This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Prevention of Postoperative Nausea and Vomiting (PONV) in Surgical Patients (NCT00757822), a randomized na study. The primary outcome is Incidence of Postoperative Nausea and Vomiting.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00757822 |
| Phase | NA |
| Condition | Postoperative Nausea and Vomiting |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Triple |
| Enrollment | 216 |
| Arms in the primary outcome | n/a |
| Lead sponsor | VA Office of Research and Development |
| Results posted | Yes |
2. Clinical Question
Population
Surgical patients in the per-protocol population. The registry record lists postoperative nausea and vomiting as the condition and an enrollment of 216.
Intervention
Dronabinol, described in the study summary as an oral drug regimen.
Comparator
Ondansetron, described in the study summary as an intravenous drug regimen.
Primary question
What was the incidence of postoperative nausea and vomiting during the post-operative care unit stay in each treatment group? A single comparison and its outcome results are not reported in the registry record.
The clinical question concerns prevention of postoperative nausea and vomiting (PONV) following surgery. The primary outcome is titled “Incidence of Postoperative Nausea and Vomiting.” Its description says that postoperative nausea and postoperative vomiting were assessed during the post-operative care unit (PACU) stay. The listed timeframe describes the PACU stay on the day of surgery, from the end of surgery until transfer to a discharge unit or another hospital unit.
The study summary characterizes the comparison as oral dronabinol versus intravenous ondansetron. The registry record identifies two drug interventions and describes a randomized, parallel-group design. It does not report the incidence values for the treatment groups, a treatment-effect estimate, or uncertainty around an estimate. It also does not reduce the primary outcome to a single comparison: the registry record notes several categories or time points. Consequently, the record supports describing the question and outcome definition, but not stating which group had a higher or lower incidence.
3. Trial Design
The registry record describes a randomized, triple-masked, parallel trial with an enrollment of 216. It lists dronabinol and ondansetron as the two drug interventions and describes the arms as dronabinol and ondansetron, respectively. The study summary specifies an oral dronabinol regimen and an intravenous ondansetron regimen. The phase is listed as not applicable.
The primary outcome is identified as the incidence of postoperative nausea and vomiting, assessed during the PACU stay. The primary population is per protocol. A per-protocol population generally includes participants who meet specified criteria for adherence to the study procedures; the registry record does not describe the criteria used to define this population. It therefore does not establish how many participants were included in the primary analysis or how exclusions were handled.
The registry record lists five secondary outcomes: PACU length of stay; post-surgery hospital admissions after an outpatient abdominal procedure; post-operative antiemetic use; willingness to take pre-operative medication; and willingness to pay extra money for preventive medication. The record also reports eight outcome measures and ten analyses, but does not explain how those counts relate to the listed outcomes or how they were organized.
The listed study status is completed. The record gives a start of 2009-12 and a primary completion of 2013-12. The sponsor is the VA Office of Research and Development. Information on the randomization procedure, allocation concealment, exact masking roles, treatment schedules, eligibility criteria, and trial-specific 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.
Before assignment: 36 participants were withdrawn prior to assignment into a treatment arm: 8 participants voluntarily withdrew prior to surgery date, 2 did not meet inclusion criteria, 6 had exclusion criteria, 3 withdrawn when study was closed to enrollment, 17 were withdrawn due to cancellation or re-scheduled surgery incompatible with study schedules.
Overall Study
| Stage | Arm 1: Dronabinol | Arm 2: Ondansetron |
|---|---|---|
| STARTED | 92 | 88 |
| Day of Surgery (DOS) Assessment | 92 | 88 |
| Withdrawal by Subject-no Intervention | 1 | 3 |
| DOS Withdrawn by Investigator | 6 | 11 |
| Received Study Intervention | 85 | 74 |
| DOS: Post-operative Assessments | 85 | 74 |
| 24-48 hr Telephone Assessment | 85 | 74 |
| 2-6 wk Post-op Assessment | 85 | 74 |
| Data Entry, QC Assessment | 85 | 74 |
| Withdrawn-low-risk for PONV | 12 | 9 |
| Withdrawn-protocol Deviation | 9 | 8 |
| Data Lock, Unblinding Analysis | 64 | 57 |
Analysis population for the primary outcome, as defined in the registry: Per protocol
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.
| Characteristic | Unit | Arm 1: Dronabinol | Arm 2: Ondansetron | Total |
|---|---|---|---|---|
| Participants analysed | 64 | 57 | 121 | |
| Age, Continuous | years | 57.8 (SD 12.5) | 57.6 (SD 13.2) | 57.7 (SD 12.7) |
| Sex: Female, Male: Female | Participants | 5 | 2 | 7 |
| Sex: Female, Male: Male | Participants | 59 | 55 | 114 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 6 | 8 | 14 |
| Race (NIH/OMB): White | Participants | 58 | 48 | 106 |
| Race (NIH/OMB): More than one race | Participants | 0 | 1 | 1 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Risk scores for PONV: K score=2 | participants | 44 | 35 | 79 |
| Risk scores for PONV: K score >2 | participants | 20 | 22 | 42 |
6. Primary Endpoint
The registry lists the primary outcome as Incidence of Postoperative Nausea and Vomiting, measured over Post-operative Care Unit (PACU) length of stay on day of surgery (time from end of surgery to transfer to discharge unit or other hospital unit).
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | percentage of participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the incidence of postoperative nausea and vomiting during the PACU stay. The registry description says that postoperative nausea and postoperative vomiting were assessed during that stay. The timeframe is the PACU stay on the day of surgery, described as running from the end of surgery until transfer to a discharge unit or another hospital unit. The primary outcome is expressed as a percentage of participants, and the population is per protocol.
In general, an incidence measure describes how often an event occurs within a defined population and observation period. Using a percentage can make event frequency interpretable relative to the number of participants assessed. Defining a specific observation period also matters: an outcome recorded during the PACU stay does not, by itself, describe symptoms outside that period.
The registry record does not report the group-specific percentages, the counts underlying them, or a single comparison. It notes that the primary outcome has several categories or time points and was not reduced to one comparison. The record therefore does not establish whether nausea and vomiting were combined, analyzed separately, or handled in another way across those categories and time points. It also does not report the endpoint’s detailed operational definition, such as the criteria used to classify an event. These omissions limit interpretation of what an endpoint estimate would represent, even before considering its precision.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record defines a randomized comparison of dronabinol and ondansetron for prevention of postoperative nausea and vomiting. It identifies the primary outcome and its assessment period, but it does not report a single primary-outcome comparison or the results needed to interpret one. In particular, group-specific incidence values, an effect estimate, a confidence interval, and a statistical test result are not reported in the registry record. No claim about which regimen was associated with more or less nausea or vomiting can be drawn from the outcome information in this record.
The record says that the primary outcome had several categories or time points and was not reduced to one comparison. That matters because separate categories or observation points can yield different estimates and different interpretations. A reader would need to know which outcome definition and time point correspond to each estimate, how participants were counted, and which comparison was designated as primary. Those details are not reported in the registry record.
The primary population is per protocol. This means the outcome is identified for a population defined by protocol adherence, but the record does not give the eligibility rules for that population, its size, or the reasons participants may have been excluded. General statistical interpretation distinguishes a per-protocol analysis from an analysis retaining all randomized participants: they answer related but not necessarily identical questions. Without the participant flow and analysis details, the potential effect of exclusions cannot be assessed.
The enrollment is 216, but enrollment alone does not establish how many participants contributed data to the primary endpoint or to each secondary outcome. Nor does it establish the precision of a treatment comparison. Precision depends on the observed data, including event counts and the number analyzed in each group. Those outcome details are not reported in the registry record.
The registry lists secondary outcomes related to PACU length of stay, hospital admissions after outpatient abdominal procedures, post-operative antiemetic use, and patient satisfaction preferences. It does not report their results or the analysis methods for them. The presence of multiple outcomes makes it important to know which comparisons were planned and how multiplicity was considered; that information is not reported in the registry record.
Accordingly, the record supports a description of the trial question, design, and outcome timing, but not an estimate of treatment effect. A missing result in the registry record is not evidence that an effect was absent, and it is not evidence that the treatments were equivalent. The registry information alone cannot establish the direction, magnitude, or precision of any difference in postoperative nausea or vomiting.
9. Statistical Methods Explained
What does randomization contribute?
In general, randomization assigns participants to treatment groups using a chance-based process. Its statistical purpose is to reduce systematic differences between groups at the point of assignment, including differences that may be known or unknown to investigators. It does not guarantee that groups will be identical, particularly in a finite trial, and it does not remove the need to describe the analysis population and missing outcome data.
The registry record identifies the allocation as randomized and the model as parallel. A parallel design compares groups assigned to different interventions, with each participant belonging to one assigned arm. The record does not describe how the random sequence was generated, how assignments were concealed, or whether any stratification or blocking was used. Those methods are not reported in the registry record.
What does masking mean for interpretation?
The masking field is listed as triple. In general, masking can reduce the influence of treatment knowledge on participant experience, care decisions, outcome assessment, or analysis. The exact people or roles masked, and the procedures used to maintain masking, are not reported in the registry record. The label alone does not identify which potential sources of bias were addressed.
What does a percentage endpoint represent?
The primary outcome is classified as a percentage of participants with an event. In general, such a measure expresses the number meeting an event definition relative to the participants assessed. Interpretation depends on the event definition, the observation window, and the analysis population. Here the registry describes assessment of postoperative nausea and vomiting during PACU stay and identifies the primary population as per protocol. It does not report group-specific event counts or percentages, nor does it specify how the nausea and vomiting categories or time points were combined or compared.
In general, a confidence interval describes a range of values compatible with the data under the assumptions of the analysis. It communicates uncertainty around an estimate, rather than guaranteeing that the true value lies within the interval. No primary-outcome confidence interval or other measure of precision is reported in the registry record. A p-value, if reported, would address compatibility with a specified statistical null model; it would not by itself convey the size or practical importance of an effect. No primary-outcome p-value is reported in the registry record.
Why does the analysis population matter?
The primary population is per protocol. In general, a per-protocol analysis focuses on participants meeting specified study-compliance criteria. Such an analysis can differ from an analysis based on all randomized participants, because exclusion or non-adherence after randomization may affect the composition of the analyzed groups. The registry record does not report the per-protocol criteria, numbers analyzed, participant flow, or reasons for any exclusions. It also does not identify an intention-to-treat analysis for the primary outcome.
Missing outcome data can affect an estimate if the chance of missingness is related to treatment assignment or the outcome. General approaches include describing the extent and reasons for missingness, defining how missing observations are handled, and assessing whether conclusions depend on assumptions about them. The registry record does not report missing-data counts or methods.
How should multiple outcomes be considered?
The record lists several secondary outcomes and reports eight outcome measures and ten analyses. It also indicates that the primary outcome has several categories or time points and was not reduced to one comparison. General statistical practice distinguishes a prespecified primary comparison from additional analyses. When many hypotheses are tested, the chance of finding at least one apparently unusual result can increase unless the analysis plan accounts for multiplicity. Possible approaches vary, and no particular approach should be attributed to this trial: the multiplicity plan is not reported in the registry record.
The record does not provide the statistical test, model, covariate adjustment, or handling of repeated observations for the primary outcome. It does not report an analysis plan or a sample-size justification. The trial’s statistical methods therefore cannot be reconstructed from the registry information. General concepts can explain what those methods would address, but they cannot substitute for the methods actually used.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists several secondary outcomes and reports eight outcome measures and ten analyses. It also notes that the primary outcome has several categories or time points and was not reduced to one comparison. These features make it important to know which endpoint, category, time point, and contrast were treated as primary, and whether the interpretation of additional analyses accounted for multiple comparisons. A multiplicity strategy is not reported in the registry record, so it is not possible to determine how the risk of chance findings across analyses was handled.
The primary population is per protocol. The criteria for that population, the number of participants analyzed, and the participant flow from enrollment to analysis are not reported in the registry record. The record also does not report missing-outcome counts, reasons for missingness, or methods for handling missing data. Without those details, it is not possible to judge whether incomplete observations or exclusions could have influenced the reported analysis.
The record does not describe an intention-to-treat analysis or explain whether any sensitivity analyses were performed. It does not report prespecified statistical hypotheses, a statistical analysis plan, or a sample-size justification. These omissions do not establish that such procedures were absent; they mean they are not reported in the registry record. As a result, the status of multiplicity control, missing-data handling, and analysis-population decisions cannot be evaluated from the registry information.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Dronabinol- Experimental Therapy | 13 | 92 | 14.1% |
| Ondansetron-control Therapy | 10 | 88 | 11.4% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Dronabinol- Experimental Therapy | 2 of 92 |
| Ondansetron-control Therapy | 6 of 88 |
Most frequent serious adverse event terms
| Event term | Organ system | Dronabinol- Experimental Therapy | Ondansetron-control Therapy |
|---|---|---|---|
| overnight hospitalization secondary to urinary retention | Surgical and medical procedures | 4 of 92 | 3 of 88 |
| overnight hospitalization secondary to unanticipated extensive surgery | Surgical and medical procedures | 3 of 92 | 3 of 88 |
| overnight hospitalization secondary to excessive postoperative pain | Surgical and medical procedures | 2 of 92 | 1 of 88 |
| post-operative complication due to surgery | Surgical and medical procedures | 3 of 92 | 0 of 88 |
| hospitalization due to co-morbid preexisting conditions | Gastrointestinal disorders | 0 of 92 | 2 of 88 |
| post-operative overnight hospitalization secondary to low sPO2 | Respiratory, thoracic and mediastinal disorders | 1 of 92 | 0 of 88 |
| hospitilization due to co-morbid preexisting conditions | Cardiac disorders | 0 of 92 | 1 of 88 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Dronabinol- Experimental Therapy | Ondansetron-control Therapy |
|---|---|---|---|
| Swelling at incision site | Surgical and medical procedures | 2 of 92 | 6 of 88 |
Serious events with the highest arm-level rate: overnight hospitalization secondary to urinary retention (4.3%), overnight hospitalization secondary to unanticipated extensive surgery (3.4%), post-operative complication due to surgery (3.3%), hospitalization due to co-morbid preexisting conditions (2.3%), overnight hospitalization secondary to excessive postoperative pain (2.2%).
The safety record separates serious adverse events from other adverse events for the two arms. For dronabinol, the registry lists 92 participants at risk, 13 affected by serious adverse events, and 2 affected by other adverse events. For ondansetron, it lists 88 participants at risk, 10 affected by serious adverse events, and 6 affected by other adverse events. These are the registry’s recorded counts; they do not, on their own, establish whether events were caused by a study drug.
The listed serious-event terms include overnight hospitalization secondary to urinary retention (4.3%), overnight hospitalization secondary to unanticipated extensive surgery (3.4%), post-operative complication due to surgery (3.3%), hospitalization due to co-morbid preexisting conditions (2.3%), overnight hospitalization secondary to excessive postoperative pain (2.2%), and hospitilization due to co-morbid preexisting conditions (1.1%). The registry record does not explain the denominators or the relationship between these listed percentages and the arm-level counts. It also does not report a comparative safety analysis or the method used to determine whether an event was treatment-related.
Deaths are not reported in the registry record. The event counts and terms should therefore be read as descriptive registry entries, not as evidence that one regimen is safer or more hazardous than the other.
12. What the Result Does, and Does Not, Mean
The registry record establishes that this was a randomized, triple-masked, parallel comparison of dronabinol and ondansetron, with an enrollment of 216. It identifies postoperative nausea and vomiting during PACU stay as the primary outcome and specifies a per-protocol population. Those details clarify the trial question and the intended setting and time period for the primary assessment.
The record does not provide a single primary-outcome comparison or group-specific outcome results. It therefore does not establish the direction or size of any difference between the interventions, how precisely a difference was estimated, or whether the observed data were compatible with a range of possible effects. The absence of those results from the registry record should not be interpreted as a null finding or as evidence of equivalence.
The primary endpoint is described as including several categories or time points, and the registry record does not explain how those were handled. It also does not report the number analyzed per arm for the primary outcome, the event counts, or the statistical model. These gaps make it impossible to assess the endpoint definition’s detailed implementation, the precision of a comparison, or the influence of the analysis population.
The registry lists secondary outcomes and adverse-event counts, but does not provide results for the secondary outcomes or a comparative analysis of safety. The listed adverse-event terms and counts are descriptive and do not establish causation. Interpretation is further limited by the absence of reported information on missing data, analysis planning, multiplicity, and the per-protocol criteria.
In general, a registry record can identify what a trial set out to study without providing enough information to assess its findings. For this trial, the design and outcome framework are recorded, but the primary efficacy results and key analysis details are not reported in the registry record. Any conclusion about relative efficacy, equivalence, or comparative safety would go beyond the information recorded.
13. Why This Trial Matters Statistically
This trial is statistically notable because its registry record identifies a clear comparative question while leaving the primary comparison unresolved in the recorded results. Randomized assignment, triple masking, and a parallel design describe important features of the study structure. The primary outcome is also tied to a defined setting: nausea and vomiting assessed during PACU stay. These elements are necessary for understanding what the trial was designed to compare.
At the same time, a defined design does not replace reporting the analyzed outcomes. The record identifies several categories or time points for the primary outcome but does not reduce them to one comparison. It does not report group-specific incidence, an effect estimate, or its precision. Readers therefore cannot evaluate whether the study produced a clear signal, a wide range of plausible effects, or results that differed across outcome definitions or time points.
The per-protocol primary population also illustrates why analysis-population details matter. General statistical interpretation depends on knowing who contributed data, how adherence was defined, and what happened to participants with missing outcomes. Those details are not reported in the registry record. Likewise, multiple listed outcomes and analyses make it important to understand which comparisons were prespecified and how multiplicity was addressed, but that information is not reported.
The broader statistical lesson is that trial design, endpoint definition, analysis population, and result reporting work together. Without outcome counts, estimates, uncertainty measures, and analysis details, the registry record can describe the question but cannot support an assessment of the comparative result. This distinction is important when interpreting any completed trial record.
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 registry record constrain interpretation. Although the primary outcome is described as incidence of postoperative nausea and vomiting during PACU stay, the record says it involved several categories or time points and was not reduced to one comparison. It does not give the category-specific definitions or clarify whether nausea and vomiting were combined or analyzed separately. Nor does it report a single primary estimate, event counts, or group-specific percentages.
The record identifies the primary population as per protocol but does not state the criteria for inclusion in that population or the number analyzed. It does not provide participant flow, explain exclusions, or report missing-outcome information. Enrollment is recorded as 216, but that figure does not establish the number contributing data to any particular outcome.
Information on the statistical analysis is also limited. The registry record does not report the statistical test or model, any covariate adjustment, the analysis plan, a sample-size justification, or the handling of multiplicity across outcomes and analyses. Details of sequence generation, allocation concealment, and the people covered by triple masking are not reported.
The safety information is presented as counts and listed event terms, without a reported comparative safety analysis or explanation of the relationship between the listed term percentages and the group-level counts. Deaths are not reported in the registry record. Finally, the record lists secondary outcomes without reporting their results. These limitations apply to what the registry record reports; they do not establish what methods or results may have been documented elsewhere.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Prevention of Postoperative Nausea and Vomiting (PONV) in Surgical Patients — NCT00757822.
- Registry record last updated 2016-05-13; status last verified 2016-04.
- Results first posted 2016-05-13.
- 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.
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18. Record Summary
The registry record describes a completed randomized, triple-masked, parallel trial of dronabinol versus ondansetron for prevention of postoperative nausea and vomiting. Enrollment was 216; the primary outcome was incidence of postoperative nausea and vomiting during PACU stay, in a per-protocol population. The record lists five secondary outcomes, along with serious and other adverse-event counts by arm.
A single primary-outcome comparison, group-specific incidence results, an effect estimate, and measures of precision are not reported in the registry record. The record notes several primary-outcome categories or time points and does not reduce them to one comparison. Analysis-population criteria, missing-data handling, multiplicity methods, and a statistical analysis plan are also not reported. The recorded information describes the trial framework, but does not permit interpretation of its comparative efficacy or a comparative safety conclusion.