Self Cranial Electrical Stimulation (CES) for Pain in Older Adults With Knee Osteoarthritis (Self CES for Knee Pain): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Self Cranial Electrical Stimulation (CES) for Pain in Older Adults With Knee Osteoarthritis (Self CES for Knee Pain) (NCT04016259), a randomized na study. The primary outcome is Clinical Pain as Assessed by a Numeric Rating Scale (NRS) for Pain.

2. Clinical Question

3. Trial Design

The registry record describes a randomized, triple-masked, parallel-group study of cranial electrical stimulation for pain in older adults with knee osteoarthritis. Participants were assigned to Self-CES or Sham-CES. The recorded enrollment was 30, with 15.0 participants in each arm for the posted primary result. The study status is completed. The recorded study start was 2019-08-01, and primary completion was 2019-11-21.

The study purpose was to assess the feasibility, safety, and preliminary efficacy of a two-week self-CES intervention on pain in older adults with knee osteoarthritis. The registry record lists the interventions as CES and Sham-CES, both devices. It does not give descriptions of the arm procedures, so details about device use, sham procedures, or participant instructions are not reported in the registry record.

Randomization means allocation was intended to occur by chance, while a parallel-group design means the trial compared separate groups assigned to different arms. Triple masking indicates that the record classifies the study as triple-masked, but it does not identify which groups of people were masked or explain how masking was maintained. Those details are not reported in the registry record. The phase is listed as not applicable. Further information about the trial setting, eligibility criteria, allocation procedures, and the original sample-size justification is not reported in the registry record.

The registry record includes a primary week 2 pain outcome and several secondary measures, including experimental pain sensitivity and psychosocial symptoms. It records 15 outcome measures, but only a subset of secondary outcome results has arm-level statistics in the record. No statistical analyses are listed as reported analyses. Accordingly, the arm comparisons discussed in the interpretation are unadjusted re-calculations from posted summary statistics, rather than an account of a reported sponsor analysis.

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 Clinical Pain as Assessed by a Numeric Rating Scale (NRS) for Pain, measured over week 2.

The primary endpoint is clinical pain at week 2, measured with a Numeric Rating Scale. The registry record describes the score as ranging from 0, meaning no pain, to 100, meaning the most intense pain imaginable. The posted outcome is a mean and standard deviation for each arm, so the comparison concerns average pain scores, not the experience of every individual participant.

A pain rating scale turns a subjective experience into a standardized numeric measure that can be summarized and compared between randomized groups. A continuous score can retain distinctions across the scale rather than reducing responses to categories such as pain present or absent. The mean describes the group average, while the standard deviation describes the spread of individual scores around that average. Neither summary by itself indicates how each participant changed over time.

The primary endpoint is recorded at week 2, consistent with the study purpose of examining a two-week self-CES intervention. The registry record does not report a baseline-adjusted analysis, a change-from-baseline outcome, or a clinically important difference threshold. Therefore, interpretation rests on the posted week 2 arm means and their unadjusted comparison, not on an estimate of individual change or a claim that a particular score difference is clinically important.

7. Results Posted in the Registry

• Self-CES: mean 27.33 versus 40.40 on control; difference -13.07 (95% CI -32.19 to 6.05), standardized effect d = -0.49; z-test p = 0.180.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Experimental Pain Sensitivity as Measured Using a Multimodal Quantitative Sensory Testing (QST) Battery - Heat Pain Threshold (HPTH)

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Self-CES: mean 41.04 versus 37.90 on control; difference 3.14 (95% CI 1.24 to 5.04), standardized effect d = 1.18; z-test p = 0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Self-CES than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Experimental Pain Sensitivity as Measured Using a Multimodal Quantitative Sensory Testing (QST) Battery - Heat Pain Tolerance (HPTO)

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Self-CES: mean 44.56 versus 43.05 on control; difference 1.51 (95% CI -0.60 to 3.62), standardized effect d = 0.51; z-test p = 0.161.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Self-CES and the control. The interval gives the range of effects that remain compatible with the data.

Experimental Pain Sensitivity as Measured Using a Multimodal Quantitative Sensory Testing (QST) Battery - Pressure Pain Threshold (PPT)

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Self-CES: mean 2.59 versus 1.06 on control; difference 1.53 (95% CI 0.75 to 2.31), standardized effect d = 1.41; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Self-CES than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The registry record includes secondary measures of experimental pain sensitivity and psychosocial symptoms. Arm-level results with comparisons are posted for three experimental pain sensitivity measures at week 2: heat pain threshold, heat pain tolerance, and pressure pain threshold. These measures assess different responses to experimental stimuli and are not interchangeable with the primary clinical pain rating. The registered psychosocial measures include anxiety, depression, sleep disturbance, and pain catastrophizing, but their arm-level results are not included in the posted secondary comparisons described in the record.

Across the three posted experimental pain sensitivity outcomes, the Self-CES arm has higher mean values than the Sham-CES arm. The interval for heat pain threshold and the interval for pressure pain threshold exclude zero, while the interval for heat pain tolerance includes zero. These outcomes therefore do not present a uniform pattern of equally precise evidence. They are secondary measurements and should not be read as independent confirmation of the primary clinical pain result.

The primary endpoint measures reported clinical pain, while quantitative sensory testing measures responses to controlled sensory stimuli. Different measures can vary in relevance and precision, and a difference on an experimental threshold measure does not automatically imply a difference in participants' clinical pain ratings. The primary comparison remains the direct registry outcome for the central pain question, and it is imprecise.

Unadjusted secondary results carry less weight because several outcomes are examined and the registry record does not report a multiplicity strategy, outcome hierarchy, or formal secondary analysis plan. When many tests are considered, some may appear notable by chance. The record also lists no reported analyses, so it is not possible to determine whether the posted secondary comparisons were prespecified or how they relate to any analysis plan. The secondary pattern is useful for generating questions for further study, but it does not settle the uncertainty in the primary comparison.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Experimental Pain Sensitivity as Measured Using a Multimodal Quantitative Sensory Testing (QST) Battery - Heat Pain Threshold (HPTH)
• Experimental Pain Sensitivity as Measured Using a Multimodal Quantitative Sensory Testing (QST) Battery - Heat Pain Tolerance (HPTO)
• Experimental Pain Sensitivity as Measured Using a Multimodal Quantitative Sensory Testing (QST) Battery - Pressure Pain Threshold (PPT)
• Experimental Pain Sensitivity as Measured Using a Multimodal Quantitative Sensory Testing (QST) Battery - Conditioned Pain Modulation (CPM)
• Psychosocial Symptoms as Measured by the Patient-Reported Outcomes Measurement Information System (PROMIS) - Anxiety Short Form
• Psychosocial Symptoms as Measured by PROMIS - Depression Short Form
• Psychosocial Symptoms as Measured by PROMIS - Sleep Disturbance Short Form
• Psychosocial Symptoms as Measured by the Pain Catastrophizing Scale (PCS)

9. Statistical Interpretation

10. Statistical Methods Explained

What does the mean difference represent?

The primary measure is continuous: each participant contributes a pain score on the 0-to-100 scale, and the arm summaries report the mean and standard deviation. A mean difference compares the two arm averages. The reported direction is Self-CES minus Sham-CES, so a negative estimate means the Self-CES average was lower. The estimate of -13.07 units is a contrast between group means at week 2. It is not a count of participants who improved, and it does not describe the change for any particular participant.

General statistical point: a group mean is a useful summary, but it does not show the full distribution of participants' scores. The standard deviation helps describe spread, but it cannot show the shape of that distribution or whether results are concentrated in a few unusual observations. The larger standard deviation in the Sham-CES arm suggests more spread in that arm's posted scores than in the Self-CES arm.

What does the p-value say?

The unadjusted p-value for the primary comparison is 0.18. A p-value measures how incompatible the observed data are with a specified null model of no mean difference, under the assumptions of the calculation. It is not the probability that the null model is true, and it does not measure the size or clinical importance of the difference. A value of 0.18 does not establish that the arms are equal; it indicates that this unadjusted result is not strong evidence against the no-difference model by conventional testing standards.

General statistical point: p-values depend on both the estimated effect and its uncertainty. A small study can have a potentially meaningful observed contrast but still yield limited evidence because the estimate is imprecise. Conversely, a small p-value alone does not establish clinical importance. Here, the interval and the p-value both need to be read alongside the modest arm sizes and the variability of the pain scores.

What does the interval add?

The posted comparison interval runs from -32.19 to 6.047 units. It includes zero and spans values favoring either arm. The interval conveys uncertainty about the mean difference more directly than a single estimate does. Its width reflects that the available data do not pin down the group contrast narrowly. The confidence level attached to the interval is not reported in the registry record, so a confidence percentage should not be inferred from the record.

General statistical point: a confidence interval is a range of effect estimates compatible with the data under a specified method. In repeated use of a valid procedure, intervals at the stated confidence level have a long-run coverage property. An interval is not a probability statement about the fixed true effect after the data have been observed. Since the confidence level and full analysis specification are not reported in the registry record, interpretation should focus on the reported bounds and whether they include no difference.

Why do the standard deviations matter?

The primary arm standard deviations are 33.79 for Sham-CES and 16.89 for Self-CES. They describe within-arm variation, not uncertainty in the mean difference itself. The comparison estimate's uncertainty depends on the number of observations and the variability in both arms. In a small sample, high variability can leave a broad range of plausible group contrasts. The standard errors of the individual arm means are also posted, but an arm's standard error is not the same quantity as the standard deviation of participant scores.

General statistical point: some continuous outcomes can have more variability than a simple normal model anticipates. Over-dispersion means observed variability exceeds what a model assumes; if not addressed, standard errors and resulting intervals may be too small. The registry entries do not report an over-dispersion assessment or a model-based adjustment, so it would be inappropriate to claim that over-dispersion occurred or was handled in this trial.

What is the status of the calculations?

The registry record lists no reported statistical analyses. The primary mean difference, interval, and unadjusted p-value are simple unadjusted re-calculations from the posted arm summaries. This means they do not incorporate an adjustment for baseline pain, other covariates, repeated measurements, or multiplicity. Whether the trial team conducted such analyses outside the registry record is not reported in the registry record. No discrepancy is flagged for the posted primary comparison.

General statistical point: an adjusted analysis may account for prespecified prognostic factors or design features, while an unadjusted comparison directly contrasts the observed arm summaries. Neither approach is automatically preferable in every circumstance; interpretation depends on the planned analysis, data structure, and assumptions. The original analysis plan, covariates, missing-data strategy, and analysis population are not reported in the registry record.

How should secondary tests be interpreted?

The posted secondary measures include heat pain threshold, heat pain tolerance, and pressure pain threshold at week 2. Their comparisons are also unadjusted re-calculations from arm summaries. The registry record does not list reported analyses for these measures. Because several endpoints are examined, separate unadjusted p-values do not by themselves control the chance of false-positive findings across the family of tests.

General statistical point: multiplicity arises when more than one hypothesis is tested. Prespecified correction methods can control an error rate across tests, while hierarchical testing can prioritize outcomes. The registry record does not report a multiplicity strategy or a hierarchy for the outcomes. Secondary findings should therefore be treated as exploratory, particularly when the primary result is imprecise and secondary analyses are not documented as a formal testing plan.

11. Confidence Intervals and Precision

The primary mean difference is -13.07 units, with a reported interval from -32.19 to 6.047. The interval includes zero, so the posted data are compatible with no difference in average week 2 pain as well as with differences in either direction. The point estimate alone suggests a lower average score in Self-CES, but its uncertainty is substantial relative to the estimate.

The lower and upper bounds are separated by a broad range of values. This means that the data do not provide a sharply localized estimate of the contrast. The interval includes a larger negative contrast than the point estimate and also extends to a positive value. It therefore does not establish either the presence or direction of a difference with precision. The unadjusted p-value of 0.18 is consistent with this uncertainty; it does not convert the result into evidence of equivalence.

General statistical point: an interval summarizes sampling uncertainty under the statistical method used. Narrower intervals generally indicate greater precision, while broader intervals leave more plausible values open. Precision depends on the amount of information and variability, not only on the observed difference. The number of participants in each arm and the variability of the pain scores are relevant to that uncertainty.

The confidence level and interval construction method are not reported in the registry record. The posted interval should therefore be quoted as reported without assigning it a confidence percentage or assuming a particular model. No baseline-adjusted estimate or alternative interval is reported in the registry record. The safest conclusion is that the observed arm contrast is uncertain and that the interval allows both no difference and effects in either direction.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm, not total participants or total events. They are planning illustrations based on the observed primary effect, not the trial's own original design calculation. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. For each planning scenario, the effect to detect is the stated fraction of the observed effect.

For planning at 100% of the observed effect, the illustration gives 66 participants per arm for 80% power and 88 participants per arm for 90% power. At 75% of the observed effect, it gives 117 participants per arm for 80% power and 157 participants per arm for 90% power. At 50% of the observed effect, it gives 263 participants per arm for 80% power and 352 participants per arm for 90% power. These are alternative hypothetical effect assumptions, not observed sample sizes.

In plain terms, 80% power describes the chance a study would detect an effect of the specified size under the calculation's assumptions if that effect were the true one. The 90% power column uses a higher target probability of detection, which requires more participants under the same assumptions. Smaller effects are harder to distinguish from random variation, so the planning illustrations require more participants per arm as the assumed effect becomes smaller.

These figures are not observed power and do not show what power the completed trial had. They are calculated from the observed effect, which is itself uncertain in a small study. The trial's original sample-size justification and design assumptions are not reported in the registry record. The planning figures should be read as illustrations of how sample size changes with assumed effect size and power target, not as evidence about the trial's design or the reliability of its result.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -13.070; pooled standard deviation σ = 26.712.
2. n = 2 × (1.96 + 0.842)² × 26.712² / -13.070² = 65.6, rounded up to 66 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- -13.07                      # observed difference in means
sigma <- 26.7117595826258                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(4016259)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 66 (80% power), 88 (90% power)
 75% of observed effect: n per arm = 117 (80% power), 157 (90% power)
 50% of observed effect: n per arm = 263 (80% power), 352 (90% power)
power.t.test: 66.5 
Simulated power at n = 66 per arm: 0.800 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry record lists a primary outcome and multiple secondary outcomes, including experimental pain sensitivity and psychosocial measures. It does not report a multiplicity adjustment, testing hierarchy, or rule for deciding which outcomes would receive confirmatory interpretation. Without such information, the individual secondary p-values should be read as unadjusted results rather than as family-wise evidence across all endpoints.

General statistical point: testing multiple outcomes creates multiple opportunities for a result to appear statistically unusual by chance. A prespecified correction can limit false-positive findings across a family of tests, and a hierarchy can reserve stronger claims for priority outcomes. Different procedures answer different questions; the appropriate approach depends on the design and analysis plan. Since no approach is reported in the registry record, none should be presumed.

Missing-data handling is not reported in the registry record. The posted arm sizes for the primary and secondary outcomes are 15.0 per arm, but the record does not explain whether these represent all randomized participants, all participants with observed endpoint data, or another analysis set. It also does not describe withdrawals, missing observations, imputation, or sensitivity analyses. No particular missing-data problem can be inferred from the absence of these details.

The analysis population is not reported in the registry record. It is therefore not possible to determine whether the results follow an intention-to-treat approach, a per-protocol approach, or another population definition. The record also does not report baseline adjustment, model specification, or a prespecified analysis plan. These omissions limit assessment of whether comparisons were planned in advance and whether all participants were handled consistently with randomization.

These reporting gaps do not invalidate the posted summaries, but they constrain what can be concluded from them. The primary and secondary comparisons should be understood as unadjusted calculations from the available arm summaries. The original approach to multiplicity, missing data, and analysis populations is not reported in the registry record.

15. 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 record reports 15 participants at risk for serious adverse events in each arm. Serious adverse events affected 0 participants in Sham-CES and 0 participants in Self-CES. Deaths were recorded as 0 in both arms. For other adverse events, the record also gives 15 participants at risk in each arm and 0 affected participants in each arm. No serious adverse event terms are listed.

These figures describe the adverse-event counts recorded for the trial. They do not establish that no adverse events of any kind occurred outside the categories or reporting period represented in the registry record. The record does not give event definitions, severity details beyond the serious-event category, relatedness assessments, or a narrative account of monitoring. Such details are not reported in the registry record.

With 15 participants per arm, zero recorded events provide limited information about uncommon harms. A zero count in a small study is not proof that an event cannot occur. The figures are best read as a description of the counts posted for this completed trial, not as a broad safety guarantee or a comparison capable of excluding rare events.

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

The primary result describes a lower mean week 2 pain score in the Self-CES arm than in the Sham-CES arm: 27.33 compared with 40.4, with an unadjusted mean difference of -13.07 units. The interval from -32.19 to 6.047 includes no difference, and the unadjusted p-value is 0.18. Thus, the posted summaries show a numerical contrast but leave substantial uncertainty about its size and direction.

The result does not establish that the groups were equivalent. Equivalence requires a prespecified margin and an analysis designed to assess whether the entire uncertainty range falls within that margin; such a margin and analysis are not reported in the registry record. Nor does the result establish that the intervention is ineffective. Failure to distinguish the observed contrast from no difference in this small study is not evidence that the true effect is exactly zero.

The result also does not establish a clinically important benefit. The registry record does not report a threshold for a meaningful change or provide a change-from-baseline estimate. The reported endpoint is a week 2 comparison of arm means, rather than a summary of individual improvements or a long-term outcome. The primary outcome's scale is useful for describing pain ratings, but the clinical meaning of the observed contrast cannot be determined from the mean difference alone.

The secondary findings concern experimental pain sensitivity and should not be substituted for the clinical pain endpoint. Their unadjusted status and the lack of reported multiplicity handling make them exploratory. Similarly, the posted adverse-event counts describe recorded events in this small sample and do not rule out uncommon harms.

The study's stated aim included feasibility and safety as well as preliminary efficacy, but specific feasibility outcomes and criteria are not reported in the registry record. The overall evidence is therefore a small randomized comparison with a lower observed mean pain score in Self-CES, an imprecise primary estimate, and limited ability to support broad conclusions. The registry record alone does not establish the treatment's effects beyond these posted results.

17. Why This Trial Matters Statistically

This trial is statistically instructive because it places a randomized comparison beside a small sample and a continuous, variable clinical outcome. The primary estimate has a clear direction and interpretable scale, but the interval is broad and crosses no difference. That distinction is important: an observed point estimate is not the same as a precise estimate, and a non-significant test is not an equivalence conclusion.

The study also illustrates why group summaries need to be read together. The mean gives the average score in each arm, while standard deviations show that participants' scores varied, especially in the Sham-CES arm. With 15.0 participants per arm, uncertainty around the comparison is substantial. The interval makes that uncertainty visible in a way that the arm means alone cannot.

The registry record identifies the study as a feasibility, safety, and preliminary-efficacy trial. That framing matters when interpreting the scope of the evidence: a small study can provide descriptive and planning information without settling an efficacy question. Planning illustrations based on an observed effect demonstrate how assumptions about effect size and target power influence sample size, but they do not reconstruct the original design justification.

Finally, the record highlights the importance of transparent analysis reporting. No reported analyses are listed, and the multiplicity strategy, missing-data approach, and analysis population are not reported in the registry record. The simple unadjusted comparisons remain informative descriptions of the posted summaries, while the absence of those details limits assessment of confirmatory inference. Readers can distinguish what the arm data show from what remains unknown about the trial's analysis process.

18. 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 randomized sample was 30 participants, with 15.0 per arm in the posted primary outcome. This provides limited information for estimating a variable pain outcome, and the primary comparison interval is broad. The record does not report a sample-size justification, so the enrollment target cannot be connected to a stated precision goal or a prespecified detectable effect.

The registry record does not provide detailed eligibility criteria, participant characteristics, study setting, or arm-specific procedures. The population is described as older adults with knee osteoarthritis, but further information needed to assess how well the enrolled participants represent other groups is not reported in the registry record. The masking classification is triple, but who was masked and how the sham device was implemented are not reported.

The primary endpoint is reported at week 2. Longer-term outcomes and persistence of any observed difference are not reported in the registry record. A baseline pain summary, change-from-baseline estimate, and clinically important difference threshold are also not reported, limiting interpretation of the endpoint as a change in symptoms or as a meaningful clinical effect.

The registry record lists no reported analyses. The analysis population, missing-data procedures, covariate adjustment, model specifications, and multiplicity handling are not reported. The posted comparisons are unadjusted re-calculations from arm summaries, and may not capture analyses that were conducted but not entered in the registry record. These reporting limitations matter especially for secondary outcomes, which include multiple measures and are not accompanied by a documented testing strategy.

Safety counts are zero for serious and other adverse events in each arm, but the sample is small and event definitions and monitoring details are not reported. These counts cannot provide strong information about uncommon events. Taken together, the available data support a descriptive comparison but leave important design, analysis, generalizability, and follow-up questions unresolved.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Self Cranial Electrical Stimulation (CES) for Pain in Older Adults With Knee Osteoarthritis (Self CES for Knee Pain) — NCT04016259.
• Registry record last updated 2020-11-16; status last verified 2020-10.
• Results first posted 2020-11-16.
• 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.

22. Record Summary

The completed randomized, triple-masked, parallel-group study examined self cranial electrical stimulation for pain in older adults with knee osteoarthritis. Enrollment was 30, with 15.0 participants in each arm for the posted primary result. The study purpose covered feasibility, safety, and preliminary efficacy over a two-week intervention period.

The primary endpoint was week 2 clinical pain on a 0-to-100 Numeric Rating Scale. Mean scores were 27.33 for Self-CES and 40.4 for Sham-CES. The unadjusted mean difference was -13.07, with an interval from -32.19 to 6.047 and an unadjusted p-value of 0.18. The interval includes no difference, leaving the estimate imprecise.

Some week 2 experimental pain sensitivity results are also posted, but secondary multiplicity procedures, missing-data methods, the analysis population, and reported statistical analyses are not reported in the registry record. Serious adverse events, other adverse events, and deaths were recorded as affecting 0 participants in either arm. The results describe this small trial and do not establish a precise or broadly generalizable treatment effect.