Gastric Ultrasound: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Gastric Ultrasound (NCT04127331), a non-randomized na study. The primary outcome is Aspiration Risk Grade.

2. Clinical Question

3. Trial Design

NCT04127331 is listed as completed, with an enrollment of 100. The study is titled “Gastric Ultrasound,” and its official title describes ultrasonographic evaluation of gastric volume and contents before surgery in children. The registry lists a start date of 2020-01-10 and a primary completion date of 2022-09-06. Its phase is listed as NA.

The design is recorded as non-randomized, with no masking and a single-group model. Point-of-Care Ultrasound is the listed device intervention. The arm descriptions refer to patients scheduled for routine outpatient surgery, urgent surgery, and emergency surgery. These labels describe clinical circumstances rather than randomized assignments. The registry record does not establish that patients in those categories were otherwise comparable, and the categories should not be read as a controlled treatment comparison.

The adverse-event section uses different group labels: Elective, Semi-urgent, and Urgent. The registry record does not explain how these labels correspond to the routine, urgent, and emergency descriptions elsewhere in the record. The difference in wording is important when reading group-specific counts; it is not a basis for mapping categories or inferring patient flow.

The stated objective includes assessment of gastric volume and contents and gall bladder size in patients scheduled for routine, urgent, and emergency surgery. The listed secondary outcomes concern NPO status at the time of injury and surgery, and pre-operative opioid administration. The record does not report a detailed protocol, eligibility criteria, enrollment by surgery category, or the basis for the planned enrollment. The statistical analysis plan is 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.

Overall Study

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 Aspiration Risk Grade, measured over Baseline.

The primary endpoint is titled Aspiration Risk Grade. It is recorded as a count of participants at Baseline. Its description defines Grade 0 as no fluid visible in the gastric antrum; Grade 1 as clear fluid visualized with volume < 1.5 mL/kg; and Grade 2 as clear fluid visualized with volume > 1.5 mL/kg, described as high risk of aspiration.

This endpoint turns ultrasound observations into ordered categories that distinguish no visible fluid, a lower-volume clear-fluid finding, and a higher-volume clear-fluid finding. In general, a categorized endpoint can make a clinical imaging observation easier to summarize as participant counts by grade. Here, the record identifies the grades and says the measure is a count, but the posted results do not report how many participants were in each grade. The endpoint’s actual distribution and any comparison between surgery categories are therefore not available in the registry record.

The threshold wording uses a less-than sign for Grade 1 and a greater-than sign for Grade 2. The description does not specify how a volume exactly equal to 1.5 mL/kg is classified. The registry record also does not report additional operational details for grading, such as how measurements were taken or how uncertain observations were handled. The endpoint is an ultrasound-based risk classification; the record does not establish that it measures aspiration events themselves.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies a participant-count endpoint with three grades, but it does not report an inferential analysis for that endpoint. The posted results therefore support discussion of what the measure means and what statistical information would be needed to interpret it, but not a conclusion about the observed grade distribution. The accompanying tables, plots, and sample-size display should be read alongside this distinction: a display cannot substitute for outcome counts or analysis results that are not reported in the registry record.

What does a participant-count endpoint show?

A count endpoint summarizes how many participants meet a defined category or have a particular recorded outcome. For Aspiration Risk Grade, the registry’s description defines categories from no visible fluid to clear fluid above a stated volume threshold. To interpret this endpoint, readers would need counts for each grade and clarity about the analysis population used to produce them. The record gives neither the grade counts nor a description of the population contributing to the endpoint. The enrollment of 100 is not, by itself, a report of how many participants had usable ultrasound observations.

Counts can be useful for describing the distribution of categories in a study. They do not automatically establish why a category was observed, whether it differs between clinical groups, or whether an observed pattern is precise. Those interpretations depend on the study design, the data, and the planned analysis. Here, the registry record does not post the outcome distribution or an analysis comparing groups.

Why does the non-randomized design matter?

In a randomized comparison, assignment is intended to create groups that can be compared under the study design. This study is described as non-randomized and single-group. Its routine, urgent, and emergency surgery categories refer to clinical scheduling circumstances, not randomized assignments. In general, non-randomized groups can differ in characteristics related to both the grouping and the outcome. A difference between groups may therefore reflect confounding or other differences in care circumstances rather than the association of interest alone.

Adjustment methods can sometimes account for measured differences, but their suitability depends on the available data and the analysis plan. The registry record does not report a statistical model, covariate-adjustment strategy, or other method for handling differences between groups. It would be speculative to assume that a particular adjustment was used. The adverse-event group labels also differ from the arm descriptions, and the record does not explain the relationship between them.

What does a confidence interval contribute?

In general, a confidence interval expresses uncertainty around an estimated quantity under the method used to calculate it. It helps readers distinguish an estimate from the range of values that remain compatible with the data and analysis assumptions. A narrow interval generally indicates more precision than a wide interval, although precision does not resolve bias or limitations in study design. The registry record does not report a confidence interval for the primary endpoint, and it does not provide the underlying primary counts from which readers could assess the observed distribution.

A p-value, in general, summarizes how unusual data would be under a specified statistical model and a null hypothesis. It is not a measure of clinical importance, and it does not establish that a result is true or false. The registry record does not report a p-value or a statistical test for the primary endpoint. No specific hypothesis test or inferential method should be inferred from the endpoint description alone.

How should the sample-size display be read?

The sample-size section is a planning illustration based on an observed effect, rather than a report of the study’s original design justification. Its stated assumptions are 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. These are assumptions for the illustration, not evidence that the trial used that design or those analysis choices. The registry record does not report the protocol’s sample-size justification or a statistical plan.

Such sample-size illustrations describe hypothetical planning requirements under their stated assumptions. They are not observed power and do not show whether a study has demonstrated an effect. Their interpretation also depends on the effect estimate used, the chosen fraction, and the suitability of the assumptions. Since the primary outcome estimate is not reported in the registry record, the displayed planning values should not be treated as a substitute for reported outcome results or as an independent finding.

Why can over-dispersion matter?

In general, count data can vary more than a simple statistical model expects. This is called over-dispersion. If present, it can make uncertainty estimates from a model that assumes less variability too small, which can make results appear more precise than they are. Methods designed for over-dispersed data may be considered when the outcome and data structure warrant them. The endpoint is described as participant counts across grades, but the registry record does not report a count model, a dispersion assessment, or any inferential analysis. This general issue should not be mistaken for evidence that over-dispersion was present in this study.

More broadly, the analysis details needed for statistical interpretation—including the analysis population, handling of missing measurements, methods for comparing categories, and uncertainty estimates—are not reported in the registry record. Without those details and the actual outcome results, readers can explain the endpoint and study structure, but cannot reconstruct or verify an inferential result.

10. Multiplicity, Missing Data and Analysis Populations

The record identifies four outcome measures and names secondary outcomes concerning NPO status at the time of injury, NPO status at the time of surgery, and pre-operative opioid administration. It does not report a multiplicity strategy. In general, when several outcomes or comparisons are assessed, the chance of at least one apparently notable result can increase. Methods for addressing that issue depend on the prespecified analysis plan and the questions being tested. The registry record does not state whether outcomes were treated as confirmatory or exploratory, or whether any adjustment was planned.

Missing-data handling is not reported in the registry record. The record does not describe whether participants lacked ultrasound assessments, how incomplete measurements were treated, or whether any imputation or sensitivity analysis was used. This matters because the enrollment figure does not establish how many participants contributed to each outcome. The primary endpoint counts and secondary outcome results are not reported, so the extent or consequences of missing data cannot be assessed.

The record also does not define analysis populations, such as which enrolled participants were included in each outcome summary. It does not report exclusions after enrollment, deviations from the planned measurement process, or a distinction between an enrolled population and an analyzed population. Those details would help readers understand the denominator behind any result. The registry record does not report an analysis plan, and no particular approach to multiplicity, missingness, or population definition should be assumed.

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.

The registry’s adverse-event section lists Elective, Semi-urgent, and Urgent groups. For Elective, 41 participants are listed at risk, with 0 serious adverse events, 0 other adverse events, and 0 deaths. For Semi-urgent, 32 participants are listed at risk, with 0 serious adverse events, 0 other adverse events, and 0 deaths. For Urgent, 27 participants are listed at risk, with 0 serious adverse events, 0 other adverse events, and 0 deaths. No serious adverse-event terms are listed.

These entries describe the counts in the registry record. They do not establish that every possible event was absent, nor do they describe how events were defined, collected, or followed. The record does not provide additional safety-analysis details. The adverse-event labels also differ from the routine, urgent, and emergency surgery categories described in the study design, and the registry record does not explain that difference. Read the figures as reported safety counts for the listed labels, not as a randomized comparison or a complete characterization of safety.

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

The study asks whether pre-operative ultrasound findings about gastric contents and volume can be described across surgery circumstances, and whether those findings relate to the stated factors of stress, pain, opioid administration, and NPO timing. It also identifies gall bladder size as an objective. The primary endpoint provides a grading scheme for gastric antral fluid observations. These details make the research question and intended measurement clear at a broad level.

However, the registry record does not report the primary grade counts, results for the secondary outcomes, estimates of association, or statistical uncertainty. It therefore does not show whether the anticipated patterns were observed, how large any differences were, or how precisely they were estimated. A completed status and an enrollment of 100 do not fill that information gap.

The design is non-randomized and single-group. Consequently, any comparison across urgency categories would be observational, not a randomized treatment effect. Clinical circumstances may differ between the categories, and the record does not report an adjustment strategy that would address such differences. The study description alone cannot establish a causal effect of surgery urgency, NPO time, pain, stress, or opioid administration on gastric volume or gallbladder size.

The endpoint is an ultrasound classification related to aspiration risk, not a report of aspiration events. The record’s label for Grade 2 describes a high-risk category, but without the grade counts or clinical outcome data, readers cannot determine how participants were distributed across categories or what the classification meant for subsequent events in this study.

The reasonable conclusion is limited to what the registry documents: the investigators planned to assess ultrasound findings before surgery and recorded a baseline grading scheme. The posted information does not provide the outcome evidence needed to judge the observed patterns or their precision. It should not be read as demonstrating a benefit, harm, or causal relationship.

13. Why This Trial Matters Statistically

This record illustrates why statistical interpretation begins with identifying what was measured, how participants were grouped, and whether results are actually posted. Here, the endpoint is defined in terms of ultrasound grades, and the study objective connects those observations with surgery circumstances and other recorded factors. But the primary grade counts and analysis results are absent from the registry record. Without them, the research question can be described but not answered from the posted data.

The design is also important. Routine, urgent, and emergency surgery categories reflect clinical circumstances in a non-randomized, single-group study. Treating them as randomized arms would overstate what the design can support. In observational comparisons, differences between groups may have multiple explanations. Statistical adjustment can be relevant in principle, but the record does not report whether or how it was used.

The safety entries demonstrate another interpretive distinction: a recorded zero is a count in the registry table, not a guarantee that an event was impossible or that all potential events were assessed in the same way. The record does not provide event definitions or further safety methods. The mismatch between safety-group labels and surgery-category descriptions adds a reason to read those entries carefully rather than infer a direct comparison.

Finally, planning illustrations and observed results answer different questions. A sample-size display can describe hypothetical requirements under stated assumptions, but it cannot replace an outcome estimate, its uncertainty, or a prespecified analysis. For clinical researchers, this trial is a useful example of the need to separate objectives, endpoint definitions, design limitations, safety reporting, and results. The registry record documents the first elements more clearly than it documents the findings.

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.

Several limitations are specific to what is documented. The primary endpoint is defined, but its participant counts by grade are not reported in the registry record. The record likewise does not report results for the listed secondary outcomes. This prevents assessment of the observed endpoint distribution and any proposed relationship with NPO timing, pre-operative opioid administration, or surgery circumstances.

The study is non-randomized and described as single-group. The routine, urgent, and emergency categories therefore should not be interpreted as randomized comparison arms. The record does not describe an adjustment method or provide enough detail to assess how differences between these clinical groups were handled. In addition, adverse-event categories use Elective, Semi-urgent, and Urgent labels, and their relationship to the arm descriptions is not reported in the registry record.

The registry gives an enrollment of 100 but does not report the numbers analyzed for the primary or secondary outcomes. It does not report analysis populations, missing-data handling, endpoint-assessment procedures, or an inferential analysis plan. The primary endpoint description also does not explain how a value exactly equal to 1.5 mL/kg is classified, despite specifying Grade 1 as below and Grade 2 as above that threshold.

These are limitations of the registry information available for interpretation; they do not establish that procedures or analyses were absent from the underlying study. The protocol details, sample-size justification, and statistical plan are not reported in the registry record. Readers should therefore distinguish what the record does not disclose from what the investigators may have done outside the posted entry.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Gastric Ultrasound — NCT04127331.
• Registry record last updated 2023-11-21; status last verified 2023-02.
• Results first posted 2023-11-21.
• 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.

18. Record Summary

NCT04127331, “Gastric Ultrasound,” is listed as completed, with enrollment of 100 and a non-randomized, unmasked, single-group design. Its objective is to evaluate gastric volume and contents and gall bladder size before surgery in children. Point-of-Care Ultrasound is the listed intervention. The primary endpoint is Aspiration Risk Grade at Baseline, defined using three descriptions of gastric antral fluid.

The registry lists secondary outcomes concerning NPO status at injury and surgery and pre-operative opioid administration. It also posts adverse-event counts by Elective, Semi-urgent, and Urgent groups; each listed group has zero serious events, zero other events, and zero deaths. The primary endpoint counts, secondary outcome results, analysis methods, missing-data approach, and statistical plan are not reported in the registry record. The study’s questions and endpoint definition can be summarized, but its principal findings and their precision cannot be assessed from the posted record.