The RELIEF™ Ureteral Stent - Assessment of Retrograde Urinary Reflux and Distal Coil Bladder Position: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The RELIEF™ Ureteral Stent - Assessment of Retrograde Urinary Reflux and Distal Coil Bladder Position (NCT03266770), a na na study. The primary outcome is Incidence of Bladder Irritation Symptoms (e.g. Frequency, Urgency, Nocturia, Urine Leakage...) Associated With the RELIEF Stent..

2. Clinical Question

The research question is focused on postoperative symptoms and on the proposed relationship between the stent design, bladder irritation, and urinary reflux. The registry’s stated rationale is that replacing the distal portion of a traditional stent with a thin material may reduce bladder irritative symptoms and allow the ureterovesical junction to coapt, thereby reducing urinary reflux. Those are hypotheses motivating the study; the single-group design does not directly estimate a treatment difference against a concurrent control.

The record also lists incidence of RELIEF Stent-Related Adverse Events as a secondary outcome. That safety description is distinct from the primary symptom score. The registry does not report a comparative question against another stent, and the posted results do not provide a numerical primary symptom estimate. Consequently, the clinical question can be described, but the magnitude of the recorded symptom outcome cannot be assessed from the registry record.

3. Trial Design

This was a completed, single-group study of the RELIEF Stent, a device evaluated in patients with ureteral obstruction. The registry lists enrollment of 24, allocation as NA, and masking as none. The study phase is listed as NA. The sponsor is University Hospitals Cleveland Medical Center. The recorded study start was 2021-06-15, and primary completion was 2022-12-12.

Participants who met the inclusion criteria and consented had the RELIEF stent inserted in the ureter during cystoscopy, described as being performed per standard care for ureteral stent placement. No separate control arm is listed. The absence of a concurrent comparator matters: the design can describe outcomes observed among participants who received the device, but it cannot isolate a difference attributable to the device relative to another stent or to no stent within this study.

The primary outcome is described as bladder irritation symptoms assessed with the Ureteral Stent Symptoms Questionnaire at 24 hours post op. The registry says that only patients with complete responses at 1-day following placement were included in the analysis. It lists a mean and standard deviation as the outcome summary, but the observed values and the analyzed sample size are not reported in the registry record.

The registry lists three outcome measures and one analysis. The secondary outcome named in the record is incidence of RELIEF Stent-Related Adverse Events. The study status is completed. The registry does not report a sample-size justification, a detailed statistical analysis plan, or whether interim analyses were planned or conducted.

The planning illustration associated with the posted results uses assumptions for a hypothetical two-arm comparison: two-sided significance level 0.05, equal allocation, and a normal approximation. It is described as computed from an observed effect and as planning rather than the trial’s own design. Since this trial is single-group, those assumptions should not be read as a description of how participants were actually assigned or as evidence of an observed power calculation. Numerical planning counts 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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Only patients with complete responses to the USSQ at 1-day following RELIEF Stent placement were included in the analysis.

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 Incidence of Bladder Irritation Symptoms (e.g. Frequency, Urgency, Nocturia, Urine Leakage...) Associated With the RELIEF Stent., measured over 24 hours post op.

The primary endpoint concerns bladder irritation symptoms, including examples such as frequency, urgency, nocturia, and urine leakage. Symptoms are assessed using the Ureteral Stent Symptoms Questionnaire (USSQ) at 24 hours post op. The registry describes the USSQ score as ranging from 19 to 220 or above, with higher scores indicating more or worse symptoms. The intended summary is a mean with a standard deviation.

A questionnaire score is useful because it turns reported symptoms into a structured measure that can be summarized across participants. A mean describes the average score in the analyzed group, while a standard deviation describes variation in scores among participants. Neither summary alone conveys every participant’s experience, and the registry record does not report the observed mean, standard deviation, or number of complete questionnaires used in the analysis.

There is a wording distinction in the record: the primary outcome title refers to incidence of bladder irritation symptoms, while the measurement description specifies a continuous USSQ score summarized by its mean and standard deviation. A score-based endpoint describes symptom burden on the questionnaire; it is not, by itself, a count of participants with at least one symptom. The record does not provide a separate threshold defining symptom incidence.

The endpoint is measured at 24 hours post op, so its stated timeframe is an early postoperative assessment. The record does not describe a longer-term symptom endpoint in the primary outcome entry. The numerical result for this primary measure is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a continuous questionnaire outcome summarized by a mean and standard deviation. This combination is common when the analytic question concerns the average score in a group. The mean locates the center of the observed scores, while the standard deviation reflects how dispersed those scores are around the mean. Interpretation requires both the score definition and the observed summary values. The definition and scoring direction are recorded, but the primary numerical summaries are not reported in the registry record.

What does the mean describe?

For this endpoint, the mean would summarize USSQ scores among patients with complete responses at 1-day following RELIEF stent placement. The registry defines higher scores as more or worse symptoms. Thus, the direction of the scale is clear even though the observed group mean is absent. The mean should not be confused with the number of participants reporting symptoms, because the measure is a score rather than a binary symptom indicator.

The standard deviation would help show whether participants’ scores were clustered near the mean or spread more widely. It is a measure of variation among observed scores, not a measure of uncertainty in the estimated mean. A confidence interval, if reported, would address uncertainty in the estimated mean. Neither the standard deviation nor a confidence interval for the primary endpoint is reported in the registry record.

Why does the analysis population matter?

The record says that only patients with complete USSQ responses at 1-day following placement were included in the primary analysis. This identifies a complete-response analysis population, but the number of complete responses is not reported in the registry record. Enrollment of 24 does not establish that all 24 contributed to the primary endpoint. Without the analyzed count, readers cannot assess how much the primary analysis population differs from enrollment or how the available responses relate to the intended study population.

Complete-response analysis is one way to calculate a score summary when some questionnaire data are incomplete. In general, excluding incomplete responses can affect the estimate if response completeness is related to symptom level or other relevant characteristics. That is a general statistical concern, not a finding about this study. The registry does not report the amount or pattern of missing questionnaire data or any method for handling incomplete items.

What does the single-group design allow?

A single-group study can describe outcomes observed among participants who received the intervention. It does not provide a concurrent estimate of what would have happened to comparable participants under a different intervention. A randomized comparison can balance measured and unmeasured factors on average through assignment; this record does not describe random allocation or a control arm. Therefore, a score observed after stent placement cannot, on its own, establish that the device caused that score or that it differs from scores with traditional stents.

Masking is listed as none. In general, lack of masking can matter when outcomes are reported by participants or assessed by people aware of the intervention, because expectations may influence reporting or measurement. The registry identifies a participant questionnaire but does not report additional procedures to address this possibility. This is a design consideration, not evidence that responses were biased.

How should planning illustrations be read?

The registry’s planning assumptions describe a hypothetical two-arm calculation with a two-sided significance level of 0.05, equal allocation, and a normal approximation. The illustration is described as using a stated fraction of an observed effect. These assumptions do not describe the actual allocation in this single-group study, and the illustration is explicitly planning rather than the trial’s own design. Numerical planning counts are not reported in the registry record.

A planning calculation asks how many participants might be required under specified assumptions to detect a target effect with a chosen statistical procedure. It does not show that the study had that probability of detecting an effect after the results were observed. Sample-size illustrations should therefore not be interpreted as observed power. The registry does not report the study’s own sample-size justification or protocol assumptions.

Normal approximations are general methods that use an approximate distribution for an estimate or test statistic. Their suitability depends on the data and model assumptions. The registry does not report diagnostics or model details that would allow an assessment of those assumptions for the primary endpoint. Also, over-dispersion is a general concern for count outcomes when variation exceeds what a model assumes; it is not the stated summary model for this mean questionnaire endpoint. The record’s planning note distinguishes time-to-event calculations, which count total events, from other planning illustrations, which express participants per arm. Those conventions do not turn this single-group study into a two-arm comparison.

Finally, the registry lists one analysis, but does not provide enough detail to identify all analytic decisions, such as treatment of incomplete questionnaire items, adjustments, or model-based covariates. A statistical result is best interpreted alongside its population definition, estimate, variability, and analysis procedure. Several of these details are not reported in the registry record.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("RELIEF Stent Placement")
n   <- c(16)
m   <- c(51.95)
sp  <- c(18.2)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  RELIEF Stent Placement  16  51.950  18.200  42.252  61.648

11. Multiplicity, Missing Data and Analysis Populations

Multiplicity concerns arise when an analysis examines multiple outcomes, time points, subgroups, or statistical contrasts. When many hypotheses are tested, the chance of at least one apparently notable result can increase unless the analysis plan accounts for the number and structure of tests. This is a general statistical principle. The registry lists three outcome measures and one analysis, but does not report a multiplicity strategy or enough detail about the analysis to determine which outcomes or contrasts were tested together. Whether any adjustment was planned or used is not reported in the registry record.

The primary endpoint is specified at 24 hours post op. The record does not describe repeated primary measurements or a hierarchy for interpreting outcomes. It also does not state whether the named secondary outcome was part of a confirmatory testing strategy or was intended to be descriptive. A prespecified hierarchy or adjustment can help distinguish a primary confirmatory claim from exploratory findings; the relevant plan is not reported in the registry record.

For missing data, the registry states that only patients with complete USSQ responses at 1-day following placement were included in the primary analysis. It does not report how many participants had complete responses, how many did not, why any responses were incomplete, or whether incomplete questionnaire items were handled in another way. No imputation or sensitivity-analysis method is reported in the registry record. The enrollment count of 24 should not be assumed to be the primary analysis denominator.

The registry does not describe a formal analysis population beyond the complete-response criterion for the primary endpoint. It does not report whether all enrolled participants, only participants who received the device, or another population was used for the safety outcome. The safety counts are presented for the RELIEF Stent Placement group with 24 at risk. These missing details limit assessment of how participants were included across outcomes and how robust the primary result would be to different missing-data assumptions.

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 lists 0 serious adverse events among 24 at risk in the RELIEF Stent Placement group. It lists 3 other adverse events among 24 at risk and 0 deaths. These are descriptive counts for the group, not a comparison with another stent or a control group. The record does not report serious adverse-event terms; the list of top serious terms is empty.

A count of 0 means that no serious adverse events are recorded for this group in the posted safety data. It does not prove that the underlying risk is zero, particularly when the study group is limited in size. The counts also do not establish whether an event was caused by the device. Attribution methods, event timing, and clinical descriptions for the other adverse events are not reported in the registry record.

The 3 other adverse events should not be treated as a measure of symptom burden on the USSQ. They are a separate safety outcome. The registry does not provide additional detail in this record to determine whether those entries refer to distinct event types, their severity, or their relationship to the stent. A descriptive safety count is useful for reporting what was recorded, but it cannot by itself establish comparative safety or rule out uncommon harms.

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

The record establishes that a completed, unmasked, single-group study evaluated the RELIEF stent and specified a postoperative USSQ assessment at 24 hours post op. It also records enrollment of 24 and reports the group’s adverse-event counts. These details describe the study’s scope and the outcomes it intended to examine.

The primary symptom outcome is not numerically reported in the registry record. Without the mean score, standard deviation, and number of complete responses, readers cannot determine the average symptom score observed, how variable the scores were, or how precisely the average was estimated. The scoring direction is described: a higher USSQ score means more or worse symptoms. That scoring information does not substitute for the observed result.

The record does not establish that the RELIEF stent reduces bladder irritation or urinary reflux. Those ideas appear in the study rationale and hypothesis. Because there is no concurrent comparator, the study does not estimate a treatment difference against a traditional stent. It also does not establish that any observed outcome was caused by the device. These are limits on what can be inferred from this design, not conclusions about whether the device is beneficial or harmful.

The recorded safety figures are 0 serious adverse events, 3 other adverse events, and 0 deaths among the listed group of 24 at risk. These counts are informative as reported observations but do not establish a comparative safety profile. The registry does not describe the other adverse events in enough detail to interpret their nature, severity, or attribution.

More broadly, statistical interpretation depends on the estimate, its uncertainty, the analysis population, and the design used to generate it. In this record, the outcome definition and population criterion are described, but the central primary estimate and its precision are absent. The study can therefore be characterized by its question, design, and posted safety counts, while the size and precision of its primary symptom finding remain unknown from the registry record.

14. Why This Trial Matters Statistically

This study raises a useful statistical distinction between measuring an outcome and establishing a comparative effect. A questionnaire can give a structured description of symptoms after a procedure. But a single-group score does not show how that score compares with what would have occurred under another stent or another treatment strategy. The absence of a concurrent comparator is central to interpreting the study’s stated hypothesis about symptom reduction and urinary reflux.

The endpoint wording also illustrates why outcome definitions need to be read closely. The primary title uses the word incidence, while the measurement description specifies a continuous USSQ score summarized as a mean and standard deviation. A score can describe symptom burden, whereas incidence ordinarily requires a defined event and a count over a specified population or period. The registry does not provide a separate threshold or symptom count. This distinction affects what the analysis can answer.

Reporting the analysis population is equally important. The primary analysis includes only patients with complete responses, but the number analyzed and the extent of missingness are not reported in the registry record. Without those details, enrollment cannot be equated with the denominator for the mean score. This limits readers’ ability to assess both representativeness and precision.

The posted safety counts illustrate another interpretive boundary. Zero serious adverse events in a group is a factual observation, not proof of no risk. Counts without comparison or event detail also cannot establish whether the device caused an event or how the safety profile compares with an alternative.

These issues are broadly relevant to clinical research: outcome wording, analysis populations, comparator structure, and uncertainty all determine what a result means. In this record, these considerations can be identified, but the missing numerical primary result prevents evaluation of the observed symptom level or its precision.

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 main trial-specific limitation is the single-group design. Allocation is listed as NA and no concurrent control arm is described. The study therefore provides no direct comparison with traditional ureteral stents, even though the stated rationale concerns possible advantages over traditional stents. Differences between observed outcomes and outcomes under another approach cannot be estimated from this record.

The primary endpoint is defined as a USSQ score at 24 hours post op, but its numerical mean and standard deviation are not reported in the registry record. The number of complete responses is also not reported. Because the analysis includes only complete questionnaires at 1-day following placement, the number enrolled cannot be assumed to equal the primary analysis population. The record does not describe missing-response patterns or methods for addressing incomplete data.

The outcome title refers to incidence, while the outcome description specifies a continuous score. No separate definition of symptom incidence or threshold is reported. This creates ambiguity about whether the title is intended as a general description of symptoms or as a distinct incidence measure. The reported scoring description supports interpretation of a questionnaire score, not a symptom count.

The study is unmasked. Since the primary endpoint is a questionnaire, awareness of the intervention is a potential general concern for subjective reporting. The registry does not describe any procedures intended to mitigate that concern. This limitation does not establish that reporting was biased.

The safety information is limited to aggregate counts: 0 serious adverse events, 3 other adverse events, and 0 deaths among 24 at risk. The record does not provide descriptions of the other events, their timing, or attribution. A sample-size justification, detailed statistical analysis plan, multiplicity approach, and interim-analysis plan are not reported in the registry record. These omissions constrain assessment of the endpoint analysis and the completeness of safety interpretation.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: The RELIEF™ Ureteral Stent - Assessment of Retrograde Urinary Reflux and Distal Coil Bladder Position — NCT03266770.
• Registry record last updated 2024-02-01; status last verified 2024-01.
• Results first posted 2024-02-01.
• 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

NCT03266770 is a completed, single-group study of the RELIEF Stent sponsored by University Hospitals Cleveland Medical Center. Enrollment was 24. The study start was 2021-06-15, and primary completion was 2022-12-12. Masking is listed as none, allocation as NA, and phase as NA.

The primary outcome is bladder irritation symptoms assessed using the USSQ at 24 hours post op, with higher scores indicating more or worse symptoms. Only complete responses at 1-day following placement were included. The numerical mean, standard deviation, and analyzed sample size are not reported in the registry record.

For the RELIEF Stent Placement group, the registry lists 0 serious adverse events, 3 other adverse events, and 0 deaths among 24 at risk. The record does not provide a concurrent comparator, a sample-size justification, or detailed analysis methods.