The Effects Upon the Bladder of Transcutaneous Tibial Nerve Stimulation in Acute Traumatic Spinal Cord Injury: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Effects Upon the Bladder of Transcutaneous Tibial Nerve Stimulation in Acute Traumatic Spinal Cord Injury (NCT02573402), a randomized na study. The primary outcome is Number of Participants With Infection.

2. Clinical Question

In statistical terms, the central question is whether the observed participant counts provide evidence of a difference between the randomized groups in the occurrence of infection during the stated timeframe. The registry record reports the counts but no analysis that estimates the size or precision of a between-group difference. Accordingly, the counts alone do not establish whether the groups differ beyond what could occur by chance.

The intended population is described broadly as people with acute spinal cord injury. Details about the participants actually enrolled, including their baseline characteristics and the analysis population for the primary endpoint, are not reported in the registry record. Those omissions make it difficult to assess how closely the enrolled participants match the broader population named in the study purpose.

3. Trial Design

The registry record describes a randomized, single-masked, parallel-group study. Participants were assigned to TTNS or sham stimulation. A parallel design compares distinct groups receiving their assigned intervention rather than comparing each participant with themself across treatment periods. Random allocation is intended to reduce systematic differences between groups, although it does not guarantee that groups will be alike in a small trial.

The registry lists enrollment of 19 participants. The posted primary outcome counts use 12 participants in the TTNS arm and 7 in the control arm. The record does not explain the allocation procedure, whether allocation was concealed, or whether all enrolled participants contributed to the primary outcome. It also does not identify which study personnel or participants were masked. “Single-masked” is recorded, but the masked role and procedures are not reported in the registry record.

The TTNS arm description specifies a 2-week protocol, while the primary endpoint timeframe is about 4 weeks. The record does not report the detailed timing of endpoint assessment, the duration or frequency of individual stimulation sessions, or the precise relationship between the intervention period and outcome measurement. The control is described as sham stimulation; further details about its delivery are not reported in the registry record.

The study status is completed. Its recorded start date is 2016-07-12, and its primary completion date is 2017-10-27. The study phase is listed as not applicable. These administrative details do not establish when participants were recruited, how long each participant was followed, or whether the posted results include every randomized participant.

Four secondary outcomes are reported in the registry record: maximum detrusor pressure and maximum bladder capacity, each appearing twice in the listed outcomes. Both are described as evaluated by urodynamic study. The record lists eight outcome measures overall, but does not report analyses for these secondary outcomes. The rationale for the repeated listings and the outcome-specific analysis methods 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 Number of Participants With Infection, measured over about 4 weeks.

The primary endpoint is the number of participants with infection during about 4 weeks. The registry description states that all infections were urinary tract infections (UTIs). This is a participant-count endpoint: it records whether participants experienced an infection, rather than reporting the total number of infection episodes. The record does not explain how an infection was defined, how it was confirmed, or how recurrent infections in one participant were handled.

A count of participants with an event is useful because it describes how many people in each group experienced the outcome during the specified period. For a randomized comparison, the outcome can be used to estimate whether the chance of an event differs between assigned groups. The count by itself, however, does not convey the precision of that comparison. Statistical interpretation also depends on the number of participants assessed, the way missing outcomes were handled, and an analysis that quantifies uncertainty.

In the posted results, 4 participants in the TTNS arm and 3 in the control arm are recorded as having infection. The corresponding arm sizes are 12 and 7. The registry record does not post an estimable two-arm comparison, a confidence interval, or a p-value for this binary endpoint. It therefore does not provide a quantified estimate of the uncertainty around a difference between groups.

The endpoint’s clinical meaning is also bounded by its definition and timeframe. The record identifies UTIs but does not report severity, recurrence, timing within the follow-up period, or other details about the infections. Those details would help distinguish a single event from repeated events and characterize the outcome more fully, but they are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

General explanation: A binary endpoint classifies each participant into one of two categories for a defined outcome period, such as having or not having an event. The registry’s primary endpoint counts participants with infection. The posted results give the number with infection and the number of participants in each arm, but the registry does not provide a statistical analysis of the between-group contrast.

General explanation: A comparison of binary outcomes can be expressed in several ways, including a difference in event proportions or a relative measure. These measures answer related but distinct questions. A difference describes an absolute contrast, whereas a relative measure describes one group in relation to the other. The registry record does not report a selected measure or an estimable comparison, so no such contrast should be inferred from the displayed counts in this interpretation.

General explanation: A confidence interval describes the range of estimates reasonably compatible with the data under the assumptions of the analysis. It conveys precision as well as direction and magnitude. Wider intervals indicate less precision; narrower intervals indicate greater precision. A confidence interval is not a guarantee that the true value lies within its endpoints. No confidence interval for the primary comparison is reported in the registry record.

General explanation: A p-value, when reported, measures how unusual data at least as inconsistent with a specified null hypothesis would be under the assumptions of a statistical model. It does not measure the probability that the null hypothesis is true, and it does not describe the size or clinical importance of an effect. The registry record does not report a p-value for the primary endpoint. Without an analysis and its assumptions, there is no basis for interpreting statistical significance.

The record indicates that a two-arm comparison for the binary endpoint was not estimable from the posted results. It also records no posted analyses. The reason a comparison could not be estimated is not reported in the registry record. The presence of arm counts does not by itself reveal which analysis was planned or why a comparison was omitted. The statistical plan, including the intended effect measure, test, confidence level, and handling of sparse data, is not reported in the registry record.

General explanation: Sparse event data can make conventional large-sample approximations unreliable. In such settings, analysts may consider methods designed for small samples or exact methods, depending on the estimand and design. The choice should be prespecified where possible and justified by the data structure. The registry record does not report which method, if any, was intended for the primary binary outcome. No alternative method should be attributed to the investigators without that information.

General explanation: Randomization supports causal comparison when participants are analyzed according to their assigned groups and outcome data are adequately collected. An intention-to-treat analysis generally retains participants in their randomized groups, regardless of adherence, while other analysis populations may apply different eligibility rules. The registry record does not identify the primary analysis population or state whether participants were analyzed according to randomized assignment.

Missing data are important for a participant-count endpoint. A participant with no recorded infection is not necessarily the same as a participant whose infection status was not assessed. The registry record does not report the number of missing primary outcomes, the reasons for any missingness, or the method used to handle it. Therefore, the posted arm counts should not be assumed to represent a particular missing-data strategy.

General explanation: Multiplicity arises when several outcomes or statistical tests are considered. Testing many outcomes can increase the chance of at least one apparently notable result if no adjustment or prioritization is used. A prespecified primary endpoint helps focus interpretation, but a complete statistical plan is needed to understand how secondary outcomes were handled. The registry lists four secondary outcomes, including maximum detrusor pressure and maximum bladder capacity, each listed twice, but does not report analyses for them or describe any multiplicity procedure.

The record describes sample-size illustrations based on an observed effect, equal allocation, a two-sided significance level of 0.05, and a normal approximation. Such illustrations are planning calculations, not observed trial results and not evidence that the trial had a particular probability of detecting an effect. The record’s actual design justification, target effect, and sample-size rationale are not reported in the registry record. No sample-size conclusion should be drawn from an illustration alone.

General explanation: Over-dispersion concerns variability greater than assumed by a particular model, and is relevant to some count-data analyses. The primary endpoint is reported as participants with an event, not as a recurrent-event count; the registry does not report a recurrent-event analysis. Whether over-dispersion is relevant to a chosen model depends on the outcome definition and analysis, neither of which is specified in a statistical plan in the registry record.

For a fuller statistical assessment, readers would need the prespecified estimand, analysis population, missing-data approach, outcome definition, and model or test, along with an estimate and uncertainty interval. These elements are not reported in the registry record. The available information supports a description of the event counts and study design, but not reconstruction of an investigator analysis.

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("Transcutaneous Tibial Nerve Stimulation", "Control")
n      <- c(12, 7)
events <- c(4, 3)
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  Transcutaneous Tibial Nerve Stimulation  12  4  33.3  9.9  65.1  13.8  60.9  13.9  61.4
ARM  Control  7  3  42.9  9.9  81.6  15.8  75.0  15.7  75.5

11. Multiplicity, Missing Data and Analysis Populations

The registry identifies infection as the primary endpoint and lists four secondary outcomes: maximum detrusor pressure and maximum bladder capacity, each appearing twice. It reports eight outcome measures overall. The reason for the repeated secondary outcome listings, the planned hierarchy among outcomes, and any adjustment for multiple testing are not reported in the registry record. No secondary-outcome analyses are reported.

Multiplicity matters when multiple outcomes or tests are examined because repeated testing can increase the chance of a nominally unusual finding. A prespecified primary outcome can help distinguish the main question from additional exploratory questions, but the registry record does not provide a statistical analysis plan describing this distinction in detail. It also does not report whether any secondary analyses were planned, conducted, or omitted.

The registry record does not state how missing primary or secondary outcome data were handled. It does not report the number of participants with missing outcome assessments, the reasons for missingness, or whether the posted counts include every randomized participant. A reader therefore cannot determine whether the analysis followed an intention-to-treat principle, used another analysis population, or applied an imputation or exclusion strategy.

These omissions do not prove that outcomes were missing or that multiple testing occurred. They mean the handling of those issues cannot be assessed from the registry record. Interpretation should remain focused on the posted primary counts and should not treat unreported secondary results as evidence of no effect.

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 non-serious adverse event terms

The registry reports serious adverse events for 0 of 12 participants in the TTNS arm and 0 of 7 participants in the control arm. It also reports 0 deaths in each arm. For other adverse events, the record lists 4 of 12 participants in the TTNS arm and 3 of 7 in the control arm. No serious adverse-event terms are listed.

These figures are participant counts, not counts of individual event episodes. The registry record does not describe the types of other adverse events, their severity, timing, relatedness to the intervention, or how events were collected. It also does not explain the definition or monitoring period for adverse events. The zero serious-event counts mean that no serious adverse events are posted for these groups in the record; they do not establish that a serious event is impossible or that the interventions have no safety risks.

With limited group sizes, observed safety counts provide only a narrow description of the participants recorded. The registry does not report a statistical comparison of adverse events, and the counts should not be interpreted as establishing a difference or equivalence between groups. Safety interpretation is further bounded by the absence of event descriptions and detailed follow-up information in the registry record.

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

The registry record documents a randomized, parallel-group study comparing a 2-week TTNS protocol with sham stimulation in people with acute traumatic spinal cord injury. Its primary outcome is the number of participants with infection over about 4 weeks, and the description specifies that all infections were UTIs. The posted primary counts are 4 participants in the TTNS arm and 3 in the control arm.

Those counts describe what was recorded in each group. They do not provide an adjusted or unadjusted estimate of a between-group effect, and the registry record does not report an estimable comparison, confidence interval, or p-value. As a result, they do not establish the size or precision of any difference. The higher raw count in one group is not, by itself, evidence that the groups differ in their underlying event risk.

The record also does not report analyses of the listed urodynamic secondary outcomes. The primary infection count cannot be used to infer changes in maximum detrusor pressure or maximum bladder capacity. Nor does the record provide details about infection severity, recurrence, or the precise assessment schedule that would expand the interpretation of the primary endpoint.

These findings do not establish whether TTNS is beneficial, harmful, or equivalent to sham stimulation. They describe a limited set of posted outcome counts and safety figures without the statistical estimates needed to quantify uncertainty. The absence of a reported comparison is not a finding of no difference. A reader should distinguish the observed counts from conclusions about the underlying effects of treatment.

The randomized design is a useful feature for a group comparison, but interpretation also requires complete outcome information, clarity about the analysis population, and an appropriate statistical analysis. Those details are not reported in the registry record. The results should therefore be read as descriptive registry results rather than a complete inferential account of the study.

14. Why This Trial Matters Statistically

This trial matters statistically because it illustrates the difference between reporting group counts and estimating a treatment contrast. Counts are a necessary starting point for a binary endpoint, but they do not state how uncertain a comparison is. An inferential result requires an estimate, an analysis method, and a measure of precision. The registry record posts the primary counts but does not provide an estimable two-arm comparison.

The study also illustrates why randomized allocation does not remove the need to report analysis details. Randomization is intended to support comparability at assignment, while a complete report should clarify the analysis population, outcome ascertainment, and handling of missing data. These details are not reported in the registry record. Without them, readers cannot assess how the posted counts relate to all randomized participants or reconstruct the intended statistical approach.

Its primary endpoint is a participant-level event count, and the event window is about 4 weeks. Clear definitions of the event and follow-up period are important for interpreting such outcomes. The record identifies UTIs but does not report the infection criteria or detailed assessment schedule. That limits the ability to understand exactly what each event count represents.

The registry also lists secondary bladder outcomes but does not report analyses for them. This highlights the value of distinguishing the primary question from secondary questions and explaining how multiple outcomes are handled. A results record is most informative when outcome listings are paired with analysis estimates and uncertainty, not just outcome names or counts.

For readers learning clinical biostatistics, the central lesson is modest but important: descriptive data can be accurately stated while remaining insufficient for a conclusion about comparative effects. A small randomized study can contribute useful observations, yet conclusions depend on transparent methods and appropriately cautious interpretation. In this record, the posted information supports description, not a quantified claim about treatment differences.

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 posted primary outcome is based on limited participant counts: 12 in the TTNS arm and 7 in the control arm. The record gives no inferential comparison or uncertainty interval, so the precision of any group contrast cannot be assessed. The reason the binary comparison was not estimable is not reported in the registry record.

The endpoint is described as participants with infection over about 4 weeks, and all infections are identified as UTIs. However, diagnostic criteria, event ascertainment procedures, recurrence handling, and severity are not reported in the registry record. The time period is approximate, and the exact start and end of outcome follow-up are not stated.

Although the study is described as randomized and single-masked, the method of randomization, allocation concealment, the masked role, and the implementation of masking are not reported in the registry record. Baseline participant characteristics and detailed eligibility criteria are also not reported, limiting assessment of group comparability and applicability beyond the broad acute traumatic spinal cord injury population.

The registry does not describe the primary analysis population, the handling of missing outcomes, or whether all randomized participants were analyzed. It lists secondary urodynamic outcomes but provides no analyses for them. The statistical plan, sample-size justification, and multiplicity approach are not reported in the registry record. These gaps constrain interpretation without showing that a particular design or analysis problem occurred.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: The Effects Upon the Bladder of Transcutaneous Tibial Nerve Stimulation in Acute Traumatic Spinal Cord Injury — NCT02573402.
• Registry record last updated 2018-09-10; status last verified 2018-08.
• Results first posted 2018-09-10.
• 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 record describes a completed, randomized, single-masked, parallel-group study of TTNS versus sham stimulation in people with acute traumatic spinal cord injury. Enrollment is listed as 19. The intervention arm is described as following a 2-week protocol, and the primary endpoint is the number of participants with infection over about 4 weeks.

The posted primary results record 4 participants with infection among 12 in the TTNS arm and 3 among 7 in the control arm; all infections were UTIs. Serious adverse events and deaths are recorded as 0 in both groups. The record also lists four secondary outcomes concerning maximum detrusor pressure and maximum bladder capacity, but reports no analyses for them.

No statistical analysis is reported for the primary comparison. The registry record does not report the analysis population, missing-data handling, detailed outcome definitions, or statistical plan. The posted counts therefore support a descriptive account, but not a quantified conclusion about the difference between groups.