Development of a New Critical Pathway for Treatment of Acute Bacterial Skin and Skin Structure Infections (ABSSSI): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Development of a New Critical Pathway for Treatment of Acute Bacterial Skin and Skin Structure Infections (ABSSSI) (NCT03233438), a non-randomized phase 4 study. The primary outcome is Number of Infection-related Total Admitted Hospital Days.

2. Clinical Question

3. Trial Design

This is a Phase 4, completed, parallel study with nonrandomized allocation and no masking. The registry lists an enrollment of 91. It identifies Allergan as the sponsor, gives a start date of 2017-07-24 and a primary completion date of 2018-10-30, and lists the study status as completed. These design details describe how the study was registered; they do not establish that the treatment groups were comparable at baseline.

The study evaluates a new critical pathway rather than only a drug against another drug. In the pathway arm, guideline-based criteria are used to identify patients, and those who meet the criteria receive dalbavancin. The registry describes the administration as a single intravenous dose of 1500 mg over 30 minutes. In the usual-care arm, treatment is prescribed by the physician as standard care in clinical practice. The registry does not report which treatments were used within usual care.

Allocation was not randomized. This means assignment was not determined through random allocation, which ordinarily helps balance measured and unmeasured characteristics across groups. The registry explicitly cautions that the arms are not a like-for-like control comparison. Differences in who entered each arm, treatment selection, clinical practice, or other factors could affect observed outcomes. The specific allocation process and any adjustment for differences between groups are not reported in the registry record.

The study was unmasked. The record does not describe masking of participants, clinicians, or outcome assessors, and none is listed. The registry identifies 31 outcome measures and 2 analyses, but does not explain the analysis procedures associated with them. The record also does not report the sample-size justification, a prespecified statistical analysis plan, or interim analyses. These omissions limit how fully the design and intended analysis can be assessed from the registry entry.

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: Full analysis set (FAS) population consists of all enrolled patients that has received at least one dose of antibiotics or one dose of dalbavancin for inclusion.

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: Full analysis set (FAS) population consists of all enrolled patients that has received at least one dose of antibiotics or one dose of dalbavancin for inclusion.

6. Primary Endpoint

The registry lists the primary outcome as Number of Infection-related Total Admitted Hospital Days, measured over 44 Days.

The primary endpoint is the number of infection-related total admitted hospital days, measured over 44 Days. It is summarized as a mean and standard deviation in the full analysis set. In practical terms, it is intended to describe the amount of hospital admission time attributed to infection-related care during the specified timeframe. It is not the same as the number of people admitted: the endpoint concerns days of admission.

Hospital days can be a useful measure of healthcare use because they reflect the duration of inpatient care, not just whether admission occurred. A mean provides an average across the analysis population, while the standard deviation describes how spread out individual observations are around that average. These summaries can help characterize typical burden and variability, although they do not show the full shape of the data or how many patients had no admitted days.

As a general statistical consideration, hospital-day measures may have an uneven distribution: many people may have relatively few days while a smaller number have longer stays. In such circumstances, the mean can be influenced by unusually long stays. The registry record does not report the observed distribution, the group means or standard deviations, or any alternative summaries. It also does not specify how infection-related days were attributed when a patient had other reasons for admission. The endpoint definition is available, but its observed value and the details needed to interpret the measurements are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes the primary endpoint as a continuous measure summarized by its mean and standard deviation. A mean is the arithmetic average of the observed measurements. It gives a compact description of the group average, but it can be pulled toward unusually large observations. The standard deviation describes the amount of variation around the mean; it does not indicate the uncertainty in the mean itself. The registry does not report either statistic for the primary endpoint.

What would a confidence interval describe?

As a general statistical explanation, a confidence interval expresses uncertainty around an estimated quantity, such as a difference in group means. It gives a range of values compatible with the data and the method used to construct it. A narrower interval indicates greater precision under that method, while a wider interval indicates less precision. An interval is not a guarantee that the true effect lies within its endpoints, and its interpretation depends on the design, assumptions, and analysis. No confidence interval for the primary comparison is reported in the registry record.

What would a p-value add?

As a general explanation, a p-value measures how unusual data at least as incompatible with a specified null hypothesis would be under the assumptions of a statistical test. It is not the probability that the null hypothesis is true, nor does it measure the size or clinical importance of an effect. A p-value cannot replace an effect estimate and its uncertainty. The registry record does not report a primary-endpoint p-value or identify the test used to produce one.

Why does allocation matter to the analysis?

In a randomized comparison, random allocation is intended to make treatment assignment independent of participant characteristics, on average. In a nonrandomized comparison, the groups can differ before treatment. For example, the criteria used to identify patients for a pathway may select patients with different clinical features from those receiving usual care. As a general principle, statistical adjustment can address measured differences if suitable information and methods are available, but it cannot automatically remove bias from unmeasured or poorly measured factors. The registry does not report baseline comparisons, an adjustment strategy, or enough detail to evaluate residual confounding.

There is a second design consideration: the pathway is a bundle of care decisions. It includes guideline-based patient identification and, for those meeting the criteria, dalbavancin. A comparison of the pathway with usual care addresses the overall strategy, not necessarily the separate effect of each component. This is a general interpretation of the intervention structure; the registry does not report analyses that separate those components.

How should the sample-size assumptions be read?

The record describes planning illustrations based on an observed effect, using a two-sided significance level of 0.05, equal allocation between the arms, and a normal approximation. The stated effect to detect is a fraction of the observed effect. For time-to-event outcomes, the planning method is described as using the total number of events; for other outcomes, it uses participants per arm. These are planning assumptions, not evidence that the study was designed with those assumptions and not a measure of observed power. The registry does not report its own sample-size justification. The observed primary effect and the resulting planning figures are not reported in the registry record, so no such figures or implications can be stated.

As a general statistical point, planning based on an observed effect can be sensitive to the estimate chosen: an unstable or biased observed effect can lead to planning values that do not represent a reliable target. A planning calculation also depends on its assumptions, including the significance level, allocation, and approximation. It does not demonstrate that an analysis was adequately powered, and it cannot compensate for nonrandomized allocation or missing outcome results. No claim of observed power follows from these assumptions.

What does the mean-based endpoint leave out?

A mean and standard deviation summarize center and spread, but do not show the distribution of individual hospital-day observations. As a general consideration, count-like healthcare-use outcomes can be skewed or include many observations at the low end. If that pattern occurs, the mean may not describe a typical participant particularly well, and the standard deviation may not capture all features relevant to interpretation. Whether that pattern occurred in this study is not reported in the registry record. The record also does not state whether any alternative summaries or sensitivity analyses were used.

The primary endpoint is defined for the full analysis set, but the registry does not describe the statistical model, the handling of missing endpoint values, or the method for comparing groups. Without those details and the actual estimates, the registry entry supports a description of the intended measure and general analytical considerations, not an assessment of the treatment effect.

10. Confidence Intervals for Each Arm

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

R code and output

arm <- c("Usual Care", "New Critical Pathway")
n   <- c(48, 42)
m   <- c(4.8, 3.2)
sp  <- c(2.55, 2.48)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Usual Care  48  4.800  2.550  4.060  5.540
CARM  New Critical Pathway  42  3.200  2.480  2.427  3.973

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 31 outcome measures and 2 analyses. It does not report a multiplicity strategy, such as whether the primary comparison was treated as the principal confirmatory test or how statistical error was to be managed across secondary outcomes. When many outcomes are examined, the chance of finding at least one apparently unusual result can increase if each is assessed separately. As a general statistical principle, multiplicity procedures may control that risk, but the choice depends on the goals and structure of the analyses. No such procedure is reported in the registry record.

The primary endpoint is defined in the full analysis set. The record describes this population as all enrolled patients who received at least one dose of antibiotics or one dose of dalbavancin for inclusion. It does not describe other analysis populations or explain whether the population definition was applied consistently to each outcome. The registry does not report the number of endpoint observations available for analysis or the extent of missing data.

Missing-data handling is not reported in the registry record. The record does not state how missing hospital-day information was treated, whether any imputation was used, or whether analyses assessed the sensitivity of results to missingness assumptions. As a general matter, missing observations can affect both estimates and their uncertainty, especially if the reasons for missingness are associated with outcomes or treatment. Without a reported approach, the impact cannot be assessed.

The statistical analysis plan, adjustment methods, and interim analyses are also not reported in the registry record. The description of planning illustrations is not a substitute for the study’s own sample-size justification or analysis plan. These omissions mean readers cannot determine from the registry entry how endpoint selection, missing information, or multiple comparisons were handled in the completed study.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: cellulitis (4.8%), vomiting (2.4%), hypoglycaemia (2.1%).

The registry lists serious adverse-event figures by group. For usual care, 1 participant was affected by a serious adverse event among 48 at risk; the count for other adverse events was 0 among 48 at risk, and the recorded number of deaths was 0. For the New Critical Pathway, 3 participants were affected by a serious adverse event among 42 at risk; the count for other adverse events was 3 among 42 at risk, and the recorded number of deaths was 0. These are the registry’s descriptive counts and denominators; they should not be read as a randomized comparison.

The record also lists Cellulitis at 4.8%, Vomiting at 2.4%, and Hypoglycaemia at 2.1% among the top serious-event terms. It does not identify a group for these terms in the information available, so they cannot be assigned to either arm. The registry entry does not describe event timing, severity details beyond the serious-event classification, relatedness assessments, or statistical comparisons.

As a general principle, sparse event counts can be imprecise, and descriptive counts alone do not establish a difference in risk. The nonrandomized design further limits causal interpretation because the groups may differ in ways that affect both treatment and adverse events. The figures describe what the registry records; they do not establish that a treatment is safe or unsafe.

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

The study’s stated aim is to assess a new critical pathway against usual care for acute bacterial skin and skin structure infections. The pathway pairs guideline-based patient identification with dalbavancin for those who meet the criteria, while usual care is prescribed by the physician in clinical practice. The primary measure is infection-related total admitted hospital days over 44 Days, summarized as a mean and standard deviation in the full analysis set.

The registry entry does not report the primary outcome results. It gives no group means, estimated difference, confidence interval, or p-value. Therefore, it does not show whether the recorded hospital-day outcome was higher or lower in either arm, how large any difference was, or how precisely a comparison was estimated. The study’s completed status and the presence of an endpoint definition do not supply those missing results.

Even with a reported difference, this nonrandomized design would call for caution. The registry says the arms are not a like-for-like control comparison. The groups may have differed in patient selection, clinical characteristics, or decisions about care. A difference could not automatically be attributed to the pathway without considering those factors and the methods used to address them. The intervention also combines patient identification criteria and dalbavancin, so the comparison would concern the strategy as implemented rather than isolate the effect of each component.

The listed secondary outcomes describe a broader set of healthcare-use and infection-related events, while the adverse-event figures describe recorded events by group. Neither set of descriptive listings answers the primary question without outcome estimates and context. The registry does not report results for the listed secondary outcomes in the record.

In short, the record supports a description of the study question, design, endpoint, and some safety counts. It does not support a conclusion about the effect of the pathway on hospital days or a causal claim about the relative performance of the two approaches. The missing estimates, uncertainty measures, and analysis details are central to interpreting what the completed study found.

14. Why This Trial Matters Statistically

This trial is statistically notable because its intervention is a care pathway, not merely a drug assigned in isolation. The pathway combines guideline-based identification with a treatment choice for eligible patients. This raises a general design question: the overall effect of a care strategy may be relevant to clinical practice, but it can be difficult to determine which part of the strategy accounts for any observed difference. The registry describes the components but does not report analyses that separate their contributions.

The nonrandomized allocation is also important. In clinical comparisons, treatment assignment can be tied to patient characteristics and clinician decisions. That creates a risk that outcome differences reflect those factors as well as the intervention. The registry explicitly warns that the arms are not a like-for-like control comparison. This makes clear reporting of baseline characteristics, adjustment methods, and uncertainty especially important, but those details are not reported in the registry record.

The primary measure focuses on admitted hospital days, a healthcare-use outcome that may reflect both illness and the organization of care. A mean can offer a useful overall summary, while potentially concealing variation in individual experience. Distributional information and a clear analysis method would help readers understand how representative the mean is. Those results and methods are not reported in the record.

Finally, the entry illustrates the difference between a registered study question and an interpretable result. The record gives the endpoint and design but not the primary estimates or their precision. Without those, statistical significance, effect magnitude, and uncertainty cannot be assessed. The study remains informative as a registered evaluation of a real-world pathway, while the available registry information does not allow a conclusion about its outcome.

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 main limitation for interpreting this study from the registry record is the absence of primary outcome results. The endpoint definition is present, but the group summaries, between-group estimate, confidence interval, and p-value are not reported. Secondary-outcome results are also not reported in the record. Without outcome estimates, neither direction nor magnitude can be assessed.

The nonrandomized allocation limits causal interpretation. The registry states that the arms are not a like-for-like control comparison, and does not report the allocation process, baseline characteristics, or adjustment methods. Potential differences in patient selection and care decisions therefore cannot be evaluated. The pathway itself combines identification criteria with dalbavancin, so even a reported group difference would not independently identify the contribution of each component.

The registry does not report how missing data were handled, how multiplicity across outcomes was addressed, or which statistical procedures were used. It also does not provide the study’s sample-size justification, interim-analysis information, or a statistical analysis plan. These gaps limit assessment of analysis choices and the reliability of any results that might otherwise be considered.

The primary outcome is described as a mean and standard deviation. The distribution of hospital days and the availability of alternative summaries are not reported, limiting assessment of whether those summaries adequately characterize the observations. The usual-care treatments are not specified, and the registry does not provide further detail on the clinical characteristics of the groups.

These are limitations of the registry information available for interpretation. They do not establish that the study failed to collect or analyze these data; those details are simply not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Development of a New Critical Pathway for Treatment of Acute Bacterial Skin and Skin Structure Infections (ABSSSI) — NCT03233438.
• Registry record last updated 2020-01-18; status last verified 2020-01.
• Results first posted 2020-01-18.
• 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

The registry record describes NCT03233438, a completed Phase 4, parallel, nonrandomized, unmasked study sponsored by Allergan. Enrollment was 91. The study evaluates a guideline-based New Critical Pathway, including dalbavancin for patients meeting the identification criteria, against physician-prescribed usual care for acute bacterial skin and skin structure infections.

The primary endpoint is infection-related total admitted hospital days over 44 Days, summarized as a mean and standard deviation in the full analysis set. The registry defines that set as enrolled patients who received at least one dose of antibiotics or one dose of dalbavancin. It lists 31 outcome measures and 2 analyses.

The registry cautions that the nonrandomized arms are not a like-for-like control comparison. It does not report the primary outcome estimate, uncertainty, or analysis method in the record. Safety counts are listed by group, but they do not establish a comparative effect. The registry’s design and endpoint can be described; the primary result cannot be interpreted from the information recorded.