Impact of Probiotics on Urinary Symptoms in Spinal Cord Injury SCI and SB: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Impact of Probiotics on Urinary Symptoms in Spinal Cord Injury SCI and SB (NCT02748317), a na phase 2 study. The primary outcome is Lactobacillus Safety.

2. Clinical Question

The study objective also addresses urinary symptoms and the urine microbiome, but the registered primary outcome is safety, not a direct measure of symptom improvement. Lactobacillus tolerability is listed as a secondary outcome. The registry record does not report numerical results for that secondary outcome or for urinary symptoms or the urine microbiome. As a result, the stated objective is broader than the outcome figures available for interpretation.

3. Trial Design

This is a phase 2, single-group study recorded as completed. The registry lists enrollment of 96 and names Medstar Health Research Institute as sponsor. The study start is recorded as 2016-01, and primary completion as 2018-10-31. These dates describe the registry entry; they do not establish when each participant began or completed the intervention.

The intervention is Lactobacillus rhamnosus GG. The brief study description presents it as part of a patient-initiated self-management approach that would begin at the time of urinary symptoms. The listed arm is adults with spinal cord injury. However, the adverse-event group is titled adults with spinal cord injury, spina bifida or MS, and the primary outcome population is described more broadly as all adult study participants. Those population labels should not be treated as interchangeable without further detail from the registry record.

The study has no reported comparator arm: allocation is listed as not applicable, the model is single-group, and masking is none. Thus, its recorded findings do not come from a randomized comparison. The design can describe observations in the enrolled group, but it cannot separate intervention-related changes from changes that might have occurred over time or from other influences using a concurrent control group.

The primary outcome concerns total adverse events per participant over months 1-18 of the study, reported as a mean with standard deviation. Lactobacillus tolerability is listed as a secondary outcome. The record lists two outcome measures and one analysis, but does not describe the analysis procedure in enough detail to identify precisely how the outcome measures were analysed. The protocol, eligibility criteria, product regimen, participant flow, adherence and detailed analysis plan are not reported in the registry record.

The sample-size assumptions describe a planning illustration using a two-sided significance level of 0.05, equal allocation between two arms and a normal approximation. Those are planning assumptions, not a description of the single-group design. The record does not report a trial-specific sample-size justification. Any planning illustration should be distinguished from the number enrolled and from evidence about the observed result.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All adult study participants

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 Lactobacillus Safety, measured over months 1-18 of study.

The primary endpoint is named Lactobacillus Safety and is defined as the total number of adverse events, including serious adverse events, per participant during months 1-18 of the study. It is a continuous outcome summarized by a mean and standard deviation. A per-participant measure can describe the overall adverse-event burden in the study group, rather than reporting only whether any event occurred. Including both serious and other adverse events makes the endpoint broad: it encompasses events with differing levels of seriousness and potentially different clinical relevance.

Safety outcomes are used to characterize harms observed during a study. Reporting a mean gives a group-level measure of event burden, while the standard deviation describes how much participant-level counts vary around that mean. The endpoint definition alone does not establish that an event was caused by the intervention. Attribution requires information about how events were assessed, and a comparison group would help contextualize whether event rates differ from those under another condition.

The registry record does not report the numerical mean or standard deviation for this primary endpoint. It does report counts of participants affected by serious and other adverse events and lists selected serious-event terms. Those counts offer descriptive safety information, but they are not a substitute for the stated mean total adverse events per participant. The registry record also does not specify the precise event-counting rules, such as how repeated events of the same type were handled.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a continuous primary outcome: total adverse events per participant, summarized by a mean and standard deviation. This is a different type of information from a count of how many participants experienced an event. An event-count endpoint focuses on the number of events attributed to each participant under the study’s counting rules. A participant-affected count instead indicates how many people had at least one event in a category. Those summaries answer related but distinct questions and cannot be substituted for one another.

What does a mean with standard deviation describe?

In general, a mean is an average across observed participant-level values. The standard deviation describes the spread of those values around the mean. A mean can communicate overall event burden, but it may conceal variation: some participants could have no recorded events while others have multiple events. The standard deviation helps describe that spread, though it does not show the full shape of the data or identify individual experiences.

For event counts, the distribution can differ from the smooth, symmetric pattern often assumed by simple methods for continuous measurements. Counts cannot be negative, and they may be concentrated at low values with a smaller number of higher values. If the spread is greater than a model assumes, standard errors and confidence intervals based on that model may be misleading. In general, over-dispersion means that observed variability exceeds what a chosen count model expects. The registry record does not report a model or diagnostic assessment for this endpoint, so it is not possible to say how the analysis addressed the distribution of participant-level event counts.

What would a confidence interval add?

In general, a confidence interval expresses uncertainty around an estimate under a specified statistical method. It helps readers assess how precisely an average or comparison has been estimated; it is not a guarantee that the true value lies within the interval. For a single-group mean, an interval could describe uncertainty in the estimated average. For a treatment contrast, an interval could show uncertainty in the difference between groups. The registry record does not report a confidence interval for the primary endpoint, nor does it report the endpoint mean or standard deviation needed to interpret such an interval.

A p-value, in general, describes how compatible data are with a specified null hypothesis under the assumptions of a statistical test. It does not measure the size or clinical importance of an effect, and it does not establish causation. The registry record does not report a primary-outcome p-value or specify the null hypothesis and test used. No p-value should be inferred from the adverse-event counts alone.

How does the design affect analysis?

In a single-group study, the analysis can describe outcomes within the observed group. It does not estimate a randomized between-group treatment effect because there is no comparator arm. A change from an initial measurement, if one were available, would still be subject to influences such as time trends, changes in care and natural fluctuation. The registry record does not report a baseline-to-follow-up estimate for urinary symptoms or the primary safety endpoint.

Masking is listed as none. In general, masking can reduce the influence of knowledge about treatment assignment on some aspects of care, assessment or reporting. Its relevance depends on the outcome and procedures. The record does not describe how adverse events were elicited, classified or assessed, so the consequences of the unmasked design for event reporting cannot be quantified.

The sample-size assumptions describe a planning illustration, not the trial’s own design justification. The illustration specifies a two-sided significance level of 0.05, equal allocation between two arms and a normal approximation, with the effect to detect expressed as a fraction of an observed effect. Those assumptions do not describe this single-group study’s allocation. The record does not report the calculated planning values or a trial-specific rationale for the enrollment target. Planning sample sizes are illustrations of assumptions, not observed power, and cannot replace interpretation of the actual estimate and its uncertainty.

The registry lists one analysis. That count does not identify the model, covariates, test, handling of repeated events or adjustment for participant characteristics. The analysis method and its assumptions are not reported in the registry record. Without them, readers cannot assess whether the reported summaries were adjusted, how uncertainty was calculated, or whether the analysis matched the endpoint’s distribution.

10. Confidence Intervals for Each Arm

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

R code and output

arm <- c("Adults With Spinal Cord Injury, Spina Bifida or MS")
n   <- c(96)
m   <- c(0.594)
sp  <- c(1.09)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Adults With Spinal Cord Injury, Spina Bifida or MS  96  0.594  1.090  0.373  0.815

11. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures and one analysis. Lactobacillus Safety is the primary outcome, and Lactobacillus Tolerability is listed as secondary. The study objective also refers to urinary symptoms and the urine microbiome, but numerical results for those domains are not reported in the registry record. The relationship between the registered outcomes and the broader objective is therefore not fully described by the available results.

In general, multiplicity arises when many outcomes, time points, subgroups or statistical tests are examined. The more opportunities there are to find a seemingly notable result, the more important it becomes to specify which questions are primary and how any multiple testing is handled. The record does not report a multiplicity adjustment, a hierarchy of secondary analyses or a complete list of planned comparisons. It is not possible to determine whether any adjustment was planned or whether the single listed analysis covers all analyses performed.

Missing-data methods are also not described. The primary endpoint is defined for all adult study participants, but the registry record does not report how many had usable endpoint data, whether follow-up was incomplete, how missing event information was handled, or whether any imputation was performed. In general, missingness can affect interpretation if participants without recorded outcomes differ from those with complete information. The available entry does not permit assessment of that possibility.

The analysis population is not described beyond the primary outcome’s label, all adult study participants. The record does not report whether analysis followed an intention-to-treat principle, included only participants who started the intervention, or used another population definition. Participant flow and reasons for exclusion are not reported in the registry record. These details matter for understanding which experiences the results represent and whether the analysis corresponds to the enrolled group.

12. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: urinary tract infection (9.4%), surgery (4.2%), fractures (2.1%), kidney infection (2.1%), pneumonia (2.1%).

The registry reports 32 participants affected by serious adverse events among 96 at risk, and 11 affected by other adverse events among 96 at risk. It also records one death. These are descriptive counts in the adverse-event group labelled adults with SCI, SB or MS. The record does not provide enough detail to establish whether the affected categories overlap, how events were attributed, or the circumstances and timing of the death.

Listed serious-event terms include urinary tract infection at 9.4%, surgery at 4.2%, and fractures, kidney infection, pneumonia and respiratory infection at 2.1% each. These percentages should be read as reported term-specific figures. The registry record does not explain their denominator or whether a participant could contribute to more than one term, so the percentages should not be summed or interpreted as exclusive shares of all events.

Safety reporting does not by itself establish causation. An event occurring during a study is not necessarily caused by the intervention. A single-group design offers no concurrent control rate for comparison, and the record does not report event-level causality assessments. The reported counts therefore describe events recorded in the study group, not the excess risk attributable to Lactobacillus rhamnosus GG.

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

The registry record documents a completed, phase 2, single-group study of Lactobacillus rhamnosus GG within a patient-initiated self-management objective. Its stated primary endpoint is a mean count of total adverse events per participant during months 1-18 of the study. The record does not report the numerical mean or standard deviation for that endpoint. It does provide descriptive adverse-event counts and selected serious-event terms, which can be read as safety observations for the recorded group.

Those observations do not estimate what would have happened to the same participants without the intervention. There is no randomized comparator, and the record does not report a controlled contrast. Consequently, the figures cannot isolate intervention effects from underlying health conditions, changes over time, other care or differences in event reporting. The registry also does not provide enough detail to judge event attribution or the impact of missing observations.

The study objective includes urinary symptom management, antibiotic use and the urine microbiome. The available record does not provide numerical findings for symptom change, antibiotic use or microbiome outcomes. Lactobacillus tolerability is listed as secondary, but its result is not reported in the registry record. Thus, the safety information should not be interpreted as evidence that the broader self-management aims were or were not achieved.

Similarly, a planning illustration based on assumed two-arm comparisons is not evidence of the actual study’s precision or power. It is distinct from an observed result, and the registry does not report the primary endpoint estimate needed to assess its precision. The defensible interpretation is limited to the design and descriptive safety counts recorded, with substantial uncertainty about the unreported outcome summaries and analysis details.

14. Why This Trial Matters Statistically

This study is statistically informative as an example of the distinction between a clinical objective and a registered primary endpoint. The objective is broad, covering a patient-initiated probiotic self-management protocol, urinary symptoms and the urine microbiome. The primary outcome is narrower: total adverse events per participant over months 1-18 of the study. Keeping that distinction clear prevents safety summaries from being mistaken for evidence about symptom response or microbiome change.

It also illustrates why a design description matters when interpreting event counts. A single-group study can document what was observed among participants, but it does not create the randomized counterfactual needed for a between-treatment contrast. Counts of affected participants and named event terms can be useful descriptions, yet they do not quantify an intervention-attributable difference without an appropriate comparison and relevant analysis.

The record further shows the importance of complete reporting. The primary endpoint is named and its summary type is stated, but its numerical mean and standard deviation are not reported. The analysis method, missing-data handling and detailed analysis population are also absent. Without these items, readers cannot assess precision, model fit or the sensitivity of findings to incomplete follow-up.

Finally, the mismatch between the two-arm planning assumptions and the recorded single-group design underscores that planning calculations must be interpreted in their proper context. Assumptions used to illustrate sample sizes are not observations from the trial. Statistical interpretation depends on connecting the design, endpoint definition, reported estimates and uncertainty; when key pieces are not reported, appropriately limited conclusions are the most reliable ones.

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.

Several limitations specific to this study’s registry record constrain interpretation. The primary safety endpoint is defined as total adverse events per participant and is described as a mean with standard deviation, but neither numerical summary is reported. The available adverse-event counts therefore do not reproduce the primary endpoint or quantify its precision.

The study is single-group, with allocation not applicable and masking none. There is no randomized comparator for contextualizing the observed safety reports or estimating a treatment contrast. The record does not report event-level attribution, timing or assessment procedures, so it is not possible to determine whether individual events were considered related to the intervention.

Population descriptions vary across entries. The title refers to SCI and SB; the listed arm describes adults with SCI; the primary outcome population is all adult study participants; and the adverse-event group includes adults with SCI, SB or MS. The registry record does not clarify how these descriptions relate to the participants contributing to each outcome.

Participant flow, outcome-specific analysis counts and missing-data handling are not reported in the registry record. Nor are the analysis method, detailed protocol, intervention regimen, adherence information or a trial-specific sample-size justification. The sample-size assumptions describe a two-arm planning illustration, which does not match the registered single-group design. These omissions make it difficult to evaluate precision, selection into the analysis, outcome ascertainment and the alignment between planned and reported analyses.

Finally, the record does not report numerical findings for urinary symptoms, the urine microbiome or Lactobacillus tolerability. As a result, the broader study objective cannot be assessed from the safety counts alone.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Impact of Probiotics on Urinary Symptoms in Spinal Cord Injury SCI and SB — NCT02748317.
• Registry record last updated 2020-05-12; status last verified 2020-04.
• Results first posted 2020-05-12.
• 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

NCT02748317 is a completed phase 2, single-group study sponsored by Medstar Health Research Institute. The registry lists enrollment of 96, a start of 2016-01 and primary completion on 2018-10-31. Lactobacillus rhamnosus GG is the listed intervention; allocation is not applicable and masking is none.

The primary outcome, Lactobacillus Safety, is defined as total adverse events per participant during months 1-18 of the study, summarized by a mean and standard deviation. The numerical primary outcome result is not reported in the registry record. The record lists Lactobacillus Tolerability as a secondary outcome, without a numerical result.

For the adverse-event group, 32 of 96 were affected by serious adverse events, 11 of 96 were affected by other adverse events, and one death is recorded. The record does not establish causation or provide a control-group comparison. The study objective also concerns urinary symptoms and the urine microbiome, but numerical results for those outcomes are not reported in the registry record.