A Trial of Transcutaneous Nerve Stimulation for OAB: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Trial of Transcutaneous Nerve Stimulation for OAB (NCT02511717), a randomized na study. The primary outcome is Patient Reported Outcome Measure (Patient Percention of Bladder Condition Question).

2. Clinical Question

3. Trial Design

The registry describes a randomized, parallel-group trial with quadruple masking. Participants were allocated to transcutaneous nerve stimulation or sham stimulation. The registry record does not describe the randomization sequence, allocation concealment, or which groups of people were included in the quadruple-masking designation. Those details should not be inferred from the masking label alone.

The record lists enrollment of 20. The posted primary-outcome summaries report 10 participants in the sham group and 10 in the transcutaneous nerve stimulation group. These are outcome-summary counts; the registry record does not explain whether they represent all randomized participants, participants assessed at the endpoint, or another analysis population.

Both regimens were described as 3x/week for 30 minutes for 12 weeks. The active intervention stimulated the bladder nerves, while the sham used a location and settings described as unrelated to those nerves. The comparison therefore concerns the active stimulation regimen versus the stated sham regimen; the record does not provide further treatment-delivery or adherence details.

The trial status is completed. The record lists a start date of 2016-01 and a primary completion date of 2019-03-01. The primary endpoint was a patient-reported perception of bladder condition at 12 weeks. Four secondary outcome measures are listed: the Overactive Bladder Questionnaire Short Form, a voiding diary, 24hr pad weights, and physician assessment of treatment benefit. Results for those secondary measures are not included in the posted outcome summaries described in the 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 Patient Reported Outcome Measure (Patient Percention of Bladder Condition Question), measured over 12 weeks.

The primary endpoint is the Patient Perception of Bladder Condition question, abbreviated in its description as PPBC. It asks participants to rate how problematic their bladder condition is. The response scale runs from 0, “My bladder condition does not cause me any problems at all,” to 5, “My bladder condition causes me many severe problems.” Higher scores indicate worse outcomes. The registry lists the measurement at 12 weeks and reports the result in units on a scale.

A patient-reported measure can capture the participant’s own assessment of how much a condition affects them. That perspective may complement measures based on diaries, pad weights, or clinician assessment, which are among the secondary outcomes listed for this trial. This is a general explanation of the role of patient-reported outcomes, not evidence that the endpoint captures every aspect of bladder symptoms or daily life.

The record specifies the median and interquartile range as the summary statistics. A median describes the middle of the ordered observations, while the interquartile range describes the spread of the middle portion of the observations. These summaries present each arm separately; they do not, by themselves, quantify uncertainty in a between-arm effect or establish whether the groups differ beyond chance.

The posted arm summaries give a median of 4 with an interquartile range from 3 to 5 for sham, and a median of 3 with an interquartile range from 2 to 4 for transcutaneous nerve stimulation. The registry record does not report a confidence interval or a formal comparison for this endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry reports the primary endpoint using a median and interquartile range for each arm. These are descriptive summaries. They tell the reader about the distribution of reported scores within each group, but do not, on their own, estimate the uncertainty in a difference between groups. No formal analysis of the primary endpoint is posted in the registry record.

What does the median describe?

In general, the median is the midpoint after observations are ordered. It is less affected by unusually high or low observations than the mean. For a bounded, ordered response such as the bladder-condition rating, the median can provide a readily interpretable summary of the typical reported category. It does not show how many participants chose each response, and different response distributions can share the same median.

What does the interquartile range add?

In general, the interquartile range describes the interval from the lower quartile to the upper quartile, covering the middle portion of the observations. It conveys how dispersed the central responses are. Here, the posted summaries give an interquartile range of 3 to 5 for sham and 2 to 4 for transcutaneous nerve stimulation. The range is not a confidence interval: it describes variation among participant scores rather than uncertainty about an estimated treatment effect.

How should the arm summaries be compared?

A direct reading of the posted summaries notes the median of 4 in the sham arm and the median of 3 in the stimulation arm, with higher scores defined as worse. That comparison is descriptive. A formal between-arm analysis would require a specified estimand and an analysis method, along with an account of which participants and observations were included. Those details are not reported in the registry record. No p-value, confidence interval, or adjusted estimate is posted, so the degree of statistical uncertainty around a comparison cannot be assessed from the record.

In general, a confidence interval gives a range of values compatible with the data and the assumptions of a particular statistical procedure. It helps communicate precision, not just the direction of an estimate. The absence of a confidence interval means the posted summaries do not quantify that precision for a treatment contrast. It would not be appropriate to infer statistical significance from the separate medians or from the amount of overlap between the interquartile ranges.

What does randomization contribute?

In general, random assignment aims to make treatment groups comparable on average with respect to factors present before assignment, including factors that were not measured. A randomized design can support a causal comparison when allocation, follow-up, outcome measurement, and analysis are conducted appropriately. The registry labels this trial randomized, but details of sequence generation and allocation concealment are not reported in the registry record. The label alone does not establish how these procedures were carried out.

Masking can reduce the influence of expectations on care, reporting, and assessment. The record labels the trial quadruple masked, but does not identify which roles were masked or explain whether masking was maintained. The sham is described as stimulation at a location and settings unrelated to the bladder nerves. No information is reported about whether participants or personnel could distinguish the regimens.

What are the sample-size illustrations?

The accompanying planning illustrations are based on the observed effect rather than the trial’s own design. Their stated assumptions are a two-sided significance level of 0.05, equal allocation, and a normal approximation; the effect to detect is expressed as a fraction of the observed effect. These are prospective planning calculations, not evidence about the probability that this completed trial detected an effect. Sample-size illustrations must not be described as observed power. The registry record does not report the original sample-size justification or show that the trial was designed around these retrospective planning assumptions.

For general context, normal approximations use a mathematical model to estimate how an analysis behaves under specified assumptions. Whether such an approximation is suitable depends on the outcome, design, and intended analysis. The registry record does not identify the statistical method used for a treatment comparison, and no formal comparison is posted. Therefore, the planning assumptions should not be mistaken for a documented analysis plan.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome and four secondary outcome measures: the Overactive Bladder Questionnaire Short Form, a voiding diary, 24hr pad weights, and physician assessment of treatment benefit. The record also lists 5 outcome measures, but does not provide posted secondary-outcome results in the results summarized for this trial. The registry records zero analyses.

When several outcomes are tested, the chance of at least one apparently unusual result can increase. This general issue is called multiplicity. Trials may address it by prespecifying a hierarchy, adjusting tests, or treating some outcomes as exploratory. The registry record does not report whether multiplicity was considered, how outcomes were prioritized beyond the primary designation, or whether any adjustment was planned. No secondary-outcome significance claims can be assessed from the posted record.

Missing-data handling is also not reported in the registry record. The endpoint summaries show 10 participants in each arm, but the record does not explain whether any participants lacked a 12-week response, how missing responses were treated, or whether the displayed counts correspond to all randomized participants. The number enrolled does not, by itself, resolve these questions about the analysis population.

The record does not describe an intention-to-treat population, a per-protocol population, or another analysis population. It also does not report participant flow by reason for withdrawal or endpoint completion. In general, missingness and analysis-population choices can affect the interpretation of a randomized comparison, especially when follow-up differs between groups or depends on outcomes. Without these details, the posted summaries cannot establish how such issues were handled.

11. 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 2% reporting threshold.

The posted safety figures list 10 participants at risk for serious adverse events in each arm and zero affected participants in each arm. The record also lists zero other adverse events in the participants at risk in each group, and zero deaths in both groups. No serious adverse-event terms are listed.

These are counts recorded for this trial, not a guarantee that an event is impossible or that a regimen is free of risk. In general, safety counts describe what was observed and recorded during the study; their interpretation depends on follow-up duration, event definitions, completeness of reporting, and the size and characteristics of the population observed. The registry record does not provide further details about safety definitions, surveillance procedures, or the duration of safety follow-up beyond the treatment schedule.

The posted figures therefore indicate that no serious adverse events, other adverse events, or deaths are recorded in these arm summaries. They do not establish that no events occurred outside the recorded categories or observation period, and they cannot precisely characterize uncommon harms. The registry record does not provide additional event narratives or further safety analyses.

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

The posted primary-outcome summaries describe participants’ reported perception of their bladder condition at 12 weeks. The sham group’s median was 4, with an interquartile range from 3 to 5; the transcutaneous nerve stimulation group’s median was 3, with an interquartile range from 2 to 4. Since higher values indicate worse outcomes, the stimulation arm’s reported median is lower. This describes the observed arm summaries and is not, by itself, a conclusion about a causal effect.

The registry record contains no formal statistical comparison, confidence interval, or p-value for the primary endpoint. It therefore does not quantify the precision of an estimated between-group difference or establish whether the observed summaries are statistically distinguishable. Nor does the record report baseline PPBC results, participant-level response distributions, or a change-from-baseline analysis. Those omissions limit what can be inferred from the endpoint summaries.

The trial’s randomized and quadruple-masked labels describe design features, but procedural details are not reported. The record also does not explain the analysis population, missing-data handling, or whether outcome assessment was complete. These details matter when considering how closely the posted summaries reflect the intended randomized comparison.

The result does not establish that stimulation is effective or ineffective, nor does it demonstrate equivalence between stimulation and sham. A lack of posted inferential analysis is not evidence of no difference. Similarly, the recorded absence of adverse events in the arm summaries cannot rule out harms that are uncommon or not captured in the registry record.

The most defensible reading is narrow: the registry reports different descriptive medians for the two arms on a patient-reported scale at 12 weeks, along with the stated within-arm interquartile ranges. The record does not provide the comparative analysis or supporting details needed to judge the magnitude and precision of an effect. The listed secondary outcomes also do not have results available in the posted outcome summaries.

13. Why This Trial Matters Statistically

This trial illustrates why a reported group summary and a treatment-effect analysis answer different questions. The medians and interquartile ranges describe the participant scores recorded in each arm. A comparative estimate, paired with an uncertainty measure, would address how large a between-arm difference is compatible with the data and the analysis assumptions. The registry record does not report that inferential comparison.

The endpoint also highlights a common feature of clinical outcomes: a patient-rated scale may be ordered without guaranteeing that each step represents the same amount of change. A median and interquartile range can summarize such responses while avoiding an assumption that the scale behaves like a continuous measurement. This is a general methodological point, not a claim that the registry explains its choice of summary statistics.

The trial’s sham comparison is statistically relevant because it offers a comparator intended to resemble the active intervention while differing in the stated stimulation location and settings. Interpretation still depends on how randomization and masking were implemented, whether participants remained in follow-up, and how outcomes were analyzed. Those details are not reported in the registry record.

The record also shows the importance of separating a completed trial’s posted results from a statistical analysis plan. The listed planning assumptions use an observed effect to illustrate future sample-size requirements. They are not a record of the original trial’s design justification and should not be read as observed power. The original sample-size rationale and multiplicity strategy are not reported.

For clinical researchers and biostatisticians, the key lesson is to distinguish descriptive findings from supported inference. The posted summaries are useful for understanding what was recorded at 12 weeks, but they do not supply the uncertainty estimates or analysis details needed for a fully evaluated treatment comparison.

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 of the posted results is that the registry record reports arm-level descriptive summaries without a formal comparison. No confidence interval, p-value, or model-based treatment estimate is available for the primary outcome. The magnitude and precision of a between-arm effect therefore cannot be evaluated from the record.

The endpoint summaries include 10 participants per arm, but the registry does not identify the analysis population or explain whether these counts represent all randomized participants. It does not report participant flow, withdrawals, reasons for missing endpoint data, or methods for handling missingness. Baseline values for the primary outcome are also not reported, so the results cannot be interpreted as a reported change from baseline.

Although the trial is labeled randomized and quadruple masked, implementation details are absent. The registry record does not describe sequence generation, allocation concealment, the roles that were masked, or assessment of whether masking was maintained. The intervention and sham schedules are described, but treatment adherence and protocol deviations are not reported.

The record lists four secondary outcome measures but does not provide their results in the posted summaries. It does not report a multiplicity strategy, a prespecified statistical plan, or the trial’s original sample-size justification. The listed planning illustrations are based on the observed effect and are not a substitute for the original design rationale.

The safety summaries record zero serious adverse events, zero other adverse events, and zero deaths in each arm. Further details on safety definitions, ascertainment, and follow-up are not reported in the registry record. These limitations mean that the posted summaries offer a restricted account of the trial’s outcomes and do not support broad conclusions about efficacy, safety, or generalizability.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Trial of Transcutaneous Nerve Stimulation for OAB — NCT02511717.
• Registry record last updated 2019-10-23; status last verified 2019-10.
• Results first posted 2019-10-23.
• 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 registry describes a completed, randomized, parallel-group trial with quadruple masking, comparing transcutaneous tibial nerve stimulation with sham stimulation in women with clinical symptoms of overactive bladder. Both regimens were scheduled 3x/week for 30 minutes for 12 weeks. Enrollment is listed as 20, with a start date of 2016-01 and a primary completion date of 2019-03-01.

The primary endpoint was the patient-reported perception of bladder condition at 12 weeks, scored from 0 to 5, with higher scores indicating worse outcomes. The sham arm median was 4 (interquartile range 3 to 5); the stimulation arm median was 3 (interquartile range 2 to 4). The registry record reports no formal analyses or comparative uncertainty estimates. Safety summaries record zero serious adverse events, zero other adverse events, and zero deaths in each arm.