Antibacterial Mouthwash for Pharyngeal Gonorrhea Prevention: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Antibacterial Mouthwash for Pharyngeal Gonorrhea Prevention (NCT04966507), a randomized phase 2 study. The primary outcome is Mouthwash Adherence - Percent of Days Mouthwash Used.

2. Clinical Question

3. Trial Design

This was a Phase 2, randomized, double-masked crossover study sponsored by the University of California, Los Angeles. The record lists enrollment of 89 and a completed status. The listed study start date is 2022-02-17, and the primary completion date is 2025-05-16. Those dates describe the registry timeline; they do not supply outcome results.

The crossover structure means participants were assigned to a sequence involving both mouthwashes: active mouthwash followed by placebo, or placebo followed by active mouthwash. The sequence descriptions report 45 participants assigned to the active-to-placebo sequence and 44 assigned to the placebo-to-active sequence. Each intervention period is described as daily mouthwash use over 12 weeks. For the first 12-week follow-up assessment, the registry reports completion by 32 participants in each sequence. Further details about completion in later periods are not reported in the registry record.

Randomization can help balance participant characteristics across assigned sequences, while masking is intended to limit expectations from influencing participants or study staff. The registry labels the study double-masked but does not report who was masked or how masking was maintained. In crossover studies, each participant may contribute information under both conditions. That feature can make within-participant comparisons useful, but interpretation depends on how period, sequence, and any carryover are handled. The actual analysis plan for those issues is not reported in the registry record.

The record describes seven outcome measures and lists pharyngeal gonorrhea laboratory testing as a secondary outcome. It reports zero analyses. The statistical analysis methods, including any model used to compare outcomes across periods or sequences, 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.

Period 1: First Intervention (12 weeks)

Period 2: Second Intervention (12 weeks)

Analysis population for the primary outcome, as defined in the registry: Among the 45 participants assigned to the active-to-placebo sequence and the 44 participants assigned to the placebo-to-active sequence, 32 participants in each sequence completed the first 12-week follow-up assessment. Among the 32 participants in active-to-placebo sequence that completed the 12-week assessment, 31 completed the 24-week assess. Among the 32 participants in placebo-to-active sequence that completed the 12-week assessment, 28 completed the 24-week assess.

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 Mouthwash Adherence - Percent of Days Mouthwash Used, measured over This outcome will be measured over each 12-week intervention period.

The registered primary endpoint is titled Mouthwash Adherence - Percent of Days Mouthwash Used. It is based on self-reported questionnaire data asking participants what proportion of days they used mouthwash during the past 3 months. The registry says the outcome is measured over each 12-week intervention period and lists the unit as participants. The available outcome description is incomplete, so the categories, scoring details, and any summary statistic used for analysis are not reported in the registry record.

Adherence is relevant to interpreting a daily-use intervention because the assigned product can only be evaluated as used within the study if participants actually use it. As a general measurement issue, self-report can capture use that may not be directly observed, but responses can be affected by recall or by how participants interpret the question. These are general considerations, not reported findings about this study.

The endpoint should not be confused with the intended clinical outcome. The study description states an aim of evaluating preliminary efficacy in reducing pharyngeal gonorrhea incidence, and laboratory testing is listed as a secondary outcome. The registered primary endpoint, however, is adherence. No adherence estimate, laboratory outcome count, or comparison between mouthwashes is reported in the registry record. Therefore the endpoint definition alone does not establish whether participants used either mouthwash consistently or whether infection incidence differed.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies a randomized, double-masked crossover design. The explanations below describe general statistical concepts relevant to such a design; they should not be taken as a description of analyses confirmed in this study. The registry record does not report the statistical analysis plan, model specifications, or analysis results.

What does randomization contribute?

Randomization assigns participants to treatment sequences by chance. In general, this can reduce systematic differences between groups in factors known or unknown at assignment. In a crossover study, randomization is to an order of conditions rather than to a single condition for the entire study. Here, the listed orders were active mouthwash followed by placebo and placebo followed by active mouthwash. Randomization does not guarantee that every characteristic is balanced in a particular study, and it does not remove the need to account for the structure of repeated observations.

Why does crossover structure matter?

In a parallel-group design, participants usually contribute observations under one assigned condition. In a crossover design, participants may contribute observations under both conditions. A comparison can therefore use information about changes within the same participant, which may help account for stable personal characteristics. At the same time, outcomes from the same participant are generally related rather than independent. Statistical methods for crossover data need to reflect that dependence if they are to estimate uncertainty appropriately.

Period and sequence can also matter. A period effect is a difference associated with when an observation is made, apart from the assigned condition. A sequence effect concerns the order in which conditions are received. Carryover refers, in general, to an effect of an earlier condition that persists into a later period. Whether these issues were relevant to the observed outcomes, and how the investigators addressed them, are not reported in the registry record. No washout procedure or related protocol details are reported in the registry record.

What does masking mean statistically?

Masking is intended to limit the influence of expectations or knowledge of assigned treatment on behavior, reporting, care, or outcome assessment. The record labels the study double-masked. It does not identify which roles were masked or explain how masking was maintained. This is particularly relevant to a self-reported adherence outcome because a participant’s knowledge or expectations can potentially influence reported use. That is a general concern and not evidence that reporting was biased in this study.

How should the adherence measure be understood?

The primary outcome asks participants to report the proportion of days they used mouthwash during the past 3 months. In general, a proportion-of-days measure represents reported frequency over a recall period; it is not the same as an objective record of product use. Its interpretation depends on the questionnaire wording, response options, scoring rules, and handling of missing answers. The record gives the question wording and says it was self-reported, but the complete outcome definition and analysis are not reported in the registry record.

A measure of adherence can describe use without showing whether the intervention changed the clinical outcome. Conversely, laboratory testing for pharyngeal gonorrhea addresses infection outcomes but does not by itself describe how consistently participants used mouthwash. The registry lists laboratory testing as a secondary outcome, but does not report its results or the method used to define and compare incidence.

What can uncertainty measures tell readers?

As a general explanation, a confidence interval communicates uncertainty around an estimated effect under the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval, while an interval spanning values compatible with different directions or magnitudes may leave the effect uncertain. A p-value, when reported, measures how incompatible the observed data are with a specified null model under its assumptions; it does not measure the probability that a treatment works. No confidence interval, p-value, or effect estimate is reported in the registry record, so precision and statistical evidence cannot be assessed.

Adjustment for other variables can address specified differences or improve estimation when done appropriately, but it does not automatically eliminate bias. The study description mentions possible adjustment for HIV status and substance use as part of the investigators’ hypotheses. It does not report whether adjusted analyses were performed, which variables were included, or what estimates resulted. The analysis model and covariate handling are not reported in the registry record.

What does the analysis count tell readers?

The registry lists zero analyses. This means the posted record does not include an analysis result to interpret. It does not establish that investigators conducted no analyses outside the registry, nor does it identify whether any analyses were planned. The statistical plan, any interim analyses, and any sample-size justification are not reported in the registry record. Without those details and outcome estimates, readers cannot assess whether the reported analysis matched a prespecified plan or how uncertainty was handled.

10. Multiplicity, Missing Data and Analysis Populations

The registry describes seven outcome measures and reports zero analyses. It does not identify a prespecified testing hierarchy, any adjustment for multiple comparisons, or which outcomes were designated for confirmatory rather than exploratory interpretation. The handling of multiplicity is not reported in the registry record. In general, testing many outcomes or subgroup comparisons can increase the chance of finding an apparently noteworthy result by chance, so the intended outcome hierarchy and interpretation plan are useful context. No inference about how that issue was handled can be made from the posted record.

Missing-data information is limited. The registry reports that 32 participants in each randomized sequence completed the first 12-week follow-up assessment, after describing sequence assignments of 45 and 44 participants. It does not provide a complete accounting of later assessments, reasons for missing assessments, or the number contributing to each endpoint analysis. No imputation method, complete-case approach, sensitivity analysis, or missing-data assumption is reported in the registry record. The reported completion figures should therefore not be treated as the analysis sample for every outcome or period.

The registry does not define an analysis population, such as intention-to-treat or per-protocol, and does not report how participants who changed or did not follow their assigned use schedule were handled. This matters generally because different analysis populations can answer different questions. For this crossover design, the record also does not state how sequence assignment, period observations, or within-participant dependence entered the analysis. These details are not reported in the registry record.

The study description mentions possible adjustment for HIV status and substance use, but does not report whether those adjustments were carried out. The planned covariate set, subgroup analyses, and approach to multiplicity across adjusted comparisons are not reported in the registry record. Without analysis details and results, neither missingness nor the population represented by an estimate can be evaluated.

11. 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 lists two intervention entries for adverse events: Listerine Cool Mint Antiseptic Mouthwash and Biotene Oral Rinse. For each entry, 89 participants are listed as at risk for serious adverse events and 0 as affected. The record also lists 89 as at risk for other adverse events and 0 as affected for each intervention. Deaths are listed as 0 in each entry. These are the posted safety counts; they are not an estimate of comparative risk.

Because this is a crossover study, intervention entries should not be interpreted as separate, independent groups of participants. The same participant may have received both mouthwashes at different periods. The registry’s at-risk counts should therefore be read as reported for each intervention, not added to create a total or used to infer the number of unique participants. The record does not provide event-level details, exposure duration for safety summaries, definitions of the event categories, or a statistical comparison between interventions.

A count of 0 affected participants in a registry summary does not, by itself, establish that an intervention is free of risk. General interpretation depends on how events were collected and classified, the amount of exposure observed, and the precision of the estimate. Those details and any safety analysis are not reported in the registry record. The posted counts describe what the registry reports, but cannot support a broader conclusion about safety.

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

The record establishes that a randomized, double-masked crossover study was conducted to examine daily antibacterial mouthwash use in a high-risk population, with Biotene Oral Rinse as the placebo comparator. Its registered primary outcome concerns self-reported adherence. The study description also identifies preliminary efficacy against pharyngeal gonorrhea as an aim and lists laboratory testing as a secondary outcome. These details show what the study set out to investigate, not what it found.

No primary outcome estimate, secondary outcome result, comparison between mouthwashes, confidence interval, or p-value is reported in the registry record. The registry lists zero analyses. As a result, the posted information cannot establish the degree of adherence, whether adherence differed by sequence or intervention, or whether laboratory-confirmed pharyngeal gonorrhea incidence differed between conditions. The hypotheses described by investigators remain hypotheses in the absence of reported estimates.

The available completion information is also limited to the first 12-week follow-up assessment. It does not explain why other participants are not included in that reported assessment count or how observations from later periods were handled. No analysis population or missing-data method is reported. Consequently, readers cannot determine which participant observations would support a statistical estimate or how representative those observations might be.

More generally, a trial design can make a question answerable in principle, but interpretation depends on outcome data, analysis methods, and uncertainty. In a crossover study, interpretation also depends on how repeated observations, periods, and sequences are addressed. The registry record does not report these methods. The appropriate conclusion is therefore limited: the study was completed and its intended questions are described, but the posted registry results do not provide evidence to quantify or judge the outcomes.

This distinction does not mean that an effect was absent, nor that an effect was present. It means that the results needed to make either statement are not reported in the registry record. The safety counts are similarly limited to the recorded adverse-event summaries and do not replace a full clinical or statistical assessment.

13. Why This Trial Matters Statistically

The study raises a statistical question in which the main registered outcome is behavior and the intended clinical outcome is infection. Adherence can help describe whether a daily-use intervention was followed, while laboratory testing addresses pharyngeal gonorrhea. Keeping those outcomes distinct is important: a finding about reported use would not, by itself, demonstrate a difference in infection incidence, and a laboratory outcome would not explain how consistently the products were used.

The crossover design also makes the analysis structure consequential. Participants were assigned to opposite treatment orders, and the record reports first-assessment completion within each sequence. A suitable analysis would generally need to reflect that repeated observations may come from the same participant, and could consider period and sequence. Those are general considerations, not reported methods for this trial. The registry does not provide the model or results required to judge how the design was analyzed.

The record is useful for identifying the randomized comparison, intervention periods, stated hypotheses, primary endpoint, and limited completion and safety information. It also makes clear that the posted result record is incomplete as a basis for statistical interpretation: zero analyses are listed, and no effect estimates or uncertainty measures are reported. This distinction matters because study completion and a detailed design description do not substitute for outcome results.

For biostatisticians and clinical researchers, the record illustrates why interpretation should track the path from endpoint definition to analysis population, statistical model, estimate, and uncertainty. Here, the endpoint is named and its self-report source is described, but the complete scoring and analysis details are not. The outcome hypotheses are stated, but their estimated effects are not reported. Statistical conclusions should remain bounded by those omissions.

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 does not report outcome values or comparative estimates for the primary adherence endpoint. Its description of that endpoint is incomplete, and the complete scoring rules, response categories, and handling of questionnaire data are not reported in the registry record. Because adherence was self-reported over a recall period, general concerns about recall and reporting apply; the record does not establish whether they affected these data.

For the secondary laboratory outcome, the record lists pharyngeal gonorrhea testing but provides no event counts, incidence estimates, or comparison results. The assessment schedule and outcome definition are not reported in the registry record. It is therefore not possible to assess the clinical endpoint from the posted results.

Participant follow-up information is partial. Although the record reports sequence assignments and completion of the first 12-week follow-up assessment, it does not report complete follow-up across later periods, reasons for missing assessments, or the analysis population. The handling of missing observations and any sensitivity analyses are not reported in the registry record.

The crossover design can require attention to within-participant correlation, period, sequence, and possible carryover. The registry does not report the protocol details or statistical methods used to address these matters. Masking is identified as double, but the masked roles and procedures are not described. Eligibility criteria beyond the broad population description, adherence support procedures, and details of outcome assessment are also not reported in the registry record.

Finally, the record lists zero analyses and does not report a statistical plan, sample-size justification, interim analyses, or multiplicity strategy. These omissions prevent assessment of precision, the basis for selecting analyses, and the extent to which the reported comparisons correspond to prespecified aims. They limit interpretation of the registry record rather than establishing any particular outcome.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Antibacterial Mouthwash for Pharyngeal Gonorrhea Prevention — NCT04966507.
• Registry record last updated 2026-07-09; status last verified 2026-06.
• Results first posted 2026-07-09.
• 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

NCT04966507 is a completed Phase 2 randomized, double-masked crossover study sponsored by the University of California, Los Angeles. It compared daily Listerine Cool Mint Antiseptic Mouthwash with daily Biotene Oral Rinse, described as a placebo, during 12-week intervention periods in a cohort of HIV-positive and high-risk HIV-negative men. Enrollment was 89.

The registered primary outcome is self-reported mouthwash adherence, expressed as percent of days used. Pharyngeal gonorrhea laboratory testing is listed as a secondary outcome. The registry reports sequence assignments of 45 and 44 and first-assessment completion by 32 participants in each sequence. Its adverse-event entries list 0 affected participants for serious events and 0 for other events in each intervention entry, with deaths listed as 0.

The registry lists seven outcome measures and zero analyses. Comparative outcome estimates, uncertainty measures, analysis methods, and a full account of missing data are not reported in the registry record. The posted information describes the trial and its aims but does not establish an adherence or efficacy result.