Pre Operative Transversus Abdominis Plane Block Laparoscopic Gynecological Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pre Operative Transversus Abdominis Plane Block Laparoscopic Gynecological Surgery (NCT01075074), a randomized na study. The primary outcome is The Quality of Recovery Questionnaire (QoR40) on the Day (24 Hours) After Surgery.

2. Clinical Question

The primary endpoint is a patient-reported measure that combines several aspects of recovery, rather than measuring pain alone. The record also lists secondary outcomes concerning pain burden during early recovery from anesthesia, opioid pain medications consumed during the first 24 hours after surgery, and time to hospital discharge readiness.

The clinical question is therefore broader than whether one block concentration differs from saline on the primary score. The study included three groups, and its posted primary analysis first compared them together, followed by pairwise comparisons. The registry record does not report a specific primary contrast or a planned hierarchy among those pairwise comparisons.

3. Trial Design

The registry identifies this as a randomized, triple-masked, parallel-group study. Its phase is listed as not applicable, and its status is completed. The recorded study start was 2010-08 and primary completion was 2011-03. Northwestern University is listed as the sponsor.

The registry reports enrollment of 75 subjects, randomized in 3 groups of 25. The arms were Ropivacaine 0.5%, Normal Saline, and Ropivacaine 0.25%. The arm descriptions specify bilateral transversus abdominis plane blocks. The saline description gives 15 cc on each side; the ropivacaine descriptions give 15 cc on each side, with the concentration stated for each arm.

There is an internal labeling inconsistency: one arm description is headed Ropivacaine 0.05%, while the description says 0.5% ropivacaine and the outcome arm is labeled Ropivacaine 0.5%. The registry's other ropivacaine arm is labeled Ropivacaine 0.25%. This discrepancy in this discussion should be kept in mind when reading the arm names.

Five subjects were excluded from analysis because the surgeon had to proceed to an open incision from a laparoscopic case during the procedure. The primary endpoint analysis reports n=24 for Ropivacaine 0.5%, n=23 for Normal Saline, and n=23 for Ropivacaine 0.25%. The registry record does not report the identities of the people masked, the method used to generate or conceal random allocation, or further details about the conduct of masking.

The primary endpoint was assessed 24 hours after surgery. The registry lists 3 secondary outcomes and 17 analyses. It does not report the protocol's sample-size justification, an interim-analysis plan, or a prespecified statistical analysis plan.

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:

Analysis population for the primary outcome, as defined in the registry: 75 subjects were randomized in 3 groups of 25, 5 were excluded from analysis because the surgeon had to proceed to an open incision from a laparoscopic case during the procedure.

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 The Quality of Recovery Questionnaire (QoR40) on the Day (24 Hours) After Surgery, measured over 24 hours after surgery.

The primary endpoint was the Quality of Recovery Questionnaire, also called QoR40, on the day 24 hours after surgery. It is a 40-question assessment of recovery following surgery, covering pain, emotional status, physical comfort, physical independence, and support. Each question is scored on a 1 to 5 Likert scale. The registry describes total scores ranging from 40, representing poor recovery, to 200, representing outstanding recovery.

This endpoint is used to capture several dimensions of a patient's reported recovery in one measure. Its breadth can complement outcomes focused on a single symptom or event. It does not, by itself, show which domain accounts for a group difference: the registry reports the total score, not separate primary results for each of the five domains.

The registry reports the median and full range for each group. The median gives the midpoint of the observed scores when ordered, while the full range describes the lowest and highest observed scores. For Ropivacaine 0.5%, the reported median was 172, with a full range of 160 to 190. For Normal Saline, the median was 157, with a full range of 148 to 169. For Ropivacaine 0.25%, the median was 173, with a full range of 165 to 189.

The measure is a patient-reported recovery score, not an objective measure of surgical recovery or a direct measure of pain alone. The registry record does not report how questionnaire items were handled if a response was missing.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The posted primary comparison uses the Kruskal-Wallis test. In general, this is a rank-based method for comparing the distributions of an outcome across multiple independent groups. It ranks the observed scores rather than requiring the analysis to compare group means under a normal-distribution model. It is often useful when outcomes are ordinal or when a distribution may not fit the assumptions of a standard analysis of means. A significant overall test indicates evidence that the groups are not all alike in their outcome distributions; it does not identify the particular groups responsible for the difference.

The registry reports medians and full ranges for QoR40. In general, a median describes the center of ordered observations, while a range gives the observed extremes. These summaries are relatively easy to interpret for a bounded questionnaire score, but they do not convey the full distribution. For example, the registry record does not report quartiles, individual scores, or a distribution plot in the registry record for interpretation.

Pairwise comparisons were reported using the Wilcoxon (Mann-Whitney) method. In general, this rank-based test compares observations between two independent groups. It is sometimes described as a test of medians, but the rank test is not automatically a test of a difference in medians unless additional assumptions about distribution shape are appropriate. The registry labels its effect estimate Median Difference (Net), and the reported estimates and confidence intervals should be understood as the posted analysis results, rather than as differences calculated from the two displayed group medians.

A confidence interval gives a range of values compatible with the data and the analysis method under its assumptions. A narrower interval generally indicates greater precision than a wider one. It is not a guarantee that the true effect lies within the interval, and its interpretation depends on the validity of the design and analysis. The reported 95% intervals for the two comparisons with saline exclude zero; the interval for the comparison between the ropivacaine groups includes zero. The latter result does not prove equivalence: the record does not report an equivalence margin or a non-inferiority margin.

The p-value measures how unusual data at least as inconsistent with a specified null hypothesis would be if that null hypothesis and the test assumptions were correct. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of a difference. The overall Kruskal-Wallis p-value addresses a three-group comparison. The pairwise p-values address separate two-group comparisons. In general, testing multiple comparisons raises a multiplicity question because the chance of at least one false-positive finding can increase across a family of tests. The registry record does not report whether a multiplicity adjustment or a prespecified comparison hierarchy was used.

The primary endpoint is reported as a median with full range, and the tests are rank-based. That pairing is consistent with describing an outcome without relying solely on means and standard deviations. However, the registry record does not state whether the choice of tests was prespecified, whether any assumptions were checked, or whether covariate adjustment was considered. The record also does not report an adjusted estimate for the primary comparison.

Sample-size illustrations are planning scenarios, not observed power. In general, such calculations ask how many participants per arm might be required to detect an assumed effect under chosen statistical assumptions. The stated assumptions for the illustrations are a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect expressed as a fraction of the observed effect. They are not the trial's own design justification and do not demonstrate the power achieved by this study. The registry record does not report the trial's original sample-size rationale.

Over-dispersion is a general concern for count outcomes when observed variation exceeds what a simple count model expects; accounting for it can improve uncertainty estimates. The primary endpoint is a questionnaire score, not a count outcome. The registry entries do not establish that an over-dispersion model was used for any secondary outcome, so no such method can be attributed to the trial.

10. Analyses Reported by the Sponsor

The registry posts the sponsor's own primary analysis as a Kruskal-Wallis comparison of all three groups, with p = 0.006, followed by three Wilcoxon (Mann-Whitney) pairwise analyses. The pairwise results report net median differences, 95% confidence intervals, and p-values. Those are the trial's reported inferential results and should be distinguished from any simple recalculation based on summary statistics.

The registry record does not flag a discrepancy between the posted analysis and a recalculation. The record does not include recalculated estimates in the registry record for this interpretation, so no separate recalculated number is presented. In general, a recalculation from group summaries is unadjusted and may not reproduce an analysis that uses participant-level data, ranks, or a different handling of missing observations. The sponsor's analysis remains the appropriate account of what the registry reports as the trial analysis.

The reported estimate is not necessarily the arithmetic difference between the group medians printed for descriptive purposes. The group summaries and the rank-based pairwise estimates answer related but not identical descriptive and inferential questions. Readers should retain the posted labels and confidence intervals rather than treating an estimate reconstructed from displayed medians as a replacement result.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 17 analyses, alongside 4 outcome measures and 3 secondary outcomes. The primary endpoint has an overall three-group test and three pairwise comparisons. When a study conducts multiple tests, interpretation depends in part on which tests were planned as primary, whether comparisons were selected in advance, and whether the analysis controlled the family-wise error rate or another measure of multiplicity. The registry record does not report a multiplicity adjustment, a testing hierarchy, or which analyses were prespecified.

Consequently, the reported p-values should be read as the results of the individual posted tests, not as evidence that multiplicity was addressed. The overall test and pairwise tests are not interchangeable: the overall test asks whether the three groups differ somewhere, while each pairwise test evaluates a particular two-group comparison. Without a stated plan, the record does not establish how the pairwise findings were intended to be interpreted together.

The registry reports that 5 subjects were excluded from analysis because the surgeon proceeded to an open incision during a laparoscopic case. It gives analyzed primary-endpoint group sizes of n=24, n=23, and n=23. The record does not report a primary-outcome analysis that includes the excluded cases, a sensitivity analysis, or a detailed account of missing questionnaire responses. It also does not say whether the analysis followed an intention-to-treat principle. The number of exclusions and their stated reason are known, but their potential effect on the comparison cannot be quantified from the registry record.

Safety reporting lists 25 at-risk subjects in each group. The registry provides zero serious adverse events in each group, and reports other adverse events in the groups. It does not list deaths, and the death entries are not reported in the registry record. The record does not explain whether adverse-event follow-up was complete for all participants or how missing safety information was handled.

12. 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.

Most frequent non-serious adverse event terms

The registry reports 0 serious adverse events among 25 at-risk subjects in each group: Ropivacaine 0.5%, Normal Saline, and Ropivacaine 0.25%. No serious adverse-event terms are listed. These figures mean that the record reports no serious adverse events in the stated groups; they do not establish that the risk is zero or rule out uncommon events.

The record also reports other adverse events in the groups: 12 in the Ropivacaine 0.5% group, 11 in the Normal Saline group, and 12 in the Ropivacaine 0.25% group, with 25 at risk in each group. These are counts as recorded; the registry entries do not specify the event types, severity, timing, or whether a subject could contribute more than one event. The counts should not be interpreted as percentages or as a comparison of event rates without that information.

Deaths are not reported in the registry record. This differs from a reported zero and should not be read as confirmation that no deaths occurred. The safety figures are limited to the registry's reporting and do not by themselves establish comparative safety.

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

The posted results show that the three groups differed on the primary QoR40 score distribution in the overall Kruskal-Wallis analysis. The group medians were 172 for Ropivacaine 0.5%, 157 for Normal Saline, and 173 for Ropivacaine 0.25%. The pairwise analyses reported differences for each ropivacaine group compared with saline, while the comparison between the two ropivacaine groups had a confidence interval that included zero and p = 1.0.

These results do not show that every participant's recovery score followed the group median, nor do they establish the size of benefit for an individual. The score is a composite of five recovery domains. Since the registry reports the total score rather than separate results for those domains, it does not show which parts of recovery account for the observed group comparisons.

A statistically significant result is not automatically clinically important. The registry record does not report a threshold for a meaningful QoR40 difference, so the clinical importance of the reported estimates cannot be determined from the posted results alone. Likewise, the comparison between the ropivacaine groups does not establish that their effects are equivalent: no equivalence design or margin is reported.

The inference is also limited to the analyzed study groups and the 24-hour measurement. Five subjects were excluded after the procedure changed from laparoscopic to open incision, and the registry does not report a primary analysis including them. The posted results do not establish effects on all secondary outcomes, longer-term recovery, or other surgical settings. They describe the comparisons and uncertainty reported for this trial, not a general rule for every patient or procedure.

14. Why This Trial Matters Statistically

This study illustrates why a three-arm trial needs both an overall comparison and careful interpretation of pairwise results. The overall test indicates whether the group distributions show evidence of difference, but it does not identify which treatment groups account for that result. Pairwise analyses add detail, yet their interpretation depends on how multiple comparisons were planned and handled. The registry record does not report that plan.

It also highlights the difference between a patient-reported composite endpoint and a single symptom measure. QoR40 covers pain, emotional status, physical comfort, physical independence, and support. A group difference in the total score can be relevant to recovery as a whole, but without domain-specific primary results it cannot reveal the contribution of each component.

The study's analysis population is important to interpreting its estimates. Five cases were excluded because an open incision was required, and the registry reports the analyzed group sizes separately. This makes clear that enrollment and analysis populations are not necessarily identical. The record does not provide sensitivity analyses to show whether the result changes under a different handling of those cases.

Finally, the data show how precision and statistical evidence should be read together. The pairwise confidence intervals give ranges of uncertainty, while the p-values summarize evidence against their respective null hypotheses. Neither alone describes clinical importance. The registry does not state a clinically meaningful difference threshold, and a non-significant comparison between the two ropivacaine groups does not demonstrate equivalence.

15. 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 gives limited detail about several design and analysis features needed to assess risk of bias. It identifies randomization and triple masking, but does not report the sequence-generation method, allocation concealment, or who was masked. It does not provide the protocol, a prespecified analysis plan, or the sample-size justification. These details are not reported in the registry record.

The primary outcome analysis excludes 5 subjects whose laparoscopic procedures required an open incision. The stated reason is clear, but the record does not report their outcomes, a sensitivity analysis, or an analysis retaining them in their randomized groups. It also does not describe how missing QoR40 responses were handled. The analyzed group sizes are reported, but the basis for each missing or excluded observation beyond the stated conversions is not described.

There is an internal arm-label inconsistency: the Ropivacaine 0.05% arm description refers to 0.5% ropivacaine, and the outcome arm is labeled Ropivacaine 0.5%. The other ropivacaine group is labeled Ropivacaine 0.25%. The registry record does not clarify the inconsistent text. The primary results are therefore best described using the outcome arm labels while noting the discrepancy.

The record reports several analyses but does not state whether p-values were adjusted for multiple testing or identify a prespecified hierarchy. It also does not report a threshold for clinically important change in QoR40. The posted endpoint summaries are medians and full ranges, which do not provide a complete account of outcome distributions. Secondary-outcome estimates and details sufficient to assess all those outcomes are not included in the registry record for interpretation.

Safety reporting is similarly limited: the registry provides serious-event and other-event counts but does not report event terms for the other events, detailed follow-up, or death counts. These limitations restrict what can be inferred about precision, clinical importance, and generalizability from the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Pre Operative Transversus Abdominis Plane Block Laparoscopic Gynecological Surgery — NCT01075074.
• Registry record last updated 2013-11-21; status last verified 2013-10.
• Results first posted 2012-04-03.
• 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.

19. Record Summary

NCT01075074 is a completed, randomized, triple-masked, parallel-group study sponsored by Northwestern University. It compared bilateral transversus abdominis plane blocks with ropivacaine at two concentrations against normal saline in outpatient laparoscopic gynecological surgery. The registry reports enrollment of 75 subjects and identifies 5 exclusions after conversion to an open incision.

The primary endpoint was QoR40 at 24 hours after surgery. The overall Kruskal-Wallis test reported p = 0.006. Pairwise Wilcoxon (Mann-Whitney) analyses reported differences for each ropivacaine group compared with saline, while the comparison between the ropivacaine groups reported p = 1.0 and a 95% confidence interval that included zero. The record also lists secondary outcomes on early recovery pain burden, opioid use during the first 24 hours, and discharge readiness.

The registry does not report a multiplicity plan, a clinically important score threshold, or detailed handling of missing outcome data. An inconsistency in one ropivacaine arm description should also be noted when interpreting the arm labels.