Prophylactic Tamsulosin Use for Prevention of Post-Operative Urinary Retention: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Prophylactic Tamsulosin Use for Prevention of Post-Operative Urinary Retention (NCT02684344), a randomized na study. The primary outcome is Number of Participants With Post-operative Urinary Retention.

2. Clinical Question

3. Trial Design

The registry describes a randomized, open-label, parallel-group trial sponsored by the University of Rochester. Its stated purpose was to evaluate tamsulosin for prevention of post-operative urinary retention. Participants were assigned to a Tamsulosin Group or an Education Group. The record describes the study as having two cohorts and lists enrollment as 5. The posted group sizes are 1 for the Tamsulosin Group and 4 for the Education Group.

The intervention combined tamsulosin with education about signs and symptoms of urinary retention. The Education Group received education alone. The registry specifies the tamsulosin schedule as 0.4mg by mouth nightly for 3 doses before the day of surgery and for 2 doses following surgery. The study was open label, meaning masking was not used. Whether knowledge of assignment influenced care or outcome assessment is not reported in the registry record.

The listed study start was 2016-02, and primary completion was 2017-12. The overall status is recorded as terminated. The reason for termination, the number of participants planned at the design stage, and any changes to recruitment plans are not reported in the registry record. The record does not provide a protocol or statistical analysis plan from which to assess planned allocation procedures, outcome ascertainment, or changes made during the study.

The primary outcome was the number of participants with post-operative urinary retention, with a timeframe of 5 days. There is 1 posted outcome measure and no posted secondary outcomes. Although the registry contains results by group, it lists no analyses. The small enrollment and lack of a reported comparative analysis mean that the design description should not be confused with an adequately characterized estimate of a treatment effect.

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:

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 Post-operative Urinary Retention, measured over 5 days.

The primary endpoint is the number of participants with post-operative urinary retention over the 5 days specified in the registry. It is a binary outcome at the participant level: a participant is counted as having the event or not having it. The registry labels the measure as a count of participants and gives the unit as participants. It does not provide a more detailed operational definition of urinary retention, the criteria used to identify an event, or the method and timing of assessment. Those details are not reported in the registry record.

As a general statistical matter, a binary endpoint can make an outcome clinically interpretable by describing whether the event occurred, while counts can show how many participants experienced it in each group. The endpoint can be useful for comparing groups when outcome ascertainment is clear and enough information is available to estimate uncertainty around the comparison. Counts alone do not establish that the groups differ, and the number of participants with an event is not itself a measure of the size or precision of a treatment effect.

The registry reports 0 participants with post-operative urinary retention in the Tamsulosin Group and 0 in the Education Group. With no events recorded in either group, the posted counts do not establish comparative effectiveness. How missing outcome assessments, if any, were handled is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The outcome is binary because each participant either experienced post-operative urinary retention during the specified assessment period or did not. The registry reports participant counts by group rather than a continuous measurement. For binary outcomes, comparative methods typically use the distribution of events and non-events in each group to estimate a contrast, then assess uncertainty around that estimate. The registry does not post a comparative analysis for this outcome, and the binary comparison is identified as not estimable.

What does “not estimable” mean in this record?

In general, an estimate requires enough observed information to define the quantity being compared. When no events are recorded in either group, the observed event counts do not provide a contrast in outcomes. Depending on the measure and statistical method, a comparative estimate may be undefined or may require additional assumptions. Because no analysis is posted, the registry does not identify a method that could support a numerical comparison. No treatment-effect estimate or confidence interval should be inferred from the reported counts alone.

In general, a confidence interval expresses uncertainty around an estimate under a chosen method. It does not remove uncertainty caused by sparse information, and it cannot supply outcome information that was not observed. The record reports no confidence interval. Consequently, there is no posted interval to interpret for either the treatment effect or its precision. The very limited group sizes make broad conclusions especially uncertain, but the record does not quantify that uncertainty with an inferential analysis.

Why do sparse binary data need care?

When events are uncommon in a dataset, small changes in the observed counts can have a large influence on a group comparison. When no events are recorded in either group, methods based on ratios or odds may encounter zero cells, and some standard estimates may not be defined without a special procedure. This is a general feature of sparse binary data, not a result calculated for this trial. The registry does not say whether a specialized method was planned or used.

General methods for binary outcomes can include comparisons of event proportions or models that relate the probability of an event to group assignment. These approaches require outcome counts and a defined analysis population; inference also depends on assumptions and the analysis plan. Here, the posted endpoint data are counts, but no inferential method or model is reported. A method should not be selected after the fact and presented as the trial’s prespecified analysis.

What role does randomization play?

Random allocation is intended, in general, to make groups comparable with respect to factors known and unknown at baseline. Randomization does not guarantee balance in a particular small trial, and it does not overcome limitations from sparse outcomes, incomplete follow-up, or departures from the planned procedures. The registry identifies allocation as randomized but does not describe the sequence-generation process, concealment, or implementation. Those details are not reported in the registry record.

The study is listed as open label, so participants and study personnel were not masked to assignment. Open-label design does not by itself determine whether an outcome is biased. The relevance depends on how the endpoint was defined, assessed, and recorded. The registry does not provide enough detail about those procedures to evaluate the possible influence of assignment knowledge on outcome ascertainment.

How should planning calculations be read?

Any sample-size illustrations associated with this record are planning illustrations, not observed power and not analyses of the trial’s results. The stated assumptions describe a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. Such planning calculations ordinarily ask what study size might be needed under specified assumptions; they do not show that the present trial had a particular probability of detecting an effect.

The record identifies the binary comparison as not estimable from the posted data. A planning illustration tied to an observed effect should not be mistaken for a validated effect estimate, particularly when the outcome counts are zero in both groups and no comparative analysis is posted. No trial-specific sample-size justification, target enrollment rationale, or statistical analysis plan is reported in the registry record. Accordingly, the planning assumptions should not be treated as evidence that the design had adequate size for its clinical question.

The registry also provides no reported adjustment, model specification, or sensitivity analysis. The statistical interpretation is therefore limited to the descriptive counts, the stated outcome timeframe, and the record’s explicit absence of a comparative analysis. General methodological explanations can clarify why these features matter, but they cannot replace the missing analysis or establish a result that the registry does not report.

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("Tamsulosin Group", "Education Group")
n      <- c(1, 4)
events <- c(0, 0)
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  Tamsulosin Group  1  0  0.0  0.0  97.5  0.0  79.3  1.3  84.2
ARM  Education Group  4  0  0.0  0.0  60.2  0.0  49.0  0.5  52.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 1 outcome measure and no posted secondary outcomes. The primary outcome is the number of participants with post-operative urinary retention during 5 days. With a single listed outcome, there is no reported set of multiple posted outcomes for which a multiplicity adjustment can be assessed. However, the registry does not report whether other outcomes or analyses were planned in a protocol, whether multiple time points or subgroups were considered, or whether any multiplicity strategy was prespecified. These details are not reported in the registry record.

Multiplicity refers, in general, to the risk of misleading findings when several hypotheses are tested or several analyses are considered. A prespecified analysis plan helps readers understand which comparisons were intended and whether adjustment was considered. No statistical analysis plan is reported, and the record lists no analyses. It is therefore not possible to determine the planned hypothesis-testing approach or whether any unposted analyses were conducted.

The registry does not report missing primary outcome data, participant-level analysis inclusion criteria, or an analysis population. It also does not state how participants with incomplete assessments, protocol deviations, or withdrawals were handled. Those items are not reported in the registry record; the listed enrollment and outcome counts should not be taken as proof that no data were missing. No intention-to-treat or per-protocol analysis is reported.

Because the trial was terminated, the absence of details about the stopping decision, analysis plan, and follow-up further limits assessment of whether the posted results represent the originally intended analysis. The reason for termination and whether outcome collection was completed as planned are not reported in the registry record.

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.

The registry reports safety counts for serious adverse events, other adverse events, and deaths by group. In the Tamsulosin Group, 0 serious adverse events and 0 other adverse events are recorded among 1 participant at risk; deaths are recorded as 0. In the Education Group, 0 serious adverse events and 0 other adverse events are recorded among 4 participants at risk; deaths are recorded as 0. No serious adverse event terms are listed.

These are descriptive counts from a very small study, not evidence that the interventions carry no risk. A zero count means that no such event was recorded among the participants represented in the registry result; it does not establish that an event could not occur. Small exposure and limited information about safety monitoring constrain what can be concluded. The registry does not report detailed methods for soliciting, classifying, or following adverse events, nor does it provide additional safety analyses.

The event counts should also be kept distinct from the primary outcome. Post-operative urinary retention is the primary endpoint, while the adverse-event fields describe separate safety categories. The registry’s safety figures do not supply a comparative safety estimate or a formal test between groups.

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

The posted result answers a narrow descriptive question: how many participants in each group were recorded as having post-operative urinary retention during the stated 5-day timeframe. The answer in the registry is 0 in the Tamsulosin Group and 0 in the Education Group. The record also states that the binary comparison is not estimable and lists no analyses.

Those counts do not establish that tamsulosin and education alone have equivalent effects. Equivalence requires a defined margin and an analysis designed to assess whether the difference falls within that margin; neither is reported. The counts also do not establish that tamsulosin prevents retention, or that it has no effect. With no recorded events in either group and very limited enrollment, the data provide no posted comparative effect estimate and no measure of its precision.

The result does not show what would happen in a larger or different population. Participant characteristics and detailed eligibility criteria are not reported in the registry record. The endpoint’s detailed definition and ascertainment procedures are also not reported, so readers cannot fully assess how urinary retention was identified. The open-label design is relevant to evaluating outcome assessment, but the record does not describe the assessment process.

Likewise, the absence of recorded adverse events in these groups should not be interpreted as proof of safety. The safety counts describe only what was reported for the participants at risk in the registry. The record provides no detailed account of safety monitoring or event collection.

The most defensible interpretation is therefore limited: no primary events were recorded in either group in the posted data, and no comparative analysis was reported. The terminated status, small enrollment, and unreported analysis details leave substantial uncertainty about the clinical question. Nothing in these results supports a treatment recommendation.

14. Why This Trial Matters Statistically

This record illustrates why the presence of a randomized design does not, by itself, make results conclusive. Randomization is a design feature intended to support fair comparisons, but interpretation also depends on the amount of information collected, the clarity of outcome measurement, and the analysis reported. Here, enrollment was 5, the group sizes were 1 and 4, and the primary outcome counts were 0 in both groups.

For a binary outcome, event counts are the information from which a group comparison must be built. When no event is recorded in either group, those counts do not reveal a separation in observed outcomes. The registry explicitly identifies the comparison as not estimable and lists no analyses. This is an important distinction between having a randomized trial record and having an interpretable estimate of effect.

The record also demonstrates the difference between descriptive reporting and inferential evidence. Descriptive counts tell readers what was recorded in the enrolled groups. A comparative estimate and uncertainty measure would address how compatible the data are with different possible effects, under a specified method. Neither is posted. Without them, the observed counts cannot establish either benefit or equivalence.

Finally, the terminated status makes transparent reporting of the study’s history and analysis especially useful. The reason for termination and the planned analysis are not reported in the registry record. Missing design and analysis details do not justify speculation, but they do define what readers cannot evaluate. The statistical value of this record is chiefly as an example of how sparse outcomes and limited reporting constrain interpretation, even when the research question is clinically clear.

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 enrollment was 5, with 1 participant assigned to the Tamsulosin Group and 4 to the Education Group. These small groups offer limited information for estimating a difference in a binary outcome. Both groups had 0 recorded participants with post-operative urinary retention, so the observed counts do not support a comparative estimate. The registry identifies the binary comparison as not estimable.

The trial is listed as terminated, but the reason for termination is not reported in the registry record. The planned target enrollment and any sample-size justification are also not reported, so it is not possible to assess the relationship between the intended design and the enrollment achieved. The status alone does not explain why the study ended or whether follow-up was completed as planned.

The registry does not report a statistical analysis plan, a comparative analysis, confidence intervals, or the analysis population. It also does not report missing outcome data or how such data would have been handled. Consequently, readers cannot evaluate whether the posted results follow a prespecified analysis or determine how participants were included in the outcome summary.

The primary endpoint is named and has a 5-day timeframe, but the detailed definition of post-operative urinary retention and the approach to outcome assessment are not reported. The open-label design may be relevant to assessment, but the record does not describe whether outcome ascertainment was standardized or performed independently of treatment assignment. Participant characteristics and detailed eligibility criteria are likewise not reported.

Safety reporting is also limited to counts. The record does not provide detailed methods for adverse-event collection, severity assessment, or follow-up. Together, these limitations mean that the registry supports a narrow reading of the posted counts, not a robust estimate of comparative effectiveness or safety.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Prophylactic Tamsulosin Use for Prevention of Post-Operative Urinary Retention — NCT02684344.
• Registry record last updated 2019-01-23; status last verified 2019-01.
• Results first posted 2019-01-23.
• 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.

19. Record Summary

The registry record describes a randomized, open-label, parallel-group study of prophylactic tamsulosin for prevention of post-operative urinary retention. The Tamsulosin Group received 0.4mg tamsulosin on the stated schedule and education; the Education Group received education alone. Enrollment was 5, and the study status is terminated. The listed start was 2016-02 and primary completion was 2017-12.

The primary outcome was the number of participants with post-operative urinary retention over 5 days. The registry reports 0 participants with the outcome in each group and lists no analyses. The comparison is identified as not estimable from the binary data. The reason for termination, statistical analysis plan, missing-data handling, and detailed endpoint definition are not reported in the registry record. The findings are descriptive and do not establish a comparative treatment effect.