This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Preventing Staphylococcal (Staph) Infection (NCT00108160), a randomized phase 4 study. The primary outcome is Re-infection With S. Aureus.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00108160 |
| Phase | Phase 4 |
| Condition | Staphylococcal Infections |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Triple |
| Enrollment | 146 |
| Arms in the primary outcome | n/a |
| Lead sponsor | US Department of Veterans Affairs |
| Results posted | Yes |
2. Clinical Question
Population
Participants had a prior history of Staphylococcus aureus infection. The primary outcome description refers to patients with prior, well-documented infections. It defines reinfection using new signs and symptoms, standardized clinical criteria, and a positive culture for S. aureus. The record describes outcome ascertainment for all enrolled participants and for those who completed each study visit.
Intervention
The active treatment was mupirocin 2% in polyethylene glycol ointment. The registry describes topical application to the nares and/or wounds twice daily for 14; the unit after 14 is not reported in the registry record. Details about which sites were treated for each participant are not reported in the registry record.
Comparator
The comparator was polyethylene glycol ointment described as placebo. The arm descriptions contain inconsistent wording about the vehicle, including PEG and PEF, and do not clarify that discrepancy. The record does not provide further information about how the placebo was matched to the active ointment.
Primary question
The primary question was whether the number of participants with S. aureus reinfection differed between the mupirocin and polyethylene glycol groups during the 18-month timeframe. Reinfection could be new or recurrent and required clinical features plus culture confirmation as described in the record. Numerical results for this outcome are not reported in the registry record, so the magnitude and precision of any group difference cannot be assessed.
3. Trial Design
The registry identifies this as a randomized, triple-masked, parallel phase 4 study. Enrollment was 146, and the study status is completed. The sponsor was the US Department of Veterans Affairs. The study start is listed as 2005-04 and primary completion as 2012-08. These dates describe the registry record; they do not establish when all follow-up or reporting activities ended.
Participants were assigned to mupirocin ointment or polyethylene glycol ointment. The record names the latter as the placebo comparator. Random allocation can help balance measured and unmeasured participant characteristics between groups on average, but the record does not describe the allocation sequence, allocation concealment, or the procedure used to assign participants. Those details are not reported in the registry record.
The masking designation is triple, but the record does not specify which groups of people were masked or how masking was maintained. It also does not report whether masking was assessed. The parallel design indicates that the study compared groups assigned to different interventions; details about treatment changes, adherence, and discontinuation are not reported in the registry record.
The arm descriptions say that ointment was applied topically to the nares and/or wounds twice daily for 14, but the unit after 14 is not reported in the registry record. The arm descriptions are nearly identical and contain inconsistent wording for the vehicle. They therefore do not supply a clear account of arm-specific procedures beyond the intervention names and stated application instructions.
The registry lists acquisition of new S. aureus strains as a secondary outcome. It identifies three outcome measures and one analysis, but the posted primary-outcome information is not reduced to a single comparison. Numerical arm-level results, analysis details, and a sample-size justification for the trial 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.
Before assignment: Patients who met study criteria and signed an informed consent were enrolled and randomized to treatment with mupirocin 2% in polyethylene glycol (PEG) ointment or treatment with a placebo (polyethylene glycol) ointment
Overall Study
| Stage | Mupirocin Ointment (Treatment) | Polyethylene Glycol Ointment (Placebo) |
|---|---|---|
| STARTED | 83 | 63 |
| Completed Visit 0 (Baseline) | 79 | 60 |
| Completed Visit 1 (2 Wks) | 72 | 54 |
| Completed Visit 2 (3 mo) | 54 | 46 |
| Completed Visit 3 (6 mo) | 44 | 38 |
| Completed Visit 4 (9 mo) | 38 | 37 |
| Completed Visit 5 (12 mo) | 37 | 37 |
| Completed Visit 6 (15 mo) | 36 | 33 |
| Completed Visit 7 (18 mo) | 34 | 31 |
| COMPLETED | 44 | 42 |
| NOT COMPLETED | 39 | 21 |
Reasons for not completing this period:
| Reason | Mupirocin Ointment (Treatment) | Polyethylene Glycol Ointment (Placebo) |
|---|---|---|
| Lost to Follow-up | 25 | 12 |
| Death | 1 | 2 |
| Withdrawal by Subject | 4 | 2 |
| Protocol Violation | 9 | 5 |
Analysis population for the primary outcome, as defined in the registry: Re-infections with S. aureus, new or recurrent, were noted for all patients enrolled in the study and for patients who completed each study visit.
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.
| Characteristic | Unit | Mupirocin Ointment (Treatment) | Polyethylene Glycol Ointment (Placebo) | Total |
|---|---|---|---|---|
| Participants analysed | 83 | 63 | 146 | |
| Age, Continuous | years | 56.7 (25 to 88) | 57.9 (22 to 80) | 57.2 (22 to 88) |
| Sex: Female, Male: Female | Participants | 4 | 9 | 13 |
| Sex: Female, Male: Male | Participants | 79 | 54 | 133 |
| Baseline S. aureus Infection Strain: MRSA Infection at Baseline | participants | 53 | 43 | 96 |
| Baseline S. aureus Infection Strain: MSSA Infection at Baseline | participants | 30 | 20 | 50 |
6. Primary Endpoint
The registry lists the primary outcome as Re-infection With S. Aureus, measured over 18 months.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | participants with S. aureus re-infection |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is titled reinfection with S. aureus and is expressed as the number of participants with S. aureus reinfection. The registry timeframe is 18 months. The endpoint description requires prior, well-documented infection and a subsequent episode with new signs and symptoms, standardized clinical criteria for infection, and S. aureus isolated on culture. This definition combines clinical evidence with microbiological confirmation rather than counting symptoms alone.
The record describes reinfections as new or recurrent. It says counts were compared between the mupirocin and polyethylene glycol groups for all participants enrolled and for participants who completed each study visit. That wording raises distinct questions about the population included at each time point: an enrolled-participant summary and visit-completer summaries need not represent the same set of people. The record does not provide details on how these populations were handled in the statistical analysis.
Counting participants with reinfection gives an interpretable way to describe how many people met the stated event definition. It does not, by itself, describe the timing of events, repeated episodes per participant, or differences in follow-up. Those aspects require additional analysis or reporting. Numerical primary-outcome results and measures of uncertainty are not reported in the registry record, so the endpoint definition can be described but its observed between-group result cannot be evaluated.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies the clinical question and outcome definition, but it does not report numerical results for reinfection. There is consequently no posted group estimate, interval estimate, or test result for the primary endpoint in the record. The data do not support a quantitative statement about the direction, size, or precision of a difference between the treatment groups.
The endpoint is reported as a number of participants with reinfection, while its description also refers to reinfections across enrolled participants and participants who completed each study visit. A count can be difficult to interpret without knowing the denominator for each comparison, how follow-up varied, and whether each participant could contribute more than one episode. Those details are not reported in the registry record. In particular, a count alone should not be read as a risk or rate unless the corresponding population and observation time are specified.
Randomization is a design feature intended to support a fair comparison between groups, and masking can reduce some influences on care or outcome assessment. These design labels do not substitute for results or for information about implementation. The record does not describe the randomization procedure, the people masked, adherence, or the analysis population. It also does not provide an estimate that can be interpreted in light of those design features.
General statistical explanation: an effect estimate describes the size and direction of a group contrast, while a confidence interval describes the range of values compatible with the data under the assumptions of the analysis. A p-value addresses compatibility with a specified null model; it does not measure clinical importance or the probability that a treatment effect is true. None of these primary-outcome quantities is reported in the registry record, so none can be interpreted for this comparison.
The registry also lists acquisition of new S. aureus strains as a secondary outcome, but numerical results for it are not reported in the registry record. The serious adverse event figures are reported separately and should not be treated as evidence about the primary reinfection endpoint. Nor can their small counts establish a comparative safety conclusion. The appropriate reading is therefore limited: the study was completed and its intended comparison is described, while the record does not provide the primary results needed to quantify the observed difference.
9. Statistical Methods Explained
What does the endpoint count?
The primary outcome is a count of participants meeting a clinical and culture-based definition of S. aureus reinfection. The definition requires new signs and symptoms, standardized clinical criteria, and S. aureus isolated on culture among patients with prior well-documented infection. This level of definition helps distinguish the outcome from a report of symptoms without confirmation. The registry timeframe is 18 months.
The outcome description also refers to all enrolled participants and those completing each study visit. These are different potential analysis populations. General statistical explanation: the interpretation of a count depends on its denominator and on how long participants were observed. If follow-up differs, raw totals can be less informative than measures that account for the population at risk or time under observation. The record does not report denominators for each outcome comparison, a time-to-event analysis, or how repeat episodes were treated.
What can randomization and masking contribute?
Random allocation is intended to make treatment groups comparable at the point of assignment, including for characteristics that were not measured. It does not guarantee identical groups in a particular trial, and it cannot correct problems that arise after assignment, such as incomplete follow-up or departures from assigned treatment. The registry labels the study randomized but does not report the sequence-generation or concealment procedures.
Masking is intended to limit the influence of knowledge about assignment on participant behavior, clinical decisions, and assessment. The record labels the trial triple-masked but does not identify who was masked or describe how masking was maintained. As a result, the designation is informative about the registered design but not enough to assess implementation.
How should a group comparison be read?
General statistical explanation: a comparison of event counts may use methods suited to the outcome’s distribution and the study design. For a binary participant-level outcome, a group contrast could be expressed as an absolute difference or a relative measure; for repeated events, a method would need to account for multiple events from the same participant. The registry does not report which measure or model was used, and no numerical primary-outcome contrast is reported.
Counts can also be more variable than a simple model expects. General statistical explanation: over-dispersion means observed variation exceeds the variation assumed by a model, and ignoring it can make uncertainty appear too small. Whether over-dispersion is relevant depends on the specific outcome and analysis. The registry record does not report a model or diagnostics, so it is not possible to say whether the trial analysis addressed it.
For outcomes measured at multiple visits, analyses may use a separate estimate at each visit or a model that incorporates the repeated measurements. Those approaches answer somewhat different questions and rely on different assumptions. The primary description refers to all enrolled participants and visit completers, and the registry notes that the outcome has several categories or time points and is not reduced to one comparison. The analysis approach and visit-specific numerical results are not reported in the registry record.
What do uncertainty measures mean?
General statistical explanation: a confidence interval conveys uncertainty around an estimated effect and is useful for assessing both the range of plausible effects and the precision of the estimate. A narrow interval is more precise than a wide one, though precision alone does not establish clinical relevance. A p-value is calculated under a statistical model and null hypothesis; it does not state the probability that the null hypothesis is true. Neither confidence intervals nor p-values are reported for the primary comparison in the registry record.
Statistical significance and practical importance are separate considerations. A small estimated difference can be precise, while a potentially important difference can remain uncertain when data are limited. Without a reported effect estimate and uncertainty interval, readers cannot distinguish these possibilities for the primary endpoint. The registry’s completed status does not fill that reporting gap.
What do the planning assumptions describe?
The registry includes sample-size assumptions for planning illustrations based on the observed effect. They specify a two-sided significance level of 0.05, equal allocation, a normal approximation, and an effect to detect expressed as a stated fraction of the observed effect. These assumptions describe planning illustrations, not the trial’s documented design rationale. The trial’s own sample-size justification is not reported in the registry record. Any sample-size figures associated with those illustrations are planning quantities, not observed power and not evidence of the trial’s achieved precision.
General statistical explanation: power is a property of a design under specified assumptions about an effect, variability, and analysis. It is not a measure of whether the observed result is reliable after the study is complete. Planning calculations can show how assumptions affect a proposed study size, but they cannot replace the observed effect estimate and its uncertainty. No trial-specific sample-size justification or interim-analysis plan is reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists acquisition of new S. aureus strains as a secondary outcome and identifies three outcome measures. It also indicates that the primary outcome spans several categories or time points and is not reduced to one comparison. Numerical results for the secondary outcome and a complete set of primary-outcome comparisons are not reported in the registry record.
General statistical explanation: when a study evaluates multiple outcomes, time points, or contrasts, the chance of at least one apparently notable result can increase if each is interpreted separately. Statistical plans may address this through a prespecified primary comparison or multiplicity adjustment. The record does not report a multiplicity strategy, a hierarchy among outcome measures, or whether any adjustment was used. It is therefore not possible to assess how multiple comparisons were handled.
The outcome description refers both to all enrolled participants and to participants completing each visit. The registry does not report how many participants contributed data at each time point, why observations might be missing, or how missing outcomes were handled. It also does not specify whether the primary analysis followed assigned groups, included only participants who completed treatment, or used another population definition. An intention-to-treat analysis, per-protocol analysis, imputation method, or sensitivity analysis is not reported in the registry record.
These gaps matter because missing observations and changing analysis populations can affect the interpretation of group comparisons. The available description identifies the intended outcome and populations of interest, but does not establish how the posted analysis accounted for incomplete follow-up or multiple outcome assessments.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Mupirocin Ointment | 1 | 83 | 1.2% |
| Polyethylene Glycol Ointment | 2 | 63 | 3.2% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Mupirocin Ointment | 0 of 83 |
| Polyethylene Glycol Ointment | 0 of 63 |
Most frequent serious adverse event terms
| Event term | Organ system | Mupirocin Ointment | Polyethylene Glycol Ointment |
|---|---|---|---|
| Underlying condition that led to death | Cardiac disorders | 1 of 83 | 1 of 63 |
| Underlying condition that led to death | Neoplasms benign, malignant and unspecified (incl cysts and polyps) | 0 of 83 | 1 of 63 |
Serious events with the highest arm-level rate: underlying condition that led to death (1.6%).
The registry lists serious adverse events for 1 of 83 participants at risk in the mupirocin ointment group and 2 of 63 participants at risk in the polyethylene glycol ointment group. It lists no other adverse events in either group. These are event counts and denominators, not a complete account of event timing, duration, severity beyond the serious classification, or relationship to study treatment.
The listed serious-event term is “Underlying condition that led to death,” with 1.6% shown. The record does not clearly link that term to a specific group in the information presented. Death counts are not reported in the registry record. The serious-event term should not be read as a reported count of deaths, or as establishing that a study intervention caused an event.
General statistical explanation: sparse event counts provide limited precision for comparing groups, and the denominator and event definition are important to interpretation. These figures alone cannot establish whether the groups differ in safety or explain the cause of an event. They also concern serious and other adverse events, not the primary reinfection outcome. The registry’s adverse-event information should therefore be read as a limited count summary rather than a complete comparative safety analysis.
12. What the Result Does, and Does Not, Mean
The registry record establishes that a completed randomized, triple-masked, parallel phase 4 trial was designed to compare mupirocin ointment with polyethylene glycol ointment in participants with a prior history of S. aureus infection. Its primary outcome was reinfection, defined through clinical criteria and culture, over an 18-month timeframe. Those details describe the research question and design, not the result.
Numerical results for the primary endpoint are not reported in the registry record. There is no reported group contrast or uncertainty measure with which to judge the size, direction, or precision of an observed difference. The absence of those results does not establish that the groups were the same, nor does it establish that they differed. It means the comparative primary-outcome finding cannot be quantified from the record.
The listed serious adverse-event counts are also limited information. They do not answer the primary question, and the record does not provide enough context to infer causation or a comparative safety effect. The listed serious-event term and percentage do not establish that a death occurred in either group; death counts are not reported in the registry record.
General statistical explanation: a trial conclusion depends on the estimated effect, its uncertainty, the analysis population, and the assumptions behind the analysis. A design label such as randomized or masked is relevant, but it does not supply missing outcome estimates. Likewise, planning illustrations do not show what happened in the trial and should not be interpreted as observed power.
The defensible conclusion is narrow: the registry describes a trial intended to assess S. aureus reinfection under the stated comparison, but it does not report the numerical primary results required to assess that comparison. No treatment recommendation or claim about efficacy follows from the registry information.
13. Why This Trial Matters Statistically
This trial is statistically interesting because the primary outcome is a clinically defined, culture-confirmed reinfection, while the description also refers to counts across enrolled participants and visit completers. Those features make the analysis population and handling of repeated events important to interpretation. A total count without clear denominators and follow-up information can leave uncertainty about what is being compared.
The registered design includes randomization and triple masking, both relevant features for limiting some sources of bias. Yet a design label does not explain how allocation was carried out, who was masked, or whether follow-up and treatment adherence were similar between groups. Those implementation details are not reported in the registry record.
There is also a reporting distinction between a completed trial and a quantitatively interpretable result. The registry identifies the primary endpoint and timeframe but does not give its numerical group results or uncertainty. This illustrates why a clearly stated outcome is not enough to assess an effect: readers also need the group data or effect estimate, denominators, and analysis details.
General statistical explanation: when an outcome is observed at multiple visits or can involve repeated episodes, the analysis must align with the scientific question. A participant-level event summary, a repeated-measures analysis, and a time-to-event analysis can emphasize different features of the data. The registry does not report which approach was used. That missing information limits both interpretation and the ability to compare the result with other studies.
The record’s planning assumptions also illustrate the difference between design calculations and trial findings. Planning illustrations rely on stated assumptions, whereas conclusions about the completed study require its observed effect and precision. Those primary outcome results are not reported in the registry record.
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 main limitation for interpretation is that numerical results for the primary reinfection outcome are not reported in the registry record. Without group-level outcome counts, denominators for each comparison, or an effect estimate, the size and direction of the primary comparison cannot be assessed. Confidence intervals and test results are also not reported.
The primary outcome description covers results among all enrolled participants and among participants who completed each study visit, but does not explain how these populations relate to the reported analysis. The number of participants observed at each visit, missing-data reasons, and methods for handling missing outcomes are not reported in the registry record. The method for handling repeat reinfections is also not reported.
The registry notes that the primary outcome includes several categories or time points and is not reduced to one comparison. It does not provide the analysis plan, identify a primary contrast among the time points, or describe any adjustment for multiple comparisons. The statistical model and its assumptions are not reported.
Intervention details are incomplete: the description says application was twice daily for 14 but does not report the unit after 14. The arm descriptions contain inconsistent PEG and PEF wording and are nearly identical, so they do not clarify the exact vehicle wording or arm-specific procedures. Allocation concealment, the people included in triple masking, adherence, and treatment discontinuation are not reported in the registry record.
The registry lists serious adverse-event counts but does not provide event timing or sufficient context to attribute the listed term to a particular group. Death counts are not reported. These limitations restrict interpretation of both efficacy and safety and should not be filled by assumptions about the protocol or analysis.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Preventing Staphylococcal (Staph) Infection — NCT00108160.
- Registry record last updated 2014-04-16; status last verified 2014-03.
- Results first posted 2014-02-04.
- 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.
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18. Record Summary
NCT00108160 is registered as a completed, randomized, triple-masked, parallel phase 4 study sponsored by the US Department of Veterans Affairs. Enrollment was 146. The study compared mupirocin 2% in polyethylene glycol ointment with polyethylene glycol ointment in participants with a prior history of S. aureus infection.
The primary outcome was the number of participants with S. aureus reinfection during an 18-month timeframe. Reinfection required new signs and symptoms, standardized clinical criteria, and culture isolation of S. aureus. Acquisition of new S. aureus strains is listed as a secondary outcome.
The registry record does not report numerical primary-outcome results, the analysis method, a trial-specific sample-size justification, or missing-data handling. Serious adverse-event counts are listed as 1 of 83 and 2 of 63 in the respective groups; deaths are not reported. These summaries do not establish a comparative treatment effect or explain the cause of adverse events.