The Effects of CBT and tDCS on Fibromyalgia Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Effects of CBT and tDCS on Fibromyalgia Patients (NCT02723175), a randomized na study. The primary outcome is Baseline Quantitative Sensory Testing (QST).

2. Clinical Question

The study is registered as a randomized, double-masked, parallel trial with an enrollment of 15. Its brief summary describes an aim to assess the effects of CBT, anodal tDCS, and combined CBT+tDCS on clinical pain and functioning in fibromyalgia. However, the intervention and arm details listed in the record describe sham and active tDCS, without setting out how CBT relates to those arms. That difference limits how precisely the planned comparison can be reconstructed from the registry record.

QST is described as a laboratory pain assessment using heat stimuli. It records temperatures associated with first sensing the stimulus, beginning to feel pain, and no longer tolerating the stimulus. The registry also lists measures of pain, mood, health status, and fibromyalgia impact as secondary outcomes. Those measures indicate a broader interest in pain and functioning, but the record does not report their analyzed results.

3. Trial Design

The registry classifies this study as randomized, double-masked, and parallel, with an enrollment of 15. Its status is completed. The recorded start is 2014-12 and primary completion is 2016-11. The phase is listed as NA, and the sponsor is the Medical University of South Carolina.

The listed arms are Sham tDCS Stimulation and Anodal tDCS Stimulation of DLPFC. The sham arm description specifies 30 minutes of sham stimulation; the active arm description specifies 30 minutes of active tDCS. The device description characterizes tDCS as a minimally invasive technique using a small amount of electricity, 2mA, to temporarily stimulate specific brain areas in awake people. The record does not give additional details about how the masking was implemented or assessed.

There is an important gap between the brief study summary and the detailed arm information. The summary describes CBT, anodal tDCS, and combined CBT+tDCS, while the listed intervention and arms specify tDCS and its sham comparator. How CBT was assigned or delivered, and whether there were additional treatment combinations, is not reported in the registry record. It is therefore not possible to define all intended treatment contrasts from the listed descriptions alone.

The registry names baseline QST as the primary outcome, with measurement before treatment and results expressed as a mean with standard deviation. The measure includes several sensory and pain-threshold or tolerance categories. Secondary outcomes include baseline mood, pain, health-survey, and fibromyalgia-impact measures, along with percent change in average daily pain at Treatment Visit 3 and a depression measure at 1 Month Follow up. The record lists 18 outcome measures and 0 analyses. It does not report participant flow, allocation concealment, protocol deviations, or the analysis population.

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 Baseline Quantitative Sensory Testing (QST), measured over Before Treatment.

Baseline quantitative sensory testing (QST) is a laboratory assessment of responses to heat stimuli. The record describes use of a Pathway Thermo-sensory Analyzer System and identifies three types of response: the temperature at which a participant first senses the stimulus, the average pain threshold, and the temperature at which the participant can no longer tolerate the stimulus. The recorded unit is degrees Celsius, and the stated temperature range is 37 degrees celsius to 50 degrees celsius.

The registry explains that a lower average pain-threshold temperature represents a lower pain threshold, while a higher temperature represents a higher threshold. It gives the corresponding direction for tolerance: a lower temperature represents lower pain tolerance and a higher temperature represents higher tolerance. Those descriptions clarify how the measurements are intended to be interpreted, but no actual participant values or group summaries are reported in the registry record.

QST is used as a structured laboratory measure of sensory and pain responses, rather than as a direct report of everyday pain or functioning. It can characterize responses under the testing conditions described in the record. The primary outcome is explicitly labeled as baseline and measured before treatment. A pretreatment measure can describe starting status, but by itself does not show a treatment effect. The registry record does not identify a single post-treatment QST value or change as the primary comparison. It also does not report the QST results, so the observed levels and the precision of any group contrast cannot be assessed from the record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods should connect the research question, the measured outcome, and the comparison being estimated. In this record, the trial is identified as randomized, double-masked, and parallel. These design labels describe how groups were intended to be formed and followed, but do not themselves establish that the treatment groups were comparable in the enrolled sample or that masking was successful. Details about randomization procedures, concealment, and assessment of masking are not reported in the registry record.

What does the primary measurement represent?

QST is a continuous measurement in degrees Celsius. The registry says the primary outcome is a mean with standard deviation and describes several response categories: sensory detection, average pain threshold, and tolerance. A mean summarizes a group’s central level on a continuous scale. A standard deviation describes the spread of participant measurements around that mean. These summaries answer different questions: the mean concerns the average level, while the standard deviation concerns variability among observations.

The category definitions also matter. A higher value does not mean the same thing for every interpretation unless the outcome component is specified. For average pain threshold, the registry says a higher temperature represents a higher threshold. For tolerance, a higher temperature represents higher pain tolerance. Sensory detection is described as when the participant first begins to feel the stimulus, but the record does not provide a directional interpretation for that category. The lack of reported category-specific results prevents applying those definitions to observed group data.

What would a treatment contrast require?

A treatment effect requires a defined contrast between groups on an outcome at a stated time or in change over time. Because the registered primary measure is baseline QST before treatment, a baseline description alone is not an estimate of a treatment effect. A post-treatment comparison, a change-from-baseline contrast, or another specified analysis would be needed to address whether the groups differed after treatment. The registry record does not report such a primary contrast. It also flags that the primary outcome includes several categories or time points and was not reduced to one comparison.

Randomization can support causal comparisons when the assigned groups, outcome measurement, and analysis are clearly specified and the trial is analyzed appropriately. It does not remove uncertainty from a small study, missing measurements, departures from assignment, or selective reporting. These are general statistical considerations; the registry record does not provide enough analysis detail to assess them for this study.

How should uncertainty be read?

A point estimate, such as a difference in group means, gives a single summary of the observed contrast. A confidence interval gives a range of values compatible with the data and the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval, but neither the estimate nor its interval is reported for the outcomes in this record. A p-value, if available, would address compatibility with a specified null model under the analysis assumptions; it would not by itself describe the size or practical importance of an effect. No p-values are reported.

Continuous outcomes can sometimes be analyzed with methods that assume approximately normal residuals and similar variability across groups. If observations are more variable than the model allows, standard errors can be too small and intervals or tests can be misleading; this is the general reason over-dispersion or excess variability matters. The registry record does not state which model was used, whether distributional assumptions were checked, or how any such departures were handled. No analysis is listed, so the method used for the registered outcomes is not reported in the registry record.

What can the planning assumptions establish?

The record describes a planning illustration based on the observed effect, using a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. It states that the effect to detect is a specified fraction of the observed effect, and that non-time-to-event planning values are expressed as participants per arm. These assumptions describe an illustrative calculation rather than the trial’s own design justification. The registry record does not report the numerical planning results or a sample-size justification used to design the trial.

Such sample-size illustrations are planning aids, not observed power. Observed power is not a substitute for an effect estimate and its uncertainty. A planning calculation depends on its assumptions and should not be read as evidence that an effect was detected. Since no outcome estimates or analysis results are reported, the planning description cannot be used to quantify the precision of this completed trial.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists 18 outcome measures and 0 analyses. It names multiple outcome domains, including QST, depression, anxiety, pain intensity, pain affect, health status, and fibromyalgia impact. Some are baseline measures; others are tied to Treatment Visit 3 or 1 Month Follow up. A broad set of outcomes can raise multiplicity concerns when many comparisons are tested, because the chance of at least one apparently unusual result can increase across a family of tests. This is a general statistical issue, not evidence that any particular result occurred in this trial.

Whether and how multiplicity was addressed is not reported in the registry record. The record does not identify a hierarchy of outcomes, a family of confirmatory tests, an adjustment procedure, or a distinction between confirmatory and exploratory analyses. It also does not report an analysis plan or results that would allow readers to determine which comparisons were conducted. The primary QST measure itself has several categories or time points and was not reduced to one comparison in the record.

Missing-data handling is also not reported in the registry record. The enrollment figure does not show how many participants contributed measurements at each time point, whether any measurements were unavailable, or how missing observations were treated. The record does not describe an analysis population, such as whether participants were analyzed according to randomized assignment, nor does it report exclusions after randomization. Those details are important because conclusions from a randomized study depend partly on how participant outcomes and missing measurements are handled. Without them, the completeness and analytic scope of the outcome data cannot be evaluated.

11. Safety Results

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

Deaths

Other (non-serious) adverse events

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

The adverse-event record lists the Sham tDCS Stimulation group with 8 at risk and 0 affected for serious adverse events, and 8 at risk and 0 affected for other adverse events. The Anodal tDCS Stimulation of DLPFC group is listed with 7 at risk and 0 affected for serious adverse events, and 7 at risk and 0 affected for other adverse events. Deaths are recorded as 0 in each group. No top serious-event terms are listed.

These figures describe what was entered in the registry’s adverse-event fields. They do not establish that no events occurred outside the recorded categories or reporting period, and they do not describe event severity beyond the serious-versus-other classification shown. The record does not provide event narratives, exposure duration, monitoring details, or a description of how adverse events were collected. A zero in an affected count should therefore be read as no affected participants recorded for that category in the registry entry, not as proof that an intervention is free of risk. The figures also do not provide a basis for estimating comparative safety beyond the recorded counts.

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

The registry record documents a completed randomized, double-masked, parallel study in fibromyalgia and chronic pain, with sham and active tDCS arms described. It identifies baseline QST and a range of secondary measures concerning pain, mood, health status, and fibromyalgia impact. These details show what the study was set up to measure, but they do not show what participants experienced or whether groups differed.

No analyzed outcome results are reported in the registry record. In particular, there are no group means, standard deviations, treatment-effect estimates, confidence intervals, or p-values for QST or the secondary outcomes. The primary measure is baseline QST before treatment, and the record does not specify a single post-treatment primary comparison. As a result, the registry entry does not support a quantitative statement about the direction, size, or precision of a treatment effect.

The record’s brief summary refers to CBT, tDCS, and combined CBT+tDCS, while its listed arms describe sham and active tDCS. The relation between CBT and the listed arms is not explained. That uncertainty limits interpretation of which intervention contrast the completed study represents. The outcomes listed as secondary likewise indicate areas of interest, not evidence of benefit or harm.

The adverse-event fields record zero affected participants in the serious and other event categories for each listed arm, as well as zero deaths. These are registry counts and should not be generalized beyond the information recorded. More complete safety interpretation would require details about collection, follow-up, and event classification, which are not reported in the registry record.

In short, the available record supports a description of the design, intervention labels, and intended outcomes, plus the entered adverse-event counts. It does not establish whether active stimulation, sham stimulation, CBT, or a combination changed pain or functioning. Nor does the absence of reported analyses establish that the study found no effect; the outcome analyses themselves are not reported.

13. Why This Trial Matters Statistically

This trial illustrates why a registered outcome name is not the same as an analyzable treatment comparison. The primary measure is labeled baseline QST and is scheduled before treatment. Baseline measurements can characterize participants, but a treatment-effect question requires an outcome contrast that follows treatment or compares change over time. The registry record does not specify a single such primary comparison.

The QST measure also contains several response categories with distinct interpretations. Sensory detection, average pain threshold, and tolerance are related to laboratory responses but are not interchangeable outcomes. A clear analysis needs to identify which component is being compared, at what time, and in which direction the result is interpreted. The record flags that the primary outcome has several categories or time points and was not reduced to one comparison, leaving that statistical target unresolved.

The mismatch between the study summary and the listed arms is another important reporting issue. The summary describes CBT and combined CBT+tDCS, while the arm descriptions identify sham and active tDCS. A reader cannot determine from the listed details how CBT fits into the randomized comparisons. Precise intervention descriptions are necessary for linking an estimate to the treatment question it is intended to answer.

Finally, the record lists many outcome measures but no analyses. Reporting the outcome definitions and safety counts is useful, yet without results, analysis methods, missing-data information, and a clear primary contrast, readers cannot assess effect size, precision, or robustness. These are general reasons complete statistical reporting matters: it allows a reader to distinguish design, measurement, analysis, and inference rather than treating registration of an outcome as evidence about its result.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The main limitation for interpreting this study from the registry record is the absence of analyzed results. The record lists 18 outcome measures and 0 analyses. It does not report arm-specific outcome summaries, estimated contrasts, uncertainty intervals, or inferential tests. Therefore, the effects and precision of the interventions cannot be assessed from the posted record.

The primary outcome is described as baseline QST before treatment and includes several response categories or time points. The registry notes that it was not reduced to one comparison. This leaves unclear which QST component and treatment-time contrast was intended as the principal test. The record also does not report a post-treatment QST result or a prespecified change measure.

Intervention details are incomplete for reconstructing the study question. The brief summary names CBT, anodal tDCS, and combined CBT+tDCS, whereas the listed intervention and arm descriptions specify sham and active tDCS. CBT delivery and its relation to the listed arms are not reported in the registry record. Participant eligibility criteria beyond the listed conditions, characteristics at baseline, and participant flow are also not reported.

Further limitations include unreported allocation procedures, analysis populations, missing-data methods, multiplicity handling, and statistical models. The registry’s adverse-event fields provide counts but not event narratives or monitoring details. A planning illustration is described, but its numerical results and the trial’s own sample-size justification are not reported. These omissions limit assessment of precision, potential bias, and how fully the posted outcomes represent the completed trial.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: The Effects of CBT and tDCS on Fibromyalgia Patients — NCT02723175.
• Registry record last updated 2018-11-28; status last verified 2018-10.
• Results first posted 2018-11-28.
• 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

NCT02723175 is a completed randomized, double-masked, parallel study sponsored by the Medical University of South Carolina. The registry lists enrollment of 15, a start of 2014-12, and primary completion in 2016-11. The conditions are fibromyalgia and chronic pain.

The listed arms are Sham tDCS Stimulation and Anodal tDCS Stimulation of DLPFC. The brief summary also discusses CBT and combined CBT+tDCS, but the registry record does not explain how CBT relates to the listed arms. The primary measure is baseline QST before treatment, and the listed secondary outcomes cover pain, mood, health status, and fibromyalgia impact.

The record lists 18 outcome measures and 0 analyses. It does not report treatment-effect estimates or outcome results. Adverse-event entries record zero affected participants for serious and other adverse events in each listed arm and zero deaths. These counts describe the registry entries and do not replace a full account of safety monitoring or outcome analysis.