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 Transversus Abdominis Plane (TAP) Block Using Liposomal Bupivacaine in Metabolic and Bariatric Surgery Patients (NCT05537883), a randomized phase 1 study. The primary outcome is Mean 24 Hour Visual Analogue Scale (VAS) Pain Score.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05537883 |
| Phase | Phase 1 |
| Condition | Morbid Obesity, Bariatric Surgery Candidate |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 72 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Wake Forest University Health Sciences |
| Results posted | Yes |
2. Clinical Question
Population
Patients undergoing metabolic and bariatric surgery, described in the registry record as people with morbid obesity who are bariatric surgery candidates. The registry lists an enrollment of 72. For the primary pain outcome, the registry notes that 35 and 34 participants received the respective treatments, but pain scores were not obtained for everyone.
Intervention
A laparoscopic Transversus Abdominis Plane (TAP) block with liposomal bupivacaine. The listed mixture contains 20 mL liposomal bupivacaine, 30 mL 0.5% bupivacaine, and 100 mL normal saline solution.
Comparator
A TAP block with a bupivacaine-only mixture: 50 mL 0.5% bupivacaine and 100 mL normal saline solution. The registry describes this as the active control group.
Primary question
What was the mean Visual Analogue Scale (VAS) pain score at Hour 24 in each group? The study summary describes an intended investigation of whether plain bupivacaine was equivalent to liposomal bupivacaine for outcomes including length of stay, morphine use, pain, and satisfaction, while costing less. The posted primary outcome is the 24-hour VAS score; it does not by itself address every part of that broader objective.
3. Trial Design
The registry describes a randomized, single-blinded, parallel-group trial of TAP block mixtures for patients undergoing metabolic and bariatric surgery. It lists the phase as PHASE1 and the enrollment as 72. The sponsor is Wake Forest University Health Sciences. The record lists the study as completed, with a start date of 2022-11-29 and a primary completion date of 2023-12-07.
Participants were assigned to a bupivacaine-only active control or a mixture containing liposomal bupivacaine as well as bupivacaine. The record gives the composition of both mixtures, but does not report the method used to generate or conceal the randomization sequence. It identifies the study as single-blinded but does not report who was blinded or how blinding was maintained. Further details about the operative procedures and the timing or delivery of the block are not reported in the registry record.
The primary outcome was the mean VAS pain score at Hour 24. The registry describes a VAS scale ranging from 1 to 10, with 1 indicating no pain and 10 the worst pain one could imagine. The listed secondary outcomes include mean VAS pain scores, mean average morphine equivalences, morphine equivalences at Week 1, postoperative nausea and vomiting, length of hospital stay, and patient satisfaction scores. Although these outcomes are listed, their results are not reported in the registry record.
The study summary describes equivalence as the intended question for plain versus liposomal bupivacaine, and mentions cost as an additional consideration. The registry record does not report an equivalence margin, a cost outcome, or the statistical procedures used to assess equivalence. Thus the design description and stated objective should be distinguished from the evidence available in the posted outcome results.
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: 3 of the subjects were not randomized or assigned
Overall Study
| Stage | Bupivacaine Only | Liposomal Bupivacaine |
|---|---|---|
| STARTED | 35 | 34 |
| COMPLETED | 0 | 0 |
| NOT COMPLETED | 35 | 34 |
Reasons for not completing this period:
| Reason | Bupivacaine Only | Liposomal Bupivacaine |
|---|---|---|
| revisional surgery | 4 | 2 |
| surgeries were cancelled | 0 | 2 |
| not being compliant with the Seamless MD app | 31 | 30 |
Analysis population for the primary outcome, as defined in the registry: The numbers analyzed meaning those who received the bupivacaine or not were 35 and 34 However, the Post-Anesthesia Care Unit team nurses did not obtain pain scores on everyone so what is listed is the data of what we had, which is less. This is why it doesn't add up.
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 | Bupivacaine Only | Liposomal Bupivacaine | Total |
|---|---|---|---|---|
| Participants analysed | 35 | 34 | 69 | |
| Age, Customized | Number of years | 44 (22 to 66) | 43 (23 to 62) | 43.5 (22 to 66) |
| Sex: Female, Male: Female | Participants | 31 | 32 | 63 |
| Sex: Female, Male: Male | Participants | 4 | 2 | 6 |
| 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 | 15 | 14 | 29 |
| Race (NIH/OMB): White | Participants | 19 | 18 | 37 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 1 | 2 | 3 |
6. Primary Endpoint
The registry lists the primary outcome as Mean 24 Hour Visual Analogue Scale (VAS) Pain Score, measured over Hour 24.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Full Range |
| Unit | score on a scale |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the mean VAS pain score at Hour 24 after surgery. A VAS is a patient-reported measure used to represent pain intensity along a defined scale. The registry describes its scale as running from 1 to 10: 1 means no pain, and 10 means the worst pain one could imagine. A group mean gives a single summary of the scores recorded in that group. It can help describe average pain at the specified assessment time, but it does not show how every individual participant scored.
The posted summaries list a mean of 1.0 for the Bupivacaine Only group and 3.0 for the Liposomal Bupivacaine group. The reported full ranges are 0.0 to 5.0 and 0.0 to 9.0, respectively. The reported minimum of 0.0 in each range does not match the scale description, which starts at 1. This discrepancy should be kept visible rather than resolved by assumption; the registry record does not explain it.
A single assessment at Hour 24 describes pain at that time, not pain over the entire postoperative period. The mean also does not communicate uncertainty about the group estimates unless accompanied by appropriate inferential statistics. Confidence intervals, a hypothesis test, and an equivalence analysis are not reported in the registry record. The endpoint is relevant to the stated pain question, but it does not alone establish equivalence or address other outcomes such as opioid use, hospital stay, satisfaction, or cost.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary outcome reports a mean 24-hour VAS score of 1.0 for Bupivacaine Only and 3.0 for Liposomal Bupivacaine. The corresponding full ranges are 0.0 to 5.0 and 0.0 to 9.0. These summaries describe the recorded pain scores; they do not establish whether the observed group contrast is statistically distinguishable from chance or sufficiently precise for a clinical conclusion. A confidence interval and inferential test are not reported in the registry record.
The outcome counts are smaller than the treatment-group counts described in the registry note. That note says 35 and 34 participants received the respective treatments, and explains that PACU team nurses did not obtain pain scores for everyone. The posted primary summaries include 29 and 27 scores. The record does not explain which participants lacked scores, why their scores were unavailable, or how missing values were handled. The available summaries therefore pertain to participants with recorded scores, and may not represent every randomized participant.
The registry's endpoint description says the VAS ranges from 1 to 10, while the observed full ranges start at 0.0 in both groups. This mismatch makes interpretation of the scale coding less certain. The record does not clarify whether zero was a permissible recorded value, whether the scale description is inaccurate, or whether the observed range reflects another recording convention.
The study summary frames the objective as investigating equivalence. Equivalence is not established simply because two group means appear close, nor is it refuted solely by a visible difference in the point summaries. An equivalence conclusion depends on a prespecified acceptable margin and an analysis that evaluates uncertainty relative to that margin. Neither an equivalence margin nor an equivalence test result is reported in the registry record. No p-value or confidence interval is reported for this comparison.
The registry lists six secondary outcomes, including pain, morphine equivalences, nausea and vomiting, length of stay, and satisfaction. Their results are not reported in the registry record. The study summary also mentions cost, but a cost outcome or cost result is not reported. Consequently, the posted primary result cannot answer the full set of questions described in the study summary. It is a descriptive comparison of the available 24-hour scores, not a complete account of comparative effectiveness, equivalence, or cost.
9. Statistical Methods Explained
Statistical interpretation starts with the design and the quantity being summarized. This trial is recorded as randomized, single-blinded, and parallel-group. Randomization is intended, in general, to make assigned groups comparable in expectation, while a parallel design assigns participants to one treatment group rather than crossing treatments within the same participant. The registry record does not report the randomization procedure, allocation concealment, who was blinded, or how blinding was implemented. These details matter when assessing possible selection and measurement biases, but they cannot be filled in from the design labels alone.
What does a group mean describe?
The endpoint is a mean pain score at Hour 24. In general, the mean is an average that summarizes recorded values in a group. It is useful for describing a group's central level, but it does not show the distribution in full or reveal whether individual scores are concentrated near the mean. The registry lists means of 1.0 and 3.0, with full ranges of 0.0 to 5.0 and 0.0 to 9.0. A range identifies the minimum and maximum reported values; it does not indicate how many participants had values near either end. A standard deviation, confidence interval, or other summary of variability is not reported.
The VAS description states a scale from 1 to 10, but both posted ranges have a minimum of 0.0. This is an internal measurement-description issue, not something that can be settled statistically from the group summaries. The registry does not explain whether the score coding included zero or whether the scale description should be read differently. Interpretations that depend on the exact scale limits should therefore be cautious.
How should uncertainty be assessed?
In general, a confidence interval gives a range of values compatible with the data and the assumptions of the analysis. Its width conveys precision: narrower intervals indicate more precise estimates, while wider intervals indicate greater uncertainty. A p-value addresses compatibility of data with a specified null hypothesis under the test's assumptions; it is not the probability that a treatment effect is true. Neither confidence intervals nor a p-value for the primary group comparison are reported in the registry record. Without them, the precision of the observed means and the statistical evidence for a difference cannot be assessed from the posted results.
The registry summary describes the study as investigating equivalence. In general, an equivalence analysis asks whether the plausible treatment difference lies within a prespecified range judged acceptably small. The margin must be defined before examining the results, and the uncertainty around the estimated difference is central to the conclusion. A finding that does not meet a conventional test for difference would not by itself prove equivalence. The equivalence margin and the planned analysis are not reported in the registry record, so the stated objective cannot be evaluated as a formal equivalence claim from the posted summaries.
What do the missing scores mean?
The registry note reports 35 and 34 participants who received the respective treatments, while the primary score summaries are based on 29 and 27 participants. It attributes the smaller outcome counts to PACU team nurses not obtaining pain scores for everyone. In general, missing outcome data can affect interpretation when participants without measurements differ from those with measurements. The direction and size of any such effect cannot be determined from counts alone. The reasons for missingness participant by participant, the missing-data assumptions, and any imputation or sensitivity analysis are not reported in the registry record.
The outcome record therefore describes a subset with recorded Hour 24 scores, rather than a complete set of scores for all participants said to have received treatment. The registry note does not explain how the analysis population was defined beyond this distinction. It does not report whether participants were analyzed according to randomized assignment, treatment received, or another rule. Such population definitions can affect the estimand, which is the treatment effect a study aims to estimate.
How should planning illustrations be read?
In general, sample-size planning uses assumptions about the effect to be detected, variability, significance level, allocation, and statistical method. Any planning illustrations associated with this record are based on the observed effect and are described as illustrations, not as the trial's original design justification. The stated assumptions include a two-sided significance level of 0.05, equal allocation, and a normal approximation; the effect to detect is framed as a stated fraction of the observed effect. Such illustrations do not show that the study had a particular probability of detecting an effect after the results were observed. Sample sizes used for planning are not observed power, and the original sample-size justification is not reported in the registry record.
The registry records zero analyses. No inferential analysis of the primary endpoint, adjustment for covariates, or approach to multiple outcomes is reported. The statistical analysis plan, including any interim analyses, is not reported in the registry record. General statistical principles can clarify what the posted summaries do and do not establish, but they cannot substitute for those missing methods or results.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists six secondary outcomes alongside the primary Hour 24 pain score, and records seven outcome measures. These include pain scores, morphine equivalences, postoperative nausea and vomiting, hospital stay, and satisfaction. The results for the secondary outcomes are not reported in the registry record. A multiplicity strategy, such as prioritizing outcomes or adjusting interpretation for several statistical tests, is also not reported. Without the analyses and results, it is not possible to determine which secondary findings were observed or how any multiple comparisons were handled.
Missing primary outcome scores are explicitly noted. The registry says that 35 and 34 participants received the respective treatments, but that scores were not obtained for everyone; the posted means and ranges are based on 29 and 27 scores. The record does not report the characteristics of participants with missing scores, the reasons for each missing score, or a statistical method for handling missingness. It also does not report sensitivity analyses evaluating how different assumptions about missing scores might affect the results.
The analysis populations and the relationship between randomized assignment and the reported outcome groups are not fully described. Although the registry identifies the study as randomized, it does not report whether the primary comparison followed an intention-to-treat, per-protocol, or other analysis population. The distinction is important, particularly for an equivalence objective, because exclusions or missing outcomes can influence the estimated comparison. These details are not reported in the registry record.
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 |
|---|---|---|---|
| Bupivacaine Only | 0 | 35 | 0.0% |
| Liposomal Bupivacaine | 0 | 34 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Bupivacaine Only | 0 of 35 |
| Liposomal Bupivacaine | 0 of 34 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Bupivacaine Only | 0 of 35 |
| Liposomal Bupivacaine | 0 of 34 |
The registry reports zero serious adverse events in the Bupivacaine Only group among 35 participants at risk and zero among 34 participants at risk in the Liposomal Bupivacaine group. It also records zero other adverse events in each group and zero deaths in each group. These are the posted counts for the groups and event categories; they do not show that every possible adverse event was assessed or that no event occurred outside the registry's reporting definitions.
The record does not list serious adverse-event terms. A zero count in a registry summary is not proof that a treatment is free of risk. It describes the events recorded for the specified groups and reporting period, but the applicable event definitions and detailed ascertainment procedures are not reported in the registry record. The record also does not provide estimates of uncertainty for these counts. Comparisons of rare events are especially limited when only counts are available and the study is not presented with a detailed safety analysis.
These adverse-event figures should be read separately from the pain-score summaries. They do not resolve the missing pain-score issue, establish equivalence on pain, or supply results for the listed secondary outcomes.
12. What the Result Does, and Does Not, Mean
The posted result establishes that the registry contains descriptive Hour 24 VAS summaries for two randomized treatment groups: a mean of 1.0 for Bupivacaine Only and 3.0 for Liposomal Bupivacaine. The full ranges are 0.0 to 5.0 and 0.0 to 9.0. The recorded outcome counts are 29 and 27, while the registry note says 35 and 34 participants received the respective treatments and that nurses did not obtain scores for everyone.
These figures do not establish that the treatments are equivalent or different. The record does not report a confidence interval, p-value, equivalence margin, or equivalence analysis. A point estimate alone does not show how precise the comparison is. In general, a formal equivalence conclusion requires the estimated difference and its uncertainty to be evaluated against a prespecified margin; that information is not reported in the registry record.
The result also does not answer whether the treatments differ in average opioid use, morphine equivalences at Week 1, postoperative nausea and vomiting, length of hospital stay, or patient satisfaction. Those outcomes are listed, but their results are not reported in the registry record. Although the study summary mentions a cost question, a cost outcome or cost result is not reported. The primary pain summary cannot stand in for those distinct outcomes.
Several uncertainties limit interpretation of the pain scores. Scores are missing for some participants said to have received treatment, and the record does not explain how missing values were handled. The stated scale starts at 1, yet the reported range includes 0.0 in both groups. The record does not clarify this discrepancy. Thus the summaries are best read as descriptions of the scores that were recorded, with uncertainty about their precision, missingness, and scale coding. They do not support medical advice or a conclusion about which treatment should be used.
13. Why This Trial Matters Statistically
This trial illustrates why a study objective and a posted result need to be distinguished. The registry summary frames the comparison as an equivalence question, but the primary result consists of group means and ranges without an equivalence margin or inferential analysis. Equivalence is not demonstrated by a descriptive comparison alone. For statistical interpretation, the target question, planned margin, analysis population, and uncertainty around the estimated contrast all matter.
The record also shows why outcome completeness is central to reading trial results. The treatment-group counts in the explanatory note are larger than the counts contributing to the pain summaries, because scores were not obtained for everyone. When missingness is documented but its handling is not, readers cannot tell whether the available scores represent the intended analysis population or whether missing outcomes could alter the comparison.
The difference between the stated VAS limits and the reported full ranges is another practical issue. Statistical summaries are meaningful only with a clear understanding of how measurements were defined and recorded. Here, the scale is described as 1 to 10, while the observed minima are 0.0. The registry does not resolve that mismatch.
Finally, the record lists multiple secondary outcomes and a broader cost objective, but does not report their results. A primary endpoint cannot answer all of those questions. The statistical lesson is to separate the scope of the stated objective from the scope of the available evidence, and to distinguish descriptive results from analyses that quantify uncertainty or test a prespecified claim.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The primary outcome summaries are based on fewer recorded scores than the treatment counts described in the registry note. The record attributes this to pain scores not being obtained for everyone, but does not report the participant-level reasons for missingness or how missing data were handled. This leaves uncertainty about whether the available scores adequately represent the intended groups.
The endpoint description defines the VAS as ranging from 1 to 10, yet the full range for each group includes 0.0. The registry record does not explain the inconsistency. It also reports means and full ranges but no standard deviations, confidence intervals, or inferential comparison for the primary endpoint. The precision of the group summaries is therefore not reported.
The registry describes the study objective as investigating equivalence, but does not report the equivalence margin or an equivalence analysis. Randomization and single blinding are identified, while the procedures for sequence generation, allocation concealment, and blinding are not reported in the registry record. The analysis population is also not specified beyond the note about treatment counts and missing pain scores.
Results for the listed secondary outcomes are not reported in the registry record, and the cost objective in the study summary is not accompanied by a reported cost outcome. These omissions prevent assessment of the broader study questions from the posted results. The registry's sample-size planning illustrations are not the trial's original design justification, which is not reported. Together, these limitations mean the primary summaries should be interpreted as descriptive information about recorded scores, not as a complete statistical assessment of the stated objectives.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Transversus Abdominis Plane (TAP) Block Using Liposomal Bupivacaine in Metabolic and Bariatric Surgery Patients — NCT05537883.
- Registry record last updated 2025-06-11; status last verified 2024-06.
- Results first posted 2025-06-11.
- 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 describes a completed, randomized, single-blinded, parallel-group Phase 1 trial sponsored by Wake Forest University Health Sciences. It lists an enrollment of 72 and compares a bupivacaine-only TAP block mixture with a mixture containing liposomal bupivacaine. The registry lists a start date of 2022-11-29 and a primary completion date of 2023-12-07.
The primary endpoint is the mean VAS pain score at Hour 24. The posted means are 1.0 for Bupivacaine Only and 3.0 for Liposomal Bupivacaine; the full ranges are 0.0 to 5.0 and 0.0 to 9.0. The registry notes that scores were not obtained for everyone. It lists six secondary outcomes, but their results are not reported in the registry record. Inferential comparisons, an equivalence margin, and an equivalence analysis are also not reported.