analyses are tested, the chance of at least one apparently unusual result can increase; methods such as prespecified testing sequences or adjusted significance thresholds can address that issue. This is general statistical context, not a description of methods used in this study.

The record does not report a missing-data strategy for the 36-month endpoint. It does not state how participants without a measurement were classified, whether imputation was used, or whether sensitivity analyses were conducted. In general, missing outcomes can affect a comparison when the likelihood of missingness is related to participant characteristics or outcome status. The direction and size of any resulting bias depend on the missingness pattern and the assumptions used to handle it. Without group-specific follow-up and analysis details, that impact cannot be evaluated.

The analysis populations are also not reported in the registry record. It is therefore unclear whether the primary analysis included all enrolled participants, participants who received the assigned device, or a subset with available endpoint data. These choices can change the interpretation of a non-randomized cohort comparison. The registry record also does not report protocol deviations or exclusions. These omissions prevent a full assessment of multiplicity, missingness, and analysis-set selection.

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: device extrusion (0.7%).

The registry lists serious adverse events for 1 of 141 participants at risk in the Solyx group and 1 of 140 participants at risk in the Obtryx II group. Other adverse events are listed for 14 of 141 and 21 of 140, respectively. Deaths are recorded as 0 in the Solyx group and 1 in the Obtryx II group. These are the registry’s counts and denominators; they are not recalculated event rates.

The registry also lists Device Extrusion at 0.7% among the top serious terms. The record does not give further context for that entry here, such as its group attribution, event timing, or relationship to the device. The categories and counts should not be treated as interchangeable: the serious and other adverse-event entries are separate registry summaries, and a death count does not itself indicate whether a death was caused by treatment.

These figures are descriptive. The registry record does not report comparative safety estimates, uncertainty intervals, event adjudication details, or attribution assessments. The non-randomized design also means that differences in participant characteristics could affect observed event counts. The counts alone cannot establish that either sling caused more or fewer events.

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

The record establishes that the study compared Solyx and Obtryx II in a prospective, non-randomized, parallel-cohort design and defined treatment success using both a cough stress test and participant-reported improvement at 36 months. It also reports selected adverse-event and death counts. These details describe the question, outcome rule, and some safety observations.

The record does not report the primary success count for either group, a comparative effect estimate, or its uncertainty. It therefore cannot show whether the groups differed in the proportion meeting the success definition, how large any difference was, or how precisely it was estimated. It also does not report the component-level outcome results, so the objective and subjective contributions to the composite cannot be distinguished.

Even if a group difference is reported elsewhere, the non-randomized design would require cautious interpretation. Treatment groups may differ for reasons other than the device, and the available record does not explain whether adjustment was used to address measured differences. Statistical adjustment cannot automatically address unmeasured confounding. The results would describe the observed cohorts, while a causal claim would require assumptions and supporting analyses not documented in this registry record.

The safety counts likewise do not establish comparative risk or device causation. They are summaries with denominators, but the record does not provide event attribution, timing, or uncertainty estimates. Taken together, the available information supports a limited account of study conduct and endpoint definitions, not a conclusion that one system is better, worse, safer, or less safe than the other.

14. Why This Trial Matters Statistically

This study raises a useful statistical issue: a clearly defined clinical endpoint does not by itself make a comparison causally interpretable. The success rule combines an objective test with a participant-reported assessment, which gives the outcome clinical breadth but also makes the component definitions and their separate results important. Without component results, the composite alone would not reveal which part of the criterion drove a group contrast.

The non-randomized design makes careful attention to cohort comparability especially important. In a randomized study, allocation is designed to reduce systematic baseline differences. In a cohort comparison, clinical or participant factors may influence which device is received. Statistical adjustment can help with observed differences, but depends on measurement and modeling choices and cannot ensure control of unmeasured factors. The registry record does not report enough detail to evaluate those choices.

The study also illustrates why outcome estimates and their precision are necessary for interpretation. The registry record describes the endpoint and reports selected safety counts, but does not report the primary group results or uncertainty. Without those quantities, readers cannot evaluate the magnitude or precision of the treatment-success comparison. A design description and an endpoint definition are not substitutes for outcome estimates.

Finally, the safety summaries show why counts require context. Denominators, event definitions, attribution, follow-up, and comparative uncertainty all affect what can reasonably be inferred. Reporting counts is informative, but counts alone do not identify cause. These considerations apply broadly to device cohort studies and other non-randomized clinical comparisons.

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 primary limitation for interpreting the study’s effectiveness comparison is that the registry record does not report the 36-month success counts by group, an effect estimate, a confidence interval, or a p-value. It therefore does not permit a quantitative assessment of the endpoint. Component-specific results are also not reported, limiting interpretation of the composite definition.

Non-randomized allocation creates potential confounding. The registry record does not describe how treatment assignment occurred, the groups’ baseline characteristics, or whether statistical adjustment was conducted. It also does not identify covariates used for adjustment or provide information to assess whether important differences remained. The absence of these details limits evaluation of any causal interpretation.

Follow-up and analysis details are not reported. The record does not give group-specific completion at 36 months, the number analyzed for the primary endpoint, the treatment of missing measurements, or the analysis populations. It also does not report protocol deviations, sensitivity analyses, or how the two listed analyses relate to the primary outcome.

For safety, the record gives selected counts but not event-level timing, attribution, adjudication, or comparative uncertainty. The Device Extrusion entry is listed as 0.7% among top serious terms, but its group and denominator context are not reported in the available record. These limitations mean the safety entries should be read descriptively rather than causally.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Post Market Study Of Single Incision Sling Versus Transobturator Sling for Stress Urinary Incontinence — NCT01784588.
• Registry record last updated 2021-02-10; status last verified 2021-01.
• Results first posted 2019-06-06.
• 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 completed, prospective, multicenter, non-randomized, parallel-cohort study of the Solyx Single Incision Sling System and the Obtryx II Sling System for stress urinary incontinence. Enrollment is recorded as 281. The primary outcome is a count meeting a composite definition of objective and subjective treatment success at 36 months.

The primary outcome results by group and the statistical comparison are not reported in the registry record. The record lists serious adverse events, other adverse events, deaths, and Device Extrusion among the top serious terms. Because allocation was non-randomized and key outcome, follow-up, and analysis details are absent, the record supports descriptive interpretation but not a causal comparative conclusion.