Effects of Light Emitting Diode Irradiation on the Conduction Parameters of the Superficial Radial Nerve: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effects of Light Emitting Diode Irradiation on the Conduction Parameters of the Superficial Radial Nerve (NCT01513148), a randomized na study. The primary outcome is Nerve Conduction Velocity (Meters Per Second).

2. Clinical Question

3. Trial Design

The registry describes a randomized, double-masked, parallel-group study marked completed. Participants were assigned to light irradiation or sham irradiation. The study summary describes nerve conduction measurements in healthy subjects, with one baseline measurement and five post-irradiation recordings at 2-minute intervals. The primary outcome timeframe also lists pre-treatment and measurements at 0, 2, 4, 6, 8 and 10 minutes after treatment. The registry lists enrollment as 32, while the study summary says the study will be conducted with 64 subjects. The record does not explain this difference. For the posted outcomes, each arm has 14 participants.

The intervention was super luminous diode irradiation over the superficial radial nerve; the sham arm received sham irradiation over the same area for the same time period. The study summary specifies a dose of 2 J/cm2 and identifies the device as a Dynatronics Solaris Model 705. The registry lists the study phase as not applicable. The sponsor is Shenandoah University. The registry gives the study start as 2006-06 and primary completion as 2008-09.

The design makes the sham arm important: it can help distinguish changes associated with irradiation from changes that also occur with repeated measurements or the passage of time. However, the available primary outcome comparisons are against a zero pre-treatment reference within each arm, rather than direct comparisons of change between randomized groups. Randomization alone does not turn those within-arm contrasts into a treatment-versus-sham estimate. The registry record does not report the original statistical analysis plan, the method used to analyze repeated measurements, or details of how masking was implemented.

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:

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 Nerve Conduction Velocity (Meters Per Second), measured over pre-treatment, 0 min, 2 min, 4 min, 6 min, 8 min and 10 min after treatment.

The primary endpoint is nerve conduction velocity, measured in meters per second, and expressed as change from the pre-treatment measurement. The registry describes readings immediately after treatment and at 2-minute intervals through 10 minutes. A positive change is defined in the record as an increase, interpreted as faster velocity; a negative change indicates a decrease from baseline.

Nerve conduction velocity measures how quickly an electrical signal travels along a nerve. In this study it serves as a physiological measure of the superficial radial nerve during a short period after irradiation. That makes it relevant to the study’s stated question about whether light exposure is associated with a change in peripheral nerve conduction. It is not itself a measure of pain relief or a clinical health outcome. The registry’s rationale connects LED research to possible mechanisms relevant to pain, but the primary endpoint records nerve conduction rather than pain.

Repeated measurements can describe the timing and persistence of any observed change. They also create an analysis challenge: readings from the same participant are related, rather than independent observations. The registry record does not report how that within-participant relationship was incorporated into the sponsor’s analysis. The posted outcome summaries report means and standard deviations at each time point, while the available calculated comparisons use a zero pre-treatment reference. These summaries are useful for describing the recorded changes, but they do not replace a direct comparison of change between randomized groups.

7. Results Posted in the Registry

• Light NCV Time 0: mean -0.36 versus 0.00 on control; difference -0.36 (95% CI -0.99 to 0.27), standardized effect d = -0.42; z-test p = 0.264.
• Light NCV Time 2: mean 0.45 versus 0.00 on control; difference 0.45 (95% CI -0.40 to 1.29), standardized effect d = 0.39; z-test p = 0.301.
• Light NCV Time 4: mean 0.15 versus 0.00 on control; difference 0.15 (95% CI -0.79 to 1.08), standardized effect d = 0.12; z-test p = 0.758.
• Light NCV Time 6: mean -0.04 versus 0.00 on control; difference -0.04 (95% CI -0.95 to 0.87), standardized effect d = -0.03; z-test p = 0.930.

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.

Negative Peak Latency (Milliseconds)

• 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:
  • Light NPL Pre-treatment: mean 0.00 versus -0.01 on control; difference 0.01 (95% CI -0.02 to 0.04), standardized effect d = 0.17; z-test p = 0.657.
  • Light NPL Time 0: mean 0.41 versus -0.01 on control; difference 0.42 (95% CI 0.19 to 0.65), standardized effect d = 1.37; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Light NPL Pre-treatment and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Light NPL Time 0 than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Temperature (Degrees C)

• 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:
  • Light Temp Time 0: mean 0.41 versus 0.00 on control; difference 0.41 (95% CI 0.19 to 0.64), standardized effect d = 1.36; z-test p = <0.001.
  • Light Temp Time 2: mean 0.99 versus 0.00 on control; difference 0.99 (95% CI 0.67 to 1.32), standardized effect d = 2.24; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Light Temp Time 0 than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Light Temp Time 2 than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The secondary outcomes are negative peak latency and temperature, each recorded over the same short post-treatment period. Their posted summaries show time-varying means in both assigned groups. The calculated comparisons include notably different patterns from the primary nerve conduction velocity summaries, but they are not sponsor-reported analyses, and the record does not provide a full inferential analysis across each outcome and time point. The overall pattern should therefore be viewed as descriptive rather than as a corroborating or contradictory test of the primary question.

These outcomes may help characterize other physiological measurements recorded during the experiment, but they do not substitute for the primary endpoint. Similar caution applies to apparent differences: an association in a secondary measure does not establish that the randomized groups differ on the primary measure, nor does it demonstrate a clinical effect. The record identifies no additional clinical outcome such as pain relief among the posted measures.

The secondary comparisons are unadjusted. General explanation: when several outcomes and time points are examined, the chance of finding one apparently unusual result by chance increases. A prespecified hierarchy or multiplicity adjustment can help control interpretation, but the registry record does not report whether either was planned or applied. The absence of a reported analysis plan means the intended status of these outcomes—confirmatory, supportive or exploratory—is not reported in the registry record. Their results should carry less weight than a well-specified primary comparison and should be interpreted alongside the uncertainty and analysis limitations affecting the primary endpoint.

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

• Negative Peak Latency (Milliseconds)
• Temperature (Degrees C)

9. Statistical Interpretation

10. Statistical Methods Explained

The outcome is continuous, so the registry reports means and standard deviations. The mean describes the central value of the observations, while the standard deviation describes how dispersed individual measurements are around that mean. A mean change can be positive or negative because each value is expressed relative to baseline. The registry defines positive change as an increase in nerve conduction velocity. These summaries describe the groups; they do not show the full distribution of participant-level measurements.

What does a confidence interval convey?

General explanation: a confidence interval describes the statistical uncertainty around an estimate under the assumptions of the method used to calculate it. A narrower interval indicates greater precision, while a wider interval indicates less precision. If an interval for a mean difference includes zero, the data are compatible with no mean difference from the reference as well as with values on either side of zero. The interval does not give the probability that the true value lies within those specific limits. The registry record does not identify the confidence-interval method used by the sponsor.

The posted comparisons pair each follow-up mean with a zero baseline reference, as indicated by the comparison estimates. These are not direct light-versus-sham comparisons at follow-up. A randomized trial’s principal comparative question is ordinarily addressed by estimating how outcomes differ between assigned groups, with appropriate treatment of baseline and the repeated measurements. The record’s available comparisons do not supply that contrast. The calculated comparisons are simple, unadjusted re-calculations from posted summary statistics and should be understood as such.

How should the p-values be read?

General explanation: a p-value describes how unusual data at least as inconsistent with a specified null hypothesis would be if that hypothesis and the analysis assumptions were true. It is not the probability that the null hypothesis is true, nor does it measure the size or clinical importance of an effect. The reported p-values are unadjusted. For example, the sham-arm 6-minute result has an unadjusted p-value of 0.006, but that value addresses its listed zero-reference comparison, not the difference between randomized arms. The light-arm p-values do not answer a treatment-versus-sham question either.

Many measurements and outcomes create multiple opportunities for an apparently notable result to occur. General explanation: when many hypotheses are tested, the chance of at least one small p-value can increase, even if none of the underlying effects is meaningful. Methods such as a prespecified testing hierarchy or multiplicity adjustment can address this issue, but the registry record does not report whether such a plan existed or was used. Without that information, the unadjusted results should be treated as exploratory rather than as a complete confirmatory analysis.

Why do repeated readings need special care?

General explanation: measurements on the same person tend to be related. Treating each time point as an independent observation can misstate uncertainty and does not use the within-person structure appropriately. Analyses may model that correlation, compare changes between groups, or summarize a prespecified time profile. Which approach is appropriate depends on the design and analysis plan. The registry gives the repeated-measure schedule but does not report the sponsor’s method for modeling these readings, the covariance structure, or whether the analysis used all time points jointly.

The posted mean and standard deviation at each time point offer a straightforward description, but the summaries cannot reconstruct every participant’s trajectory or the correlation between readings. The posted comparisons therefore cannot establish whether the observed time pattern differs by randomized group. For this question, an estimated between-group contrast over time, with its uncertainty and a clearly described analysis method, would be more directly informative.

What is not documented?

The registry record reports zero posted analyses for the outcomes and does not include sponsor-reported inferential analyses. It does not report the original statistical plan, the sample-size justification for the trial, any interim analyses, the analysis population, or procedures for missing observations. These omissions limit the ability to determine whether the posted comparisons were planned, how they relate to the original protocol, or how completely the repeated-measure data are represented. The planning illustrations based on observed effects are separate from the original design assumptions, which are not reported in the registry record.

The study summary describes a randomized, double-masked, parallel-group design. Randomization can balance measured and unmeasured characteristics on average, but it does not resolve the difference between a within-arm change and a randomized between-arm contrast. Masking may reduce some risks of biased behavior or assessment, but the registry does not describe who was masked or how. Interpretation should consequently keep the available estimand, the short follow-up, and the uncertainty of the posted summaries in view.

11. Confidence Intervals and Precision

The confidence intervals are central to judging how precisely the short-term changes are estimated. In the light arm, the posted 95% intervals for the primary outcome are -0.987 to 0.271 at 0 minutes, -0.400 to 1.293 at 2 minutes, -0.788 to 1.082 at 4 minutes, -0.953 to 0.871 at 6 minutes, -0.663 to 1.223 at 8 minutes and -1.009 to 1.209 at 10 minutes. Every one includes zero. The estimates therefore do not pin down a direction of change from the zero reference with high precision, and plausible values within each interval include both decreases and increases.

In the sham arm, the 6-minute estimate is 1.116, with an interval from 0.315 to 1.917. The interval excludes zero for that particular unadjusted comparison. The other listed sham intervals include zero. This difference in interval placement does not establish a difference between groups. A confidence interval for the direct light-versus-sham contrast would be needed to quantify the uncertainty in that randomized comparison, and such a contrast is not included among the posted calculations.

General explanation: intervals reflect both the observed estimate and its uncertainty, which is affected by the amount of information and variability in the data. The posted standard deviations and group sizes of 14 participants per outcome arm indicate why precision deserves attention in interpreting these estimates. An interval that includes zero does not prove the absence of an effect; it indicates that the estimate remains compatible with a range of values including no mean change relative to its reference. Likewise, an interval excluding zero does not by itself settle the treatment-versus-sham question or account for multiple testing.

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 sample-size illustrations translate an observed standardized effect into hypothetical group sizes for future planning. These are participants per arm, not total events, because the outcomes are continuous. The listed assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Each row considers detecting the stated fraction of the observed effect: 100%, 75% or 50%. The original trial’s own design assumptions and sample-size justification are not reported in the registry record.

The 80% power column gives the estimated participants per arm for a hypothetical study to have an 80% chance of detecting the specified effect under those planning assumptions, if that effect and the assumptions were correct. The 90% power column gives the corresponding group size for a 90% chance. Higher planned power generally requires more participants. The illustrations use the observed effect as their starting point, so they should not be treated as independent evidence that the effect is real or as a reconstruction of the trial’s original design.

Smaller effects need more participants to detect with the same planned power, because they are harder to distinguish from random variation. The estimates can change substantially across time points because the observed effects and variability differ. In particular, planning calculations based on estimates close to zero can imply extremely large group sizes; such values are highly sensitive to the observed estimate and should not be read as practical recommendations. These calculations are not observed power. They are hypothetical planning illustrations, not a measure of how likely the completed study was to find an effect.

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 = -0.358; pooled standard deviation σ = 0.849.
2. n = 2 × (1.96 + 0.842)² × 0.849² / -0.358² = 88.2, rounded up to 89 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 <- -0.358                      # observed difference in means
sigma <- 0.848528137423857                     # 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(1513148)
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 = 89 (80% power), 119 (90% power)
 75% of observed effect: n per arm = 157 (80% power), 210 (90% power)
 50% of observed effect: n per arm = 353 (80% power), 473 (90% power)
power.t.test: 89.2 
Simulated power at n = 89 per arm: 0.801 (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 study includes repeated measurements at multiple post-treatment times and posts more than one outcome. Each additional comparison creates another opportunity for a nominally notable result. Because the available p-values are unadjusted, they do not account for the family of tests across time points or outcomes. General explanation: multiplicity procedures can limit the overall chance of false-positive findings, but they may also change the threshold for interpreting individual results. The registry record does not report a multiplicity strategy, a hierarchy of outcomes, or whether any results were intended to be confirmatory.

Missing-data handling is also not reported in the registry record. The available outcome summaries list 14 participants in each arm at each displayed time, but those summaries alone do not explain whether all assigned participants contributed data, whether any measurements were missing, or how missing observations were handled. The registry enrollment is 32, while the study summary describes 64 subjects; the reason for this difference is not reported. The record does not provide an account of participant flow that resolves it.

The analysis population is not reported in the registry record. It is therefore unclear whether the posted summaries represent all randomized participants, participants who completed the measurements, or another defined group. The record also does not state whether participants were analyzed according to assignment, whether exclusions occurred, or how deviations from the assigned intervention were handled.

These gaps matter because incomplete follow-up, selective analysis, and repeated testing can affect both the estimated effects and their uncertainty. They do not prove that the results are biased, but they constrain what can be concluded from the registry record. The record also does not report the original statistical plan or interim analyses. Without those details, it is not possible to determine whether the displayed time points and outcomes were selected before analysis or how the reported calculations relate to the intended confirmatory approach.

15. 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 0% reporting threshold.

The registry lists 16 participants at risk for serious adverse events in the light therapy group and 16 in the sham irradiation group. It records zero serious adverse events affecting participants in either group. The figures therefore indicate that no serious adverse events were posted for the listed at-risk participants during the safety reporting period described in the record.

The death counts are null for both groups, which means deaths are not reported in the registry record; a null entry should not be read as a documented count of zero. The record also lists zero participants affected by other adverse events in each group among 16 at risk. These entries are limited to what is posted and do not establish that no event of any kind occurred outside the recorded categories or reporting period. The registry record does not report the safety follow-up duration or provide additional details about event collection. The numbers should be read as registry safety reporting, not as a guarantee about safety.

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

The posted primary outcome data describe changes in nerve conduction velocity from a zero pre-treatment reference over a short period after light or sham irradiation. In the light group, the means vary over time, and all listed unadjusted confidence intervals include zero. In the sham group, the 6-minute within-arm estimate has an interval excluding zero, while the other listed intervals include zero. These findings describe the reported measurements; they do not establish a difference in effect between the randomized groups.

The distinction is essential. A change within the light group is not the same as a change caused by light relative to sham. Likewise, observing a nonzero change in one group and not another does not demonstrate that the groups differ. A direct between-group comparison of change, with its confidence interval and a suitable repeated-measures analysis, would address the randomized contrast more directly. That comparison is not reported among the available results.

The primary endpoint is a physiological measure, not a direct measure of pain relief or of a clinical benefit. Although the registry summary frames the work as fundamental research about a possible mechanism relevant to pain, these data do not establish whether participants experienced pain relief. The short measurement window also does not address longer-term outcomes. The registry record does not report a clinical outcome beyond the posted conduction, latency and temperature measures.

The small posted outcome groups, uncertainty around many estimates, unadjusted tests, and lack of a reported sponsor analysis plan all warrant restraint. Secondary findings may add descriptive context, but they are not a replacement for the primary randomized comparison and carry less weight when multiplicity handling is unknown. The appropriate conclusion is that the record presents short-term physiological summaries with limited precision and does not provide a clear estimated treatment-versus-sham effect for the primary endpoint.

17. Why This Trial Matters Statistically

This study is statistically instructive because its design and its posted comparisons answer different questions. Random assignment to light or sham is intended to support a comparison between groups. Yet the available primary calculations compare each follow-up mean with a zero baseline reference within an arm. Those summaries can describe change over time but do not isolate how much the change differs between the randomized groups. Recognizing the estimand—the quantity an analysis is intended to estimate—is necessary before interpreting a p-value or confidence interval.

The repeated measurement schedule also highlights an important design feature. Readings from one participant across time are related, so analyses need to account for that structure if they are to estimate a time profile or a treatment-by-time difference appropriately. The registry record does not report the sponsor’s method for doing so. Meanwhile, multiple time points and secondary outcomes make unadjusted findings more vulnerable to selective emphasis and chance patterns.

Finally, confidence intervals provide more information than a binary significant/not-significant label. The primary light-arm intervals show substantial uncertainty around the change estimates, while a single sham time point has an interval excluding zero. The latter is not a direct randomized treatment contrast. Together, these features make the record a useful example of why study design, analysis target, multiplicity and precision need to be considered together, rather than treating an isolated p-value as the study’s answer.

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 most important trial-specific limitation is that the available primary comparisons do not directly compare change between the light and sham arms. Instead, the listed calculations use a zero reference for the time-point change within each arm. This prevents the displayed estimates from directly answering whether assignment to light irradiation differed from assignment to sham.

There is also an unexplained difference between registry enrollment of 32 and the study summary’s description of 64 healthy subjects. The posted outcome groups contain 14 participants per arm, but the record does not provide participant flow or explain the difference between the enrollment and summary figures. The relationship between the registry’s Peripheral Neuropathy condition listing and the study summary’s healthy-subject population is likewise not clarified.

The study measured outcomes over a short period, through 10 minutes after treatment. The record therefore does not address longer-term nerve conduction or clinical outcomes such as pain relief. The posted primary estimates have broad confidence intervals, and the groups are small. Multiple time points and secondary outcomes are presented with unadjusted comparisons, while multiplicity handling is not reported.

The registry record does not report the original statistical analysis plan, analysis population, approach to repeated measurements, missing-data procedures, interim analyses or original sample-size justification. These absences limit assessment of whether the reported comparisons match the prespecified analysis and how complete the analyzed data are. They should be treated as uncertainties in interpretation, not as evidence that any particular procedure was or was not used.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Effects of Light Emitting Diode Irradiation on the Conduction Parameters of the Superficial Radial Nerve — NCT01513148.
• Registry record last updated 2013-07-29; status last verified 2013-07.
• Results first posted 2013-07-04.
• 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 registry describes a completed, randomized, double-masked, parallel-group study of LED irradiation versus sham irradiation over the superficial radial nerve. The study summary describes healthy subjects and a short series of nerve conduction measurements, while the registry lists Peripheral Neuropathy as a condition. Enrollment is listed as 32, but the summary describes 64 subjects; the record does not explain the difference. Posted outcome groups contain 14 participants per arm.

The primary outcome is change in nerve conduction velocity through 10 minutes after treatment. The light-arm intervals include zero at all listed times; the sham arm has one unadjusted within-arm interval excluding zero at 6 minutes. The available comparisons are not direct randomized contrasts of change between arms. Secondary outcomes are negative peak latency and temperature. No sponsor-reported analyses are posted, and the statistical plan, analysis population, missing-data approach and multiplicity handling are not reported in the registry record.