Prostatic Urethral Lift in Subject With Acute Urinary Retention: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Prostatic Urethral Lift in Subject With Acute Urinary Retention (NCT03194737), a non-randomized na study. The primary outcome is Successful Trial Without Catheter Peri-procedurally.

2. Clinical Question

3. Trial Design

This was a completed, non-randomized, parallel study with no masking. The record lists the phase as not applicable. Enrollment was 101. The study began on 2018-03-24, and primary completion was recorded as 2019-01-21. NeoTract, Inc. is listed as the sponsor.

The prospective arm received the UroLift System procedure. The other arm was retrospective: medical charts were reviewed for invasive BPH surgeries performed at the site from June 1, 2015 to December 31, 2015. Listed examples are TURP and HoLEP. The prospective arm’s information was collected prospectively, while trial-without-catheter information for the retrospective arm was recorded as available from medical records. These different sources and collection methods matter when interpreting any comparison.

Because allocation was not randomized, assignment did not create exchangeable groups by design. Differences between arms could reflect characteristics of the people treated, the procedures, the periods or settings represented, or how information was recorded. The record does not report methods to adjust for such differences. The retrospective group is therefore not a like-for-like control comparison, and any contrast should be treated as descriptive rather than as a randomized estimate of a procedure effect.

The registry lists two outcome measures and zero analyses. It gives a definition and timeframe for the primary endpoint, but does not report the observed primary endpoint counts or a statistical test. The record also lists a secondary outcome concerning serious adverse events related to BPH intervention. The missing outcome and analysis information limits what can be concluded from the registry entry.

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.

Before assignment: Retrospective cohort enrollment was separate from the 52 enrolled in the prospective cohort. Retrospective enrollment was based on a retrospective chart review between Jun 1, 2015 and December 31, 2015.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Trial Without Catheter information for retrospective arm was recorded as available from medical record, information from the UroLift System was prospectively collected

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 Successful Trial Without Catheter Peri-procedurally, measured over 3 days (± 1 day) from index procedure.

The primary endpoint counts participants who had a successful trial without catheter peri-procedurally. It was assessed 3 days (± 1 day) from the index procedure. The definition requires spontaneous voiding of at least 100 mL, a post-void residual volume measured by ultrasound <300 mL, and no need for re-catheterisation. These criteria combine a minimum voided volume, a limit on residual urine, and avoidance of another catheter placement within the defined assessment period.

A binary endpoint of this kind can make a clinical event easier to summarize: each participant either meets the stated success definition or does not, and the registry’s stated unit is participants. It is important, however, to distinguish the endpoint definition from the endpoint result. The registry record describes how success was to be classified but does not report how many participants met the criteria in either arm.

Using the same stated definition and assessment window for each group would be necessary for a meaningful descriptive comparison. In this study, the record says prospective UroLift information was collected prospectively, while retrospective trial-without-catheter information was taken from medical records as available. That difference in ascertainment may affect whether the required details were documented consistently. The registry record does not report how missing or incomplete measurements were handled, so the extent of any such effect is unknown.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Study structure. This was a non-randomized, parallel study with no masking. In a randomized trial, random allocation is intended to balance measured and unmeasured participant characteristics across groups on average. Here, the record explicitly identifies non-randomized allocation, so that protection is absent. A parallel structure means the registry presents separate groups, but the existence of groups does not make them comparable. The UroLift arm was prospective, while the retrospective arm was assembled from records of invasive BPH surgery. Their different sources and collection methods are central to interpretation.

Outcome type. The primary outcome is a participant count for a binary success definition. A binary outcome classifies each participant according to whether the endpoint criteria were met. The specified criteria concern spontaneous voiding, residual volume by ultrasound, and re-catheterisation, within 3 days (± 1 day) from the index procedure. The record does not give the counts meeting the definition. Without those counts, an observed event proportion, between-group estimate, or uncertainty interval cannot be interpreted from the registry entry.

Descriptive counts and comparisons. A group count describes how many participants had a recorded event, while a comparison asks how the event frequency differs between groups. Statistical inference adds an assessment of uncertainty around a comparison, often through a confidence interval or a hypothesis test. A confidence interval is a range of values compatible with the data and statistical assumptions; its width indicates precision. These are general explanations. The registry record reports zero analyses and does not give a primary endpoint comparison, confidence interval or p-value. Accordingly, no inferential conclusion can be drawn from the listed primary endpoint definition alone.

Why non-randomization matters. In general, non-randomized groups can differ in prognosis, eligibility, clinical history, or other factors. Differences may also result from changes in practice or recordkeeping over time. The retrospective group comprised invasive procedures recorded at the site during June 1, 2015 to December 31, 2015, whereas the UroLift arm was prospectively collected. The record does not report covariate adjustment, matching, weighting, or another method to address group differences. It also does not report enough detail to assess whether the groups had comparable eligibility or baseline characteristics. An unadjusted contrast, if one were available, would therefore remain vulnerable to confounding and measurement differences.

Precision and sample size. The registry record does not report a sample-size justification or the assumptions used in designing the study. The planning illustration described for the statistical presentation uses a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. Such a calculation is a planning exercise, not observed power and not evidence that the study was adequately powered. Its interpretation depends on the observed effect and other calculation inputs; the primary endpoint result and numerical planning outputs are not reported in the registry record. No sample size should be inferred from the enrollment alone.

In general, power calculations describe how often a design might detect a specified effect under stated assumptions if the study were repeated. They do not measure the probability that a result is true, and post hoc calculations based on an observed effect do not repair design limitations. Equal allocation is an assumption of the illustration, not a statement that the observed arms were randomized. The record’s group sizes at risk are listed as 52 and 49 for the safety entries, but those figures do not establish the allocation method or the number with primary endpoint data.

Over-dispersion and time-to-event methods. For count outcomes, over-dispersion means that variability exceeds what a simple model assumes. In general, ignoring over-dispersion can make standard errors too small and uncertainty appear narrower than warranted. The primary endpoint is described as a count of participants meeting a binary definition, not as a rate of recurrent events; the record does not report an over-dispersion assessment or a model. Time-to-event methods address the timing of events and may account for censoring; they are not described for the primary endpoint in this record. No time-to-event analysis is reported in the registry record.

Multiplicity and analysis choices. When multiple endpoints or statistical tests are examined, the chance of at least one apparently notable result can increase unless the analysis plan addresses multiplicity. The registry lists two outcome measures, but does not report a multiplicity strategy, a hierarchy of hypotheses, or analysis details. It also does not report interim analyses, a statistical analysis plan, or analysis populations. These absences prevent assessment of which analyses were prespecified or how incomplete outcome information was treated. General statistical principles cannot fill in those unreported decisions.

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("UroLift System Procedure", "Retrospective Arm")
n      <- c(52, 49)
events <- c(29, 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  UroLift System Procedure  52  29  55.8  41.3  69.5  42.3  68.4  42.3  68.4
ARM  Retrospective Arm  49  0  0.0  0.0  7.3  0.0  7.3  0.1  7.1

11. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures and zero analyses. It does not report whether a multiplicity strategy was specified, whether one outcome was formally prioritized over another for statistical testing, or whether any outcome hierarchy was used. In general, testing several outcomes can raise the chance of obtaining an apparently unusual result by chance; multiplicity methods are intended to manage that issue. No particular method can be attributed to this study from the registry record.

The primary endpoint definition is available, but its result is not reported in the registry record. The record also does not report missing-data counts, the number with an evaluable primary endpoint, or a method for handling missing, incomplete, or unevaluable measurements. Since retrospective trial-without-catheter information was recorded from medical records as available, completeness of those records could be relevant, but the extent and treatment of any missing information are not reported.

Analysis populations are not described. The record does not state whether results were based on all enrolled participants, those who received the procedure, or another defined group. It does not report exclusions from analysis or how deviations from the planned procedure were handled. Interim analyses and a statistical analysis plan are also not reported in the registry record.

These gaps make it difficult to assess the risk of selective analysis or the robustness of any outcome estimate. They do not establish that data were missing, that analyses were changed, or that multiplicity was mishandled. They mean that those aspects cannot be evaluated from the registry entry.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: haematuria (3.8%), urinary tract infection (3.8%), blood clot in urine (1.9%), intestinal bleeding (1.9%), lucunar stroke (1.9%).

The registry’s safety entries list 52 participants at risk in the UroLift System Procedure group and 49 in the Retrospective Arm. Serious adverse events affected 7 participants in the UroLift group and 2 in the retrospective group. Other adverse events affected 36 and 29 participants, respectively. The record lists zero deaths in each group. These are descriptive counts; they do not by themselves show that the procedures caused or prevented events.

The secondary outcome is described as the number of participants with serious adverse events related to BPH intervention. The group-level counts do not include a reported statistical comparison or uncertainty interval, and the registry record does not report an adjudication or attribution method. The retrospective and prospective collection approaches may also differ in how events were identified and documented. Consequently, the counts should not be read as a like-for-like causal comparison.

The listed serious-event terms include haematuria and urinary tract infection at 3.8% each, and blood clot in urine, intestinal bleeding and lacunar stroke at 1.9% each. The record does not provide further detail establishing the denominator, group distribution, or causal attribution for each listed term. These percentages and terms are descriptive registry entries, not estimates of comparative risk.

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

The registry record establishes that a non-randomized study evaluated the feasibility and safety of the UroLift System procedure in people with acute urinary retention associated with BPH. It defines success for a trial without catheter and specifies an assessment window of 3 days (± 1 day) from the index procedure. It also records group-level adverse-event counts and selected serious-event terms. These details describe what the study set out to assess and some safety information entered in the registry.

The record does not report the primary endpoint counts or an analysis comparing the prospective procedure group with the retrospective surgical group. It therefore does not show the frequency of endpoint success in either group, the size or precision of a difference, or whether a statistical test found evidence of a difference. No conclusion about comparative efficacy can be drawn from the available endpoint information.

The safety counts likewise do not establish a causal effect. Participants were not randomized, the comparator was retrospective, and information was collected differently across groups. Any observed contrast could reflect differences in participants, procedures, time, record completeness, or other factors. The registry record does not report adjustment methods or analyses that would address those issues.

The absence of reported results should not be interpreted as proof that the procedure had no effect, nor as proof that it had a beneficial or harmful effect. It indicates that the primary result and inferential comparison are not reported in the registry record. The posted safety counts are useful as descriptive entries but do not resolve comparative safety or establish that listed events were caused by a particular procedure. Further conclusions would require outcome results, analysis details, and information about data completeness and comparability that are not reported in the registry record.

14. Why This Trial Matters Statistically

This study illustrates a recurring statistical challenge in clinical research: a clearly defined endpoint does not guarantee that the registry contains the results needed to evaluate it. The primary endpoint is described with a threshold for spontaneous voiding, a residual-volume criterion, and a defined timeframe. Yet the endpoint counts and statistical analyses are not reported in the registry record. Readers can understand the intended measure, but cannot assess its observed frequency or precision.

The design also highlights why a comparator’s source matters. A prospective procedure arm and a retrospective group assembled from medical records can differ in participant selection, documentation, and event ascertainment. Non-randomized allocation adds the possibility of systematic differences between groups. These are not minor technical details: they determine how confidently an observed contrast could be attributed to the intervention rather than to other differences.

The safety entries show why descriptive counts should not be mistaken for comparative effects. Counts can identify the number of participants recorded with events, but a causal interpretation requires attention to group comparability, event definitions, follow-up, attribution, and uncertainty. The registry record does not provide enough analysis detail to resolve those questions.

Statistically, the most important lesson is the distinction between a planned question and a reported result. Endpoint definitions, enrollment, and safety counts are informative, but they cannot substitute for endpoint outcomes, a prespecified analysis, and an account of missing information. The record is therefore useful for understanding design and reporting gaps, while leaving the primary comparative question unanswered.

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 endpoint result is not reported in the registry record, despite a detailed success definition and assessment timeframe. The record lists zero analyses, so no primary endpoint estimate, statistical test, confidence interval, or adjustment is available for interpretation. The outcome measure cannot be evaluated based on its definition alone.

The non-randomized design limits causal interpretation. The retrospective arm is not a randomized, like-for-like control comparison and reflects chart review of invasive BPH surgeries performed at the site from June 1, 2015 to December 31, 2015. The prospective and retrospective arms also used different information-collection approaches. The registry record does not report baseline characteristics, adjustment methods, or procedures for making the groups comparable.

There is no reported account of primary endpoint completeness, missing-data handling, analysis populations, or exclusions. This is particularly relevant because retrospective trial-without-catheter information was recorded as available from medical records. The record does not establish whether the required measurements were documented consistently or how incomplete records were treated.

The safety figures are descriptive and lack reported uncertainty estimates or a comparative analysis. The record does not give details of event attribution or enough information to evaluate whether ascertainment was comparable across groups. The listed event percentages are not accompanied by a detailed explanation of their denominator or group distribution.

Finally, a sample-size justification, interim analysis plan, multiplicity strategy, and statistical analysis plan are not reported in the registry record. These omissions prevent evaluation of planned precision and analysis choices. They do not prove that such procedures were absent in practice, but they are not documented in the registry entry.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Prostatic Urethral Lift in Subject With Acute Urinary Retention — NCT03194737.
• Registry record last updated 2021-07-16; status last verified 2021-05.
• Results first posted 2021-07-16.
• 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

NCT03194737 is a completed, non-randomized, parallel study with no masking and enrollment of 101. It assessed the UroLift System procedure in people with acute urinary retention associated with BPH, with a retrospective arm based on invasive BPH surgeries documented at the site from June 1, 2015 to December 31, 2015. The primary endpoint was successful trial without catheter peri-procedurally, assessed 3 days (± 1 day) from the index procedure.

The registry record lists two outcome measures and zero analyses. It does not report the primary endpoint counts, a comparative estimate, or inferential results. Safety entries list serious adverse events affecting 7 of 52 participants in the UroLift group and 2 of 49 in the retrospective group, other adverse events affecting 36 and 29 participants, respectively, and zero deaths in each group. Because the arms were not randomized and were collected differently, these counts are descriptive rather than causal evidence. The primary comparative question remains unanswered by the registry results.