Reletex Versus Standard of Care Therapy for Post-Operative Nausea Control in Patients Undergoing Foregut Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Reletex Versus Standard of Care Therapy for Post-Operative Nausea Control in Patients Undergoing Foregut Surgery (NCT01510379), a randomized na study. The primary outcome is Comparison of Postoperative Nausea and Vomiting Scores Between Groups Treated With a ReletexTM Device and Those Without the Device..

2. Clinical Question

The registry describes a randomized comparison of Reletex added to medication-based prevention and treatment versus medication-based care alone. The primary outcome focuses on patients’ reported nausea and vomiting during the first 24 hours after surgery. The planned hypothesis was that adding the device would reduce postoperative nausea and vomiting and reduce anti-emetic medication use.

The record also reports a secondary outcome: the amount of phenergan used over one week. This helps describe medication use alongside the symptom score, but it is a separate outcome and does not replace the primary comparison. Both groups received scheduled ondansetron and could receive promethazine as needed, so the contrast is the addition of Reletex to that shared medication regimen, rather than Reletex alone versus no treatment.

The registry lists enrollment of 100. The posted primary-outcome results include 49 participants in the Reletex group and 51 in the control group. The record does not report further details about which specific operations participants received or how many had each operation.

3. Trial Design

This was a randomized, parallel-group trial with no masking listed in the registry. The registry lists enrollment of 100 and the study status as completed. The listed start was 2011-08 and primary completion was 2012-07. The phase is recorded as not applicable.

Participants were assigned to one of two groups. The Reletex group received the device plus scheduled intravenous ondansetron, with intravenous promethazine as needed during the hospital stay and promethazine elixir at the same stated dose and frequency after discharge. The control group received the same medication plan without the device. The brief summary describes wearing the device after surgery for 7 days. The registry does not report further details about the method used to generate or conceal assignments, or how adherence to device use was assessed.

The primary outcome was a postoperative nausea and vomiting Likert score from 0 to 10, with the registry defining 0 as no postoperative nausea and vomiting and 10 as the worst postoperative nausea and vomiting. Its stated timeframe was 24 hours. The posted values are group means and standard deviations. The secondary outcome was the amount of phenergan used, measured in milligrams over one week, also reported as group means and standard deviations.

The primary-outcome summaries include 49 participants in the Reletex group and 51 in the control group. The secondary-outcome summaries list the same group counts. Although the trial is described as randomized, the registry record does not report the original sample-size justification, detailed statistical analysis plan, analysis populations, or reported sponsor analyses. There are no posted analyses listed in the record. The between-group estimates discussed in the posted comparison results are recalculated from the group summary statistics, rather than identified as sponsor-reported analyses.

The record gives no further description of masking, so the stated design should be read as unmasked rather than interpreted as evidence that any particular assessment procedure was or was not masked. The registry also does not report details of follow-up completeness, protocol deviations, or the handling of missing outcome data.

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: Enrolled participants were not excluded from the trial before assignment to groups.

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 Comparison of Postoperative Nausea and Vomiting Scores Between Groups Treated With a ReletexTM Device and Those Without the Device., measured over 24 hours.

The primary endpoint is a postoperative nausea and vomiting Likert score assessed at 24 hours. It ranges from 0 to 10, with lower values representing less reported nausea and vomiting according to the scale definition in the registry. The outcome is continuous for the posted analysis, and each group is summarized with a mean and standard deviation.

A patient-reported score can capture symptom severity in a way that is directly relevant to the trial question: whether the device, when added to the medication regimen, is associated with a different level of postoperative nausea and vomiting. A mean gives a group-level summary, while the standard deviation describes how spread out the individual scores are within each group. Neither summary shows the full distribution of scores or how many participants had a particular score.

The stated measurement time is 24 hours, so the result concerns symptoms at that time point. It does not by itself describe symptoms over the full 7-day period during which the device was intended to be worn. The registry record does not report further details about how the score was collected, whether the diary was the source for the primary measure, or how scores were handled if a participant did not complete the assessment.

The primary outcome is distinct from the secondary measure of phenergan use. Symptom scores and medication amounts describe related but different aspects of postoperative care: a difference in one need not imply a corresponding difference in the other. The endpoint should therefore be interpreted within its specified scale and timeframe, and alongside the design and precision of the comparison.

7. Results Posted in the Registry

• Reletex: mean 1.81 versus 2.03 on control; difference -0.22 (95% CI -1.21 to 0.77), standardized effect d = -0.09; z-test p = 0.662.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Quantify the Amounts of Phenergan Used Between the Two Groups.

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Reletex: mean 42.00 versus 57.60 on control; difference -15.60 (95% CI -56.66 to 25.46), standardized effect d = -0.15; z-test p = 0.456.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Reletex and the control. The interval gives the range of effects that remain compatible with the data.

The registry reports one secondary outcome: phenergan use in milligrams over one week. Its group summaries and recalculated comparison point in the same negative direction as the primary mean difference, with lower observed use in the Reletex group. However, the secondary interval includes zero and is wide, and the groups’ medication-use values show substantial variation. The result therefore adds context about medication use but does not provide a precise, independent confirmation of the primary finding.

Symptom scores and medication use are related questions, but they are not interchangeable measures. The primary endpoint records nausea and vomiting scores at 24 hours; the secondary endpoint captures medication amounts across one week. Their timeframes differ, and medication use can reflect more than symptom severity alone. For example, the registry describes use of scheduled ondansetron in both groups and promethazine as needed. The record does not report details that would allow medication use to be interpreted as a direct substitute for symptom measurement.

Secondary outcomes generally carry less confirmatory weight when they are not the primary focus, especially when the record does not describe a prespecified hierarchy or adjustment for multiple comparisons. Testing multiple outcomes can increase the chance of obtaining an apparently notable result by chance. Here, the registry does not report a multiplicity plan, and the secondary outcome is presented as a single measure without a listed sponsor analysis. Its unadjusted result should be treated as exploratory rather than as proof supporting a broader conclusion.

The overall pattern is therefore a directionally similar set of group estimates, accompanied by uncertainty in both outcomes. Agreement in direction can be informative as a descriptive pattern, but it does not remove the uncertainty in the estimates or establish that the outcomes reflect the same underlying effect. The primary result remains the main basis for interpreting the trial’s stated question, while the secondary measure provides additional, limited context.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Quantify the Amounts of Phenergan Used Between the Two Groups.

9. Statistical Interpretation

10. Statistical Methods Explained

The posted between-group estimates are unadjusted recalculations using the group means, standard deviations, and sample sizes. They are not listed as analyses reported by the trial sponsor; the registry record lists no reported analyses. A recalculated estimate is useful for describing the numerical contrast in the posted summaries, but it may not match an analysis that accounts for design details or participant-level data unavailable in the record.

What does the mean difference describe?

For the primary endpoint, the mean difference is expressed as the Reletex group mean minus the control group mean. The reported estimate is -0.22. A negative estimate indicates that the Reletex group had a lower observed mean score. The estimate is on the original 0-10 scale, which keeps its meaning tied to the outcome rather than to a transformed or standardized scale.

A mean difference summarizes the contrast between group averages. It does not say that every participant in one group had a lower score than every participant in the other group. The standard deviations—2.17 for Reletex and 2.83 for control—show that individual scores varied within both groups. Individual-level distributions and the number of participants at each score are not reported in the registry record.

What do the confidence interval and p-value convey?

A confidence interval describes the statistical uncertainty around an estimate under the assumptions of the method used. The primary 95% interval runs from -1.206 to approximately 0.766. Because it includes zero, it does not distinguish a negative difference from no difference or a positive difference with high precision. The unadjusted p-value is 0.662. A p-value measures how compatible the observed data are with a specified null hypothesis under a statistical model; it is not the probability that the null hypothesis is true, nor a measure of the size or importance of an effect.

These recalculations use summary statistics and an unadjusted comparison. They do not account for covariates, stratification, repeated measurements, or other design features unless those are captured in the summaries; the registry does not report whether such features were part of the original analysis plan. No adjustment for multiple outcomes is reported. The posted estimate should therefore be read as a simple comparison rather than a documented adjusted model.

Why does variability matter?

Standard deviation describes dispersion among observations. The primary-score standard deviations are larger than the estimated mean difference in absolute size, indicating that participants’ scores varied substantially around the group averages. When outcome variability is large relative to a mean difference, distinguishing a group contrast from random variation generally requires more information, often through more participants or a more precise measurement.

Over-dispersion is a general concern when observed variability exceeds what a model assumes. It can make standard errors too small if the model underestimates variation, which in turn can make intervals too narrow and tests too optimistic. That is a general statistical point, not a finding that this trial had over-dispersion: the registry does not report a model diagnostic or an analysis addressing it. The displayed standard deviations alone are not enough to establish that a particular model assumption failed.

What assumptions are not documented?

The record does not report the original analysis plan, sample-size justification, choice of primary analysis population, treatment of missing scores, or whether any interim analyses were planned or conducted. It also does not state whether the score was analyzed using a particular parametric model or whether assumptions were checked. No imputation or sensitivity analyses are listed. These absences mean that the posted summary comparisons cannot be taken as a complete account of the trial’s intended statistical methods.

Randomization supports a comparison between assigned groups when allocation is implemented and outcomes are analyzed appropriately, but the registry description alone does not establish that every relevant procedural detail is known. No masking was listed. For a self-reported symptom measure, awareness of assignment could matter in general, but the record does not report an assessment of that possibility. This is a design consideration, not evidence that reporting was biased.

Finally, statistical significance and clinical importance are different questions. The p-value and confidence interval describe statistical evidence and precision under the calculation’s assumptions. The registry does not state a minimum important score difference, so the clinical meaning of the estimated contrast cannot be judged against a prespecified threshold from this record.

11. Confidence Intervals and Precision

The primary mean difference is -0.22 score units, with a 95% confidence interval from -1.206 to approximately 0.766. This interval is broad enough to include differences in both directions, including zero. The point estimate alone gives a single best estimate from the recalculation, but the interval makes clear that the underlying contrast is not precisely determined by these data.

In general, a confidence interval gives a range of values reasonably compatible with the observed data under the statistical model and its assumptions. It is not a range containing a known proportion of individual participants’ scores, and it does not mean that there is a 95% probability that the true effect lies inside this particular calculated interval. Its usefulness is in showing both the estimate and the uncertainty around it.

The primary group standard deviations were 2.17 and 2.83. These are measures of participant-level spread, not uncertainty in the group means. The interval for the mean difference incorporates uncertainty in comparing the group averages, including the variation and sample sizes used in the recalculation. The record does not provide participant-level results or an alternative adjusted confidence interval.

For the secondary medication-use outcome, the recalculated interval runs from -56.66 to 25.46 mg around a mean difference of -15.6 mg. This interval also includes zero and spans values in both directions. Its breadth reflects limited precision for that outcome; the registry’s group summaries also show considerable variation in the amount used.

Neither interval should be read as proof of no effect simply because it includes zero. Conversely, the point estimates’ negative direction does not establish a true reduction. The estimates are compatible with a range of possibilities, and the registry record does not provide a clinical threshold against which to judge whether any value in those ranges would be important.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm, not total event counts. The sample-size assumptions listed for these illustrations are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set to the stated fraction of the observed effect. The trial’s original design assumptions and sample-size justification are not reported in the registry record.

The 80% power column gives the illustrative number of participants per arm for a design with an 80% chance of detecting the specified effect under the stated assumptions, if that effect were the true one. The 90% power column gives the corresponding illustration for a 90% chance. These are planning concepts: power depends on the assumed effect, variability, analysis, and design. The figures are not evidence about the chance that the trial’s result is correct.

As the effect assumed for planning becomes smaller, more participants are needed to distinguish it from random variation under the same assumptions. The displayed rows therefore consider planning for 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. The corresponding per-arm figures are illustrations based on those effect assumptions, not enrollment recommendations.

These numbers are not observed power. Observed power calculated from an observed estimate would largely restate the result and does not resolve uncertainty. The illustrations instead show how strongly planning sample sizes can depend on the assumed effect size. Because the registry’s own design assumptions are not reported, they should not be treated as the original justification for enrolling 100 participants.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -0.220; pooled standard deviation σ = 2.528.
2. n = 2 × (1.96 + 0.842)² × 2.528² / -0.220² = 2,073.3, rounded up to 2,074 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- -0.22                      # observed difference in means
sigma <- 2.52835390509077                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(1510379)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 2,074 (80% power), 2,776 (90% power)
 75% of observed effect: n per arm = 3,686 (80% power), 4,935 (90% power)
 50% of observed effect: n per arm = 8,294 (80% power), 11,103 (90% power)
power.t.test: 2074.3 
Simulated power at n = 2,074 per arm: 0.801 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome and one secondary outcome, but it does not report a plan for handling multiplicity. Multiplicity arises when statistical conclusions are drawn across several outcomes, time points, or comparisons. If each is tested separately, the chance of at least one apparently positive result can increase. A prespecified hierarchy or statistical adjustment can address this issue, but neither is described in the registry record.

The posted p-values are unadjusted recalculations. They should not be interpreted as results corrected for multiple comparisons. The primary outcome is the principal endpoint for the stated research question; the secondary medication-use result is less confirmatory in the absence of a reported hierarchy. The registry does not report additional endpoint analyses or a broader analysis plan that would establish how the sponsor intended to interpret the outcomes together.

The record also does not report how missing scores or medication-use observations were handled, whether all randomized participants were included in each analysis, or the definitions of any analysis populations. Although the outcome summaries list 49 and 51 participants, the record does not explain whether these counts represent all randomized participants, all participants with observed outcomes, or another analysis set. The registry does not report reasons for any missing data or provide a flow of participants through follow-up.

These gaps matter because missingness can affect group comparisons if the probability of having an observed outcome is related to symptoms, treatment assignment, or other factors. Statistical approaches to missing data rely on assumptions; without a reported approach and sensitivity analyses, the robustness of the estimates to missing observations cannot be assessed from the registry record.

The record does not report whether interim analyses were planned or conducted. It also does not report the original sample-size justification or the trial’s detailed statistical analysis plan. These omissions do not establish that such procedures were absent; they mean that they are not documented in the registry record. Interpretation should therefore remain anchored to the posted group summaries and their unadjusted recalculated comparisons.

15. 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 5% reporting threshold.

The adverse-event record lists 0 serious adverse events among 49 participants at risk in the Reletex group and 0 among 51 participants at risk in the control group. It also lists 0 other adverse events in each group, with the same at-risk counts. No serious adverse-event terms are listed.

These figures describe what is recorded for the study groups; they do not establish that the interventions have no safety risks. A zero count in a trial of this size can coexist with uncommon events that were not observed during the study. The registry record does not provide further details about adverse-event definitions, collection procedures, severity categories beyond the posted serious and other groupings, or the duration of safety follow-up.

Deaths are not reported in the registry record. The blank death entries should not be read as a confirmed count of zero. The adverse-event figures also do not explain whether any participants discontinued or whether events were judged related to the device or medications. No such attribution is reported in the registry record.

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

The posted results describe a randomized comparison of Reletex added to scheduled ondansetron and as-needed promethazine versus those medications alone. At 24 hours, the mean symptom score was 1.81 with Reletex and 2.03 with control, and the recalculated mean difference was -0.22. The confidence interval includes zero, and the unadjusted p-value is 0.662. These data do not establish a statistically clear difference in the primary outcome.

That conclusion is not the same as demonstrating that the groups were identical. The interval includes a range of possible differences in either direction, and the record does not specify a threshold for a clinically important change. The estimates therefore leave uncertainty about both the magnitude and practical meaning of any difference.

The secondary measure of phenergan use has a negative estimated difference, but its confidence interval also includes zero. It should be read as a less definitive, separate outcome rather than as confirmation that the device changes medication use. The secondary endpoint covers one week, whereas the primary score is specified at 24 hours.

The comparison does not test the device in the absence of medication-based care. Both groups received scheduled ondansetron and could receive promethazine as needed. The results also do not establish how outcomes might differ in other surgical settings, in patients unlike those enrolled, or with a different medication plan. The record does not report the distribution of specific operations or further participant characteristics that would support detailed subgroup interpretation.

Finally, a trial result is an estimate with uncertainty, not a medical recommendation. The posted data can be used to understand the observed group summaries and the limits of their precision. They do not justify a general claim that Reletex works or does not work, and they do not substitute for clinical judgment or evidence beyond this registry record.

17. Why This Trial Matters Statistically

This trial is a useful statistical example of why a randomized design and a numerical difference do not, by themselves, settle a research question. The primary estimate is in one direction, but the confidence interval includes zero and extends across values on both sides of it. Reporting the estimate together with its uncertainty gives a more complete account than focusing only on the direction of the group means.

The outcome is a bounded 0-10 symptom scale, and the analysis summarizes it with means and standard deviations. That makes the result straightforward to express in score units, while also leaving important details unresolved: the registry does not report the full score distribution, missing-data handling, or the original analysis plan. The record therefore illustrates the value of documenting statistical methods as well as numerical results.

The trial also compares an added device within a shared medication regimen. Clear description of the comparator is essential for interpreting what the randomized contrast represents. Here, the results concern the addition of Reletex to scheduled ondansetron and as-needed promethazine, not the device as a stand-alone treatment.

Finally, the planning illustrations show how assumptions about effect size influence the number of participants required for a future study. Their scale depends on an observed effect that is uncertain, and they are not the original design justification. This distinction matters: planning calculations can inform discussion of future research without being mistaken for evidence that the current trial was adequately or inadequately powered.

18. 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 leaves several trial-specific limitations difficult to assess. It describes the study as randomized and unmasked but does not report the allocation-generation or concealment methods. Because the primary outcome is a symptom score, the absence of masking is relevant to interpretation in general, but the record does not provide information about how participants or outcome assessors were involved in scoring.

The primary score is reported at 24 hours, while device wear was described for 7 days. The record does not provide repeated symptom measurements or a time course that would show whether the observed score pattern persisted beyond the primary assessment. It also does not report details about the diary process, adherence to device use, or the completeness of outcome collection.

The posted results are group summaries rather than participant-level data. The registry does not report an adjusted analysis, missing-data approach, analysis populations, or sensitivity analyses. It is consequently not possible to determine from the record whether the comparison is robust to missing observations, protocol deviations, or other analysis choices. The record also does not give the distribution of operation types or other participant characteristics needed to assess how broadly the findings may apply.

The trial’s original sample-size justification and detailed statistical plan are not reported. The planning illustrations use the observed effect and are not a substitute for the design assumptions used when the study was planned. No clinically important difference is stated, so statistical uncertainty cannot be translated into a prespecified threshold for patient-relevant importance.

Safety reporting is also limited to the posted event counts. Definitions, collection methods, follow-up duration, and attribution are not described, and deaths are not reported in the registry record. These limitations concern what can be established from the registry entry; they do not demonstrate that the procedures or analyses were absent from the conduct of the trial.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Reletex Versus Standard of Care Therapy for Post-Operative Nausea Control in Patients Undergoing Foregut Surgery — NCT01510379.
• Registry record last updated 2014-03-05; status last verified 2014-01.
• Results first posted 2014-03-05.
• 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.

22. Record Summary

The registry describes a completed randomized, parallel-group trial without masking, comparing Reletex plus scheduled ondansetron and as-needed promethazine with the same medication regimen alone after foregut surgery. Enrollment is listed as 100. The primary endpoint was a 0-10 postoperative nausea and vomiting score at 24 hours; the secondary endpoint was phenergan use in milligrams over one week.

The primary group means were 1.81 for Reletex and 2.03 for control. The recalculated mean difference was -0.22, with a 95% confidence interval from -1.206 to approximately 0.766 and an unadjusted p-value of 0.662. The secondary comparison was also uncertain, with an interval that included zero. The registry lists no reported analyses. The original sample-size justification, detailed statistical plan, missing-data methods, and deaths are not reported in the registry record.