The Efficacy of Solifenacin With or Without Tamsulosin in Adult Women With Overactive Bladder (OAB): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Efficacy of Solifenacin With or Without Tamsulosin in Adult Women With Overactive Bladder (OAB) (NCT01533597), a randomized phase 4 study. The primary outcome is Change in Mean Number of Micturition Episodes Per 24 Hours.

2. Clinical Question

The central statistical question is whether the two treatment strategies were associated with different changes in daily micturition frequency over the study period. The registry record identifies this as a prospective randomized multicenter study, but it does not report the detailed randomization procedure or how the primary analysis was conducted.

The primary endpoint is a continuous measure: each arm is summarized by a mean change. This describes an average change in the recorded frequency, not the experience of every participant. The posted results give an estimate for each arm and an interval expressing uncertainty around that arm's mean. They do not directly quantify the difference between arms, so the arm-level results alone do not establish the size or precision of a treatment contrast.

The registry lists numeric change in urgency episodes per 24 hours, OABSS, IPSS, PVR, and Qmax as secondary outcomes. These provide additional outcome domains, but the record does not post analyses for them.

3. Trial Design

The registry describes a prospective randomized multicenter study with a parallel-group design and no masking. It is listed as phase 4 and completed. Enrollment is reported as 70. The recorded study start is 2010-12, and primary completion is recorded as 2013-12. The sponsor is Soonchunhyang University Hospital.

Participants were assigned to one of two drug arms: solifenacin alone or solifenacin plus tamsulosin. Randomized allocation can, in general, help balance measured and unmeasured characteristics between groups, but the registry record does not describe the sequence-generation method, allocation concealment, or how assignment was implemented. With no masking, participants and study personnel were not described as blinded; the record does not explain whether outcome assessors were masked.

The comparison is parallel rather than a crossover: the listed arms represent separate treatment groups. Detailed arm descriptions are absent. Dose, treatment schedule, adherence procedures, rescue treatment, and criteria for stopping or changing treatment are not reported in the registry record. The record also does not describe eligibility criteria beyond the adult-women population with overactive bladder identified in the study title and condition.

Enrollment is not the same as the number contributing to a particular endpoint. The primary outcome results list n=29 for solifenacin and n=25 for solifenacin plus tamsulosin. The registry does not explain how those endpoint counts relate to enrollment, nor does it provide a participant-flow account or reasons for missing outcome measurements.

These design details define the scope of the comparison: randomized treatment assignment in a completed, unmasked, parallel study. They do not, on their own, reveal the adequacy of follow-up, adherence, or analysis procedures. Those details are not reported in the registry record.

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 Change in Mean Number of Micturition Episodes Per 24 Hours, measured over at week 24 relative to baseline.

The primary endpoint is the change in the mean number of micturition episodes per 24 hours at week 24 relative to baseline. Micturition episodes refer to urination events; the endpoint therefore summarizes the frequency recorded over a day. It is reported as a continuous measure in episodes, with a mean and a 95% confidence interval for each arm.

Daily frequency is a direct count-based way to characterize one aspect of overactive bladder symptoms. An endpoint expressed as a continuous change can capture the average degree of change across participants rather than reducing results to a simple category such as improved or not improved. The registry names this as the primary outcome, but does not explain the rationale for selecting it or provide its operational definition, including how episodes were collected or averaged.

The posted mean changes are -1.9 episodes for solifenacin and -2.2 episodes for solifenacin plus tamsulosin. Their respective 95% confidence intervals are -2.5 to -1.2 and -3.0 to -1.4. These are arm-specific summaries. They are not a direct estimate of the difference between treatment arms, and they do not describe the range of individual participant outcomes.

The record does not provide baseline means, individual-level data, or the precise formula used to calculate change. The direction of a negative change is ordinarily read as a lower follow-up value than baseline, but the registry does not state its change-score coding convention. Interpretation should therefore stay close to the reported endpoint and its stated timeframe.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary measure is continuous, so the registry reports an arm-level mean rather than an event count or a proportion. A mean condenses the values observed across participants into a single central summary. It is useful for describing the average change, but it does not show how values are distributed, whether a few unusual observations influence the average, or how much participants differ from one another. The registry does not report a standard deviation or other measure of participant-to-participant spread for this endpoint.

What does a 95% confidence interval express?

A confidence interval gives a range of values that is compatible with the observed data under the method used to construct it. In general statistical terms, the confidence level describes the long-run performance of the interval procedure across repeated samples; it is not a probability statement that the particular fixed interval contains the true mean. The intervals posted accompany the mean in each arm. They communicate uncertainty in those arm means, not uncertainty in a treatment difference.

For solifenacin, the reported mean is -1.9 and its interval is -2.5 to -1.2. For solifenacin plus tamsulosin, the mean is -2.2 and its interval is -3.0 to -1.4. The registry does not identify the method used to calculate these intervals. It does not report the model, standard errors, distributional assumptions, or any adjustment for baseline values. These details should not be inferred from the presence of a confidence interval alone.

Why is an arm comparison different from two arm summaries?

The randomized question is comparative: it asks whether outcomes differ between assigned strategies. Each arm's mean is a separate summary, whereas a treatment contrast directly estimates the difference between groups. The uncertainty in that contrast depends on the data and analysis for both groups. A confidence interval around each arm mean cannot be repurposed as the interval for the contrast, and looking at the arm intervals alone is not a formal test of a treatment effect.

The registry record does not report a two-arm estimate, its confidence interval, or a p-value for the primary outcome. It also lists no analyses. For this continuous endpoint, the record indicates that values needed for a two-arm comparison are missing or not estimable. Consequently, no recalculated comparison is presented. There is no sponsor analysis for a contrast in the posted results that could be used to resolve this gap.

What does randomization contribute?

In general, random assignment aims to make treatment groups comparable at the point of assignment, including with respect to factors that may not have been measured. This supports a causal comparison when follow-up and analysis preserve the randomized groups and when relevant sources of bias are controlled. Randomization does not guarantee that groups are identical in a particular trial, and it does not compensate automatically for missing outcomes, treatment nonadherence, or analysis choices. The registry labels the study randomized but does not report enough procedural detail to assess those issues.

How should the planning assumptions be understood?

General sample-size planning asks how many participants per arm might be needed to detect a prespecified effect under chosen assumptions. The record's planning description specifies a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation; the effect to detect is defined as a stated fraction of the observed effect. These are planning assumptions, not evidence that the trial was designed using that approach. No sample-size justification or specific planning estimate is reported in the registry record.

Any planning illustration based on an observed effect is conditional on that effect estimate and the stated assumptions. It is not observed power, does not establish that the trial had adequate power, and is not a substitute for the missing between-arm analysis. General power calculations describe design scenarios; they do not add inferential evidence to the results already observed.

Why can variation between participants matter?

For continuous outcomes, an analysis must account for how variable measurements are across participants. If variation is larger than a simple model assumes, uncertainty may be understated unless the analysis handles that extra variation appropriately. This is a general concern rather than a finding about this trial: the registry does not report participant-level spread or the model used, so the adequacy of any variance assumptions cannot be assessed.

10. Multiplicity, Missing Data and Analysis Populations

The registry names five secondary outcomes: numeric change in urgency episodes per 24 hours, change in total OABSS score, change in IPSS score, change in PVR, and change in Qmax. It reports six outcome measures overall, but posts no analyses. The record does not state whether these outcomes were tested, how they were ordered, or whether any multiplicity adjustment was planned. When several outcomes are examined, the chance of at least one apparently unusual result can increase; methods such as prespecifying a primary outcome or adjusting inference can address aspects of that issue. Whether such methods were used is not reported in the registry record.

Information about missing primary outcome data is also limited. The registry gives endpoint counts of n=29 for solifenacin and n=25 for solifenacin plus tamsulosin, while overall enrollment is 70. It does not explain the relationship between those counts and enrollment, give reasons for unavailable measurements, or describe a missing-data method. A participant-flow account and the handling of withdrawals are not reported in the registry record.

The analysis population is not specified. The record does not say whether the primary endpoint analysis followed randomized assignment, included only participants with observed week 24 measurements, or used another population definition. It also does not report imputation, sensitivity analyses, protocol deviations, or treatment adherence. These omissions limit assessment of whether the posted means represent all randomized participants or a subset defined by outcome availability.

Multiplicity and missingness are distinct issues: adjustment for testing several outcomes does not address unavailable observations, and a missing-data method does not control the error rate across multiple outcomes. Neither set of procedures can be evaluated from the registry record.

11. 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 non-serious adverse event terms

The registry lists 35 participants at risk for serious adverse events in the solifenacin group and 35 in the solifenacin plus tamsulosin group. It records 0 participants affected by serious adverse events in each group. These figures describe what was recorded in the registry; they do not show that the risk of serious events is exactly zero, nor do they establish equivalence between the treatments.

For other adverse events, the record lists 2 affected participants in each group, with 35 at risk in each group. The event terms and their severity details are not provided in the posted information. The record also does not state whether events were considered related to treatment, how they were collected, or whether follow-up was the same for every participant.

Deaths are not reported in the registry record. No serious adverse-event terms are listed. A count of zero recorded serious events is not the same as proof that no event could occur; rare events and differences in surveillance may not be well characterized by these summaries. The safety figures should therefore be read as descriptive counts in the registry, not as a comparative safety analysis or a complete account of harms.

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

The registry record supports a limited descriptive statement: it reports a mean change in daily micturition episodes for each arm at week 24 relative to baseline, together with an arm-specific 95% confidence interval. The estimates are -1.9 for solifenacin and -2.2 for solifenacin plus tamsulosin. These figures describe the posted results for the participants included in each arm's outcome summary.

The results do not establish which strategy produced a larger change, because a direct between-arm estimate is not reported. The apparent difference between the arm means should not be calculated from the posted summaries. Without an estimated contrast and its uncertainty, the record does not provide a formal answer to the randomized comparative question. It also does not provide a basis for concluding that there is or is not a meaningful treatment difference.

The confidence intervals express uncertainty about the arm means, not the range of responses among individual women and not the uncertainty around a treatment contrast. The registry does not report baseline endpoint values, participant-level data, or a detailed analysis method. It is therefore not possible to assess how the change scores were constructed or how robust the estimates are to analysis choices.

The safety counts are similarly descriptive. Recorded serious adverse events are 0 in each group, and other adverse events affected 2 participants in each group. These counts do not support a claim of equal safety, especially without detailed event descriptions, follow-up information, or a comparative analysis.

More broadly, the record does not report analyses for the listed secondary outcomes, the analysis population, or methods for missing data and multiplicity. These gaps matter when interpreting both the strength and scope of the evidence. The results describe reported arm-level outcomes, but they do not settle the efficacy or safety of either regimen.

13. Why This Trial Matters Statistically

This trial is statistically notable because it poses a randomized comparison but the registry record reports only arm-level results for its primary continuous endpoint. That distinction is central to clinical-trial interpretation. A mean in each group can describe what happened within those groups, yet a comparative question requires a treatment contrast with an appropriate measure of uncertainty. The contrast is not reported.

The example also illustrates why confidence intervals need to be read in relation to the quantity they accompany. Each posted interval describes uncertainty around one arm's mean change. It does not directly answer whether the randomized treatment strategies differ. Treating separate arm intervals as if they were a direct comparative analysis would overstate what the record establishes.

The registry identifies randomization, a parallel design, and a primary endpoint, all of which help frame the intended comparison. At the same time, the absence of a reported analysis, analysis population, and missing-data procedures limits evaluation of how the randomized design carried through to the posted endpoint results. The endpoint counts and enrollment are also not reconciled in the record.

Finally, the listing of secondary outcomes without posted analyses highlights the importance of distinguishing outcomes named in a registry from results actually available for interpretation. Multiplicity procedures, if used, would affect how multiple results should be read, but they are not described. The record is therefore useful for understanding the design and the reported descriptive summaries while also showing why transparent comparative analyses are essential for answering the clinical question.

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.

Several trial-specific limitations restrict interpretation of the posted results. The most consequential is the absence of an estimable two-arm comparison for the primary continuous endpoint. The means and confidence intervals are reported by arm, but no treatment contrast, confidence interval for that contrast, or p-value is posted. The record therefore does not quantify the randomized comparison that motivates the study.

Enrollment is reported as 70, while the primary outcome results list n=29 and n=25 for the two arms. The registry does not explain how those endpoint counts relate to enrollment or describe participant flow. Reasons for missing measurements, withdrawals, and exclusions are not reported. Without that information, the completeness and representativeness of the endpoint summaries cannot be assessed.

The record does not state the analysis population, the statistical model, adjustment for baseline, or the method used to construct the confidence intervals. It provides no standard deviations or individual-level outcome distributions. Thus, the assumptions underlying the summaries and their precision cannot be independently examined from the registry record.

The trial is described as unmasked, but the record does not specify whether outcome assessors were masked or how the daily episodes were recorded. Dose and treatment schedule are also absent from the arm descriptions. These gaps limit assessment of measurement procedures and treatment implementation.

Although five secondary outcomes are listed, no analyses are posted, and multiplicity methods are not reported. Safety information is limited to brief counts without event terms or detail; deaths are not reported in the registry record. These limitations do not negate the descriptive information, but they constrain the strength and breadth of conclusions that can be drawn from it.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: The Efficacy of Solifenacin With or Without Tamsulosin in Adult Women With Overactive Bladder (OAB) — NCT01533597.
• Registry record last updated 2015-01-27; status last verified 2015-01.
• Results first posted 2015-01-27.
• 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.

18. Record Summary

The record describes a completed, phase 4, prospective randomized multicenter study with a parallel design and no masking. It compares solifenacin alone with solifenacin plus tamsulosin in adult women with overactive bladder. Enrollment is 70; the recorded study start is 2010-12 and primary completion is 2013-12.

The primary endpoint is change in mean micturition episodes per 24 hours at week 24 relative to baseline. The arm-level means are -1.9 for solifenacin and -2.2 for solifenacin plus tamsulosin, with 95% confidence intervals of -2.5 to -1.2 and -3.0 to -1.4, respectively. A two-arm comparison is not reported as estimable.

Five secondary outcomes are named, but no analyses are posted. Serious adverse events are recorded as 0 in each group; other adverse events affected 2 participants in each group. The registry record does not report the analysis population, missing-data methods, or multiplicity procedures.