Efficacy of Lidocaine Patch in Acute Musculoskeletal Pain in the Emergency Department: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Efficacy of Lidocaine Patch in Acute Musculoskeletal Pain in the Emergency Department (NCT03571737), a randomized phase 3 study. The primary outcome is Change in Numerical Pain Rating Scale.

2. Clinical Question

The clinical question is whether the posted short-term pain-score results differ between the two randomized groups. The registry describes follow-up for pain scores and return visits, and lists the return visit for the same chief complaint within 1 week as a secondary outcome. Because the primary results are presented separately by arm, they describe each group’s observed change but do not by themselves quantify the uncertainty around the difference between groups.

The record identifies the study as a prospective randomized controlled study. Randomization is intended, in general, to make treatment groups comparable on average, but it does not ensure that small groups will be alike in every relevant respect. The record does not report further eligibility criteria, participant characteristics, or a detailed account of how randomization was conducted.

3. Trial Design

The registry describes a Phase 3, randomized, parallel-group study with no masking. The study was conducted to evaluate adding a lidocaine patch to ibuprofen for acute musculoskeletal pain. One group received ibuprofen alone; the other received ibuprofen with lidocaine patch 4%. The registry lists East Carolina University as the sponsor and marks the study completed.

The record lists an enrollment of 23 participants. The posted arm results include 13 participants in the ibuprofen control group and 10 in the ibuprofen-plus-lidocaine group. These are the arm sizes shown with the results; the registry record does not explain whether every enrolled participant contributed to every outcome or how any missing observations were handled.

The primary endpoint was change in the Numerical Pain Rating Scale at 60 minutes. The stated assessment compares baseline pain with pain 60 minutes after intervention. The scale runs from 0 to 10, with higher values described as worse pain and lower values as better pain. A secondary endpoint was the number of participants with a return visit for the same chief complaint, assessed within 1 week.

In a randomized parallel-group design, participants are assigned to one group and the groups receive their respective interventions. In general, this design supports a direct comparison of assigned strategies, provided the analysis preserves the randomized groups and the outcome data are appropriately handled. Here, however, the primary endpoint is posted as an arm-specific mean and confidence interval, without a registered primary between-group analysis result.

The registry does not report the trial’s sample-size justification, its detailed allocation procedure, or a protocol-level statistical analysis plan. It also does not report an interim-analysis plan or masking procedures beyond listing masking as none. The record’s completion status and posted outcome data allow description of the results, but do not fill in those design and analysis details.

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

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 Change in Numerical Pain Rating Scale, measured over 60 minutes.

The primary endpoint is change in the Numerical Pain Rating Scale, a self-reported measure of pain intensity. Participants’ pain was assessed before intervention and again 60 minutes after intervention. Each item is scored from 0 to 10, with higher values indicating worse pain and lower values indicating better pain, according to the registry description.

A change score is used to describe how a measurement differs from its baseline value over a specified interval. In general, measuring change can focus attention on improvement or worsening after an intervention, while also making the interpretation dependent on how the change is coded. The registry record does not specify whether the posted change values are expressed as follow-up minus baseline or baseline minus follow-up. The results should therefore be read as the posted mean changes and intervals, without assigning a direction beyond the endpoint description.

The record reports a mean and 95% confidence interval for each group at 60 minutes. A confidence interval conveys uncertainty around an estimated group mean under the analysis used. It does not directly provide a confidence interval for the difference between treatment groups. The registry record does not post a primary between-group estimate, standard error, test, or p-value.

This endpoint captures pain at a short-term follow-up. It does not, on its own, describe later pain, function, or other outcomes. The registry lists a return visit within 1 week as a secondary endpoint, which addresses a different aspect of follow-up.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry’s primary outcome is continuous: it summarizes pain-score change with a mean and a 95% confidence interval. The reported results are given separately for the ibuprofen group and the ibuprofen-plus-lidocaine group. No direct primary comparison is posted. That distinction matters: two group summaries describe the observed data in each arm, whereas a treatment comparison estimates how far apart the arms are and the uncertainty around that contrast.

What does a confidence interval describe?

In general, a confidence interval expresses the uncertainty associated with an estimated quantity under the statistical method used. A narrower interval indicates greater precision for that estimate, while a wider interval indicates less precision. The 95% confidence intervals in the primary results apply to each group’s mean change, not to the difference between groups. They cannot be treated as though they were a comparative confidence interval.

In general, the overlap or lack of overlap between separate group confidence intervals is not a formal test of the difference between those groups. A direct comparison needs its own estimate and uncertainty calculation, using an analysis appropriate to the design and data. The registry does not report a primary comparative estimate, test statistic, or p-value, so those cannot be reconstructed from the posted group intervals.

How should the pain change score be read?

The registry says pain was measured before intervention and 60 minutes afterward, on a 0–10 scale, with higher scores described as worse. It reports the outcome as change in pain score, but does not state the arithmetic order used to form that change. In general, reversing the subtraction order reverses the sign of a change while leaving the underlying observations unchanged. Without a stated convention, the safest interpretation is to retain the posted values and not infer a precise direction from the sign alone.

The record presents a mean, which summarizes the average observed change in each group. A mean can be useful for a continuous outcome, but it does not show the distribution of individual responses. The registry does not post a standard deviation, participant-level results, or a distribution plot in the registry record for this endpoint. The interval supplies some information about precision of the mean, but cannot reveal whether responses were tightly grouped or varied substantially.

What does the secondary risk difference mean?

The secondary outcome is a count of participants with a return visit for the same chief complaint. The registry also posts a risk difference comparing the experimental group with the control group. In general, a risk difference expresses the contrast between the event proportions in two groups; a value of zero corresponds to no difference in those proportions. The posted estimate is 0.154, with a 95% confidence interval from -0.042 to 0.35 and an unadjusted p-value of 0.194. Because the interval includes zero, the result is compatible with no difference as well as with differences in either direction within the interval.

The registry also includes a risk ratio summary for this comparison. A risk ratio compares event proportions as a ratio rather than a difference. The presence of more than one effect measure does not change the fact that this is a secondary endpoint and the reported comparison is unadjusted. No adjusted analysis or multiplicity procedure is reported.

What do the sample-size illustrations represent?

The sample-size section contains planning illustrations based on the observed effect, not the trial’s own design. The registry’s stated illustration assumptions are a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation; the effect to detect is expressed as a stated fraction of the observed effect. In general, such calculations ask what sample size might be needed under specified assumptions. They are not the number of participants actually studied, and they are not observed power. The registry record does not report the trial’s own sample-size justification.

Planning illustrations based on an observed effect should be interpreted cautiously. In general, the observed estimate is uncertain, especially in a small study, so planning around it does not establish that the trial had adequate power or that a particular effect is realistic. The calculated sample-size section should be read as a hypothetical planning aid, separate from the study design and the posted outcome evidence.

What is not available about the analysis?

The registry lists no primary analyses and does not report an analysis population, missing-data method, covariate adjustment, or a detailed statistical analysis plan. It is therefore not possible to tell from the registry whether the reported arm summaries include all randomized participants, how incomplete follow-up was handled, or whether any other prespecified analytical choices were made. Those omissions limit assessment of the results beyond the summaries and comparison that are posted.

10. Multiplicity, Missing Data and Analysis Populations

The registry record does not report a multiplicity plan. In general, multiplicity arises when investigators assess several outcomes, time points, treatment contrasts, or statistical tests. If many tests are considered without an adjustment or prespecified hierarchy, the chance of at least one apparently positive result can increase. This concern is one reason to distinguish the primary endpoint from secondary endpoints and to give unadjusted secondary findings less weight.

The registry identifies change in Numerical Pain Rating Scale at 60 minutes as the primary outcome and return visit for the same chief complaint within 1 week as a secondary outcome. It does not describe whether other outcomes were planned, whether a testing hierarchy was used, or whether any adjustment for multiple comparisons was applied. The secondary comparison is reported as unadjusted. No multiplicity-adjusted result is posted.

Missing-data handling is also not reported in the registry record. The record gives an enrollment of 23 and arm-specific result counts, but it does not say how participants with missing measurements were treated, whether all randomized participants were included in each analysis, or how withdrawals and incomplete follow-up were handled. It would be inappropriate to assume that the analysis followed an intention-to-treat approach or any other specific population definition.

The registry does not report an analysis population for the primary outcome, nor does it give a missing-data method, sensitivity analysis, or imputation procedure. In general, missing outcome data can affect both the estimated group result and its uncertainty, particularly if missingness differs between groups or is related to the unobserved outcome. Without the relevant reporting, the extent and direction of any such influence cannot be assessed.

The record also does not report a full statistical analysis plan, interim analyses, or details of protocol deviations. These are gaps in the available reporting, not evidence that a particular method was or was not used. They limit how completely the posted results can be audited and interpreted.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry reports zero serious adverse events in each group and zero other adverse events in each group. It also reports zero deaths in both groups. The counts at risk are 13 in the ibuprofen control group and 10 in the ibuprofen-plus-lidocaine group. No serious adverse-event terms are listed.

These figures describe what was recorded in this trial. They do not establish that no adverse events occurred beyond those captured and reported, nor do they precisely characterize event risk. In general, when a study includes a small number of participants, an absence of recorded events provides limited information about uncommon events. The registry record does not describe how adverse events were solicited, classified, or followed.

The safety figures should be read as descriptive counts, not as proof of safety or as a comparison showing equal risk. The groups are small, and the registry does not post a comparative safety analysis or confidence interval. These results cannot determine whether the treatment strategies differ in safety.

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

This record describes a randomized comparison of ibuprofen alone with ibuprofen plus lidocaine patch 4% in participants with acute musculoskeletal pain in the emergency department. It posts mean pain-score changes and 95% confidence intervals for each group at 60 minutes, along with a secondary comparison for return visits within 1 week. These results provide a limited account of the outcomes recorded in the study.

The posted primary data do not include a direct estimate of the between-group difference. As a result, the arm-specific means cannot show how precisely the treatment groups differed or whether the observed contrast is compatible with no difference. The registry also does not state the sign convention for the pain change score, so the numerical changes should not be translated into a definitive direction of improvement based only on their signs.

The secondary endpoint has an unadjusted comparison with an interval that includes zero. It does not provide precise evidence of a difference in return visits, and it addresses a different outcome from short-term pain change. The secondary result cannot fill the gap in the primary analysis.

In general, a randomized design can support a treatment comparison when allocation and analysis are appropriately conducted, but the design label alone does not establish that every potential source of bias has been addressed. The registry record does not report enough information to assess eligibility in detail, missing observations, analysis populations, or the full statistical plan. The enrolled cohort was 23 participants, limiting the amount of information available in the posted results.

These results do not establish whether either treatment strategy works or does not work, and they do not provide medical advice. They describe the registry’s posted outcomes and the uncertainty visible in those summaries. Further claims would require details or analyses not reported in the registry record.

13. Why This Trial Matters Statistically

This trial is statistically instructive because it separates a randomized design from the information needed to interpret an estimated treatment contrast. The record describes random allocation and two parallel groups, but the primary outcome is presented only as a mean and confidence interval within each arm. A direct comparison is needed to quantify the difference of interest and its precision.

The example also illustrates why endpoint definition matters. The primary outcome is a change score, but the registry does not state the order of subtraction. Since the scale is oriented so that higher pain scores are worse, the interpretation of a signed change depends on that coding convention. Retaining the posted results without silently assigning a sign is more accurate than imposing an unstated definition.

The secondary endpoint highlights another general issue: unadjusted secondary analyses are not equivalent to a primary analysis. The posted return-visit comparison is uncertain and addresses a different outcome. Without a reported multiplicity plan, it should not be elevated into a definitive conclusion.

The record also demonstrates the difference between a planning illustration and the study’s actual design. Sample-size calculations based on the observed effect are hypothetical planning exercises; they do not establish what sample size investigators planned, justify the number enrolled, or describe observed power. The registry does not report the trial’s own sample-size justification.

Finally, transparent reporting of analysis populations, missing-data handling, and direct treatment contrasts is essential for independent interpretation. Their absence does not prove that these matters were neglected, but it limits what can be concluded from the registry record. The statistical importance of this study lies in reading the available summaries at the level they support, without treating incomplete reporting as a complete comparative analysis.

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 interpretation is that the registry posts arm-specific mean changes and confidence intervals but no direct between-group estimate. This leaves the central comparative question without a reported primary contrast. The record also does not specify the direction used to calculate change from baseline, which limits interpretation of the signs of the posted values.

The study enrolled 23 participants, and the outcome summaries are based on small arm counts. In general, estimates from small groups are often imprecise, and confidence intervals can remain wide. The posted intervals should be considered when reading the means; a point estimate alone does not describe the range of uncertainty.

The registry does not report participant characteristics or detailed eligibility criteria. It is therefore not possible to judge how closely the enrolled participants represent other groups with acute musculoskeletal pain. The record also does not provide enough intervention-delivery or adherence detail to assess whether participants followed the listed regimens as intended.

Several analysis details are absent: the analysis population, missing-data handling, protocol deviations, and a full statistical analysis plan are not reported in the registry record. The record also does not state whether covariates were considered or whether any sensitivity analyses were conducted. These omissions make it difficult to assess the robustness of the posted summaries.

The primary assessment was at 60 minutes, while the secondary return-visit outcome covered 1 week. These timeframes address different aspects of follow-up and do not describe longer-term outcomes. The secondary result is unadjusted, and no multiplicity procedure is reported. Finally, the adverse-event figures are descriptive counts without further collection or classification details. Each limitation narrows what can be inferred from this registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Efficacy of Lidocaine Patch in Acute Musculoskeletal Pain in the Emergency Department — NCT03571737.
• Registry record last updated 2024-03-25; status last verified 2024-03.
• Results first posted 2024-03-25.
• 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

The registry record describes a completed, Phase 3 randomized parallel-group study with no masking, sponsored by East Carolina University. It lists enrollment of 23 participants and evaluates ibuprofen alone against ibuprofen with lidocaine patch 4% for acute musculoskeletal pain in the emergency department.

The primary outcome was change in Numerical Pain Rating Scale at 60 minutes. The record posts a mean and 95% confidence interval for each arm, but no primary between-group analysis. The secondary outcome was a return visit for the same chief complaint within 1 week; an unadjusted comparison is posted. Serious adverse events, other adverse events, and deaths are reported as zero in both groups.

The registry record does not report the trial’s sample-size justification, detailed statistical analysis plan, analysis population, or missing-data approach. The posted results should therefore be interpreted as limited summaries rather than a complete account of comparative evidence.