Urinary Cytokines in Patients With Overactive Bladder (OAB): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Urinary Cytokines in Patients With Overactive Bladder (OAB) (NCT00868621), a registered phase not stated study. The primary outcome is Number of Participants With Elevated Cytokines (Levels of Pro-inflammatory).

2. Clinical Question

The clinical question concerns whether urinary cytokine measurements distinguish the described groups, especially whether elevated pro-inflammatory cytokines are found among participants with OAB. The registry record describes OAB patients as having urgency of urination with a negative UTI assessment. It describes the UTI group as symptomatic, with dysuria, urgency, and frequency and a positive urine culture. Healthy controls were age-matched volunteers with no urinary symptoms.

The study is not described as a treatment comparison. Its stated purpose was identification of urinary cytokines, with further research on anticholinergic drugs mentioned as a possible next step if cytokines were found to be significantly present. That future research is not an outcome of this study. The registry record does not report which cytokines were measured by name, participant-level results, or a comparison estimate. It therefore does not establish whether the groups differed or whether any marker could distinguish OAB from UTI or healthy status.

3. Trial Design

The record describes a study with three participant groups: healthy controls, patients with OAB, and patients with UTI. The control group consisted of healthy age-matched volunteers without urinary symptoms. The OAB group was defined by urgency of urination, with a negative UTI assessment. The UTI group was defined by urinary symptoms and a positive urine culture. The registry record lists an enrollment of 60.

The allocation method is not stated, and the record does not describe random assignment. Its own note cautions that the arms are not a like-for-like control comparison. Accordingly, the group descriptions should not be treated as evidence of randomized treatment allocation or equivalent baseline characteristics. The registry record does not report group-specific enrollment, participant characteristics, recruitment procedures, or details of follow-up beyond the primary outcome timeframe of 18 months.

The study status is completed. The recorded start was 2007-03 and primary completion was 2008-09. The sponsor was The Cleveland Clinic. The record lists one primary outcome measure and no reported analyses. It does not describe a treatment administered to participants, a prespecified statistical model, or a sample-size justification for the study itself. The stated future possibility of studying anticholinergic drugs is not part of the design or results described for this 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: Aliquots of urine were centrifuged, frozen and stored at -80 degrees celcius. Samples were shipped on dry ice to co-authors by overnight courier. Co-authors were blinded to which samples were OAB, control or UTI.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Normal Patients - Control:Urine analysis showing no UTI Overactive Bladder Patients: Urgency of urination, but negative UTI Urinary Tract Infection: Symptoms + Positive urine culture

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 Elevated Cytokines (Levels of Pro-inflammatory), measured over 18 months.

The primary endpoint is the number of participants with elevated pro-inflammatory cytokine levels. It is a count of participants, rather than a continuous measurement of cytokine concentration. The record says urine was assessed using a commercial human cytokine chip. Its description frames the research question as whether certain cytokines were significantly present in urine from OAB patients compared with a standard, using p < 0.05 as the stated criterion.

A participant count can express how many people meet a defined outcome criterion, but interpretation depends on a clear definition of elevation and on knowing how many participants were assessed in each group. The registry record does not identify the cytokines, specify the relevant concentration thresholds or reference standard, or report the group-specific counts. It also does not state whether the outcome was defined separately for each cytokine or as a combined measure.

The endpoint was chosen to address the study’s biomarker-identification aim: determining whether pro-inflammatory cytokines were elevated in urine among people with OAB. The registry record does not report the resulting counts, comparisons, uncertainty estimates, or p-values. The stated criterion is therefore an endpoint description, not evidence that a cytokine met the criterion.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies a count outcome: participants with elevated pro-inflammatory cytokines. It does not report a statistical analysis, and it does not give outcome counts or group-specific denominators. The explanation below distinguishes what the endpoint and stated criterion mean in general from what can be concluded from this record.

What does a participant count represent?

In general, a count endpoint records how many participants meet a defined condition. For a group comparison, interpreting that count requires knowing how many participants were evaluated in each group, how the condition was defined, and how missing assessments were handled. A count alone does not show how common the finding was within a group when the denominator is unknown. The registry record gives total enrollment of 60 but does not report the group-specific denominators or the elevated-cytokine counts.

The record describes the assay as a commercial human cytokine chip, but does not name the cytokines or provide an operational threshold for elevated levels. It also does not specify whether each cytokine was assessed as a separate endpoint or whether participants were classified using a combined rule. Those details affect the meaning of a count and the interpretation of any statistical comparison.

How should the stated significance criterion be read?

The endpoint description says that cytokines would be considered significantly present if the comparison with a standard met p < 0.05. In general, a p-value measures how unusual data at least as extreme as the observed data would be under a specified null hypothesis and analysis model. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of an effect. The registry record does not report a p-value or the details needed to identify the statistical test, null hypothesis, or standard used in the comparison.

A threshold written as p < 0.05 is a decision criterion, not a finding. It cannot establish that a result crossed the threshold unless the observed test result is reported. No such result appears in the registry record. The threshold also does not convey precision; confidence intervals are one general way to describe uncertainty around an estimated effect, but none are reported.

What can group comparisons establish?

In general, comparisons among groups can describe associations between group membership and an outcome. Causal interpretation requires an appropriate design and assumptions, along with sufficient information about how participants entered each group and whether important characteristics differed. The registry record describes symptom and urine-culture criteria for the groups, states that allocation is not stated, and cautions that the arms are not a like-for-like control comparison. It does not provide baseline characteristics or an adjusted analysis. Thus, no causal conclusion about OAB or UTI can be drawn from the group descriptions alone.

The registry record does not specify whether the primary comparison was OAB versus controls, OAB versus UTI, or a set of comparisons across all groups. It also does not report a statistical model, covariate adjustment, or approach to repeated or correlated cytokine measurements. These omissions prevent a detailed appraisal of the intended inferential method.

What do the planning assumptions mean?

The record describes planning illustrations based on 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. These are planning assumptions, not a report of the study’s own design justification. The registry record does not report a sample-size justification for the study, and it does not provide the observed effect needed to interpret such an illustration. Planning estimates describe hypothetical requirements under assumptions; they are not observed power and do not substitute for the actual result.

In general, a two-sided test allows for departures in either direction from the null value. Equal allocation is an assumed balance of group sizes for the planning calculation. A normal approximation uses a normal distribution to approximate the sampling behavior of a test statistic. Whether those assumptions are appropriate depends on the endpoint, group sizes, and analysis method; the record does not report enough detail to assess that for this study.

What remains unavailable?

The registry record lists no analyses. It does not report the analysis population, missing-data handling, multiplicity procedure, model diagnostics, or sensitivity analyses. General statistical interpretation would require these details alongside the observed counts and denominators. Without them, readers cannot assess the robustness of a reported comparison or the precision of an estimated difference. The appropriate conclusion is limited to the stated study objective and endpoint definition; no inferential result is reported.

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("Normal Patients - Control", "Overactive Bladder Patients", "Urinary Tract Infection")
n      <- c(20, 20, 16)
events <- c(20, 20, 16)
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  Normal Patients - Control  20  20  100.0  83.2  100.0  83.9  100.0  83.9  99.9
ARM  Overactive Bladder Patients  20  20  100.0  83.2  100.0  83.9  100.0  83.9  99.9
ARM  Urinary Tract Infection  16  16  100.0  79.4  100.0  80.6  100.0  80.5  99.9

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary outcome measure but describes the assessment of certain cytokines without naming them or saying how many were evaluated. If multiple cytokines were tested separately, that would raise a general multiplicity question: conducting multiple tests can increase the chance of at least one apparently significant result under null conditions. The record does not state whether multiple tests were performed, whether the primary outcome combined markers, or whether any multiplicity adjustment was planned or used. No adjusted or unadjusted analysis is reported.

Missing-data procedures are not reported in the registry record. It does not state how many participants had usable urine samples, whether any assay measurements were unavailable, or how incomplete observations would be handled. Group-specific denominators and participant flow are also not reported. These gaps make it impossible to assess whether the analyzed participants, if any, represented the enrolled groups.

The record does not identify an analysis population, such as all enrolled participants or only participants with evaluable samples. It also does not report a prespecified statistical analysis plan, protocol deviations, or sensitivity analyses. These details matter because analysis choices can affect which participants contribute to a result and how uncertainty is assessed. The registry record lists no analyses, so no reported estimates can be checked against a defined analysis population or missing-data approach.

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

The record supports a limited description of the research question: urine from control, OAB, and UTI groups was to be assessed for elevated pro-inflammatory cytokines using a commercial human cytokine chip. It also documents the endpoint as a count of participants with elevated cytokines and gives the intended criterion of p < 0.05 compared with a standard.

It does not report the number of participants with elevated cytokines, the cytokines identified, a comparison between groups, or any measure of uncertainty. It therefore does not show whether OAB participants had a different cytokine pattern from healthy controls or participants with UTI. The absence of reported results should not be interpreted as evidence that no cytokines were elevated or that groups were identical.

Nor does the study record establish that a cytokine can diagnose OAB, distinguish OAB from UTI, explain urinary symptoms, or predict an outcome. Those claims would require relevant analyses and validation evidence, neither of which is reported. The mention of possible future research on anticholinergic drugs does not provide evidence about the effects of those drugs; no treatment comparison is described.

In general, a biomarker finding can be statistically detectable without being clinically useful, and a non-significant finding does not by itself prove absence of an association. Both interpretations depend on the estimate, its precision, the study design, and the analysis. Those results are not reported in the registry record. The appropriate reading is that the registry documents an intended biomarker assessment, while the posted results do not permit an assessment of its findings.

13. Why This Trial Matters Statistically

This study raises a useful statistical distinction between identifying a biomarker and demonstrating that it can reliably separate clinical groups. The registry record describes a biological measurement across healthy controls, people with OAB, and people with UTI. Because urinary symptoms and infection status define the groups, the comparator structure is central to what any observed difference could mean. The record itself cautions that the arms are not a like-for-like control comparison.

The endpoint is expressed as a participant count, while the underlying assessment concerns cytokine levels measured with a chip. That distinction makes transparent outcome definitions important. A reader needs to know which markers were assessed, what counted as elevated, which participants were evaluable, and how counts were compared. Those details and the results are not reported in the registry record.

The study also illustrates why an intended significance threshold is not a result. The stated p < 0.05 criterion sets a proposed decision rule, but without test results, effect estimates, and uncertainty, it cannot answer whether the groups differed or how informative any difference might be. If several markers were assessed, the analysis would also need to address the interpretation of multiple tests; the registry record does not say whether or how that issue was handled.

Finally, a biomarker-identification study and a later treatment study answer different questions. The record’s suggestion of future research on anticholinergic drugs is a rationale for subsequent investigation, not an inference from this study. Statistically, keeping the endpoint, comparison, and evidential limits distinct prevents a study aim from being mistaken for a demonstrated finding.

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 registry record leaves important design and reporting details unspecified. Allocation is not stated, and the record cautions that the arms are not a like-for-like control comparison. It does not report how participants were recruited, how group eligibility was assessed beyond the brief symptom and urine-culture descriptions, or whether group characteristics differed. These omissions limit interpretation of any potential group contrast.

The endpoint lacks key operational details. The record does not name the cytokines, define the threshold for elevation, identify the standard used for comparison, or explain whether the participant count was determined separately for each marker. Group-specific enrollment, outcome counts, assay completion, and results are not reported. No confidence intervals, test statistics, or p-values are available in the registry record.

The registry record lists no analyses and does not report a statistical analysis plan, multiplicity handling, missing-data methods, or an analysis population. It also does not provide a study-specific sample-size justification. Although planning assumptions are described, the record does not report the observed effect or study outcome needed to interpret planning illustrations as evidence about the actual study.

The primary outcome timeframe is 18 months, but the record does not explain when samples were collected or whether the endpoint reflects a single assessment or repeated assessments. It does not report adverse-event deaths; those values are not reported in the registry record. Together, these gaps prevent evaluation of outcome completeness, precision, and robustness.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Urinary Cytokines in Patients With Overactive Bladder (OAB) — NCT00868621.
• Registry record last updated 2024-07-29; status last verified 2024-07.
• Results first posted 2024-07-29.
• 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.

18. Record Summary

The registry record for NCT00868621, titled Urinary Cytokines in Patients With Overactive Bladder (OAB), describes a study of urine cytokines in healthy controls, OAB patients, and UTI patients. The sponsor was The Cleveland Clinic. Enrollment was 60; the recorded start was 2007-03, primary completion was 2008-09, and status is completed.

The primary outcome was the number of participants with elevated pro-inflammatory cytokines, assessed with a commercial human cytokine chip over a timeframe of 18 months. The record describes a significance criterion of p < 0.05 compared with a standard, but does not report cytokine-specific results, participant counts, or analyses. Allocation is not stated, and the record cautions that the groups are not a like-for-like control comparison. The record therefore documents the research question and planned endpoint, but does not provide results for evaluating group differences.