Preventing the Spread of Infection in Nursing Homes: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Preventing the Spread of Infection in Nursing Homes (NCT03319368), a na na study. The primary outcome is Rates of Staphylococcus Aureus Acquisition: Percentage of Short Stay Participants Who Acquired MRSA or MSSA (or Both) During the Study Period.

2. Clinical Question

The underlying concern is whether targeted protective equipment use can be implemented in routine nursing-home care as a strategy related to Staphylococcus aureus acquisition and infection. The primary outcome is acquisition, assessed through swabs at admission or the start of the study period and again at discharge or the end of the study period. It is a measure of newly detected colonization, rather than a direct measure of invasive infection.

The record identifies this as a feasibility and pilot study intended to guide a multicenter stepped-wedge cluster trial. That future-study aim should not be mistaken for evidence that this pilot itself was a randomized or stepped-wedge trial. Its allocation is recorded as NA, and the study is classified as single group. The results therefore cannot establish a causal contrast between intervention and control groups. The registry record does not report the primary outcome values, so it does not establish how acquisition rates differed across the periods.

3. Trial Design

This completed feasibility and pilot study evaluated a strategy of targeted gown and glove use in community-based nursing homes. The intervention description specifies additional gowns and gloves for high-risk care activities. Its stated purpose was to evaluate whether more frequent use could be directed to specific high-risk moments of care involving specific nursing-home residents, with the broader goal of preventing Staphylococcus aureus acquisition and infection.

The registry records an overall enrollment of 367 and dates of 2017-12-18 for study start and 2018-07-26 for primary completion. The primary endpoint timeframe is described as 5 months: 2 months in the baseline period, one month to prep the intervention, then 2 months in the intervention period. This is a single-group study, with allocation recorded as NA and masking recorded as NONE. The record does not describe a randomized assignment to intervention and control groups.

The outcome population is narrower than the overall enrollment: it consists of short-stay participants with both admission and discharge swabs collected who were not co-colonized with MRSA and MSSA on admission swabs. Swabs were collected from the anterior nares and inguinal fold. The primary outcome concerns acquisition during the study period; a secondary outcome concerns transmission from another study participant.

The official title frames the pilot as a way to guide a multicenter stepped-wedge cluster trial. This describes the intended use of the pilot findings, not the design of the completed study in this record. The registry lists the study as completed and phase as NA. It does not report the number of nursing homes, detailed implementation procedures, or a statistical analysis plan.

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: Long stay residents (n=42) were enrolled in the study specifically to examine if they transmitted S. aureus to short stay residents for the secondary outcome measure. They were excluded from all other study analyses.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All short stay participants who had admission and discharge swabs collected and who were not co-colonized with MRSA and MSSA on admission swabs.

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: Participants who had both admission and discharge swabs collected during the study period. Both sets of swabs need to be collected to assess for acquisition of Staph aureus.

6. Primary Endpoint

The registry lists the primary outcome as Rates of Staphylococcus Aureus Acquisition: Percentage of Short Stay Participants Who Acquired MRSA or MSSA (or Both) During the Study Period, measured over 5 months: 2 months in the baseline period, one month to prep the intervention, then 2 months in the intervention period.

The primary endpoint is the percentage of eligible short-stay participants who acquired MRSA or MSSA, or both, during the study period. Acquisition is assessed by comparing swabs taken at admission or the start of the study period with swabs taken at discharge or the end. Swabs were collected from the anterior nares and inguinal fold. The eligible population excludes participants who were co-colonized with MRSA and MSSA on admission and requires both admission and discharge swabs.

This endpoint is used because the study's stated objective is to evaluate a strategy intended to prevent Staphylococcus aureus acquisition. A measure of newly detected colonization is close to that objective and can be assessed during a feasibility study. It is distinct from invasive infection: the primary outcome does not count invasive infections, and the registry record does not report an infection endpoint as the primary measure.

For interpretation, the percentage depends on both the number of eligible participants with acquisition and the number included in the defined population. The registry record describes these eligibility rules but does not report the primary outcome values, denominators, or a period-specific estimate. As a result, the endpoint's observed magnitude and precision cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a binary event at the participant level: a participant either meets the acquisition definition or does not. The registry describes the result as a percentage, while its outcome parameter is recorded as a count of participants. In general, a percentage for a binary outcome is formed by relating the event count to the eligible denominator. The record does not report those primary counts or denominators, so no period-specific percentage can be interpreted.

What does the baseline-to-intervention comparison represent?

The study has a baseline period followed by preparation and an intervention period. This is a comparison across periods within a single-group study, not a randomized comparison between independently assigned groups. A period contrast can describe what happened over time, but other changes over time may also contribute. General causal inference requires a design or analysis that addresses such alternative explanations; the registry record does not report such an analysis.

The protocol description places swabs at admission or study-period start and at discharge or period end. This paired timing is intended to identify acquisition during the observation interval. However, the registry does not report whether every participant had complete paired samples, how missing swabs were handled analytically, or whether any sensitivity analyses were conducted. Requiring both swabs defines the reported endpoint population, but it does not explain why other participants may lack samples.

How should uncertainty be assessed?

In general, a confidence interval describes the range of effect estimates reasonably compatible with the data and the statistical model. Its width reflects precision: a narrower interval indicates greater precision under that model, while a wider interval indicates more uncertainty. A p-value addresses compatibility with a specified null hypothesis under the test assumptions; it is not a measure of effect size or clinical importance. The registry record does not report a confidence interval, p-value, or primary-outcome estimate, so these concepts cannot be applied to a specific acquisition result.

Participants are cared for in nursing-home settings, where experiences within a home may be related. In general, such dependence can make methods that assume every participant's outcome is independent underestimate uncertainty. Cluster-aware methods can account for within-home correlation when the design and data support them. The pilot's record does not report the number of homes or an analysis accounting for clustering. The future multicenter stepped-wedge cluster trial mentioned in the official title is not evidence that this pilot used that design or those methods.

What do the planning assumptions mean?

The planning illustration is described as using the observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. For time-to-event tables, it gives the total number of events using Schoenfeld; for other outcomes, it gives participants per arm. These are planning assumptions, not the trial's own design or evidence of observed power. The record does not give the pilot's primary outcome effect needed to assess the illustration from the registry information alone.

In general, planning calculations estimate the sample size needed to detect a target effect under specified assumptions. An illustration based on an observed effect does not show that the original study had adequate power, and it is not a substitute for a prespecified design justification. No sample-size justification, original power target, or statistical plan is reported in the registry record.

What is not specified?

The registry record does not report the statistical test or model used for the primary or secondary outcome, any covariate adjustment, handling of repeated observations, or a method for accounting for nursing-home clustering. It also does not report an interim-analysis plan or analysis population beyond the primary endpoint eligibility description. Because zero analyses are listed, there are no posted analysis details on which to base a more specific account. These omissions limit appraisal of both the estimated effects and their uncertainty.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Baseline Period", "Intervention Period")
n      <- c(101, 120)
events <- c(17, 8)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Baseline Period  101  17  16.8  10.1  25.6  10.8  25.3  10.8  25.3
ARM  Intervention Period  120  8  6.7  2.9  12.7  3.4  12.6  3.5  12.6

11. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures: the primary outcome of acquisition and a secondary outcome of transmission from another study participant. It lists zero analyses, and outcome results are not reported in the registry record. The record does not describe a multiplicity strategy, such as a hierarchy of hypotheses or adjustment for testing more than one outcome. Without posted estimates and a stated plan, the extent to which multiple testing was considered cannot be assessed.

The primary endpoint population requires admission and discharge swabs and excludes participants co-colonized with MRSA and MSSA at admission. This defines who is eligible for the endpoint, but the record does not state how many participants met these criteria. It also does not explain how missing swabs, withdrawal, or other incomplete observations were handled, whether any values were imputed, or whether analyses included participants outside this defined population.

The record does not report a prespecified intention-to-treat or per-protocol population, nor does it describe exclusions beyond the endpoint definition. The recorded overall enrollment is not a substitute for the denominator in the primary outcome analysis. Because no primary analysis is posted, it is not possible to assess missing-data sensitivity, the impact of exclusions, or whether the analyzed population followed a prespecified plan.

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

Serious events with the highest arm-level rate: hospitalization (6.3%), death (1.9%).

The registry's serious-event fields list the baseline period as 158 at risk and 28 affected, and the intervention period as 167 at risk and 28 affected. The recorded deaths are 3 in the baseline period and 0 in the intervention period. The registry also lists hospitalization at 6.3% and death at 1.9% among the top serious terms. These entries are descriptive; the record does not provide a statistical comparison between periods.

The at-risk and affected fields should be read as registry safety entries, not as evidence that the intervention caused or prevented events. The record does not explain the timing of each event relative to intervention exposure, whether an individual could contribute more than one event, or how the top-term percentages relate to the period-specific fields. The figures therefore cannot establish a treatment-related risk difference or a safety effect.

There is also no reported safety analysis plan or adjustment for differences between periods. Because this was a single-group study with baseline and intervention periods rather than randomized safety groups, changes in these descriptive entries should not be interpreted as causal evidence.

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

The study addresses a practical implementation question: whether gown and glove use can be targeted to specific high-risk care activities in nursing homes. It defines a microbiological primary outcome based on acquisition of MRSA or MSSA, or both, among eligible short-stay participants with paired swabs. The registry also records a secondary transmission outcome and period-specific serious-event information.

What the record does not establish is the observed acquisition percentage in either period. It reports no primary or secondary outcome analysis, estimate, or uncertainty measure. Consequently, the record cannot show whether acquisition was more or less common during the intervention period, quantify any difference, or establish whether a difference was compatible with chance. It also cannot show that targeted gown and glove use prevented acquisition or invasive infection.

The period structure is useful for describing feasibility and organizing observations before and during intervention implementation. It is not a randomized control comparison. Changes between periods could have multiple explanations, and the registry record does not describe an analysis that isolates the intervention's contribution. The future multicenter stepped-wedge cluster trial in the official title is an intended next step, not a result of this pilot.

The safety entries should likewise be interpreted descriptively. They do not establish a causal benefit or harm, and the registry does not report a comparative safety analysis. More generally, an absence of posted outcome analyses is not evidence that no events occurred; it means that the record does not report the results needed to evaluate the outcomes.

The strongest interpretation is therefore about the question and measurement approach, not effectiveness. The record documents a feasibility-oriented intervention and a defined acquisition endpoint, but it does not provide the outcome data needed to estimate the intervention's association with acquisition.

14. Why This Trial Matters Statistically

This study is statistically instructive because it distinguishes a pilot's measurement and feasibility purpose from an efficacy conclusion. The primary endpoint is clearly framed as acquisition detected through admission and discharge swabs, but the registry record does not report the corresponding outcome estimates. Defining an endpoint is important, yet a definition alone cannot establish the size or precision of an observed effect.

The study also illustrates why study structure matters when interpreting a period comparison. The intervention follows a baseline period, but allocation is NA and the study is classified as single group. A before-and-after contrast is not equivalent to randomization. Time-related changes and other explanations remain possible unless the design or analysis addresses them, and no such analysis is reported in the record.

The population definition highlights another statistical issue: the endpoint applies only to participants with paired swabs who meet the admission colonization criterion. Enrollment and analysis denominators are not interchangeable. Without the number meeting the endpoint criteria and information about missing samples, readers cannot assess how representative the analyzed population would be.

Finally, the official title places the pilot in the context of planning a multicenter stepped-wedge cluster trial. That progression makes it important to learn from feasibility work while keeping the designs separate. A later cluster trial would need methods suited to its assignment structure and within-home dependence; this record does not document such methods for the pilot. The absence of posted analyses underscores that design, outcome reporting, and uncertainty estimates are all necessary for statistical interpretation.

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.

The central limitation for interpreting results is that the registry record does not report the primary or secondary outcome results, despite listing two outcome measures. It also lists zero analyses. There is therefore no acquisition estimate, uncertainty interval, or period comparison to evaluate.

The single-group design and non-randomized baseline-to-intervention sequence limit causal interpretation. The record does not report a control group, allocation process, or analysis that addresses alternative explanations for changes over time. Although the official title refers to a future multicenter stepped-wedge cluster trial, the pilot itself is not described as that trial.

The primary endpoint applies only to short-stay participants with both admission and discharge swabs who were not co-colonized with MRSA and MSSA at admission. The number of participants meeting these criteria, the extent of missing swabs, and reasons for missingness are not reported. The registry also does not specify whether or how clustering by nursing home was handled, nor does it report the number of nursing homes.

Other unreported details include the statistical model, covariate adjustment, multiplicity plan, interim analyses, missing-data methods, and original sample-size justification. The serious-event entries are descriptive and lack a reported comparative analysis. Together, these gaps prevent assessment of the primary outcome's magnitude, precision, robustness, and causal interpretation.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Preventing the Spread of Infection in Nursing Homes — NCT03319368.
• Registry record last updated 2024-03-21; status last verified 2023-09.
• Results first posted 2024-03-21.
• 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

NCT03319368 is a completed feasibility and pilot study titled “Preventing the Spread of Infection in Nursing Homes,” sponsored by University of Maryland, Baltimore. The registry records enrollment of 367, a study start of 2017-12-18, and primary completion on 2018-07-26. Phase is recorded as NA.

The single-group study evaluated targeted gown and glove use, described as additional gowns and gloves for high-risk care activities. Its primary outcome was the percentage of eligible short-stay participants who acquired MRSA or MSSA, or both, during the study period. The secondary outcome concerned acquisition through transmission from another study participant. The record lists two outcome measures and zero analyses.

The primary outcome results and statistical analysis are not reported in the registry record. Serious-event fields list 28 affected in each period, with 158 at risk in the baseline period and 167 at risk in the intervention period; recorded deaths are 3 and 0, respectively. These safety entries are descriptive and do not constitute a comparative analysis.