Prevention of Catheter-Associated Urinary Tract Infection in Incontinence and Reconstructive Pelvic Surgery Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Prevention of Catheter-Associated Urinary Tract Infection in Incontinence and Reconstructive Pelvic Surgery Patients (NCT01108757), a randomized na study. The primary outcome is Number of Participants With Urinary Tract Infection.

2. Clinical Question

The trial asked whether giving Bactrim rather than placebo at the time of catheter removal was associated with a different number of urinary tract infections in women undergoing incontinence or reconstructive pelvic surgery. The registry describes a randomized, parallel-group comparison and reports the primary outcome over the 7 days following catheter removal. Infection required confirmation by urine culture, with a threshold of >100,000 colony forming units/mL.

The clinical question is therefore a comparison of event counts between the randomized groups over a specified short follow-up interval. The posted results do not describe infections outside that interval as part of this primary outcome, and they do not provide a separate estimate for different types of surgery. The registry’s hypothesis was that prophylactic antibiotics would reduce infection, but the data should be read as an estimate with uncertainty rather than as a definitive answer about the hypothesis.

3. Trial Design

The registry describes a randomized, triple-masked, parallel-group trial. Participants were assigned to Bactrim or placebo, with 26 participants reported in each arm and 52 enrolled overall. The trial was conducted in women undergoing incontinence or reconstructive pelvic surgery. The registry identifies the sponsor as The Cleveland Clinic and lists the phase as not applicable.

The study summary states that participants would receive an antibiotic or placebo at the time of catheter removal. The two listed interventions are Bactrim and placebo. The registry does not report details of the randomization sequence or allocation concealment. Although masking is described as triple, the identities of the groups who were masked are not reported in the registry record. Additional details of the treatment regimen, adherence, and catheter management are not reported in the registry record.

The registry lists a start date of 2010-04 and a primary completion date of 2013-08. Its status is terminated, and the primary outcome description notes that the study terminated early. The reason for early termination and the timing of the decision are not reported in the registry record. The posted outcome includes equal arm denominators and event counts, but does not describe the participant flow leading to those analysis groups or whether every enrolled participant contributed outcome data.

The primary outcome was the number of participants with urinary tract infection in the 7 days following catheter removal, with infection diagnosis confirmed by urine culture and defined using a threshold of >100,000 colony forming units/mL. The registry lists one outcome measure and no posted analyses. It does not report a protocol, detailed statistical analysis plan, planned sample size, or analysis-population definition. Those omissions mean that the design can be described from the registry fields, but some procedural and analytic choices cannot be assessed.

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

Analysis population for the primary outcome, as defined in the registry: Study terminated early.

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 Urinary Tract Infection, measured over 7 days following catheter removal.

The primary endpoint counts participants diagnosed with a urinary tract infection during the 7 days following catheter removal. A qualifying diagnosis required confirmation with a urine culture microbiology report, and infection was defined as >100,000 colony forming units/mL. The reported outcome is a count of participants with an event, rather than a count of all infection episodes or a measure of infection severity.

A binary endpoint of this kind allows the arms to be compared by the proportion of participants who experienced the specified event during the stated follow-up window. Its clinical relevance comes from measuring the infection the trial set out to prevent after catheter removal. Culture confirmation also gives the outcome a defined laboratory criterion in addition to a clinical diagnosis. The registry does not report further diagnostic procedures or rules for handling uncertain or unavailable culture results.

The posted counts are 6 participants with infection among 26 in the Bactrim arm and 6 among 26 in the placebo arm. These counts describe the endpoint as registered; they do not capture infections outside the specified interval or outcomes not included in the registry’s primary measure. The record does not list secondary outcome measures.

7. Results Posted in the Registry

• Drug: 23.1% (6/26) versus 23.1% (6/26) on control; risk difference 0.0 percentage points (95% CI -22.9 to 22.9), risk ratio 1.00 (0.37–2.70); unadjusted two-proportion z-test p = 1.000.

8. Statistical Interpretation

9. Statistical Methods Explained

The posted comparison concerns a binary outcome: each participant either met the defined urinary tract infection endpoint during the 7 days following catheter removal or did not. For a binary outcome, the event count and the number of participants assessed in each arm are the basic ingredients for estimating risk. Here, the Bactrim arm had 6 events among 26 participants, and the placebo arm had 6 among 26. The registry does not describe an adjusted model or additional covariates in the analysis.

What does the risk difference express?

The risk difference subtracts the event risk in the placebo group from the event risk in the Bactrim group. A value of zero corresponds to equal observed risks; a positive value would mean a higher observed risk in the Bactrim arm, and a negative value would mean a lower observed risk in that arm. The posted risk difference is 0.0. Its confidence interval, -0.229 to 0.229, describes the uncertainty around the estimate on the absolute-risk scale. Since the interval includes zero and extends in both directions, the estimate does not precisely distinguish between possible decreases, no difference, and possible increases.

How do relative measures differ?

The risk ratio compares the risk in the Bactrim arm with the risk in the placebo arm by division. A ratio of 1.0 represents equal risks. The posted risk ratio is 1.0, with a confidence interval from 0.371 to 2.698. The odds ratio compares odds rather than risks; an odds ratio of 1.0 likewise represents equal observed odds. Its posted estimate is 1.0, with a confidence interval from 0.275 to 3.634. General statistical point: when event information is limited, relative-effect intervals can be wide, and an estimate at the null value does not by itself imply precise evidence of no effect. The risk difference and relative measures express contrasts on different scales, so each needs its own interpretation.

What does the p-value contribute?

The unadjusted p-value is 1.0. General statistical point: a p-value describes how unusual data at least as discrepant as those observed would be under a specified null model and its assumptions. It is not the probability that the null hypothesis is true, and it does not quantify the size or clinical importance of an effect. The registry does not provide a detailed account of the test procedure, its assumptions, or any adjusted analysis. The p-value should therefore be read alongside the effect estimates and their confidence intervals, not as a stand-alone conclusion.

Why does uncertainty matter with event counts?

General statistical point: estimates based on relatively few events tend to have limited precision. Even when observed counts match exactly, the underlying risks may differ; sampling variability can produce equal counts in groups whose true risks are not equal. A confidence interval makes this uncertainty visible by indicating a range of effect values compatible with the data under the method’s assumptions. The interval is not a list of values each equally likely, and it does not guarantee that the true effect falls inside it.

The registry reports 52 enrolled participants and 26 participants in each arm for the posted outcome. The outcome description notes early termination, but the reason and the prespecified enrollment goal are not reported in the registry record. It is therefore not possible to determine from the record whether the enrollment was below a planned target or whether any sample-size decision was made during the study. The registry also does not report interim analyses or stopping rules. Those details should not be inferred from the termination status alone.

The posted results identify the comparison and give unadjusted estimates, but do not describe a full statistical analysis plan. Information about covariate adjustment, handling of missing outcome data, the analysis population, and sensitivity analyses is not reported in the registry record. No secondary outcome measures or analyses are posted. These gaps limit evaluation of whether the presented estimates were the only planned analyses and how protocol deviations or unavailable cultures were handled.

General statistical point: over-dispersion is relevant to count outcomes when observed variability exceeds what a chosen count model expects. This endpoint is reported as the number of participants with a binary event, rather than a recurrent event count or continuous measure; the registry does not report a model for which over-dispersion would be assessed. It would not be appropriate to assume an over-dispersed count analysis was used.

The sample-size assumptions described in the registry are planning assumptions, not observed evidence about power. They specify a two-sided significance level of 0.05, equal allocation, and a normal approximation, with effects defined as fractions of the observed effect. Such planning illustrations cannot establish that the trial had adequate power, and sample-size calculations based on the observed effect are not a substitute for a prespecified design justification. No trial-specific sample-size justification is reported in the registry record.

10. Confidence Intervals and Precision

The confidence interval for the risk difference is -0.229 to 0.229, around a point estimate of 0.0. General statistical point: a confidence interval is a range produced by a statistical procedure that, under its assumptions and repeated use, has a stated coverage property. It describes uncertainty in the estimated contrast; it is not a guarantee about the true value in this particular trial or a range of equally likely effects.

For this result, the interval includes zero and extends to negative and positive risk differences. It therefore does not resolve the direction of the underlying difference. The estimate itself is exactly at zero because the two arms had the same reported number of events and the same reported denominators, but that equality in the observed data does not imply that the underlying risks are exactly equal. The interval indicates that the data have limited precision for distinguishing among possible effects.

The relative-effect confidence intervals are also broad: 0.371 to 2.698 for the risk ratio and 0.275 to 3.634 for the odds ratio. Both intervals include 1.0, the null value for those measures. Their width conveys uncertainty on the relative scales; it should not be translated directly into absolute-risk differences without a separate calculation. No such additional calculation is needed to interpret the posted estimates.

Precision is important when interpreting a non-significant comparison. A p-value of 1.0 is not evidence that all meaningful differences have been ruled out. The registry does not report a prespecified equivalence or non-inferiority margin, so the estimates cannot be judged against such a criterion. The early termination is documented, but its reason and the study’s enrollment target are not reported in the registry record. The data therefore warrant emphasis on the confidence intervals and on the limits of what the observed sample can establish.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure, the number of participants with urinary tract infection, and no secondary outcome measures. It reports no analyses. This means the registry record does not provide a family of posted outcome comparisons for which a multiplicity adjustment can be assessed. It does not establish that no other analyses were considered or conducted; that information is not reported in the registry record.

A multiplicity strategy addresses the increased chance of false-positive findings when many outcomes, time points, subgroups, or analytic choices are tested. General statistical point: the relevance of multiplicity depends on the set of analyses planned and interpreted together. The registry does not report whether any adjustment was planned, whether the primary outcome was selected before examining the data, or whether subgroup or interim analyses were conducted. The unadjusted p-value should consequently be understood as the posted comparison, not as evidence that all possible analytic choices have been accounted for.

The registry gives 26 participants in each arm for the primary outcome, but does not report how missing cultures, withdrawal, or other unavailable outcome information were handled. The analysis population is not described; it is not reported whether the analysis was intention-to-treat, per-protocol, or another population. The posted denominators should not be taken as proof that all enrolled participants had complete outcome ascertainment.

Details of imputation, exclusions, protocol deviations, and sensitivity analyses are not reported in the registry record. These omissions matter because missing outcome data can affect the interpretation of event proportions, especially when the missingness differs by arm or relates to infection status. The record does not indicate that such differences occurred; it also does not provide enough information to evaluate them. The reported results should therefore be read as the registry’s posted counts and estimates, with the analysis-population and missing-data handling limitations kept explicit.

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.

The registry reports no serious adverse events, no other adverse events, and no deaths in either arm. For each arm, 26 participants were listed as at risk for serious adverse events and for other adverse events, and 26 were listed in the death count’s group denominator. These figures describe what was posted for the reported safety categories.

Zero reported events is not proof that no adverse events could occur. It means none were recorded in these categories in the registry results. The record does not describe the safety observation period, event-collection procedures, severity grading, or whether all participants were assessed for the full period. It also lists no serious adverse event terms. Because the trial terminated early and involved a limited number of participants, absence of a recorded event should not be interpreted as evidence that the groups have identical safety profiles or that rare events are excluded.

The safety counts are separate from the primary urinary tract infection endpoint. The registry does not explain whether or how the primary infections were classified within the adverse-event categories. No relationship between the outcome and safety reports should be inferred beyond the information in the record.

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

The posted results show the same primary endpoint count in both arms: 6 of 26 participants in the Bactrim group and 6 of 26 in the placebo group had a culture-confirmed urinary tract infection during the 7 days following catheter removal. The estimated risk difference was 0.0, and the risk ratio and odds ratio were each 1.0. These are descriptions of the observed sample, not proof that the treatments produce identical underlying risks.

The confidence intervals are wide enough to leave substantial uncertainty about the direction and size of a possible difference. The risk-difference interval runs from -0.229 to 0.229; the relative-effect intervals also include their respective null values. The unadjusted p-value of 1.0 does not demonstrate equivalence and does not rule out effects that the trial was not precise enough to identify. No equivalence or non-inferiority margin is reported in the registry record.

The record states that the study terminated early, but gives no reason. It does not report a planned enrollment target, interim analyses, or a stopping rule, so the circumstances behind termination cannot be evaluated from the registry. Statistical analysis details, missing-data handling, and the analysis population are also not reported. These limitations qualify the conclusions that can be drawn from the posted estimates.

The result does not establish that Bactrim prevents urinary tract infection, nor does it establish that it has no effect. It reports an observed comparison in a specific surgical population and over a defined follow-up interval, with limited precision. It also does not speak to infections outside the 7-day window, different regimens, or populations not described in the registry. The appropriate statistical reading is descriptive and cautious: equal observed counts, coupled with uncertainty that remains substantial.

14. Why This Trial Matters Statistically

This trial illustrates why the point estimate alone is not enough when interpreting a clinical comparison. Equal event counts and equal denominators yield a risk difference of 0.0 and relative-effect estimates of 1.0. Those numbers are easy to summarize, but they do not show how precisely the underlying treatment contrast has been estimated. The confidence intervals are essential: they display uncertainty extending across values on both sides of no difference.

The registry also highlights the distinction between a non-significant result and evidence of equivalence. A p-value of 1.0 does not demonstrate that the arms are the same, and no equivalence margin is reported. The broad intervals make clear why a null point estimate should not be presented as a conclusive null effect. This distinction is especially important when the study terminated early and the reason and planned enrollment are unknown.

Finally, the record shows how incomplete statistical reporting constrains interpretation. Randomization, masking, the outcome definition, arm counts, and effect estimates are reported, but key details about analysis populations, missing observations, interim monitoring, and the analysis plan are not. Readers can interpret the posted comparison while recognizing that these omissions prevent a fuller assessment of design and analysis choices. The trial is a useful case in reading event counts together with interval estimates and registry limitations, rather than treating a single p-value as the whole result.

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 record identifies early termination but does not report its reason, timing, or whether it followed a planned stopping rule. It also does not state the intended enrollment target or provide a trial-specific sample-size justification. Consequently, the extent to which early termination affected the amount of outcome information cannot be evaluated from the registry record.

Details needed to assess participant flow and outcome ascertainment are not reported in the registry record. The posted outcome denominators are 26 in each arm, but the record does not describe withdrawals, exclusions, missing cultures, or whether all enrolled participants were included in the analysis. It does not specify the analysis population or explain how unavailable outcome information was handled.

The registry gives a definition of infection and a 7-day follow-up period, but does not report further diagnostic procedures, adjudication, or the handling of borderline results. Treatment dose, route, and adherence are not described. Masking is labeled triple, but which parties were masked is not stated. Randomization methods and allocation concealment are also not described.

No detailed statistical analysis plan, interim analyses, subgroup analyses, or adjusted analyses are reported. The registry lists no secondary outcomes or analyses, which limits the range of posted results available for review but does not establish that no additional analyses occurred. The posted safety results contain zero events, while safety follow-up and collection methods are not described. Together, these reporting gaps mean that the numerical comparison can be read as posted, but its full conduct and analytic context cannot be independently assessed from the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Prevention of Catheter-Associated Urinary Tract Infection in Incontinence and Reconstructive Pelvic Surgery Patients — NCT01108757.
• Registry record last updated 2017-10-18; status last verified 2017-10.
• Results first posted 2017-10-18.
• 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 describes a randomized, triple-masked, parallel-group trial of Bactrim versus placebo at catheter removal among women undergoing incontinence or reconstructive pelvic surgery. The study enrolled 52 participants, with 26 reported in each arm, and its status is terminated. The primary outcome was culture-confirmed urinary tract infection during the 7 days following catheter removal, defined as >100,000 colony forming units/mL.

The posted primary outcome count was 6 participants in each arm. The risk difference was 0.0, with a confidence interval from -0.229 to 0.229 and an unadjusted p-value of 1.0. The risk ratio and odds ratio were both 1.0, with intervals that include their null values. The registry reports no serious adverse events, other adverse events, or deaths in either arm.

The study terminated early, but the reason is not reported in the registry record. A detailed statistical plan, analysis population, and missing-data approach are also not reported, limiting further assessment of the result.