Preemptive Analgesia Following Uterine Artery Embolization: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Preemptive Analgesia Following Uterine Artery Embolization (NCT01555073), a randomized phase 4 study. The primary outcome is Post Operative Pain Control.

2. Clinical Question

In statistical terms, the study question concerns whether pain outcomes differed among the listed regimens over the stated follow-up period. The registry describes a randomized, blinded comparison, but its analysis information does not specify which treatment contrasts were primary. It therefore is not possible to identify a single prespecified statistical comparison from this record. The registry lists quality of life as a secondary outcome, but does not provide a numerical result for that outcome either. These omissions limit what can be concluded from the posted record: it describes the intended question and treatment groups, but does not supply results with which to estimate the size or precision of any group differences.

3. Trial Design

The study, NCT01555073, is titled “Preemptive Analgesia Following Uterine Artery Embolization.” Northwestern University is listed as the sponsor. The registry identifies it as a phase 4, randomized, triple-masked study, with enrollment of 23. Its recorded start is 2011-10, primary completion is 2013-08, and status is terminated.

The intervention descriptions identify four groups: pregabalin/celecoxib, pregabalin/placebo, celecoxib/placebo, and placebo. The active regimen descriptions refer to twice-daily dosing for 13 days. For the placebo group, the record also describes two placebo tablets on the day of surgery. The registry's study-model field says “single group,” which does not match the four groups listed in the intervention and arm descriptions. That internal inconsistency makes the design metadata less clear; the record does not explain it.

Randomization means that assignment is intended to use a chance-based process. In general, random assignment can reduce systematic differences between groups at the start of a study, although it cannot guarantee balance in a small trial. Masking is intended to limit the influence of knowledge about treatment assignment on care, reporting, or assessment. The record labels masking as triple but does not identify which roles were masked or describe how masking was maintained.

The registry describes immediate and longer-term post-operative pain control as the main focus, with quality of life listed as a secondary outcome. It gives an expected average timeframe of 12 weeks for the primary outcome. Early termination is linked in the outcome description to loss of follow-up for the primary outcome at 3 months. Details of recruitment, allocation procedures, follow-up schedules, and the reasons for the stated group sizes are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Early termination due to lost of follow-up for primary outcome at 3 months

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: Baseline Analysis population description

6. Primary Endpoint

The registry lists the primary outcome as Post Operative Pain Control, measured over Expected average of 12 weeks.

The stated primary endpoint is post-operative pain control. The record says this outcome was intended to evaluate pain in the immediate period after uterine artery embolization and in the months following the procedure. Its expected average timeframe is 12 weeks. Pain is a patient-centered outcome: in general, measuring it can describe the symptom burden that patients experience during recovery, rather than relying only on procedural or laboratory measures.

The registry does not specify the pain instrument, scale, scoring direction, measurement schedule, or summary measure. It also does not identify a threshold for a clinically important difference. The outcome fields for units and statistical parameters are blank, so the endpoint cannot be interpreted as a particular mean, change score, category, or event rate from this record alone. No group-level pain values, treatment-effect estimates, confidence intervals, or tests are reported.

The endpoint description notes early termination because of loss of follow-up for the primary outcome at 3 months. This matters because missing follow-up can affect both the amount of information available and the interpretation of the observed outcomes. The registry does not report how much follow-up was available at each time point or how missing measurements were handled. Quality of life is listed separately as a secondary outcome, but the record does not provide its measurement method or results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods are important because they define how observations are turned into estimates and how uncertainty is assessed. The registry record identifies randomization and masking, but does not report a detailed statistical analysis plan or outcome analysis. The explanations below describe general principles and do not imply that a particular method was used in this trial.

What does randomization contribute?

In general, randomization assigns participants to groups by chance. Its purpose is to reduce the risk that treatment groups differ systematically in factors that could influence outcomes. Randomization does not ensure that groups will be identical, especially when group sizes are limited. Baseline descriptions and an analysis plan are useful for understanding the achieved groups, but detailed baseline results are not reported in the registry record.

Masking is a separate design feature. In general, masking can reduce the influence of treatment knowledge on behavior, outcome reporting, or outcome assessment. The registry labels the study triple-masked, but does not say which people were masked or how the masking procedure worked. The label alone does not establish whether masking was maintained throughout follow-up.

What comparison is being estimated?

A treatment effect is defined relative to a specific contrast. With four listed regimens, possible questions include comparing a regimen with placebo or comparing one active regimen with another. These comparisons are not interchangeable: each addresses a different scientific question. The registry names post-operative pain control as the primary outcome but does not identify one primary contrast. The statistical analysis plan, including the planned contrast and any adjustment for multiple comparisons, is not reported in the registry record.

In general, an outcome measure must also be defined precisely. A pain score at a specified time, a change from baseline, and a summary over follow-up are distinct endpoints. Their interpretation and statistical analysis can differ. The registry describes pain control during the immediate period and months after the procedure, but does not identify the measurement instrument, scoring rule, or method for combining measurements across time. It also does not report a numerical result that could be interpreted using any of these approaches.

How should uncertainty be understood?

In general, an effect estimate describes the observed contrast between groups, while a confidence interval conveys uncertainty around that estimate. A narrower interval indicates greater precision under the assumptions of the analysis; a wider interval indicates less precision. A p-value, when reported, addresses how compatible the data are with a specified null hypothesis under a statistical model. It is not a measure of effect size, and it does not establish clinical importance. No effect estimates, confidence intervals, or p-values for the trial's outcomes are reported in the registry record.

For outcomes measured repeatedly over time, the analysis should account for the fact that measurements from the same person are related. In general, treating repeated observations as independent can understate uncertainty. Different approaches can summarize trajectories, compare outcomes at selected times, or estimate an average across follow-up. The registry record does not report which times were analyzed or which modeling approach was used. The phrase “Expected average of 12 weeks” gives a timeframe, but does not define a repeated-measures model or a single summary statistic.

What do the planning assumptions mean?

The record describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says that the effect to detect is a stated fraction of the observed effect. For time-to-event calculations, the stated convention is a total number of events using the Schoenfeld approach; other calculations are expressed as participants per arm. These are planning assumptions, not a report of the trial's own design rationale. The sample-size justification used by the investigators is not reported in the registry record.

A planning illustration is conditional on its assumptions. In general, changing the assumed effect, allocation, variability, or analysis can change the sample size required for a target level of power. Such an illustration is not observed power and does not show that a completed study was adequately powered. The registry information does not include the numerical planning outputs or enough endpoint results to assess a recalculation in this explanation.

Over-dispersion is a general issue for count data: it occurs when variability is greater than a simple model assumes. If present, an analysis that ignores it can underestimate uncertainty. This trial's primary outcome is described as pain control, but the registry does not specify a count outcome or report a statistical model, so over-dispersion cannot be identified as a feature of its analysis.

How do missing observations affect analysis?

Missing outcome data reduce the information available and may create bias if the chance of missingness is related to treatment or outcome. In general, complete-case analysis, imputation, and likelihood-based methods rely on different assumptions. No approach to missing data is reported in the registry record. Because the primary outcome description cites loss of follow-up at 3 months, the handling and extent of missing measurements would be important to interpretation, but cannot be evaluated from the posted record.

10. Multiplicity, Missing Data and Analysis Populations

The record lists four treatment groups and identifies post-operative pain control as the primary outcome, with quality of life as a secondary outcome. It does not identify a primary pairwise contrast, specify whether every active regimen was to be compared with placebo, or say whether comparisons among active regimens were planned. A multi-group study can generate several possible comparisons, and testing several hypotheses can increase the chance of at least one false-positive finding if multiplicity is not addressed. In general, an analysis plan can specify a hierarchy, an adjustment method, or a limited set of primary comparisons. Such a strategy is not reported in the registry record.

There is also no detailed account of whether pain was to be analyzed at one time point or across the stated follow-up period, nor how multiple measurements would be combined. The expected average timeframe is 12 weeks, while the outcome description refers to immediate post-operative pain and the months after the procedure. The registry does not resolve how these elements were to define the primary analysis.

Missingness is especially relevant because the outcome description notes early termination due to loss of follow-up for the primary outcome at 3 months. The number of missing observations by group and time point, reasons for missingness, and statistical handling are not reported in the registry record. It is therefore not possible to assess whether missingness was balanced or whether the analysis depended on assumptions about unobserved outcomes.

The record does not state which analysis population was intended, such as all randomized participants or only those with outcome data. It also does not report an interim analysis plan, a stopping rule, or a strategy for protocol deviations. These details should not be inferred from the randomized and triple-masked labels. Without the prespecified analysis strategy, the registry record does not establish how multiplicity, missing data, or analysis populations were addressed.

11. 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 entries report 0 serious adverse events and 0 other adverse events for each listed group. The at-risk counts attached to those entries are 7 for pregabalin/celecoxib, 3 for pregabalin/placebo, 7 for celecoxib/placebo, and 6 for placebo. These figures describe what the registry reports for the listed groups; they do not provide a comparison adjusted for exposure time or other differences.

A recorded zero means that no event in that category was entered for the stated at-risk group in the registry record. It does not show that the true risk is zero or establish that no events occurred outside the reporting definitions or observation period. The record does not provide adverse-event definitions, surveillance methods, follow-up duration for safety, or details on how events were attributed. Death counts are marked null, so deaths are not reported in the registry record. No serious adverse-event terms are listed.

These safety entries should be read separately from the missing primary pain results. They do not provide evidence about comparative pain control, and the registry's lack of outcome analyses limits conclusions across the study as a whole.

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

The registry record is useful for identifying the study question, treatment groups, stated outcome, and reporting status. It describes a randomized, triple-masked study of pre-emptive analgesia following uterine artery embolization and lists post-operative pain control as the primary outcome. It also identifies quality of life as a secondary outcome and records early termination.

It does not provide numerical results for either outcome. Without group summaries or estimated contrasts, the record cannot show whether pain or quality-of-life outcomes differed among regimens, how large any difference was, or how uncertain an estimate would be. The record likewise does not support a claim that groups had identical outcomes. An absence of posted estimates is an information gap, not a finding of no effect.

The adverse-event entries show zero reported serious and other adverse events in the listed at-risk groups. Those entries are limited by the lack of reported definitions and observation details, and the death field is not reported. They should not be used to make a broad claim about safety or comparative risk.

General statistical interpretation requires both the estimated effect and a measure of its uncertainty, along with a clear account of the outcome definition and analysis population. Those elements are not reported for the primary outcome in the registry record. The primary outcome description also notes loss of follow-up at 3 months, making missing-data handling relevant but unknown.

Accordingly, the posted information can support a factual description of the trial's design and limitations. It cannot establish the magnitude, precision, or clinical importance of any treatment difference. Any stronger conclusion about the comparative outcomes would require results and analysis details not reported in the registry record.

13. Why This Trial Matters Statistically

This trial illustrates an important distinction between a study question and an answer to that question. The registry describes a randomized comparison of four regimens and names post-operative pain control as the primary outcome. However, it reports no numerical outcome estimates or analyses. A design can indicate how investigators intended to compare treatments, but without results readers cannot assess the observed treatment contrasts.

The record also illustrates why the comparison must be specified. Four listed regimens allow different scientific questions, including comparisons with placebo and comparisons among active regimens. Without a stated primary contrast or multiplicity plan, it is unclear which comparison should carry the main inferential weight. This matters even when the treatment groups and outcome are clearly named.

Early termination and loss of follow-up for the primary outcome at 3 months make reporting about the analysis population and missing observations particularly important. In general, incomplete follow-up can reduce precision and can bias estimates under some patterns of missingness. The registry does not say how these issues were handled, so their impact cannot be quantified.

The record's model designation of single group also conflicts with its four listed treatment groups. Clear and internally consistent design metadata help readers understand allocation, estimands, and planned analyses. Here, the treatment descriptions identify multiple groups, but the registry does not explain the conflicting model label.

These features make the record statistically instructive without supporting a treatment-effect conclusion. They show why complete outcome reporting, explicit contrasts, uncertainty estimates, and transparent missing-data methods are essential for interpreting a clinical trial.

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 limitation for interpreting this trial is the absence of numerical outcome results. The registry names post-operative pain control as the primary outcome and quality of life as a secondary outcome, but reports no estimates, uncertainty intervals, or analyses for either. It also does not specify the pain scale, scoring method, measurement schedule, or threshold for an important difference. This prevents assessment of the outcome's magnitude and precision.

The record states that the trial was terminated and links early termination to loss of follow-up for the primary outcome at 3 months. It does not report the number of missing measurements at each visit, their distribution across groups, or the method used to address them. Consequently, the effect of incomplete follow-up on the results cannot be evaluated.

Design information is also incomplete or inconsistent. The registry identifies the study as randomized and triple-masked, but does not describe the randomization or masking procedures. Its single-group model designation does not align with the four intervention groups and arm descriptions. The record does not explain this discrepancy or define a primary treatment contrast among the listed groups.

Further limitations include the lack of a reported statistical analysis plan, analysis population, multiplicity strategy, sample-size justification, and interim analysis information. Details of safety-event definitions and observation periods are also not reported. These are limitations of what can be learned from the registry record; they do not establish what was or was not done outside it.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Preemptive Analgesia Following Uterine Artery Embolization — NCT01555073.
• Registry record last updated 2016-07-28; status last verified 2016-06.
• Results first posted 2014-09-18.
• 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.

18. Record Summary

NCT01555073 is a phase 4 randomized, triple-masked study sponsored by Northwestern University, with registry enrollment of 23 and status terminated. Its recorded start is 2011-10 and primary completion is 2013-08. Four regimens are listed: pregabalin/celecoxib, pregabalin/placebo, celecoxib/placebo, and placebo. The registry model label says single group, which conflicts with those group descriptions.

Post-operative pain control is the primary outcome, with an expected average timeframe of 12 weeks; quality of life is listed as a secondary outcome. The outcome description notes early termination due to loss of follow-up at 3 months. The registry reports 0 serious and 0 other adverse events in each listed group, while deaths are not reported. No outcome analyses or numerical efficacy results are reported in the registry record.