Empower Opioid Misuse & Chronic Pain: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Empower Opioid Misuse & Chronic Pain (NCT04184362), a randomized na study. The primary outcome is Pain Intensity Score Measures.

2. Clinical Question

This question addresses whether the recorded pain-intensity summaries differed between the randomized groups during the stated period. The registry describes the intervention as peripheral nerve stimulation and the study as involving people with chronic non-cancer pain and opioid misuse. It also lists opioid craving and use among the effects the study evaluates, but the primary endpoint posted for this record is pain intensity. General Health Monitored is listed as a secondary outcome. Further detail about the secondary outcome is not reported in the registry record.

3. Trial Design

The registry identifies this as a randomized, parallel-group study with no masking. Participants were assigned to an active treatment site or a sham control treatment site. The registry status is Completed, and the recorded enrollment is 10. The arm results list 5 participants in the active group and 5 in the sham group. These are the posted group counts; further details about participant flow, withdrawals, or the number contributing data to each outcome are not reported in the registry record.

The study start date is 2019-11-20, and the primary completion date is 2022-03-21. The registry lists the phase as NA. The sponsor is the University of California, San Francisco. These details describe the registry entry and do not establish how the study was conducted beyond the design information explicitly recorded.

The intervention is named Empower Neuromodulation System Transcutaneous Electrical Nerve Stimulation. The active arm description says the device was tested at the active treatment site; the sham arm description says it was tested at the sham control treatment site. The registry summary states that participants were randomized to receive active or sham control treatment for the duration of the study. Treatment duration beyond that description, stimulation procedures, and adherence information are not reported in the registry record.

The listed masking status is none. The record therefore does not describe the study as blinded. It does not report whether outcome assessors or analysts were masked, how randomization was generated or concealed, or whether any departures from assigned treatment occurred. Those details should not be inferred from the randomized, parallel design label.

The registry records a continuous primary outcome expressed as a mean pain-intensity score, with standard deviation as the measure of dispersion. The stated timeframe is Baseline to Week 3. Although the study is marked completed, that status alone does not supply missing methods or an inferential comparison. No analysis results are posted for the two-arm continuous endpoint.

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 Pain Intensity Score Measures, measured over Baseline to Week 3.

The primary endpoint is the mean of daily pain-intensity ratings recorded from baseline to Week 3. Participants used the Empower app to record pain levels on a 0-100 scale, with 0 indicating a lack of pain outcome and 100 indicating the maximum pain score. The app prompted participants to complete a Numeric Rating Scale immediately before and after treatment or sham treatment. The posted measure is described as the mean average of daily scores across the period, incorporating ratings from before and after treatment.

Pain intensity is used as a patient-reported measure of the symptom targeted by the study. Repeated daily ratings can describe pain over the recorded period rather than relying on a single rating. Combining ratings taken before and after treatment into the stated mean also means the posted summary is not a separate estimate of an immediate pre-to-post change. The registry record does not report a separate analysis of those individual time points.

The active group has a posted mean score of 55.0 with a standard deviation of 25.0, based on 5 participants. The sham group has a posted mean score of 57.0 with a standard deviation of 22.0, based on 5 participants. These are descriptive summaries. The registry does not post a confidence interval, p-value, or other inferential estimate for the primary comparison, and the values alone do not establish the precision or statistical significance of a group difference.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What do the group means describe?

For a continuous outcome, a mean is the arithmetic average of the observed measurements in a group. In this study, the posted pain score is described as the mean average of daily ratings from baseline to Week 3, including scores immediately before and after treatment or sham treatment. The active group mean is 55.0 and the sham group mean is 57.0. A mean offers a compact description of the group’s recorded scores, but it does not show the full distribution or how individual participants’ ratings changed over time.

The group standard deviations are 25.0 for active treatment and 22.0 for sham treatment. In general, a standard deviation describes the spread of observations around a group mean. It is distinct from the standard error, which describes uncertainty in an estimated mean, and from a confidence interval, which expresses uncertainty around an estimate under specified assumptions. No confidence interval or standard error for the comparison is reported in the registry record.

What would an unadjusted comparison mean?

In general, an unadjusted comparison contrasts the observed outcome summaries between randomized groups without accounting for additional covariates. Such an estimate can be useful as a direct description of the group contrast, but it still requires an appropriate measure of uncertainty to support inference. The registry record does not post a two-arm inferential analysis for this continuous outcome; it states that values are missing or not estimable for that comparison. No recalculated comparison is therefore available to interpret.

The record lists no analyses. A missing analysis result should not be treated as a null finding, as proof that the groups are equivalent, or as evidence that the endpoint was not measured. The endpoint description and group summaries indicate that pain ratings were reported, while the formal comparison is not available in the registry record.

Why does variability matter?

General statistical interpretation depends on both the observed group summaries and the variability in the measurements. Greater variability can make a mean less precise, all else equal. The standard deviations give some information about spread within each arm, but they are not enough to reconstruct every element of the analysis or to know which participants contributed data at each point. Participant-level observations, missing-data handling, and a specified analysis model are not reported in the registry record.

Over-dispersion is a general issue that arises when data vary more than a statistical model assumes. When present, it can make model-based uncertainty estimates too small if the model does not account for it. The posted primary endpoint is a continuous score, and no model-based analysis is reported; therefore, over-dispersion should not be asserted as a feature of this study. More generally, model assumptions should be checked against the data and design rather than inferred from a pair of means and standard deviations.

What do the planning assumptions describe?

The sample-size planning illustration is described as using the observed effect, two-sided significance level 0.05, equal allocation between arms, and a normal approximation. The effect to detect is framed as a stated fraction of the observed effect. These are assumptions for a planning calculation, not evidence about the study’s original design or analysis plan. The registry record does not report the trial’s sample-size justification, its original target, or its statistical plan.

In general, a planning calculation estimates the sample size needed to detect a chosen effect under specified assumptions. It does not measure the probability that the completed trial found a true effect, and it is not observed power. The planning results should be interpreted as illustrations rather than retrospective proof that the study was adequately or inadequately powered. No numerical planning results are described in the registry record.

The normal approximation is a general calculation method that relies on assumptions about the sampling distribution of an estimate. Its usefulness depends on the outcome, sample size, variability, and design. Equal allocation is a planning assumption in the described illustration; it does not change the fact that the posted arm counts are 5 participants each. The registry record does not report the derivation of an observed effect or a separate justification for these planning assumptions.

What can be inferred from the record?

Inference requires more than a difference in group summaries: it also requires a statistical model or method, uncertainty estimates, and a clear definition of the analysis population and endpoint. The record supplies descriptive means, standard deviations, and group counts, but it does not post an inferential result for the primary comparison. The appropriate reading is therefore limited to those descriptive summaries and the stated endpoint definition. General statistical principles cannot replace unreported trial-specific methods.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Experimental Group Tested at the Active Treatment ", "Control Sham Group Tested at the Sham Control Trea")
n   <- c(5, 5)
m   <- c(55, 57)
sp  <- c(25, 22)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Experimental Group Tested at the Active Treatment   5  55.000  25.000  23.958  86.042
CARM  Control Sham Group Tested at the Sham Control Trea  5  57.000  22.000  29.683  84.317

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one secondary outcome, General Health Monitored, and reports four outcome measures overall. It does not provide details about how those measures were grouped into outcomes, which analyses were planned, or whether multiple comparisons were addressed. The multiplicity strategy is not reported in the registry record. In general, testing multiple outcomes or comparisons can increase the chance of at least one apparently notable result, so prespecified outcome hierarchies or other multiplicity procedures can matter. No particular procedure should be attributed to this study.

The primary outcome description says participants recorded pain daily from baseline to Week 3, with ratings before and after treatment or sham treatment contributing to the reported mean. The record does not report how missing daily ratings were handled, whether participants with incomplete records were included, or whether any imputation or sensitivity analysis was performed. It also does not report the number of participants with complete primary-outcome data or any reasons for missing observations. Missing-data methods are therefore not reported in the registry record.

The record identifies randomized groups but does not define an analysis population, such as an intention-to-treat population or a per-protocol population. It does not report whether participants were analyzed according to assigned group, whether exclusions occurred, or how adherence was considered. Those analysis-population details are not reported in the registry record and should not be inferred from randomization alone.

These omissions constrain interpretation because the estimated group comparison can depend on which participants and measurements are included and how incomplete data are handled. Since no two-arm inferential analysis is posted, there is no reported analysis result to evaluate for multiplicity, missingness, or population definition. The descriptive group summaries remain the available primary-outcome results, with their contribution rules not further specified.

12. 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 posted adverse-event figures list 5 participants at risk for serious adverse events in each arm. The number affected by serious adverse events is 0 in the active group and 0 in the sham group. The record also lists 5 participants at risk for other adverse events in each arm, with 0 affected in each. Deaths are listed as 0 in both groups. No serious adverse-event terms are listed.

These figures describe the safety entries in the registry record. A zero in the affected field means that no affected participants are recorded for that category in the posted results; it does not establish that an event is impossible or that the treatment is free of risk. Safety interpretation depends on the reporting period, event definitions, completeness of follow-up, and ascertainment procedures. Those details are not reported in the registry record.

The listed at-risk counts match the posted group counts, but the registry does not give further detail about exposure duration or whether all participants completed safety follow-up. With limited group counts, the absence of recorded events should be read descriptively, not as a precise estimate of safety. No conclusion about safety beyond these posted figures is supported by the registry entry.

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

The result means that the registry posts descriptive pain-intensity summaries for the active and sham groups over baseline to Week 3. The mean is 55.0 in the active group and 57.0 in the sham group; the corresponding standard deviations are 25.0 and 22.0. Each group result is based on 5 participants. The pain score is a 0-100 scale, and the posted mean includes daily ratings from before and after treatment or sham treatment.

The record does not post an inferential comparison for these group summaries. It therefore does not provide a confidence interval or p-value for the primary endpoint, and it does not establish whether a group contrast is statistically distinguishable from chance variation. The descriptive values should not be taken as proof of a treatment effect, proof of no effect, or evidence that active and sham treatment are equivalent.

The endpoint also does not represent every outcome mentioned in the study summary. The registry describes evaluation of opioid craving and use and pain, while the primary result addressed is the pain-intensity score. Detailed results for opioid craving and use are not reported in the registry record. General Health Monitored is listed as a secondary outcome, but detailed results are not reported in the registry record.

The result does not establish effects beyond the stated timeframe, which is Baseline to Week 3. The registry does not report longer-term pain outcomes, separate estimates for before and after treatment, or a distinct analysis of daily trajectories. It also does not report an adjusted result or details of how missing daily ratings were handled. Those limits prevent stronger conclusions about the pattern or persistence of the observed scores.

In practical statistical terms, the posted information is a set of descriptive group summaries rather than a complete analysis of the randomized comparison. The completed status and randomized design do not substitute for a reported effect estimate with uncertainty. Any interpretation should stay within the reported endpoint, period, and descriptive results, without extending to outcomes or methods that the registry does not report.

14. Why This Trial Matters Statistically

This trial is statistically notable as a randomized comparison with a clearly described continuous, patient-reported primary outcome, but the registry result is descriptive rather than inferential. It reports group means, standard deviations, and participant counts for active and sham treatment. The design label supports understanding the intended comparison, while the absence of a posted comparison analysis limits what can be concluded from the results.

The endpoint illustrates why the definition of a summary measure matters. Participants entered daily ratings before and after treatment or sham treatment, and the reported score averages ratings across baseline to Week 3. A single mean condenses those repeated observations, but it does not show the time course, within-person variability, or the distinction between pre-treatment and post-treatment ratings. Those questions would require additional analyses that are not reported in the registry record.

The record also makes a useful distinction between observed summaries and planning illustrations. Planning calculations can describe what sample size might be needed under chosen assumptions, but they are not observed power and do not replace an analysis of the completed trial. The original sample-size justification and statistical plan are not reported in the registry record. The stated planning assumptions should therefore be read as planning inputs, not as confirmation of the trial’s design rationale.

More broadly, the registry entry shows how a completed randomized study can have posted endpoint summaries without a posted test or interval for the primary comparison. This matters because readers need both an estimate and its uncertainty to judge how informative a result is. The available information supports description of the recorded pain scores and the stated design, while leaving the comparative precision unresolved.

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 main trial-specific limitation in the registry record is the absence of an inferential analysis for the two-arm continuous primary endpoint. Although group means and standard deviations are posted, no confidence interval, p-value, or other formal estimate of the active-versus-sham comparison is reported. The registry explicitly indicates that values are missing or not estimable for that comparison.

The posted arm counts are 5 participants each. The record does not provide participant-level results, distributions, or analysis details that would show how much individual observations influenced the summaries. It also does not report whether all randomized participants contributed to the primary endpoint, how withdrawals or incomplete daily reports were handled, or whether any outcome data were missing. Those details are not reported in the registry record.

The endpoint combines daily ratings from baseline to Week 3 and includes measurements before and after treatment or sham treatment. Separate estimates by time point, changes from baseline, and daily trajectories are not reported. The endpoint description therefore limits interpretation to an aggregate mean score over the stated period; it does not allow assessment of immediate responses or temporal patterns.

The record lists no masking and does not describe how the sham condition was implemented, how allocation was concealed, or whether outcome assessment was independent of treatment assignment. The registry does not report adherence, treatment fidelity, or the analysis population. These features may be important when interpreting a patient-reported outcome in a device study, but no study-specific conclusion about their impact can be drawn from the record.

Finally, detailed results for the listed secondary outcome and the opioid-related outcomes mentioned in the study summary are not reported in the registry record. The available endpoint and safety entries do not establish effects on those outcomes or beyond Week 3.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Empower Opioid Misuse & Chronic Pain — NCT04184362.
• Registry record last updated 2023-08-03; status last verified 2023-07.
• Results first posted 2023-08-03.
• 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

The registry identifies a completed, randomized, parallel, unmasked study sponsored by the University of California, San Francisco. It describes active versus sham testing of the Empower Neuromodulation System Transcutaneous Electrical Nerve Stimulation device in veterans with chronic pain and opioid misuse. Enrollment is listed as 10, with 5 participants in each arm. The recorded start date is 2019-11-20, and the primary completion date is 2022-03-21.

The primary endpoint is mean pain intensity from baseline to Week 3, based on daily app ratings on a 0-100 scale, including ratings before and after treatment or sham treatment. The active-group mean is 55.0 with standard deviation 25.0; the sham-group mean is 57.0 with standard deviation 22.0. No inferential comparison is posted for this continuous endpoint. The record lists 0 serious adverse events, 0 other adverse events, and 0 deaths in each arm. Further details about analysis methods, missing data, and secondary-outcome results are not reported in the registry record.