Ondansetron and the QT Interval In Adult Emergency Department Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Ondansetron and the QT Interval In Adult Emergency Department Patients (NCT01759420), a registered phase not stated study. The primary outcome is Change in QTc Interval With Ondansetron Administration.

2. Clinical Question

The clinical question concerns short-term change in an ECG measurement after a routinely used anti-nausea medication in emergency department patients. The registry summary notes earlier study in anesthesia and cancer patients and frames this study as an assessment in an emergency department setting. That context explains the intended population, but it does not establish whether the measured response in this study is different from response in other settings.

The endpoint is a within-person change: each observed QTc is compared with that participant’s baseline, and the largest prolongation during follow-up contributes to the mean maximal change. The record describes monitoring over 20 minutes; it does not report the resulting mean, interval estimate, participant-level results, or any comparison with an untreated group. Accordingly, the record sets out a question and measurement plan but does not furnish a numerical answer to the primary question.

3. Trial Design

The registry identifies this as an observational study of IV ondansetron in adult emergency department patients. The arm description refers to patients receiving 4mg of IV ondansetron as part of their treatment plan. There is no stated randomized assignment, and no control arm is described as a like-for-like comparison. The study therefore focuses on changes after medication administration rather than estimating a randomized between-group treatment contrast.

The stated enrollment is 28. The registry dates the study start to 2012-12 and primary completion to 2014-05, and lists its status as COMPLETED. These administrative details do not indicate whether all enrolled participants contributed usable measurements or whether the planned follow-up was completed for each participant.

The primary endpoint is change in QTc interval, measured from baseline to 20 minutes. The registry description says an ECG would be obtained at baseline and then every 2 minutes after drug administration until 20 minutes had passed. The objective is to calculate the mean maximal QTc change from baseline, using the Bazett formula. The registry lists Number of Adverse Events as a secondary outcome.

The record lists two outcome measures and no analysis records. It does not describe the analysis population, the handling of repeated ECG measurements, missing observations, or the statistical model used to estimate the mean. A confidence interval is named as the primary measure of dispersion, but its numerical limits are not reported in the registry record.

Because the study is observational and no comparator is described, the design cannot separate a post-administration change from other influences on the measurement. The recorded baseline offers a reference for within-person change, but does not supply the counterfactual outcome that would have been observed without ondansetron. This distinction is important when reading any change estimate that might be reported elsewhere. In this registry record, the primary estimate itself is not available.

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:

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 Change in QTc Interval With Ondansetron Administration, measured over Baseline to 20 minutes.

The primary endpoint is the mean maximal prolongation in QTc interval from baseline, assessed from baseline through 20 minutes after ondansetron administration. QTc is an ECG measurement adjusted using the Bazett formula. The record describes ECG acquisition every 2 minutes during the follow-up period, with each participant’s greatest observed prolongation contributing to the endpoint.

Using a maximum within a fixed observation period is intended to capture the largest recorded increase during that period, rather than only the value at the final measurement. Taking the mean of these participant-level maximum changes describes the average maximal change in the observed group. It is a continuous outcome, so its estimate can be accompanied by a confidence interval to express statistical precision.

In general, a confidence interval represents a range of values reasonably compatible with the data and the assumptions of the analysis; it is not a guarantee that the true value falls within that specific interval. The registry names a 95% Confidence Interval as the measure of dispersion, but does not report its limits or the mean maximal change. Thus, the endpoint definition is available, while the magnitude and precision of the observed result are not.

The registry does not explain why the Bazett formula was selected or describe any alternative correction method. Nor does it report the raw interval measurements, participant-level maxima, or the timing of any maximum. These omissions limit independent assessment of the endpoint calculation from the record alone.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Several statistical ideas help define what the registry’s endpoint could convey, even though its numerical estimate is not reported. The primary outcome is continuous: QTc change is measured on a scale, rather than represented only as an event count or category. The registry specifies a mean maximal change, which is an average across participants of each participant’s largest observed prolongation from baseline during the observation period.

What does the mean describe?

In general, a mean gives a single summary of the center of a set of numeric observations. Here the stated target is the mean of individual maximum changes, not the mean of all ECG readings combined. That distinction matters because a person with several repeated readings contributes a maximum to the described endpoint rather than each reading being treated as a separate participant-level outcome. The numerical endpoint value is not reported in the registry record, so the direction and size of the average change cannot be evaluated.

What does the confidence interval add?

The registry specifies a 95% Confidence Interval for the primary result. In general, a confidence interval expresses uncertainty about an estimate under the method’s assumptions and repeated-sampling framework. It can help readers judge whether a mean is estimated with relatively high or low precision. It does not describe the spread of every participant’s values, and it is not a probability statement about the specific interval after it has been calculated. The interval limits and the method used to calculate them are not reported in the registry record. Consequently, readers cannot use the stated confidence level alone to judge precision.

Why do repeated measurements matter?

The planned ECG schedule creates repeated observations within each participant: a baseline reading followed by readings every 2 minutes through 20 minutes. In general, readings from the same person are likely to be related, because they share that person’s characteristics and measurement context. Treating repeated readings as though they were independent observations can misstate uncertainty. An analysis may instead first form a participant-level outcome, such as the maximum change described in the registry, or use a method that explicitly accounts for within-person correlation. The registry specifies a maximum-based endpoint but does not report the detailed calculation or inferential method.

Taking a maximum also has a statistical consequence in general: it summarizes the largest observed value within the chosen observation window and can be affected by measurement variability and the number and timing of observations. That does not invalidate the endpoint; it means interpretation depends on the measurement schedule and definition. The registry describes the schedule and endpoint but does not report how missing ECG readings, if any, were handled or how a maximum was determined when observations were incomplete.

What is over-dispersion, and does it apply?

In general, over-dispersion describes count data whose variability exceeds what a simple model assumes. It can matter for event counts when choosing a statistical model or assessing uncertainty. The primary outcome in this record is a continuous mean, not a count, so over-dispersion is not the central issue for that endpoint. The secondary outcome is Number of Adverse Events, but the registry record does not describe a count model or an event-rate analysis. The posted safety summary gives event counts and numbers at risk, without enough methodological detail to infer a statistical model.

Why do design and analysis assumptions matter?

The study is observational and has no described like-for-like control group. A baseline-to-follow-up change can describe temporal change in the observed participants, but does not by itself identify the effect attributable to the medication. In general, other time-related influences, measurement variation, and characteristics of participants can affect an observed change. The registry record does not report an adjustment strategy or a statistical model addressing such factors. No causal interpretation can be established from the design details.

The record identifies two outcome measures and no analysis records. It does not report a prespecified statistical analysis plan, an approach to multiplicity, a missing-data method, or a definition of the analysis population. These are not small technical details: choices about which participants and measurements to include can affect both the estimate and its uncertainty. Because no primary estimate or interval is posted in the registry record, the calculations and assumptions cannot be checked against reported numerical output.

The sample-size assumptions described for planning illustrations are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a fraction of the observed effect. These are planning assumptions, not evidence that the observational study used equal allocation or had a two-arm control comparison. The illustrations are described as based on the observed effect and not as the trial’s own design. They should be understood as hypothetical planning quantities, not as observed power. The registry record does not report the observed effect or a prospective sample-size justification.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures: the primary QTc endpoint and the secondary outcome Number of Adverse Events. It does not report an analysis record, a statistical analysis plan, or whether any other outcomes were examined. The record therefore does not say whether the study adjusted for testing more than one outcome, used a hierarchy of outcomes, or treated the secondary outcome as descriptive. No multiplicity correction should be inferred from the listed outcome count alone.

In general, multiplicity matters when several hypotheses are tested, because repeated testing can increase the chance of at least one apparently notable result under a set of null hypotheses. An adjustment may be used depending on the goals and analysis plan. The registry record does not report whether this issue was considered, so the implications for any inferential claims cannot be assessed. No primary p-value or confidence interval is reported to interpret in relation to multiplicity.

Missing-data methods are also not reported in the registry record. Although the planned measurement schedule is described, the record does not state whether every participant had all scheduled ECGs, how incomplete follow-up was handled, or whether any values were excluded. It does not report an imputation method or a sensitivity analysis. These omissions matter because a maximum-based endpoint depends on the observations available during follow-up.

The analysis population is not reported. The enrollment is 28, while the adverse-event summaries list 23 at risk in each category; the record does not explain the denominators or identify the number included in the primary analysis. It is therefore not possible to determine whether the endpoint analysis used all enrolled participants or a subset. The registry does not report an intention-to-treat population, a per-protocol population, or another analysis-set definition. These terms should not be assigned to the study without documentation.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The posted adverse-event summary lists 23 participants at risk for serious adverse events and zero serious adverse events. It also lists 23 participants at risk for other adverse events and zero other adverse events. These are the event counts recorded in the registry summary for the stated groups. The summary lists no serious adverse event terms.

Zero events in a registry summary means that no events are listed in that category for the reported at-risk group; it does not demonstrate that an event could never occur, nor does it establish that every possible event was detected or recorded. The record does not describe the event definitions, surveillance procedures, reporting window, or completeness of follow-up. The deaths entry is not reported in the registry record and should not be interpreted as zero deaths.

The enrollment is 28, whereas the safety summaries use 23 participants at risk in each category. The registry does not explain this difference, so the denominator should be read as reported rather than reconciled with enrollment by assumption. These counts are not comparative risk estimates: no control group is described, and no between-group safety contrast is available. The summary is limited to what the registry reports and does not provide a detailed clinical account of events or individual participant outcomes.

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

The record establishes the study’s question and intended measurement approach: assess mean maximal QTc change from baseline after IV ondansetron in adult emergency department patients, using the Bazett formula and ECG follow-up through 20 minutes. It also identifies the study as observational, lists enrollment as 28, and records the study status as COMPLETED. These details clarify the setting and the kind of outcome the investigators aimed to measure.

The registry record does not report the numerical primary endpoint result or its 95% Confidence Interval. Therefore, the magnitude and precision of QTc change cannot be described from the posted record. Completion status does not mean that numerical findings are available, and enrollment alone does not reveal the analysis sample or the result.

The design also limits what a change from baseline can establish. Without a described control group, the observed before-and-after change cannot distinguish an effect of the medication from other influences that may occur over the same period. The study is not presented as a randomized comparison, and the registry does not state an allocation method. The record therefore does not support a causal comparison with no treatment or with another treatment.

The adverse-event summary lists zero serious and zero other adverse events among 23 at risk in each category. This is a descriptive registry count, not proof of absence of risk. The record does not explain why the at-risk groups differ from the stated enrollment, provide event definitions, or report the deaths value. Those gaps limit interpretation of safety reporting.

What can be concluded is narrower: the registry documents a completed observational study with a specified short-term ECG endpoint and a posted safety summary. What cannot be concluded from this record is whether QTc changed by a particular amount, how precisely any change was estimated, or whether a change was caused by ondansetron. A fuller statistical interpretation would require the numerical endpoint results, their uncertainty, and details of the analysis population and methods.

13. Why This Trial Matters Statistically

This study matters statistically because it illustrates the difference between a clearly stated endpoint and an interpretable result. The registry defines a continuous, within-person outcome: the mean maximal QTc change from baseline over a specified monitoring period. It also names a confidence interval as the measure of dispersion. Yet the numerical mean and interval are not reported in the registry record. Endpoint definitions are essential, but they cannot replace estimates when the question is how large a change was observed and how precisely it was measured.

The design highlights a second issue: before-and-after measurements are not the same as a controlled comparison. Repeated ECG measurements can describe the timing and pattern of change in the observed group, and a participant-level maximum can address the largest recorded change during follow-up. But an observational measurement sequence without a stated comparator cannot isolate the contribution of the medication from other influences. This is a design limitation, not a calculation that can be repaired by a confidence interval alone.

The record also demonstrates why enrollment, analysis denominators, and safety denominators must be distinguished. Enrollment is 28, while the safety summaries list 23 participants at risk in each category. The record does not explain the difference or report the primary analysis population. Without that information, readers cannot assume that all enrolled participants contributed to every endpoint.

Finally, the posted safety counts are useful descriptive information, but they do not supply a complete account of event ascertainment or establish absence of risk. The registry’s limited reporting makes transparent interpretation especially important: identify what the endpoint was, distinguish descriptive counts from comparative evidence, and avoid converting an unreported result into a conclusion. The key statistical lesson is that design, denominators, uncertainty, and result availability all shape what a reader can infer.

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 specific to this record constrain interpretation. First, the primary outcome is defined but its numerical result is not reported. The mean maximal QTc change and the limits of the stated 95% Confidence Interval are absent, so neither effect magnitude nor precision can be evaluated. The registry status of COMPLETED does not resolve that missing result.

Second, this is an observational study with no like-for-like control comparison described, and allocation is not stated. Within-person measurements have a baseline reference, but without a comparator they cannot show what would have happened over the same period in the absence of ondansetron. The registry does not report an adjustment method that might address other influences on the measurements.

Third, the enrollment of 28 differs from the 23 participants listed at risk in each adverse-event category. The record gives no explanation, and does not state the primary analysis denominator. It also does not report participant characteristics, detailed eligibility criteria, or how incomplete follow-up was handled. The planned ECG schedule is described, but completion of every scheduled measurement is not documented in the registry record.

Fourth, statistical methods are sparsely described. The record names the endpoint, the Bazett formula, and a confidence interval, but does not report the calculation method, handling of missing measurements, analysis population, or multiplicity approach. The deaths entry is not reported, and the adverse-event summary does not include serious-event terms. These gaps should not be filled by assuming that a blank or missing detail represents a zero or a standard analysis choice.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Ondansetron and the QT Interval In Adult Emergency Department Patients — NCT01759420.
• Registry record last updated 2014-06-26; status last verified 2014-06.
• Results first posted 2014-06-26.
• 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

The registry record concerns NCT01759420, titled Ondansetron and the QT Interval In Adult Emergency Department Patients. It lists C.R.Darnall Army Medical Center as sponsor, an enrollment of 28, a start date of 2012-12, primary completion at 2014-05, and status COMPLETED.

The study is observational and describes adult emergency department patients receiving 4mg of IV ondansetron. Its primary outcome is mean maximal QTc change from baseline to 20 minutes, using the Bazett formula. The record describes ECGs every 2 minutes during that period and names a 95% Confidence Interval. The primary numerical estimate and interval are not reported in the registry record.

Number of Adverse Events is listed as a secondary outcome. The adverse-event summary lists 23 participants at risk and zero serious events, and 23 at risk and zero other events. The deaths value is not reported. The registry lists two outcome measures and no analysis records; it does not report the primary analysis population or explain the difference between enrollment and safety denominators.