Cranberry for UTI Prevention in Residents of Long Term Care Facilities: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Cranberry for UTI Prevention in Residents of Long Term Care Facilities (NCT00596635), a randomized na study. The primary outcome is Number of Urine Cultures Collected Out of the Total Number Expected to be Collected..

2. Clinical Question

These details define what the registry record makes possible to ask, and also set limits on interpretation. The stated primary measure addresses whether planned urine-culture collection was achieved. It does not, by itself, estimate whether cranberry capsules reduce UTI occurrence. The record also lists secondary outcomes concerning participants with E. coli isolated from urine culture and participants with more than 100,000 colony-forming units per milliliter of any organism isolated. Numerical results for those outcomes are not reported in the registry record.

The study is described as a prospective cohort pilot intended to inform the design of a larger placebo-controlled trial. That stated aim is about feasibility and preliminary information. The registry does not provide enough outcome results to characterize a cranberry-versus-control effect on infection, nor does it report a formal comparison of the capsule regimens.

3. Trial Design

The registry identifies this as a completed study with randomized allocation and enrollment of 56. It lists three groups: no cranberry capsules, one cranberry capsule, and two cranberry capsules. The corresponding descriptions specify no capsules, one 650 mg capsule daily, and one 650 mg capsule twice daily. Masking is listed as none. The phase is listed as not applicable.

There is a design-label ambiguity in the record: it describes allocation as randomized, but also labels the model as single-group. Three group descriptions are listed, yet the registry does not explain how these labels relate to the study conduct or to the intended statistical comparisons. The allocation sequence, concealment procedures, and any details of how participants entered groups are not reported in the registry record. It is therefore safest to describe the listed groups without asserting a more specific design structure than the record supports.

The primary measure covers urine cultures over 6 months. The description says cultures were collected at baseline and monthly for six months, and defines the measure as the number collected out of the total expected. The registry lists two additional outcomes related to urine-culture findings: E. coli isolated from culture, and more than 100,000 colony-forming units per milliliter of any organism isolated.

The registry’s summary describes the work as a prospective cohort pilot study intended to evaluate feasibility and provide preliminary data for a larger placebo-controlled trial. The stated study goal is therefore broader than testing a definitive treatment effect. The record lists a start of 2007-01 and primary completion in 2008-08. It does not report the planned sample-size justification, a detailed statistical analysis plan, or a protocol-defined approach to comparing the three listed groups.

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: If a participant could not provide a baseline urine specimen or met an exclusion criterion prior to group assignment but after consent, he or she was not enrolled.

Overall Study

Reasons for not completing this period:

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 Urine Cultures Collected Out of the Total Number Expected to be Collected., measured over 6 months.

The primary measure is the number of urine cultures collected out of the total number expected over 6 months. The registry says cultures were collected at baseline and monthly for six months. This measure describes completeness of scheduled specimen collection, rather than a direct clinical outcome such as the number of UTIs or the proportion of participants who developed an infection.

Feasibility measures are useful in pilot work because they can indicate whether planned procedures can be carried out in the intended setting. In this study, culture collection is relevant to the stated goal of designing a larger study: urine-culture data are needed to characterize infection-related outcomes. If expected cultures are not obtained, the available information about those outcomes may be less complete. That is a general interpretation of a collection measure, not a finding about the completeness of collection in this study.

The registry describes the primary result as a count relative to an expected total, but does not provide either number. It also does not report a numerical estimate, uncertainty interval, or comparison for this endpoint. Accordingly, the posted record does not establish how many expected cultures were collected or how complete collection was. It does not report an endpoint result that can be used to quantify feasibility.

The listed secondary outcomes concern microbiological findings in urine cultures. They are conceptually distinct from the primary collection measure: a culture must be available to assess findings, while collection itself concerns whether the planned specimen was obtained. Numerical results for the secondary outcomes are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a count endpoint tell the reader?

In general, a count records how many events or items occurred, while a denominator gives the context for interpreting that count. The primary measure in this study is the number of urine cultures collected relative to the number expected. The numerator and denominator are both important: a collected count alone would not show how much of the planned collection it represents, and the expected count alone would not show what was obtained. The registry describes the measure but does not report its numerical values.

Count data can be analyzed in different ways depending on the question and how observations are generated. For example, an analysis might compare counts, model a rate using time or another exposure measure, or model whether a planned collection was completed. These are general possibilities, not a description of the analysis used in this study. The registry does not report the statistical method for the primary measure, or any analysis results.

Why can repeated observations matter?

General statistical principle: measurements taken repeatedly from the same participant are often related to each other. Treating every measurement as independent can understate uncertainty if that relationship is ignored. The registry says urine cultures were scheduled at baseline and monthly for six months, but it does not report how repeated cultures were handled analytically, whether participant-level patterns were considered, or how missing collections were treated.

Counts may also vary more than a simple model expects. In general, over-dispersion means that observed variability exceeds what a model assumes; failing to account for it can make uncertainty estimates too narrow. This is a general consideration for count outcomes, not evidence that over-dispersion occurred in this study. The registry does not report a model, a dispersion assessment, or diagnostics.

What do allocation and comparison require?

Random allocation can, in general, support fair comparisons when the allocation process is implemented and analyzed appropriately. The registry records randomized allocation and lists three groups. It also records a single-group model label, so the intended comparison structure is unclear. Details of the sequence generation, allocation concealment, and analysis by assigned group are not reported in the registry record. The presence of group descriptions alone does not establish which statistical contrast was planned or performed.

A valid comparison also depends on defining the outcome, analysis population, and treatment contrast. For instance, a comparison of one capsule with no capsules asks a different question from a comparison of the two capsule regimens. The registry does not identify a reported primary contrast, and it lists no analyses. Therefore, no comparative estimate can be reconstructed from the record.

What does statistical uncertainty mean?

General explanation: an estimate is a summary of the observed data, while a confidence interval expresses uncertainty around that estimate under a specified method and assumptions. A narrow interval generally indicates greater precision than a wide interval, but precision is not the same as clinical importance. A p-value, when reported, describes how compatible the data are with a specified null model; it does not measure the size or importance of an effect. The registry record does not report a primary-outcome estimate, confidence interval, or p-value.

The record’s planning note describes sample-size illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Those are planning assumptions, not an account of an analysis conducted in the trial. The study lists three groups, and the registry does not explain how the two-arm planning assumptions map to them. Numerical planning results are not reported in the registry record. Planning illustrations are not observed power and should not be interpreted as evidence that the study had a particular ability to detect an effect.

What can be learned from the posted methods information?

The registry identifies the primary measure, its 6-month timeframe, the planned collection schedule, the listed groups, and the broad feasibility purpose. It does not provide the statistical plan needed to assess a model or reproduce an analysis. Details such as a prespecified estimand, handling of incomplete observations, adjustment for baseline characteristics, and any interim analyses are not reported in the registry record. Their absence from the record does not establish what was or was not done outside the registry; it means that readers cannot evaluate those choices from the posted information.

For this study, the central methodological issue is not choosing among hypothetical models from the record. It is recognizing that the numerical endpoint results and analysis methods are absent. General statistical concepts can explain why denominators, dependence, dispersion, and uncertainty matter, but they cannot substitute for outcome data or a stated analysis. The reported information supports a description of the study’s aims and measures, not a numerical estimate of a treatment effect.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary measure and two secondary outcomes. Considering multiple outcomes can raise a multiplicity issue: in general, the more statistical tests conducted, the greater the chance of at least one apparently notable result arising by chance if each is interpreted without accounting for the set of tests. Whether adjustment is needed depends on the study’s objectives, prespecification, and interpretation plan. The registry does not report a multiplicity strategy or any outcome analyses.

Missing data are especially relevant to the primary measure because it concerns cultures collected relative to cultures expected. The record describes the collection schedule but does not report how many cultures were expected or collected, reasons for missing collections, or how missing observations were handled. It is therefore not possible to determine collection completeness or assess whether missingness might have affected the culture-based outcomes.

Analysis populations are also not described. The registry does not state whether analyses included all randomized participants, only participants with available cultures, or another population. It does not report participant flow by group, exclusions, or adherence to the capsule regimens. Such details are important for understanding which participants contribute to a result and what question the analysis answers.

No interim analyses or stopping rules are reported in the registry record. The absence of these details should not be taken as evidence about whether such procedures occurred; their status is not reported. Overall, multiplicity handling, missing-data methods, and analysis populations cannot be evaluated from the posted registry information.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 1% reporting threshold.

Most frequent non-serious adverse event terms

The registry lists serious adverse events for three groups: 0 affected among 17 at risk with no cranberry capsules, 0 among 20 at risk with one cranberry capsule, and 0 among 19 at risk with two cranberry capsules. It lists other adverse events affecting 3 participants in the no-capsule group, 5 in the one-capsule group, and 3 in the two-capsule group. These are descriptive counts, not estimates from a reported statistical comparison.

Zero listed serious adverse events does not mean that the study establishes the absence of serious risk. A study’s ability to characterize uncommon events depends on the amount and duration of observation and on how events are defined and collected. Those details are not reported in the registry record. The record also does not provide a serious-event term list.

The “other” adverse-event counts should not be treated as counts of distinct event types, or as evidence that the groups differ, because event definitions and analysis details are not reported. The registry gives numbers at risk and numbers affected, but does not report a formal safety comparison or uncertainty intervals. Death counts are not reported in the registry record.

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

The record supports a limited description of a pilot study intended to assess the feasibility of cranberry use in long-term care residents and inform a larger trial. It identifies a culture-collection measure over 6 months, lists capsule and no-capsule groups, and reports some adverse-event counts. These details describe the study’s purpose and recorded outcomes; they do not establish a comparative treatment effect.

The primary measure is the number of urine cultures collected out of the total expected. Because the numerical result is not reported, the posted record cannot show how complete collection was. The secondary outcomes concern E. coli and high colony counts in urine cultures, but their numerical results are also not reported. No analyses are listed. There is consequently no reported estimate, uncertainty interval, or test result for whether the groups differed on infection-related outcomes.

The registry’s description of randomized allocation may suggest an intended group comparison, but the single-group model label and lack of a reported analysis leave the comparison framework unclear. The listed safety counts can be read descriptively, but they do not support a conclusion about relative safety. In particular, zero serious events recorded in the listed groups does not establish that serious events cannot occur.

General interpretation principle: absence of a reported result is not evidence that the result was zero, nor is it evidence that groups were equivalent. It means the registry record does not report the information needed to make that assessment. Similarly, enrollment and study completion alone do not establish whether the trial met its feasibility aims.

The registry frames the study as preliminary work for a larger placebo-controlled trial. Its record can therefore be understood as documenting an intended feasibility investigation, while leaving key outcome results and statistical methods unavailable. It cannot be used to claim that cranberry capsules prevent UTI, that they do not prevent UTI, or that one regimen is better than another.

13. Why This Trial Matters Statistically

This study is statistically relevant because its stated primary measure is a feasibility measure rather than a direct estimate of UTI prevention. Pilot studies can help establish whether procedures such as scheduled specimen collection are workable and can inform the design of later studies. The registry’s focus on urine-culture collection fits that purpose: culture availability is necessary for evaluating culture-based outcomes in a future investigation.

The distinction between feasibility and efficacy is important. A measure of whether cultures were collected answers a process question. A comparison of infection outcomes would answer a different question. The registry lists secondary culture-based outcomes but reports no numerical results or analyses for them. Readers should therefore not treat the stated prevention aim as though it were a reported efficacy finding.

The record also illustrates why clear design and analysis descriptions matter. It records randomized allocation, lists three groups, and labels the model single-group. Without explanation of the intended contrasts, analysis population, or methods, readers cannot assess how an effect would have been estimated. Likewise, without the expected and collected culture counts, the primary feasibility outcome cannot be quantified.

For researchers planning later studies, this record identifies the broad practical domain under consideration: repeated urine-culture collection among long-term care residents and the use of cranberry capsule regimens. It does not, however, supply the numerical feasibility findings or comparative effects needed to judge the precision of future planning assumptions. Any planning illustrations should be understood as planning exercises rather than observed power or trial results.

The statistical lesson is that a stated endpoint and study objective do not replace a reported result. Transparent outcome counts, denominators, analysis methods, and uncertainty measures are needed to evaluate what a pilot has established. In this registry record, those elements are incomplete, so the defensible interpretation remains descriptive and limited.

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 most direct limitation of the posted record is the absence of numerical results for the primary measure. Although it defines culture collection relative to the number expected, it does not give the collected or expected counts. The record also does not report numerical results for the listed secondary outcomes, and it lists no analyses. No outcome effect estimate or precision measure is available.

The design description is not fully clear. Randomized allocation is recorded, three groups are listed, and the model is labeled single-group. The registry does not explain the relationship among these entries or identify the intended comparisons. Details of randomization, participant flow, group assignment, adherence, and analysis populations are not reported in the registry record.

The primary culture measure is described over a repeated collection schedule, but the record does not specify how missing cultures were handled or whether repeated observations were analyzed at the participant level. Reasons for missed collections and completeness by group are not reported. These omissions prevent assessment of the possible impact of missing information on feasibility or culture-based outcomes.

The safety record is also limited. It gives counts for serious and other adverse events but does not report event definitions, detailed event terms, observation duration for safety, or statistical comparisons. Death counts are not reported in the registry record.

Finally, the registry describes the work as a pilot intended to inform a future study, but does not report a sample-size justification or a detailed statistical analysis plan. The planning note mentions assumptions for illustrations, but numerical planning results and their relationship to the listed three groups are not reported. These limitations concern what can be evaluated from the registry record and do not establish what may have been documented elsewhere.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Cranberry for UTI Prevention in Residents of Long Term Care Facilities — NCT00596635.
• Registry record last updated 2013-03-29; status last verified 2013-03.
• Results first posted 2010-09-23.
• 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

This completed pilot concerns cranberry capsules and UTI prevention among residents of long-term care facilities. The registry records enrollment of 56, randomized allocation, no masking, and a single-group model label. It lists a no-capsule group, a one-capsule daily group, and a twice-daily capsule group.

The primary measure is urine cultures collected out of the total expected during 6 months, with collection described at baseline and monthly. Secondary outcomes concern E. coli and high colony counts in urine cultures. The registry does not report numerical results for these outcomes or list statistical analyses.

Safety counts include no listed serious adverse events in the three groups and other adverse events affecting 3, 5, and 3 participants, respectively. The record does not report a comparative safety analysis or death counts. Overall, the registry describes a feasibility-oriented pilot but does not provide the numerical outcome findings needed to assess culture-collection completeness or comparative effects.