Alcohol Screening and Pre-Operative Intervention Research Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Alcohol Screening and Pre-Operative Intervention Research Study (NCT03929562), a randomized na study. The primary outcome is Mean Alcohol Weekly Use.

2. Clinical Question

3. Trial Design

The registry record describes a randomized, double-masked, parallel-group study. It lists the phase as NA and the status as completed. Enrollment is recorded as 65. The sponsor is the University of Michigan. The record lists Alcohol Drinking as the condition.

The study dates are recorded as a start on 2019-08-20 and primary completion on 2021-07-19. The study's stated purpose was to examine acceptability and initial efficacy of pre-operative alcohol use reduction interventions in relation to health before and after scheduled surgery.

Participants were assigned to one of two behavioral approaches. The brief advice arm involved one brief advice session, a resource brochure, standard of care, and an infographic about alcohol and surgical health at a pre-existing pre-operative clinical visit. The health coaching arm involved two health coaching sessions, a resource brochure, and standard of care. The registry record does not describe the randomization procedure, the allocation concealment process, or which individuals were masked. The label double-masked does not by itself identify who was unaware of assignment.

The primary outcome was mean weekly alcohol use, assessed using a timeline followback measure. A secondary outcome concerned intervention acceptability, measured by a post-intervention evaluation. The record lists two outcome measures but does not report an analysis for either. It also does not report further details about the study setting, recruitment, treatment fidelity, or the timing of the post-intervention evaluation.

Because both listed arms received a behavioral intervention and standard of care, the design addresses a comparison between these approaches. The registry record does not list a usual-care-only or untreated arm. The stated study purpose includes initial efficacy, but the record does not provide the numerical outcome findings needed to estimate comparative efficacy.

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: 14 of 65 enrolled participants were not assigned to groups because they did not meet eligibility requirements after enrollment (i.e. surgery cancelation).

From Baseline to 1 Month Follow Up

Reasons for not completing this period:

1 Month Follow Up to 4 Month Follow Up

Reasons for not completing this period:

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Mean Alcohol Weekly Use, measured over Baseline through 4 months.

The primary endpoint is mean alcohol use per week, expressed as drinks consumed per week, assessed from baseline through 4 months. The registry describes use of the timeline followback measure: participants report the number of standard drinks consumed each day during an assessment period using a calendar format. In the United States, one standard drink is defined as a beverage containing 0.6 oz or 14 grams of pure alcohol.

A mean is a summary of the measured values across the participants included in an analysis. It can describe the average reported weekly use in an arm, while the standard deviation describes how spread out individual measurements are around that average. Both are useful because a group average alone does not convey how much participants' reported use varies.

Weekly alcohol use is relevant to the study's stated focus on pre-operative alcohol reduction. Repeated assessment across the stated timeframe can describe change over time, but interpretation depends on how measurements at different times are analyzed and compared. The registry record notes multiple categories or time points and does not reduce the primary outcome to one comparison. It does not report arm-specific means, standard deviations, changes, or a between-arm estimate. As a result, the outcome definition is available, but the size and precision of any observed contrast are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the mean describe?

The primary endpoint is a continuous measure: reported drinks consumed per week. For a continuous outcome, the mean gives the arithmetic average of the measurements used in an analysis. It offers a compact description of typical measured use in an arm, but it does not show whether values are tightly clustered or widely dispersed. The registry identifies standard deviation as the dispersion measure. A standard deviation describes variation among the measurements around the mean; it is not the same as uncertainty in the mean or uncertainty in a comparison between arms.

Means can be useful for comparing groups, particularly when the distributions and analysis assumptions make an average an interpretable summary. Yet a mean may not fully describe a distribution that is strongly skewed or influenced by extreme values. Individual alcohol-use reports can vary, and the record does not provide distributional information with which to judge the shape of this endpoint. The displayed summary statistic alone would not establish whether assumptions for a particular model were appropriate.

Why does the timeframe matter?

The endpoint is described as covering baseline through 4 months, and the registry notes several categories or time points. Measurements made at more than one time can be analyzed in different ways. An analysis might focus on a value at a specified follow-up, a change from baseline, or a pattern across time. Those choices answer different questions and can use the repeated measurements differently. The registry record does not identify a single reduced comparison or specify which time-point contrast was intended for the reported primary analysis.

Repeated measurements from the same participant are generally related: a person's measurements over time are not usually treated as independent observations. General statistical methods for longitudinal data account for this within-participant association and can model how outcomes change over time. The appropriate method depends on the chosen estimand, the timing of assessments, the data structure, and assumptions about missing measurements. Those analysis details are not reported in the registry record, so the approach cannot be reconstructed from the endpoint description.

How should a between-arm estimate be read?

In general, a between-arm estimate expresses the contrast in the outcome between the randomized groups under a specified analysis. Its interpretation depends on the scale and on whether the comparison is adjusted or unadjusted. A confidence interval communicates the uncertainty around an estimate: it identifies values that are reasonably compatible with the data and the model, rather than guaranteeing that the true effect lies within a particular range. A p-value is another summary of evidence relative to a null hypothesis, but does not convey the magnitude or precision of a contrast by itself.

No numerical primary-outcome estimate, confidence interval, or p-value is reported in the registry record. A recalculation from summary statistics is therefore not available from the reported information. The record gives no sponsor analysis to compare with a recalculation, so there is no basis for evaluating a discrepancy. In general, when a sponsor's own analysis and an unadjusted recalculation differ, the sponsor's analysis takes precedence for describing the trial's reported analysis, while the recalculation should be identified as a separate, simple unadjusted analysis.

What does the planning illustration represent?

The record describes a planning illustration based on the observed effect, not the trial's own design. Its stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. For non-time-to-event outcomes, such illustrations are expressed as participants per arm for a specified power. These are hypothetical planning quantities, not observed trial results and not observed power.

The numerical observed effect and the numerical planning estimates are not reported in the registry record. Consequently, no particular planning requirement or effect size can be interpreted from the record. A planning illustration cannot retrospectively establish whether the trial was adequately powered, especially when the effect used for planning comes from an observed estimate that is itself uncertain. The record does not report a sample-size justification or establish that this illustration was used when the study was designed.

Why can variability affect inference?

General statistical methods need to account for how variable the measurements are and how they are distributed. When variability is greater than a model assumes, uncertainty may be understated if the method does not accommodate it. Over-dispersion is a term used when observed variation exceeds what a model expects. It matters because standard errors, confidence intervals, and tests can be unreliable under a poorly fitting variance assumption. The registry record does not characterize the outcome distribution or report an over-dispersion assessment; this is a general consideration, not a finding about this trial.

For repeated continuous outcomes, analysts also need to consider within-participant correlation and missing observations. For binary or count outcomes, the relevant model and variance assumptions differ. The primary endpoint is continuous, and the registry identifies a mean and standard deviation, but it does not describe a fitted model, covariate adjustment, or diagnostic checks. No specific model performance or assumption should therefore be inferred.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome spans baseline through 4 months, and the registry record states that it has several categories or time points rather than one reduced comparison. Testing multiple time points or contrasts can raise a multiplicity issue: when many hypotheses are examined, the chance of finding an apparently notable result by chance can increase. Statistical plans can address this through a prespecified primary contrast, adjustment procedures, or a clearly defined hierarchy of outcomes. The registry record does not report how multiplicity was handled or identify a single primary time-point contrast.

The listed secondary outcome is acceptability measured by a post-intervention evaluation. The record does not provide its results, the instrument details, or an analysis plan describing how the secondary outcome relates to the primary outcome. Whether any adjustment was planned across outcomes is not reported in the registry record.

Missing data are important when an endpoint is assessed repeatedly. If participants lack measurements, an analysis may depend on assumptions about why observations are missing and how the method handles them. The registry record does not report missing-data counts, reasons for missingness, imputation, sensitivity analyses, or the assumptions used for incomplete outcome data. Enrollment alone does not indicate the number included in each analysis.

The analysis populations are also not reported in the registry record. The record does not specify whether analyses were intended to include participants as randomized, only those who received an intervention, or another population. It lists zero analyses, so no actual analysis set or analytic handling can be verified from the posted record. These omissions limit assessment of how the outcome comparisons were defined and how robust they may be to missingness or analytic choices.

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 serious adverse event terms

Serious events with the highest arm-level rate: post-op surgical complications, surgical and medical procedures (12.0%).

The registry lists serious adverse event figures separately for the two arms. In brief advice, 26 participants were listed as at risk and 1 as affected by a serious adverse event. In health coaching, 25 were listed as at risk and 3 as affected. The record lists zero other adverse events and zero deaths in each arm. These are the counts recorded, not a comparative analysis or an estimate of the relative safety of the interventions.

The leading serious adverse event term is listed as “Post-op Surgical complications, Surgical and Medical Procedures” at 12.0%. The registry record does not provide further detail in the available information about the event term's denominator, timing, severity breakdown, or attribution to an intervention. It also does not describe how events were collected or adjudicated. The listed term and percentage should therefore be read as registry safety reporting, not as evidence that an intervention caused those events.

Serious adverse events and other adverse events are distinct reporting categories. The figures do not describe alcohol-use outcomes, and they cannot substitute for the missing primary endpoint comparison. Counts alone also do not account for differences in follow-up, ascertainment, or uncertainty. No causal or comparative safety conclusion can be drawn from these figures without the fuller methods and context, which are not reported in the registry record.

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

The registry record establishes that the study was a randomized, double-masked, parallel comparison of brief advice and health coaching. It describes both behavioral approaches, the timeline followback measure, and mean weekly alcohol use from baseline through 4 months as the primary endpoint. It also lists an acceptability outcome. These details clarify the question the study addressed.

The posted information does not establish whether health coaching or brief advice was associated with lower weekly alcohol use, whether the groups differed in acceptability, or how large or precise any differences were. Primary-outcome results are not reported as a single comparison, and the record lists zero analyses. The result therefore cannot be characterized as favoring either arm, showing equivalence, or demonstrating a clinically important difference.

In general, failure to report a statistical difference is not evidence that groups are equivalent. Equivalence or non-inferiority requires a prespecified framework, a defined margin, and an analysis suited to that question. The registry record does not report such a framework. Similarly, a study's randomized design does not guarantee that a reported estimate is precise; precision depends on the data, measurement variability, missingness, and analysis.

The enrollment figure is not enough to infer the number analyzed for the primary endpoint or the adequacy of the study's power. The planning illustration described in the record is not an observed-power result and is not evidence about the trial's actual design rationale. Without outcome estimates and uncertainty, readers cannot assess whether the study's findings, if analyzed, are compatible with a range of effects or too imprecise to distinguish among them.

The serious adverse event counts are descriptive and do not establish causation or comparative safety. Overall, this record supports an account of the study's design, interventions, measurement, and selected safety reporting. It does not provide the quantitative efficacy and acceptability results needed to judge the comparative outcome findings.

13. Why This Trial Matters Statistically

This study is statistically notable for asking a comparative question about two behavioral approaches in a pre-operative setting while measuring alcohol use over time. Its primary endpoint is a continuous measure based on reported daily consumption, summarized as mean weekly use. Such an endpoint can capture a range of values and offers a direct description of average reported use, while the standard deviation conveys variability.

The timeframe also raises an important analysis question. Measurements spanning baseline through 4 months may support a trajectory-based analysis or a specified follow-up contrast, but those approaches do not answer exactly the same question. A primary contrast needs to be clearly defined when the outcome includes multiple time points. The registry record notes that multiple categories or time points were not reduced to one comparison, and it does not report the analysis plan or results.

Comparing two active behavioral arms can be informative about their relative performance, but it does not directly estimate the contrast between an intervention and no intervention. Both listed approaches included standard of care, and the brief advice arm included additional materials and contact. The registry record does not isolate the contribution of any one component.

The absence of a reported primary comparison is important for statistical interpretation. A randomized design is valuable for controlling confounding in expectation, but the observed estimate and its uncertainty are still needed to assess what the trial found. The record's enrollment figure and planning illustration cannot replace the missing outcome analysis, and the acceptability outcome is also not numerically reported. The study therefore illustrates why trial design information and outcome evidence are separate: the former describes how a question was posed, while the latter is needed to estimate the answer.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The registry record does not report arm-specific primary-outcome summaries, a between-arm estimate, or uncertainty around an estimate. It notes multiple categories or time points and does not reduce the primary endpoint to one comparison. This prevents assessment of the direction, magnitude, and precision of the primary result.

The record lists zero analyses and does not report numerical results for the secondary acceptability outcome. It also does not describe the analysis populations, outcome-specific denominators, missing-data handling, model specification, covariate adjustment, or sensitivity analyses. Those details are needed to judge how the measured data were converted into an estimate and how dependent that estimate may be on assumptions.

Further design information is not reported in the registry record, including eligibility criteria, recruitment and setting details, the randomization procedure, allocation concealment, and the identities of those masked. The record does not describe intervention fidelity, participant adherence, or the detailed content of health coaching. It is therefore not possible to assess whether the interventions were delivered as intended or how broadly the enrolled population represents other surgical populations.

The primary outcome is self-reported through a calendar-based timeline followback measure. The registry describes that method but does not report validation details, completeness of reporting, or any independent verification. Self-report can be affected by recall and reporting behavior; this is a general measurement consideration, not evidence that reporting was inaccurate in this study.

The safety information is limited to the listed counts and leading event term. Additional details about ascertainment, timing, attribution, and denominators are not reported in the registry record. The planning illustration is not identified as the trial's design rationale and does not provide a substitute for a reported power calculation or outcome analysis.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Alcohol Screening and Pre-Operative Intervention Research Study — NCT03929562.
• Registry record last updated 2022-11-15; status last verified 2022-10.
• Results first posted 2022-11-15.
• 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

NCT03929562 is a completed, randomized, double-masked, parallel-group study sponsored by the University of Michigan. The record lists enrollment of 65 and dates from 2019-08-20 to primary completion on 2021-07-19. It compares brief advice with health coaching for pre-operative alcohol use.

The primary endpoint is mean drinks consumed per week, assessed with timeline followback from baseline through 4 months. The listed secondary outcome is intervention acceptability measured by a post-intervention evaluation. The record lists serious adverse event counts by arm, but does not report a primary-outcome comparison, numeric acceptability findings, or analysis details. Consequently, the design and outcome definitions can be described, but comparative efficacy and precision cannot be assessed from the registry record.