Povidone-Iodine for Nasal Decolonization: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Povidone-Iodine for Nasal Decolonization (NCT05529173), a randomized phase 4 study. The primary outcome is Change in S. Aureus/MRSA Colony Forming Units (CFU) in Nasal Swab Specimen After Treatment in Patients Who Presented With a Positive for S. Aureus/MRSA Pre-interventional Nasal Swab Specimen..

2. Clinical Question

The primary outcome is framed as a comparison of nasal bacterial counts before and after the study application. Its definition makes the direction of change interpretable: a positive change means fewer colony-forming units at the later measurement than at baseline, while a negative change means more. That definition describes how to read the measure; it does not establish the direction or size of any observed result.

The trial also lists surgical site infections as a secondary outcome. The registry record does not give a numerical result for that outcome. It therefore does not support a conclusion about whether the arms differed in surgical site infections. The stated clinical question is specifically about short-term nasal culture findings, rather than a reported estimate of later surgical infection.

3. Trial Design

The registry describes a prospective, randomized, single-blind, placebo-controlled, parallel-group trial. It is listed as Phase 4 and completed. Enrollment is reported as 192. The study evaluated a preoperative application of 10% povidone-iodine against 0.9% sodium chloride solution in patients undergoing same-day surgery.

In the treatment arm, povidone-iodine was applied to the nares before surgery; in the placebo arm, 0.9% sodium chloride solution was applied to the nares before surgery. The record identifies the study as single-blind, but does not specify which people involved in the trial were masked. The allocation ratio, sequence generation, concealment procedures, and details of how the masking was maintained are not reported in the registry record.

The primary outcome concerns change in S. aureus/MRSA colony-forming units in nasal swab specimens among participants whose pre-interventional swab was positive for S. aureus. Measurements were planned at 1, 2, and 3 hours after application. The outcome is described using a median and inter-quartile range, and the change is defined as baseline count minus the count at the later time point.

The registry lists surgical site infections as a secondary outcome. It reports 2 other adverse events in the treatment group and 0 in the placebo group, with 0 serious adverse events and 0 deaths in both groups. These safety counts do not supply details about the event types, timing, severity beyond the serious/non-serious classification, or attribution.

The record does not report the statistical analysis plan, sample-size justification, interim analyses, or the methods used to analyze the primary outcome. Although the trial is marked completed, numerical primary-outcome estimates and corresponding uncertainty measures are not reported in the registry record. The study dates are not necessary to interpret the posted outcome information, and the record does not supply a numerical result that establishes the direction or magnitude of the primary comparison.

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: Nasal samples (NS) taken from 42 participants out of 95 assigned to the treatment group, and 47 out of 97 assigned to the placebo group that tested positive for S. aureus before the intervention were analyzed at every following time point: 1, 2, and 3 hours after the intervention (AI). NS taken from 32 participants out of 95 assigned to the treatment group, and 35 out of 97 assigned to the placebo group were positive for MRSA at baseline and were analyzed for MRSA at 1,2, and 3 hours AI.

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.

Population: Nasal samples were analyzed for 88 participants randomized to the treatment group and 91 participants randomized to the placebo group.

6. Primary Endpoint

The registry lists the primary outcome as Change in S. Aureus/MRSA Colony Forming Units (CFU) in Nasal Swab Specimen After Treatment in Patients Who Presented With a Positive for S. Aureus/MRSA Pre-interventional Nasal Swab Specimen., measured over 1, 2, and 3 hours after application of Povidone-Iodine or saline solution.

The primary endpoint measures change in S. aureus/MRSA colony-forming units in nasal swab specimens after application of povidone-iodine or saline. The registry defines the change as the baseline count minus the count at a later measurement. Under that definition, a positive value represents a decrease in measured colony-forming units, and a negative value represents an increase.

The planned follow-up measurements were at 1, 2, and 3 hours after application. The stated population for this endpoint is participants with a positive pre-interventional S. aureus nasal swab. The registry reports that nasal samples from 42 of 95 participants assigned to treatment and 47 of 97 assigned to placebo were analyzed at every listed follow-up time. It does not report the remainder of the endpoint population description.

The outcome is summarized as a median with an inter-quartile range. General statistical explanation: colony-forming units are a count-based measure, and count data can be unevenly distributed, particularly when many observations are low or zero and some are much higher. A median describes the middle of the observed distribution, while the inter-quartile range describes the spread of its central portion. These summaries can be more informative than a mean and standard deviation when a distribution is skewed.

Nasal culture counts are relevant to the stated decolonization question because they measure the presence of the target bacteria in the sampled site. They are not, by themselves, a direct measure of surgical site infection. The registry lists surgical site infections separately as a secondary outcome, but does not report a numerical result for that outcome.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The trial is identified as randomized, single-blind, and parallel-group. Randomization is intended to make assigned groups comparable, on average, with respect to both measured and unmeasured characteristics. It does not guarantee identical groups, and its protection depends on appropriate implementation. The registry does not report the randomization method, allocation concealment, or the details of who was masked. Those implementation details should not be inferred from the design labels alone.

What does the primary measure represent?

The primary outcome is a within-participant change in nasal colony-forming units between a pre-interventional specimen and later specimens. Its sign is defined as baseline minus later count. Consequently, positive changes represent reductions in the measured count and negative changes represent increases. The outcome is measured at 1, 2, and 3 hours after application, so it contains measurements across multiple follow-up times rather than a single summarized time point.

The record specifies a median and inter-quartile range. General statistical explanation: the median is the central observation in an ordered set of values, and the inter-quartile range spans the central half of a distribution. These summaries are often useful when data are skewed or contain extreme values. For count outcomes, the distribution may also include many low counts or zeros. A median and inter-quartile range describe the distribution, but do not alone quantify an adjusted treatment contrast or its uncertainty.

Why can count data need special care?

General statistical explanation: counts are non-negative integers, and their variability may not match the assumptions of a simple model with constant variance. Over-dispersion means that the observed variation is greater than a model expects. If present and ignored, standard errors and inferential conclusions can be unreliable. Count outcomes may also have many zero values or a long upper tail. Analysts can use methods suited to such features, but the registry record does not report which model or distributional assumptions were used for the primary outcome.

The endpoint is also a change score. General statistical explanation: change scores compare a follow-up measurement with baseline, which can make the direction of within-participant change easy to express. Their interpretation depends on the chosen subtraction order, and their statistical properties depend on the variability and relationship between baseline and follow-up values. The registry supplies the subtraction definition but does not report whether the primary analysis compared change distributions directly, adjusted for baseline, or used another approach.

How should multiple follow-up times be understood?

The primary outcome description names three post-application times. Measurements at multiple times can answer whether the response differs over time, but they can also create multiple potential comparisons. General statistical explanation: when many hypotheses are tested, the chance of at least one apparently unusual result can increase unless the analysis accounts for multiplicity or defines a primary contrast in advance. The registry record does not report how the time points were combined, whether one was designated as the principal comparison, or whether multiplicity adjustments were used. The primary outcome has several categories or time points and is not reduced to a single comparison in the recorded results.

The registry lists one analysis and two outcome measures, but that information does not specify the statistical model or the number of tests conducted. It also does not identify whether the analysis was prespecified, adjusted for covariates, or based on an intention-to-treat population. These details are not reported in the registry record.

What does the analysis population mean?

The endpoint population is described as participants with a positive pre-interventional S. aureus nasal swab. The record reports analyzed samples from 42 of 95 assigned to treatment and 47 of 97 assigned to placebo at each follow-up time. General statistical explanation: restricting an analysis to a subgroup defined by a baseline test can focus inference on people who had the target organism detected at the start. However, the resulting estimate applies to that described analysis population and does not automatically represent all randomized participants. How the subgroup was defined, whether every eligible participant had complete follow-up, and how missing measurements were handled are not reported in the registry record.

Randomized assignment and analyzed sample are not interchangeable concepts. General statistical explanation: an intention-to-treat analysis generally retains participants in their assigned groups regardless of treatment received, while a per-protocol analysis may exclude participants who do not meet specified protocol criteria. The registry does not state which analysis population was used for the reported endpoint. It also does not explain why the analyzed sample counts differ from the assigned-group counts.

What evidence is available about precision?

A treatment comparison should be interpreted using an estimated contrast and its uncertainty, not only by the direction of a point estimate or a significance label. General statistical explanation: a confidence interval conveys uncertainty around an estimate; a narrow interval indicates greater precision than a wide interval, while both depend on the model and sampling assumptions. The registry record does not report numerical primary-outcome estimates, confidence intervals, standard errors, or p-values. It is therefore not possible to judge the precision or statistical evidence for the primary comparison from the recorded results.

The record contains planning assumptions for a sample-size illustration: two-sided significance level 0.05, equal allocation, and a normal approximation, with the effect defined as a stated fraction of the observed effect. It also distinguishes the participant-per-arm convention from the total-event convention for time-to-event outcomes. Those assumptions describe a planning illustration, not the trial's own design justification or an observed-power analysis. The numerical planning outputs and the trial's original sample-size justification are not reported in the registry record. The illustration cannot substitute for missing primary-outcome estimates or establish the trial's precision.

Overall, the registry provides enough methodological information to identify the randomized arms, endpoint definition, measurement times, and a described positive-baseline subgroup. It does not provide enough information to reproduce the primary analysis or assess its inferential conclusions. The statistical analysis plan, handling of missing data, model specification, and multiplicity approach are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome includes measurements at 1, 2, and 3 hours after application. This creates multiple time-specific observations, but the registry does not report whether the primary analysis treated each time separately, combined them, or selected a particular time as the main contrast. It also does not report a multiplicity adjustment or a prespecified hierarchy of comparisons. Because the results are not reduced to a single comparison, the number and interpretation of any time-specific tests cannot be determined from the registry record.

General statistical explanation: multiplicity concerns arise when several hypotheses or outcomes are examined. Without a prespecified analysis strategy, interpreting an isolated small p-value can overstate the strength of evidence. The registry lists surgical site infections as a secondary outcome in addition to the nasal culture endpoint, but does not state how testing across outcomes was handled. Numerical results and p-values for the primary and secondary outcomes are not reported in the registry record.

The endpoint population is described as participants with a positive pre-interventional S. aureus swab. The registry reports samples from 42 of 95 assigned to treatment and 47 of 97 assigned to placebo at the stated follow-up times. It does not explain the non-inclusion of other assigned participants in this analysis. Reasons for absent specimens, missingness patterns, imputation methods, or sensitivity analyses are not reported in the registry record.

The analysis population is not identified as intention-to-treat, per-protocol, or another defined set. It is also not reported whether participants were analyzed according to randomized assignment if treatment was not received as intended. The statistical analysis plan and the handling of deviations from protocol are not reported in the registry record. These omissions limit assessment of whether the endpoint analysis preserves the advantages of randomization and how robust it is to missing observations.

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 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports 0 serious adverse events among 95 participants at risk in the treatment group and 0 among 97 at risk in the placebo group. It records 2 other adverse events among 95 at risk in treatment and 0 among 97 at risk in placebo. Deaths are recorded as 0 in both groups. No serious adverse event terms are listed.

These are event counts as recorded; they do not establish that the other adverse events were caused by the assigned application. The registry does not report the event descriptions, timing, severity details beyond the serious versus other classification, duration, or investigator attribution. The period during which adverse events were collected and the method of ascertainment are not reported in the registry record.

General statistical explanation: zero recorded serious events does not demonstrate that an event is impossible or that no risk exists. Rare outcomes can remain uncertain when few events are observed, and the amount of uncertainty depends on the size and follow-up of the safety population. No confidence intervals or comparative safety analysis are reported. The adverse-event counts should therefore be read descriptively, not as proof of equivalent safety or as a complete account of tolerability.

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

The registry record supports a description of the question and design: a randomized, single-blind, placebo-controlled comparison of nasal 10% povidone-iodine with 0.9% sodium chloride solution before same-day surgery. The primary endpoint concerns changes in S. aureus/MRSA colony-forming units among participants with a positive pre-interventional S. aureus nasal swab, with measurements planned at 1, 2, and 3 hours after application.

The record does not report numerical primary-outcome results. It therefore does not establish whether counts decreased or increased in either arm, how large any change was, how the arms compared, or how precise an estimated difference might be. The endpoint definition explains that positive changes correspond to decreases, but a definition is not an observed result. The study summary's stated expectation of a decrease is likewise not evidence that the decrease occurred.

The record also lists surgical site infections as a secondary outcome but does not report a numerical result for it. Nasal culture counts and surgical site infections are separate outcomes; findings for the former should not be treated as findings for the latter. The available adverse-event counts are descriptive and do not provide a comparative estimate of risk or a detailed assessment of tolerability.

General statistical explanation: a trial's interpretation depends not only on the point estimate but also on uncertainty, analysis choices, and completeness of outcome reporting. A confidence interval can indicate how compatible the data are with a range of treatment differences, while a prespecified analysis plan helps clarify which comparisons were intended. Neither numerical primary estimates nor their uncertainty, nor the statistical analysis plan, are reported in the registry record.

Accordingly, the posted information allows readers to understand the trial framework and outcome definition, but not to judge the trial's observed efficacy result. It does not justify a claim that either application changed nasal colonization or that either was superior. It also does not establish an effect on surgical site infections or a definitive safety comparison.

13. Why This Trial Matters Statistically

This trial raises a statistical question that is broader than whether a bacterial count is lower after an application. The endpoint is measured repeatedly after treatment, is based on counts, and is described for a subgroup selected by a positive baseline swab. Each feature affects the interpretation of an estimated treatment comparison.

General statistical explanation: repeated measurements can reveal whether an outcome changes over time, but they require clarity about which time-specific contrasts matter and how correlated measurements are handled. Count outcomes may have skewed distributions or more variability than simple models assume. A baseline-positive subgroup can be clinically focused, but the resulting estimate applies to that subgroup rather than automatically to every randomized participant. Clear reporting of these choices helps readers judge whether an analysis answers the stated question.

The registry record makes the sign convention explicit: baseline minus later count, with positive values denoting a decrease. That detail reduces a common ambiguity in change-score reporting. It also states the planned follow-up times and the endpoint summary format. Yet the lack of numerical results means readers cannot connect this clear definition to an observed effect or its uncertainty.

The contrast between a microbiological measure and a clinical outcome is also important. Nasal colony-forming units are the primary measure, while surgical site infections are listed separately as secondary. Statistical interpretation should keep those endpoints distinct, since a change in a culture count is not itself a reported estimate of infection outcomes.

Finally, the record illustrates why outcome estimates, uncertainty intervals, missing-data explanations, and analysis methods matter together. Design labels alone do not reveal the analysis population or the treatment contrast actually estimated. The posted record leaves those statistical details and the numerical primary findings unreported, so the trial question can be identified but its result cannot be assessed from the registry information.

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 principal limitation for interpreting this trial from the registry record is that numerical results for the primary outcome are not reported. Although the outcome is defined and measurement times are specified, no median changes, inter-quartile ranges, treatment contrasts, confidence intervals, or p-values are given. The direction and magnitude of any observed change therefore cannot be assessed.

The endpoint population description is incomplete in the registry record. It states that samples from 42 of 95 assigned to treatment and 47 of 97 assigned to placebo tested positive for S. aureus before intervention and were analyzed at every follow-up time, but the remaining population text is truncated. The reasons participants assigned to the arms are not included in the stated endpoint sample are not reported. Missing-data handling and sensitivity analyses are also not reported.

Three follow-up times are named, but the analysis strategy for these measurements is not described. The registry does not specify how multiple time points were summarized or compared, whether any primary time-specific contrast was selected, or whether multiplicity was addressed. The statistical model, covariate adjustment, and analysis population definition are not reported.

The record identifies the design as single-blind but does not specify who was masked or how masking was maintained. It also does not report allocation concealment, the randomization procedure, or adherence to the assigned application. These details are relevant to judging how the study was conducted, but should not be inferred.

Surgical site infections are listed as a secondary outcome without a numerical result. Safety information is limited to counts of serious and other adverse events and deaths; descriptions, collection period, and attribution are not reported. The registry's planning-illustration assumptions do not provide the trial's original sample-size justification. These reporting gaps limit conclusions about efficacy, precision, safety, and the robustness of the analysis.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Povidone-Iodine for Nasal Decolonization — NCT05529173.
• Registry record last updated 2024-11-13; status last verified 2024-10.
• Results first posted 2024-11-13.
• 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

NCT05529173 is a completed, randomized, single-blind, parallel-group, placebo-controlled Phase 4 trial of nasal 10% povidone-iodine before same-day surgery. The comparator was 0.9% sodium chloride solution. The registry reports enrollment of 192.

The primary outcome is change in S. aureus/MRSA colony-forming units from baseline at 1, 2, and 3 hours after application, among participants with a positive pre-interventional S. aureus nasal swab. Positive change is defined as a decrease. The record reports analyzed samples from 42 of 95 assigned to treatment and 47 of 97 assigned to placebo at each follow-up time, but does not provide numerical primary results.

Surgical site infections are listed as a secondary outcome, with no numerical result reported. The safety record lists 0 serious adverse events in each group, 2 other adverse events in treatment and 0 in placebo, and 0 deaths in both groups. The statistical analysis plan, missing-data approach, and numerical estimates of treatment effect and precision are not reported in the registry record.