Transcranial Direct Current Stimulation for Pain Treatment in Gulf War Illness.: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Transcranial Direct Current Stimulation for Pain Treatment in Gulf War Illness. (NCT03547869), a randomized na study. The primary outcome is Pain Symptom Changes Will be Measured by a Visual Analogue Scale for Pain ..

2. Clinical Question

This is a question about both the scale of pain symptoms and their course over time. A comparison at one time could describe a difference at that measurement point, while an analysis across repeated measurements could assess how scores change over the follow-up period and whether the groups' patterns differ. The record says the results would be compared between the groups to study possible differences occurring throughout the sessions, but it does not specify the statistical model or testing strategy. Because the outcome results and analyses are not reported in the registry record, the planned question cannot be answered from the posted results.

3. Trial Design

The registry describes a randomized, double-masked, parallel-group study of active tDCS and sham tDCS for pain treatment in Gulf War Illness. The sponsor was The University of Texas at Dallas. The listed condition is Gulf War Syndrome, and the phase field is recorded as NA. The registry lists enrollment as 9. The study start date is 2018-03-12, and the primary completion date is 2022-01-25. Its status is TERMINATED.

In a parallel-group design, participants are assigned to a group and the groups receive different interventions. Randomization is intended to make allocation less dependent on participant characteristics or investigator choice; the record does not state how the random sequence was generated, concealed, or implemented. Double masking indicates that the trial was registered with that masking designation, but the record does not identify who was masked or describe the procedures. It therefore does not establish whether masking was maintained.

The registry lists active tDCS and sham tDCS as device interventions. It does not report detailed device settings, the number or duration of sessions, or the specific features that distinguished sham from active stimulation. The primary outcome was a pain Visual Analogue Scale, measured at baseline, immediately after the intervention, and at follow-up times extending to 24 weeks after the last tDCS session.

The record states that data collection had to stop because of COVID, as the IRB did not allow continued collection of human data. The trial is marked terminated. These details indicate that the record does not describe an ongoing study, but they do not establish how many planned measurements were completed or why the study was terminated beyond the stated data-collection constraint. An enrollment figure is not evidence that every participant contributed every scheduled outcome. The registry record does not report the analysis population or the number of participants with outcome data at each time.

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

Analysis population for the primary outcome, as defined in the registry: We had to stop collection of our data-collection due to COVID, as the IRB did not allow us to continue to collect human data.

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 Symptom Changes Will be Measured by a Visual Analogue Scale for Pain ., measured over Before tDCS stimulation (baseline), immediately after (immediate-post) tDCS intervention measurements and 1 week, 4 weeks, 12 weeks and 24 weeks after the last tDCS session..

The primary endpoint is change in pain symptoms measured with a Visual Analogue Scale for pain. The registry describes the outcome as a mean, with standard deviation as the measure of dispersion, and gives the unit as a score on a scale. The scale description identifies 0 as no pain and 100 cm as the maximum pain a person can imagine. The outcome was to be compared between active tDCS and sham tDCS.

A visual analogue scale is used to represent a person’s reported symptom intensity along a continuum. Using a consistent scale at repeated visits can describe both the level of symptoms and how that level changes over follow-up. Reporting a group mean describes its average score; the standard deviation describes variability among scores around that mean. Neither statistic alone captures every individual’s experience, and a group average does not indicate that all participants had similar scores.

The planned measurement times were before tDCS stimulation (baseline), immediately after the intervention, and 1 week, 4 weeks, 12 weeks, and 24 weeks after the last session. These repeated time points could support comparisons at particular visits or an analysis of the overall pattern over time. The registry record does not report pain scores, standard deviations, changes from baseline, or a statistical comparison. It therefore does not provide a numerical estimate of the endpoint result or its precision.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registered design is randomized, double-masked, and parallel-group. These labels describe important design features, but they do not provide a complete statistical analysis plan. Randomization is generally used to reduce systematic differences in allocation between groups. Masking is generally intended to limit the influence of knowledge about assignment on behavior, measurement, or interpretation. The registry record does not report the method of randomization, concealment procedures, or who was masked. It is therefore not possible to assess these procedures in detail from the record.

What does a mean and standard deviation describe?

The primary outcome is continuous: a Visual Analogue Scale pain score. The record specifies a mean as the summary parameter and standard deviation as the dispersion measure. In general, a mean gives the average of observed scores within a group, while the standard deviation describes how spread out those scores are around the mean. The mean can be useful for comparing group averages, but it does not show the full distribution or the experience of each participant. The standard deviation is not the same as the uncertainty in the estimated mean or in a between-group contrast.

To assess a group comparison, analysts commonly estimate a contrast such as the difference between group means. A confidence interval can express uncertainty around that estimate. Its interpretation depends on the study design and statistical model, and a narrow interval indicates greater precision than a wide interval. The registry record gives no endpoint means, standard deviations, contrasts, or confidence intervals, so none of these quantities can be interpreted for this trial.

Why does the repeated-measures structure matter?

Pain was to be assessed at baseline, immediately after the intervention, and at follow-up 1 week, 4 weeks, 12 weeks, and 24 weeks after the last session. These measurements are repeated within participants. In general, measurements from the same person tend to be related rather than independent. A statistical method for repeated measures should account for that within-person association; treating all measurements as unrelated can misstate the uncertainty of a comparison. The registry record does not report a repeated-measures model or any other method used to account for that association.

Several analytic targets are possible in a repeated-measures study. An analysis might estimate a group difference at each visit, compare changes from baseline, or estimate whether the pattern over time differs between groups. These questions are not interchangeable, and they can produce different estimates. The registry describes comparisons between the groups to study possible differences throughout the sessions, but does not identify the exact estimand, contrast, or primary follow-up time.

How should multiple time points be considered?

When an analysis tests several outcomes or time points, the chance of at least one apparently notable result can increase if each test is interpreted separately without accounting for multiplicity. In general, multiplicity methods can control the interpretation of a family of tests, but the appropriate approach depends on which comparisons were planned and which claim is intended. The registry record does not report a multiplicity strategy, hierarchy of tests, or prespecified contrast. It also does not report any analyses from which to determine how the time points were treated.

What do the planning assumptions mean?

The registry describes a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between the arms, and a normal approximation. The effect to detect is described as a stated fraction of the observed effect. These are planning assumptions, not evidence about what the trial observed, and the illustration is not observed power. The record does not report the trial’s own sample-size justification. It also does not report an observed effect estimate in the outcome results, so the planning basis cannot be independently evaluated from the posted results.

In general, a sample-size calculation relates assumptions about the effect to detect, variability, significance level, allocation, and desired power. Its output is a planning quantity, not a measurement of the trial’s actual power after data collection. A calculation based on a noisy or unavailable observed effect may also be uncertain. No numerical sample-size estimate is included in the registry record, so the planning assumptions alone do not establish what enrollment was intended to achieve.

What can be concluded from the registered method?

The record establishes the broad design, outcome type, summary measure, intervention groups, and measurement schedule. It does not report the statistical model, effect estimate, uncertainty interval, hypothesis test, missing-data method, or analysis population. Those omissions prevent a full appraisal of whether the statistical analysis matched the intended clinical question. General statistical principles explain what such methods would need to address, but they cannot fill in an analysis that is not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The primary pain outcome was scheduled at baseline, immediately after the intervention, and at follow-up 1 week, 4 weeks, 12 weeks, and 24 weeks after the last tDCS session. Considering results across several time points can raise a multiplicity question: repeated tests can make an isolated finding harder to interpret unless the analysis plan identifies the main comparison or explains how multiple tests will be handled. The registry record does not report a prespecified multiplicity strategy, a hierarchy among visits, or an analysis of the repeated measurements.

The record states that data collection stopped because of COVID, as the IRB did not allow continued collection of human data. This explains the stated interruption, but the record does not report which participants had measurements at which visits, how much follow-up was completed, or why any particular measurement was absent. The registry record does not report a missing-data method, such as an approach to incomplete repeated measurements, nor does it describe sensitivity analyses for missing outcomes.

The registry lists enrollment as 9 but does not report the number included in a primary outcome analysis or an analysis population. It does not state whether all randomized participants were analyzed as assigned, whether any participants were excluded, or how deviations from the assigned intervention were handled. The record lists zero analyses, so there is no reported analysis set to evaluate. These gaps limit interpretation because conclusions from repeated-measures data can depend on which observations are available and on assumptions about missingness. The posted results do not permit assessment of those assumptions or of the effect of incomplete follow-up on the intended comparison.

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 1% reporting threshold.

The registry’s adverse-event summary lists serious adverse events for the active tDCS group with 6 at risk and 0 affected, and for the sham tDCS group with 3 at risk and 0 affected. Deaths are listed as 0 in both groups. For other, non-serious adverse events, the record lists 6 at risk and 0 affected in the active tDCS group, and 3 at risk and 0 affected in the sham tDCS group. No serious adverse-event terms are listed.

These are reported counts in the registry record, not a complete measure of risk. A count of zero affected means that the record lists no affected participants for that category; it does not establish that an event is impossible or that the interventions have no risk. The record does not describe the adverse-event reporting period, the method of monitoring, or whether reporting was complete after data collection stopped. The listed at-risk counts also do not establish how many participants contributed pain outcomes or how long each participant was observed for safety.

Because the study was terminated and the registry lists enrollment as 9, the adverse-event summary should be read as a limited description of reported events, not as a precise estimate of event frequency or comparative safety. The registry record does not provide event rates, uncertainty estimates, or a detailed account of safety assessments.

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

The registry record establishes that a randomized, double-masked, parallel-group study was intended to compare active tDCS with sham tDCS for pain symptoms in Gulf War Illness. It identifies a Visual Analogue Scale for pain as the primary outcome, describes the scale anchors, and lists repeated measurement times through 24 weeks after the last tDCS session. It also states that data collection stopped because of COVID, when the IRB did not allow continued collection of human data.

Those design details do not establish whether pain scores differed between groups. The registry record does not report outcome values or analyses. There is no reported estimate of a group difference, no confidence interval describing its precision, and no p-value for a statistical test. The direction and size of any effect therefore cannot be inferred from the posted results. The absence of an analysis should not be interpreted as evidence of no effect, equal outcomes, or benefit.

The record’s adverse-event counts are similarly limited. It lists zero affected participants for serious and other adverse events in both groups, with the corresponding at-risk counts, but does not report the assessment period or completeness of monitoring. These entries describe what the registry records, not the full range of possible safety outcomes or a definitive comparison of safety between groups.

As a result, the trial record is informative about the question that was to be studied and the interruption to data collection, but it does not support a conclusion about the primary pain outcome. No medical or treatment conclusion follows from an outcome analysis that is not reported. The missing results also mean that neither the magnitude nor the precision of any possible difference can be assessed. Readers should distinguish the registered design and planned measurements from findings that would require reported participant data and statistical analyses.

13. Why This Trial Matters Statistically

This trial is statistically notable because its registry record contains a clearly identifiable clinical question and a repeated-measures pain outcome, but no reported outcome analysis. That distinction matters: registering an endpoint and measurement schedule establishes what was intended to be measured, whereas interpreting an intervention comparison requires outcome estimates and information about uncertainty. Without those results, the record cannot show the direction, size, or precision of a difference between active and sham tDCS.

The study also illustrates why study status and data availability are important context for statistical interpretation. The record is marked TERMINATED and states that data collection stopped because of COVID and an IRB restriction on continued human data collection. Those details explain the stated interruption but do not reveal which measurements were completed or how incomplete follow-up was handled. A study can have a defined outcome and follow-up plan while still lacking the reported data needed to answer its question.

The repeated pain measurements make analysis choices important. A comparison at a selected visit, a comparison of change from baseline, and a model of the trajectory over time address different questions. If several visits are tested, multiplicity can also affect how isolated findings should be interpreted. The registry record does not report which analytic approach was used, whether any adjustment was planned, or any results from an analysis. This makes clear why a protocol-level description alone cannot substitute for a statistical report.

Finally, the adverse-event entries demonstrate the difference between a recorded zero count and a comprehensive estimate of safety. The record lists zero affected participants in the reported categories, but does not describe monitoring duration or completeness. In statistical terms, the information is descriptive and limited; it does not establish the absence of risk. Taken together, the record highlights the value of transparent reporting of estimates, uncertainty, analysis populations, and missing-data methods alongside trial design details.

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.

Several limitations specific to this trial restrict interpretation. The registry marks the study as TERMINATED and states that data collection stopped because of COVID, as the IRB did not allow further collection of human data. The record does not report how many planned pain measurements were obtained or how much follow-up was completed. Enrollment is listed as 9, but that entry does not establish how many participants contributed to each scheduled outcome measurement.

The registry record does not report the primary outcome results, group means, standard deviations, between-group contrasts, confidence intervals, or p-values. It lists zero analyses. Accordingly, the magnitude and precision of the intended comparison cannot be evaluated. The record also does not report an analysis population, exclusions, or a method for handling incomplete outcome data.

The endpoint involved repeated assessments, but the statistical model and target contrast are not reported. The record does not explain whether the main comparison was intended at a particular visit, across visits, or as a change-from-baseline comparison. It also does not report how multiplicity across time points was addressed. This limits assessment of whether a statistical analysis would have aligned with the stated clinical question.

Design details are also incomplete in the record available for this analysis. It does not describe the randomization procedure, masking procedures, device settings, session schedule, or a sample-size justification. These omissions do not establish that such procedures were absent; they mean they are not reported in the registry record.

The adverse-event summary lists zero affected participants in the serious and other categories, but the reporting period, monitoring process, and completeness are not stated. The small enrollment and interrupted data collection make the event counts a limited description rather than a precise safety comparison. Overall, the registry record documents the intended design and the reason data collection stopped, but it does not provide the outcome evidence required to interpret efficacy or quantify uncertainty.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Transcranial Direct Current Stimulation for Pain Treatment in Gulf War Illness. — NCT03547869.
• Registry record last updated 2025-02-03; status last verified 2025-01.
• Results first posted 2025-02-03.
• 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.

18. Record Summary

NCT03547869 is a randomized, double-masked, parallel-group study sponsored by The University of Texas at Dallas. It compared active tDCS with sham tDCS for pain symptoms in Gulf War Illness. The registry lists enrollment as 9, gives a study start date of 2018-03-12 and a primary completion date of 2022-01-25, and records the status as TERMINATED. The phase field is NA.

The primary outcome was a mean pain score on a Visual Analogue Scale, with standard deviation as the dispersion measure. Measurements were scheduled from baseline through 24 weeks after the last tDCS session. The record states that data collection stopped because of COVID and an IRB restriction on continued human data collection. It reports no outcome analyses or pain results. Adverse-event entries list zero affected participants in the reported serious and other categories, with no deaths listed. The record does not report the analysis population, missing-data approach, or statistical model.