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 Evaluation of Addition of Dexamethasone to Transversus Abdominis Plane (TAP) Peripheral Nerve Block (NCT01303003), a randomized na study. The primary outcome is Time to First Request of Additional Analgesia.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01303003 |
| Phase | NA |
| Condition | Prostate CA |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | Single |
| Enrollment | 24 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Steward St. Elizabeth's Medical Center of Boston, Inc. |
| Results posted | Yes |
2. Clinical Question
Population
Patients in a study associated with prostate cancer who were to receive postoperative analgesia after abdominal surgery. The registry record lists an enrollment of 24, but does not report further eligibility criteria or participant characteristics.
Intervention
A bilateral transversus abdominis plane (TAP) block using bupivacaine with dexamethasone. The arm description specifies 40cc. of 0.125% bupivicaine and 0.5cc. dexamethasone (2mg.) per side.
Comparator
A bilateral TAP block using bupivacaine with sterile saline instead of dexamethasone. The arm description specifies 40cc. of 0.125% bupivicaine and 0.5cc. sterile saline per side.
Primary question
Does adding dexamethasone to the TAP block change the time until a patient first requests additional analgesia during the 24 hours post-op? The registry record lists this endpoint but reports no outcome data.
The study description frames the question around whether dexamethasone extends the duration of blockade and pain relief when added to a TAP block. Its active comparison is between two versions of the block: one containing dexamethasone and one containing saline. Both descriptions include bupivacaine, so the stated contrast concerns the adjunct rather than the presence or absence of a TAP block.
The registry record identifies prostate cancer as the condition and describes TAP blocks as being used after abdominal surgery. It does not report further details about the enrolled population, the surgery, eligibility criteria, or how participants were assigned to the two treatments in the crossover design. Therefore, the intended clinical question can be described, but the population and treatment sequence cannot be characterized more specifically from the record.
3. Trial Design
The registry classifies the study as randomized, single-masked, and crossover, with an enrollment of 24. Its status is completed. The study dates are recorded as starting in 2010-12 and reaching primary completion in 2012-11. The sponsor is Steward St. Elizabeth's Medical Center of Boston, Inc. The phase is listed as NA.
The two treatment descriptions are bilateral TAP blocks. Treatment Arm 1 combines 40cc. of 0.125% bupivicaine with 0.5cc. dexamethasone (2mg.) per side. Treatment Arm 2 combines 40cc. of 0.125% bupivicaine with 0.5cc. sterile saline per side. The registry lists dexamethasone as a drug and TAP block as a procedure.
In general, a crossover design compares treatments across periods, with participants potentially serving as their own comparison. The registry classification alone does not establish the exact conduct of the crossover. The treatment sequence, timing of periods, whether every participant received both treatments, and any washout or carryover precautions are not reported in the registry record. These details matter when interpreting a crossover comparison because treatment effects may depend on order or persist beyond a period.
Single masking means that some aspect of treatment assignment was masked, but the masked party or parties are not reported in the registry record. The record also does not describe allocation procedures, concealment, treatment administration, or adherence. Randomization can reduce systematic differences in assigned treatments, but the protections it affords depend on how it was implemented and analyzed. Those operational details are not available in the registry record.
The record describes a prospective, randomized, and blinded comparison in its summary, while the structured design classification specifies single masking. It does not provide further detail to resolve who was masked or how masking was maintained. The study is completed, but completion status does not mean that outcome results are available: the primary outcome description explicitly says no data are available for reporting.
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: No data are available for this study, due to the fact that the PI has left the institution. Multiple efforts were made, by Research and senior leadership, to contact the PI, prior to and after his leaving the institution, with no response. Sincere efforts were made to obtain the data for reporting, but the data is unavailable.
Overall Study
| Stage | Treatment Arm 1 | Treatment Arm 2 |
|---|---|---|
| STARTED | 0 | 0 |
| COMPLETED | 0 | 0 |
| NOT COMPLETED | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: No data are available for this study, due to the fact that the PI has left the institution. Multiple efforts were made, by Research and senior leadership, to contact the PI, prior to and after his leaving the institution, with no response. Sincere efforts were made to obtain the data for reporting, but the data is unavailable.
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.
Population: No data are available for this study, due to the fact that the PI has left the institution. Multiple efforts were made, by Research and senior leadership, to contact the PI, prior to and after his leaving the institution, with no response. Sincere efforts were made to obtain the data for reporting, but the data is unavailable.
| Characteristic | Unit | Treatment Arm 1 | Treatment Arm 2 | Total |
|---|---|---|---|---|
| Participants analysed | 0 | 0 | 0 | |
| Age, Categorical: <=18 years | — | — | — | |
| Age, Categorical: Between 18 and 65 years | — | — | — | |
| Age, Categorical: >=65 years | — | — | — | |
| Sex: Female, Male: Female | — | — | — | |
| Sex: Female, Male: Male | — | — | — | |
| Region of Enrollment: United States | participants | — | — | — |
6. Primary Endpoint
The registry lists the primary outcome as Time to First Request of Additional Analgesia, measured over 24 hours post-op.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is titled “Time to First Request of Additional Analgesia,” with a timeframe of 24 hours post-op. It is intended to measure the elapsed time between the postoperative period beginning and a patient's first request for additional analgesia. The endpoint description says that the study would document the time required until that first request.
Time to first request is a time-to-event outcome: the event is the request for additional analgesia, and the measured quantity is the time until that event. In general, this type of endpoint can capture both whether an event occurs during a defined observation period and when it occurs. Its interpretation depends on how timing is recorded, how the observation period is handled, and how participants without a recorded event are treated analytically. These details are not reported in the registry record.
The endpoint is relevant to the study's stated question because the investigators aimed to examine whether the dexamethasone adjunct prolonged blockade and pain relief. A later request could be consistent with a longer interval before additional analgesia is sought, but the endpoint by itself does not directly measure pain intensity or establish why a request was delayed. Patient requests may also depend on factors beyond the block. The registry lists visual analog scales, total opioid use during the first 24 hours post-op, and provider assessments among secondary outcome aims, but does not report their results.
No primary endpoint values or treatment comparison are reported. The registry record attributes the absence of data to the principal investigator's departure from the institution and unsuccessful efforts to obtain the data.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The central interpretive fact is that the registry record contains no data for the primary endpoint. Although the study was completed and the endpoint is defined as time to first request of additional analgesia during the 24 hours post-op, there are no arm-specific estimates, event counts, measures of uncertainty, or reported comparison. The direction and magnitude of any treatment contrast therefore cannot be assessed from the posted results.
The registry's primary outcome description says that no data are available because the principal investigator left the institution. It also says that research staff and senior leadership made multiple efforts to contact the investigator before and after the departure, without response, and made sincere efforts to obtain data for reporting. This account explains the missing result in the registry; it does not reveal what the unreported measurements would have shown.
The record's secondary outcome description names visual analog scales, total opioid use during the first 24 hours post-op, and provider assessments. Their results are not reported in the registry record. The record lists two outcome measures, but does not provide usable secondary outcome estimates or analyses. Consequently, the posted information cannot support a statistical comparison for those measures either.
The adverse-event fields show zero counts for serious and other events, deaths, and the corresponding at-risk fields in each treatment arm. These entries should not be interpreted as evidence that no adverse events occurred. When the at-risk counts are recorded as zero and no further adverse-event detail is reported, the record does not provide an interpretable estimate of event frequency or comparative safety.
The registry lists no analyses. It does not report an effect estimate, confidence interval, p-value, or model for the primary outcome. Without these results, statistical precision and compatibility with a range of possible effects cannot be evaluated. No recalculation from posted summary statistics is possible because outcome summaries are absent.
The sample-size assumptions describe a planning illustration based on an observed effect, using a two-sided significance level of 0.05, equal allocation, and a normal approximation. The record does not provide an observed effect or numerical planning results in the information available for this analysis. Such an illustration is not the trial's observed result, and a planning calculation is not observed power. Since no effect estimate is reported, the illustration cannot fill the gap in the primary outcome evidence.
Overall, the registry establishes the intended comparison and endpoint, but it does not establish whether the dexamethasone-containing block was associated with a longer or shorter time to request additional analgesia. The missing outcome data prevent an efficacy or statistical-significance conclusion from the posted results.
9. Statistical Methods Explained
The registry identifies the study as randomized and crossover, and describes it as single-masked. These classifications provide broad information about the planned comparison, but do not amount to a complete statistical analysis plan. In particular, the randomization method, crossover sequence, period structure, masking details, and outcome analysis are not reported in the registry record.
What does randomization contribute?
In general, randomization assigns treatments by chance to reduce systematic differences between treatment groups. In a crossover study, assignment may concern the order in which treatments are received. A valid analysis must respect that structure rather than treat repeated observations from the same participant as independent. The registry does not state the sequence allocation or the method used to analyze within-participant measurements, so it is not possible to verify how the crossover structure was handled.
In general, crossover designs can control for stable participant characteristics because comparisons may be made within the same person. That advantage depends on suitable treatment periods and assumptions about carryover, period effects, and the outcomes' timing. The registry does not report the period schedule, washout procedures, or any assessment of carryover. No particular crossover analysis can therefore be attributed to this study based on the record.
How should the primary endpoint be analyzed?
Time to first request of additional analgesia is a time-to-event endpoint. In general, time-to-event methods account for both the timing of an event and the possibility that some participants have no recorded event by the end of observation. The registry names a 24 hours post-op timeframe but does not report how observations without a request in that period were handled, whether any records were censored, or what statistical model or test was planned or used.
For a time-to-event comparison, an effect estimate would ordinarily be accompanied by a measure of uncertainty so readers can assess its precision. The registry does not report a treatment contrast, confidence interval, or p-value for this outcome. A confidence interval, in general, describes a range of values compatible with the data and the method's assumptions; it does not replace the underlying data or resolve missing outcome reporting. No interval can be interpreted for this study because none is reported.
What do the planning assumptions say?
The registry records sample-size assumptions for a planning illustration: a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. The planned effect to detect is described as a stated fraction of the observed effect. These assumptions describe a calculation framework, not the trial's own design justification or its observed analysis. The registry does not report a sample-size justification, and no numerical planning results are available in the record information.
In general, a planning sample size depends on the effect targeted, variability or event behavior, the chosen significance level, and the desired power. A calculation based on an observed effect is a retrospective planning illustration, not observed power. It should not be interpreted as evidence that the completed study had adequate power or that any treatment effect was present. Here, the absence of primary outcome results also means the observed effect used for such an illustration cannot be independently assessed from the registry record.
For time-to-event planning, event counts may be central to the calculation; other designs may report participants per arm. The record's assumptions state that time-to-event tables give total events and other tables give participants per arm. No numerical planning outputs or reported event totals are available to interpret.
What cannot be inferred from the posted analysis?
The registry lists zero analyses and does not state a statistical model, covariate adjustment strategy, analysis population, handling of missing observations, or approach to multiple outcomes. No conclusion about the appropriateness of a statistical procedure can be reached without those details and the results. General statistical explanations describe how methods work; they do not substitute for evidence that a method was used in this trial.
10. Multiplicity, Missing Data and Analysis Populations
The registry record does not report a statistical plan for handling multiple outcomes or repeated assessments. The primary endpoint is time to first request of additional analgesia, and the secondary outcome description refers to visual analog scales, total opioid use during the first 24 hours post-op, and provider assessments. The record does not specify whether these outcomes had separate hypotheses, how their timing or scoring was defined, or whether any adjustment for multiple comparisons was planned.
In general, when several outcomes or analyses are examined, the chance of at least one apparently notable result can increase unless the analysis plan accounts for multiplicity. An adjustment is not automatically required in every setting, but the intended hierarchy and interpretation should be clear. Because the registry does not report an analysis plan or outcome results, the impact of multiplicity cannot be evaluated for this study.
Missing data are the major interpretive limitation. The primary outcome description states that no data are available for reporting after the principal investigator left the institution and could not be reached despite multiple efforts. The record does not say whether the measurements were never collected, were collected but unavailable to the reporting team, or were incomplete for some participants. The missingness mechanism and any recovery or imputation procedures are not reported in the registry record.
The record does not describe an intention-to-treat, per-protocol, or other analysis population, and it provides no participant flow or crossover completion details. It is therefore unclear which participants or treatment periods would have contributed to a planned analysis. These omissions, together with the absence of outcome results and analyses, preclude assessment of how missing observations or the analysis population might affect the treatment comparison.
11. What the Result Does, and Does Not, Mean
The registry record establishes what the investigators intended to compare: a bilateral TAP block with bupivacaine and dexamethasone versus a bilateral TAP block with bupivacaine and saline. It also identifies the primary endpoint as time until the first request for additional analgesia during the 24 hours post-op. It does not report the measurements needed to determine how the arms compared.
Accordingly, the record does not show that adding dexamethasone lengthened or shortened the time to a request. It also does not show whether any observed difference, if one existed, was large or small, precise or uncertain, or statistically distinguishable from chance. Those questions require treatment estimates and uncertainty measures, none of which are reported for the primary endpoint.
The same boundary applies to other outcomes. The registry describes intended assessment of visual analog scales, opioid use, and provider assessments, but no results are reported. The adverse-event entries contain zeros in both the event and at-risk fields; they are not interpretable as evidence that adverse events were absent or that the treatments had equivalent safety.
In general, absence of posted results is not evidence of no effect, and it is not evidence of an effect. It is an evidence gap. The record's explanation for why results are unavailable provides context for that gap, but it cannot substitute for the outcome data or establish what the study found.
The completed status and enrollment of 24 describe the registry record, not the completeness or validity of the analyses. Without information on participant flow, crossover periods, missing observations, or statistical methods, it is also not possible to judge how the intended design was implemented. The responsible interpretation is limited to the study question and design as registered, alongside the fact that its outcome comparison cannot be evaluated from the posted results.
12. Why This Trial Matters Statistically
This study illustrates an important distinction between a registered clinical question and an interpretable statistical result. The registry identifies a randomized crossover comparison, specifies two versions of a bilateral TAP block, and names a time-to-event primary endpoint. Those elements make the intended contrast understandable. But without outcome data, the central statistical task—estimating the contrast and its uncertainty—cannot be completed.
The crossover classification also highlights why design details matter. In general, crossover studies can use within-participant comparisons, but interpretation depends on treatment order, period effects, and possible carryover. These features affect how data should be organized and analyzed. The registry does not report the details needed to assess them, so the design label alone cannot establish that the statistical benefits of a crossover approach were realized.
The record also shows why a zero in an adverse-event field requires context. An event count without a meaningful at-risk population does not provide a usable frequency estimate. In this record, the corresponding at-risk fields are also zero, so the entries cannot be treated as reassurance about event occurrence.
Finally, planning calculations and trial results answer different questions. A sample-size illustration based on an observed effect can explore hypothetical planning assumptions, but it is not a treatment estimate and is not observed power. When the observed outcome summaries are unavailable, planning arithmetic cannot recover the missing evidence. The case therefore emphasizes the value of accessible outcome data, analysis methods, and clear reporting of the populations included in analyses.
13. 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 most consequential limitation is the absence of primary outcome data. The registry record says that no data are available for reporting because the principal investigator left the institution and did not respond to multiple contact efforts. Without outcome values, the intended treatment contrast cannot be estimated or interpreted.
Other reporting gaps limit evaluation of the design and analysis. The registry does not report eligibility criteria, participant characteristics, sequence allocation, crossover period details, washout procedures, masking roles, or treatment adherence. It does not describe the analysis population, handling of missing observations, or statistical methods. These details would be needed to assess whether the planned crossover comparison was carried out and analyzed as intended.
The secondary outcome aims are described, but their results are not reported. The adverse-event fields record zero values for both events and at-risk counts, which do not support a meaningful assessment of adverse-event occurrence. The registry also lists no analyses and offers no effect estimates, confidence intervals, or p-values.
Enrollment is reported as 24, but the record does not provide a participant flow or indicate how many participants contributed usable measurements to either treatment period. Enrollment alone cannot establish the analyzed sample or the completeness of follow-up. The record's completed status therefore should not be confused with complete outcome reporting.
These limitations are specific to the registry information available for this study. They do not establish that measurements were never collected or that the intervention had a particular effect; the registry explanation is that data could not be obtained for reporting. The statistical result remains unavailable.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: Evaluation of Addition of Dexamethasone to Transversus Abdominis Plane (TAP) Peripheral Nerve Block — NCT01303003.
- Registry record last updated 2018-09-21; status last verified 2018-09.
- Results first posted 2018-09-21.
- 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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17. Record Summary
The registry record describes a completed randomized, single-masked crossover study with an enrollment of 24 and a condition of prostate cancer. It compares bilateral TAP blocks using bupivacaine with dexamethasone or sterile saline. The primary endpoint is time to first request of additional analgesia during the 24 hours post-op.
The record reports no primary outcome data, attributing their unavailability to the principal investigator's departure and unsuccessful contact efforts. Secondary outcome results and statistical analyses are not reported. Adverse-event fields contain zero event and at-risk counts in both arms, which do not permit an interpretable safety comparison. The intended comparison is clear, but its treatment effect and precision cannot be evaluated from the posted results.