This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Gentamicin Bladder Instillations to Prevent Urinary Tract Infections in Patients With Spinal Cord Injury (NCT03503513), a na phase 2, phase 3 study. The primary outcome is Number of Urinary Tract Infections (UTI) Over Time.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03503513 |
| Phase | Phase 2, Phase 3 |
| Condition | Urinary Tract Infections, Spinal Cord Injuries, Spinal Cord Diseases |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 23 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Michigan |
| Results posted | Yes |
2. Clinical Question
Population
Participants with spinal cord injury or disease and neurogenic bladder. The primary-outcome population is described as eleven participants with recurrent urinary tract infections, defined as two or more during the six months before treatment.
Intervention
Gentamicin sulfate given by bladder instillation every night for a treatment period of six months. Instillations were to stop if a participant developed a urinary tract infection, then resume after treatment for that infection.
Comparator
The primary outcome compares the six months before treatment with the six months during treatment in the same study context. There is no randomized control arm; the allocation is listed as not applicable and the study model as single group.
Primary question
How did the rate of reported urinary tract infections per person-month differ between the pre-treatment and during-treatment periods? The registry describes the measure but does not report the rate estimates or their comparison.
This is a question about change over time in a treated group, not a randomized comparison of gentamicin with an untreated or alternative-treatment group. The registry’s brief summary also describes evaluation of bladder complications, quality of life, community living, and participation. Two listed secondary outcomes concern change in Neurogenic Bladder Symptom Severity and Neurogenic Bowel Dysfunction scores.
The clinical question is bounded by the outcome population and observation periods specified in the record. The primary outcome focuses on urinary tract infections documented by participants and in medical charts. It therefore concerns reported and documented events, rather than every possible infection or a broader measure of health. The record does not report the numerical change in infection rate, results for the secondary outcomes, or findings for quality of life, community living, and participation. Those outcomes cannot be interpreted from the registry information available.
3. Trial Design
The registry identifies this as a completed, non-randomized, single-group study with no masking. Its phase is listed as Phase 2 and Phase 3. The University of Michigan is named as sponsor. The study began on 2018-08-24, and its primary completion date is 2023-09-08. Enrollment is listed as 23.
Participants received gentamicin sulfate by intravesical instillation. The arm description states that participants initiated nightly instillations for a six-month treatment period. If they developed a urinary tract infection, instillations were stopped during treatment for that infection and then resumed. The remaining arm-description text is incomplete in the registry record, so further practical details of the procedure are not reported in the registry record.
The primary outcome uses a before-and-during structure: urinary tract infections in the six months before treatment are considered alongside infections during six months of treatment. This creates a within-study time comparison, but it is not equivalent to a randomized comparison. The record does not describe a concurrent control group, and allocation is listed as not applicable. Without random assignment to a comparison group, differences across periods may reflect factors other than the intervention, including changes over time or differences in observation and reporting.
The primary-outcome population is described as eleven participants with spinal cord injury or disease, neurogenic bladder, and recurrent urinary tract infections in the pre-treatment period. That number is distinct from the overall enrollment of 23. The registry does not explain the relationship between overall enrollment and the primary-outcome population, or report why participants may not be included in that outcome population. Eligibility details beyond the stated outcome population, recruitment procedures, and the rationale for the study’s enrollment are not reported in the registry record.
The registry lists three outcome measures and five analyses. It does not provide enough information to identify all analysis populations or to establish which analyses correspond to each outcome. A formal protocol, detailed statistical analysis plan, and sample-size justification 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.
Before assignment: Of 23 eligible persons who consented, only 19 started on treatment due to several reasons including changes in necessary study procedures associated with the COVID outbreak, changes in medical status due to complications and personal decisions to proceed with treatment.
Overall Study
| Stage | Gentamicin Sulfate |
|---|---|
| STARTED | 23 |
| Began Treatment | 19 |
| Completed More Than 4 Months of Treatment | 12 |
| COMPLETED | 11 |
| NOT COMPLETED | 12 |
Reasons for not completing this period:
| Reason | Gentamicin Sulfate |
|---|---|
| First cohort faced a clinical hold which caused disruption in treatment; | 4 |
| Second cohort faced changes due to pandemic, resulting in declining participant count | 2 |
| Physician Decision | 3 |
| Withdrawal by Subject | 2 |
| Lost to Follow-up | 1 |
Analysis population for the primary outcome, as defined in the registry: Eleven participants with spinal cord injury or disease and neurogenic bladder with recurrent urinary track infections (2 or more) during the 6 months prior to treatment.
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.
Population: Baseline data is provided for all participants who started treatment
| Characteristic | Unit | Gentamicin Sulfate |
|---|---|---|
| Participants analysed | 19 | |
| Age, Continuous | years | 46 (26 to 76) |
| Sex: Female, Male: Female | Participants | 7 |
| Sex: Female, Male: Male | Participants | 12 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 0 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 18 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 1 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 |
| Race (NIH/OMB): White | Participants | 18 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 1 |
| Region of Enrollment: United States | Participants | 19 |
| Type of spinal lesions: Spinal Cord Injury (SCI) | Participants | 14 |
| Type of spinal lesions: Spinal Cord Disease (SCD) | Participants | 5 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Urinary Tract Infections (UTI) Over Time, measured over 6 months prior to treatment and 6 months during treatment.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | 95% Confidence Interval |
| Unit | UTI events per person months. |
| Endpoint classification | Event-Rate Endpoint |
The primary endpoint is the number of urinary tract infections over time, expressed as UTI events per person-month. The registry describes events reported by participants and documented in medical charts, counted for each person across the six months before treatment and the six months during treatment. The stated purpose of expressing the count as a rate is to relate events to time under observation rather than presenting event counts without an exposure-time denominator.
For the primary-outcome population, the registry describes a denominator based on eleven participants over six months, stated as 66 person-months. The record says the rate is formed by dividing the total number of UTIs in a period by the total person-months for that period. It specifies a 95% confidence interval as the measure of dispersion. The event totals, rate estimates, confidence intervals, and numerical comparison between the periods are not reported in the registry record.
As a general statistical concept, an event rate can be useful when the amount of observed time matters: it expresses how frequently events occurred relative to exposure time. It does not, by itself, describe how events were distributed among participants. A group rate could reflect a similar event burden across participants or a concentration of events in a smaller number of people. The registry record does not provide participant-level event distributions, so that distinction cannot be assessed.
The endpoint also depends on event ascertainment. Here, its description refers to participant reports and medical-chart documentation; the record does not provide further detail about adjudication or how disagreements between sources were handled.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record gives the design and definition of the primary endpoint but does not report the outcome values. In particular, it does not report the number of urinary tract infections in either observation period, the corresponding person-month rates, the 95% confidence intervals, or a statistical test of change. Consequently, the direction and magnitude of any observed change cannot be established from this record.
The comparison is between a pre-treatment period and a treatment period in a single group. Even if numerical results were available, a before-and-during change would describe what happened across those periods among the analyzed participants; it would not by itself isolate an intervention effect. Without a randomized control group, other influences that vary over time could contribute to a difference. The record does not report adjustments for such influences or describe a causal analysis.
The stated primary-outcome population consists of eleven participants with recurrent infections before treatment. The overall enrollment is 23. These figures refer to different descriptions in the registry, and the record does not explain how participants moved from overall enrollment to inclusion in the primary-outcome analysis. It also does not report how many participants contributed complete observations in each period. This limits assessment of how representative the analyzed group is of the enrolled participants.
A 95% confidence interval is intended, as a general statistical interpretation, to convey uncertainty around an estimate under the assumptions of the analysis. A narrower interval generally indicates greater precision than a wider one, but precision is not the same as protection from bias. Since no interval limits or estimates are reported, precision cannot be judged for this endpoint. The registry’s mention of a confidence interval does not supply enough information to identify the interval method.
The listed secondary outcomes concern changes in neurogenic bladder symptom severity and neurogenic bowel dysfunction. Their numerical results are not reported in the registry record. The brief summary also mentions bladder complications, quality of life, community living, and participation, but the record does not provide numerical results for those aims. The list of three outcome measures and five analyses does not establish which results were favorable, how outcomes related to one another, or which analyses were primary beyond the named primary endpoint.
The appropriate reading is therefore descriptive and limited: the study was designed to examine urinary tract infection rates before and during nightly gentamicin instillations, and the registry records the endpoint’s intended construction. The posted results in the registry record do not allow an estimate of the observed change or its uncertainty. They also do not support a conclusion about whether treatment changed the rate.
9. Statistical Methods Explained
The primary endpoint is a rate: the number of urinary tract infection events divided by person-time at risk or under observation. In this record the unit is UTI events per person-month. As a general statistical concept, rates allow event counts to be interpreted in relation to observation time. This matters when participants contribute different amounts of time, although the registry describes the intended denominator for this endpoint as the number of participants multiplied by the six-month period.
The outcome description specifies a six-month pre-treatment period and a six-month treatment period. It says that reported and medically documented infections form the event count, and that the total number of UTIs in each period is divided by total person-months. For the stated primary-outcome population, the registry gives eleven participants over six months as 66 person-months. It does not provide the event totals or the resulting rates. The numerical comparison therefore cannot be reconstructed from the record.
What does a confidence interval communicate?
The endpoint lists a 95% confidence interval. In general, a confidence interval communicates the statistical uncertainty around an estimated quantity, under the assumptions of the method used. The interval’s width is informative about precision: a wider interval indicates less precision than a narrower interval. An interval does not eliminate possible bias, and it cannot account for unmeasured differences between the pre-treatment and treatment periods simply by being reported. The confidence limits and the method used to calculate them are not reported in the registry record.
Rate data may have greater variability than a simple model assumes. As a general concept, over-dispersion occurs when observed variation exceeds the level expected under a model’s assumptions. If a rate analysis ignores substantial over-dispersion, uncertainty estimates can be too small. However, the statistical model used for the primary endpoint, any assessment of over-dispersion, and any response to it are not reported in the registry record. It would therefore be inappropriate to attribute a particular rate model or variance correction to this study.
How should the before-and-during structure be understood?
Each period is part of a single-group study rather than a randomized comparison between separate groups. In general, a pre-treatment comparison can be useful for describing change within a group, but it cannot alone distinguish an intervention-associated change from other changes over time. Potential influences could include changing health status, changes in exposure or clinical care, or differences in recording. These are general considerations, not claims that any particular influence occurred in this study. The registry does not report methods to adjust for time-related influences.
Rates summarize total events relative to total observation time. As a general point, that summary may conceal variation among participants: event counts could be spread across the group or concentrated in some participants. Participant-level data or a distribution of individual rates can help clarify that pattern, but such information is not reported in the registry record. The record also does not say whether recurrent events within one participant were modeled as statistically related.
What is known about planning assumptions?
The record includes assumptions for a planning illustration based on an observed effect: a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says that the effect to detect is a stated fraction of the observed effect, and distinguishes total event counts for time-to-event illustrations from participants per arm for other illustrations. The numerical planning outputs and the observed effect used for those illustrations are not reported in the registry record. These planning assumptions do not establish the original study’s design rationale, and the record does not report that they were used to choose enrollment. They are not observed power.
In general, a sample-size calculation estimates the amount of information needed to detect a specified effect under chosen assumptions. It does not show whether a study actually observed that effect, nor does it repair limitations in design or measurement. The listed equal-allocation, two-arm assumption is not a description of the trial’s actual single-group, non-randomized structure. The registry does not report an original sample-size justification, power target, or interim-analysis plan.
The registry lists five analyses across three outcome measures, but it does not detail the statistical procedures for each. The primary endpoint’s confidence-interval label is not enough to infer a model, test, covariate adjustment, missing-data approach, or multiplicity strategy. Those methodological details are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists three outcome measures and five analyses. It names the urinary tract infection rate as the primary outcome and lists changes in Neurogenic Bladder Symptom Severity and Neurogenic Bowel Dysfunction as secondary outcomes. The brief summary also refers to bladder complications, quality of life, community living, and participation. The record does not explain how the five analyses map to the outcomes, which measures were included in each analysis, or whether additional analyses were planned.
Multiplicity arises when several outcomes, time points, groups, or statistical tests are examined. As a general statistical concept, the more analyses conducted, the more important it is to understand which questions were prespecified and how results were interpreted across them. Adjustment methods or other multiplicity procedures are not reported in the registry record. It is also not reported whether there was a prespecified hierarchy among the secondary outcomes.
The record describes the primary-outcome population as eleven participants, while overall enrollment is 23. It does not explain the difference, state how many participants had outcome data in each period, or define analysis populations such as all enrolled participants or participants with complete observations. Missing-data counts, reasons for missingness, imputation methods, and sensitivity analyses are not reported in the registry record.
As a general consideration, missing observations can affect an estimate when the likelihood of having data is related to participant characteristics or outcomes. A complete-case analysis, if used, would answer a question about participants with observed data; an imputation procedure would rely on additional assumptions. The registry does not identify which approach, if any, was used. Accordingly, neither the handling of missing data nor the scope of the analyzed population can be determined from the record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Gentamicin Sulfate | 4 | 19 | 21.1% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Gentamicin Sulfate | 0 of 19 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Gentamicin Sulfate | 17 of 19 |
Most frequent serious adverse event terms
| Event term | Organ system | Gentamicin Sulfate |
|---|---|---|
| Renal stone removal | Renal and urinary disorders | 1 of 19 |
| Gross hematuria | Renal and urinary disorders | 1 of 19 |
| Post-COVID 19 pneumonia | Respiratory, thoracic and mediastinal disorders | 1 of 19 |
| pulmonary embolism | Respiratory, thoracic and mediastinal disorders | 1 of 19 |
| bowel obstruction | Gastrointestinal disorders | 1 of 19 |
| Urinary Tract Infection | Renal and urinary disorders | 1 of 19 |
| Serratia tissue infection | Skin and subcutaneous tissue disorders | 1 of 19 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Gentamicin Sulfate |
|---|---|---|
| Urinary Tract Infection | Renal and urinary disorders | 12 of 19 |
| COVID-19 | Infections and infestations | 4 of 19 |
| bladder spasms | Renal and urinary disorders | 3 of 19 |
| flu-like symptoms | Infections and infestations | 3 of 19 |
| Clinically significant labs | General disorders | 2 of 19 |
| abdominal stoma issue | Infections and infestations | 2 of 19 |
| heel wound | Skin and subcutaneous tissue disorders | 2 of 19 |
| GI upset | Gastrointestinal disorders | 2 of 19 |
| nasal discharge | Respiratory, thoracic and mediastinal disorders | 1 of 19 |
| urinary discharge | Renal and urinary disorders | 1 of 19 |
Serious events with the highest arm-level rate: renal stone removal (5.3%), gross hematuria (5.3%), post-covid 19 pneumonia (5.3%), pulmonary embolism (5.3%), bowel obstruction (5.3%).
The registry lists 19 participants at risk for serious adverse events, of whom 4 were affected. It lists 19 at risk for other adverse events, of whom 17 were affected. The death count is 0. The record does not report the observation period for these figures or provide further detail about how adverse events were collected or classified.
The listed serious adverse-event terms are renal stone removal, gross hematuria, post-COVID 19 pneumonia, pulmonary embolism, bowel obstruction, and urinary tract infection. Each term is listed with 5.3%. These are registry-listed terms and percentages; the record does not explain whether a term represents a participant, an event, or another counting basis. The percentages should not be treated as mutually exclusive categories or added together without that information.
Adverse events occurring in a study do not, on their own, establish that the study intervention caused them. The record does not provide event-level timing, investigator assessments of relatedness, severity details beyond the serious-event classification, or a comparison group. The safety figures describe reported events in the listed group, but do not establish causation or permit a comparative safety estimate.
12. What the Result Does, and Does Not, Mean
The record establishes that the study was designed to examine urinary tract infection rates during treatment compared with the six months before treatment in a single group. It describes nightly gentamicin instillations, a six-month treatment period, and an outcome expressed in events per person-month. These details identify the intended question and the general structure of the comparison.
The record does not report the observed infection counts, rates, confidence intervals, or numerical change between periods. It therefore cannot establish whether the rate increased, decreased, or remained similar, nor how precisely a change was estimated. The secondary outcome results are also not reported in the registry record. No conclusion about those outcomes follows from their inclusion in the study.
Even with numerical before-and-during results, a single-group comparison would describe change over time without providing the same basis for causal interpretation as a randomized comparison. Other differences between periods could contribute to a change. The registry identifies no randomized control arm, and it does not report an analysis that separates the intervention’s contribution from other influences.
The overall enrollment of 23 and the primary-outcome population of eleven are both reported, but the record does not explain their relationship. That uncertainty matters for judging how much of the enrolled group contributed to the primary outcome. The record also does not report missing-data procedures or participant-level event patterns.
The safety listing records serious and other adverse events in the study group, including the stated death count of 0. These entries do not establish that an event was caused by gentamicin, and the registry does not provide a concurrent comparison for interpreting the counts. Taken together, the available information supports a description of the study’s design, planned outcome, and listed safety events, but not a claim about efficacy or comparative safety.
13. Why This Trial Matters Statistically
This study’s statistical question is about recurrent events over time. Counting urinary tract infections without considering observation time can make comparisons difficult when the amount of time observed differs. The registry’s choice to express events per person-month makes the exposure-time basis explicit and offers a rate-based way to describe the primary outcome.
The design also illustrates an important distinction between a within-group time comparison and a controlled treatment comparison. Measuring outcomes before and during treatment can describe temporal change. It does not, on its own, show that treatment caused that change. A single-group design has no randomized concurrent control arm, so statistical interpretation must remain aligned with that design.
The record also raises a practical issue about analysis populations. Overall enrollment is listed as 23, while the primary-outcome population is described as eleven participants. Without an explanation of inclusion, follow-up, or missing observations, readers cannot determine how the outcome population relates to everyone enrolled. Clear accounting of participants and observation time is particularly relevant for rate outcomes.
Finally, the registry specifies a 95% confidence interval but does not report the interval or the underlying rates. Naming an uncertainty measure does not itself show how precise an estimate is. This distinction is useful across clinical research: endpoint definitions, design information, numerical results, and uncertainty estimates each answer different questions. In this record, the design and endpoint are described, but the primary numerical findings needed to assess the observed change are not reported.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The main limitation for interpreting the primary endpoint is that the registry record does not report the event counts, rate estimates, confidence intervals, or a formal comparison between the pre-treatment and treatment periods. The endpoint is described, but its observed result cannot be assessed. The statistical method used to form the confidence interval is not reported in the registry record.
The study is listed as non-randomized, single group, and unmasked. The pre-treatment period provides a within-group reference, but the record does not describe a concurrent randomized control. As a result, any change across periods would not by itself distinguish an intervention-associated change from other temporal influences. The record does not report adjustment for such influences.
The population accounting is also unclear. Overall enrollment is 23, while the primary-outcome population is eleven participants with recurrent infections in the prior six months. The registry does not explain this difference, report the number with complete data in each period, or describe missingness. Eligibility and follow-up details beyond the primary-outcome population are not reported in the registry record.
Further limitations include the absence of reported participant-level event distributions, details on event adjudication, and a description of the analysis model. The registry lists three outcome measures and five analyses but does not report multiplicity procedures or the analysis populations. Numerical findings for the listed secondary outcomes and the broader aims in the brief summary are not reported. The adverse-event listing lacks a stated observation period and does not provide event relatedness or a comparison group. These gaps limit both statistical and clinical interpretation.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Gentamicin Bladder Instillations to Prevent Urinary Tract Infections in Patients With Spinal Cord Injury — NCT03503513.
- Registry record last updated 2024-06-25; status last verified 2024-05.
- Results first posted 2024-06-25.
- 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.
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18. Record Summary
The registry describes a completed, non-randomized, unmasked, single-group study sponsored by the University of Michigan, with Phase 2 and Phase 3 listed and enrollment of 23. The intervention was nightly intravesical gentamicin sulfate for a six-month treatment period, with instillations paused during treatment for a urinary tract infection and resumed afterward.
The primary outcome was urinary tract infection events per person-month, comparing six months before treatment with six months during treatment. Its population description identifies eleven participants with recurrent urinary tract infections before treatment. The registry specifies a 95% confidence interval, but does not report the event counts, rates, interval limits, or comparison result.
The record lists secondary changes in neurogenic bladder symptom severity and neurogenic bowel dysfunction. It also lists serious and other adverse-event counts, including 0 deaths. The registry does not report the detailed statistical plan, missing-data handling, multiplicity procedures, or results for the primary and secondary efficacy outcomes.