Research Study to Determine Sensitivity to Gentle Touch and Pressure During an Active Migraine Attack.: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Research Study to Determine Sensitivity to Gentle Touch and Pressure During an Active Migraine Attack. (NCT00329771), a registered phase not stated study. The primary outcome is Proportion of Subjects With Allodynia During a Migraine Attack.

2. Clinical Question

This is a descriptive question about sensory discomfort during an attack, not a test of whether a treatment changes symptoms. Brush allodynia was defined in the outcome description as discomfort with normal sensation. Participants were to rate discomfort after brushes at specified sites on the head, neck and forearms. The record identifies the intended measurement approach, but does not report the threshold or rule used to classify a participant as having allodynia. Without the participant-level classification rule and the observed count, the central question remains unanswered by the posted results.

3. Trial Design

The registry lists a completed study sponsored by Thomas Jefferson University. Its recorded start is 2006-03, and its primary completion is 2006-12. Enrollment is reported as 28. The listed condition is migraine, and the group description identifies eligible subjects with episodic migraine, with or without aura.

The record describes an assessment study rather than a randomized treatment comparison. Its intervention entry is “No intervention: We are testing for the presence of allodynia.” The allocation method is not stated. A comparator group is not listed, so the design does not support a between-group treatment contrast. The purpose described in the registry is to collect and evaluate data on allodynia during an actual episodic migraine attack.

The primary outcome is the number of participants with allodynia during a migraine attack. The stated assessment window is within 4 hours from onset of migraine head pain. Brush discomfort was to be assessed at pre-specified sites on the head, neck and forearms, using a 100 mm visual analog scale. The registry identifies the intended outcome population as participants who completed the allodynia test, but does not report how many completed it.

The registry record does not report a protocol, a statistical analysis plan, an allocation procedure, or a sample-size justification. It reports one outcome measure and zero analyses. The completed status and enrollment count describe the study record, but they do not establish that the primary outcome was analyzed or that a result was posted. The number of participants contributing to the primary outcome and the observed result are not reported in the registry record.

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: Participants who completed allodynia test

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 Proportion of Subjects With Allodynia During a Migraine Attack, measured over allodynia assessed within 4 hours from onset of migraine head pain.

The primary endpoint is the number of participants with allodynia during a migraine attack. Allodynia is described in the record as discomfort with normal sensation. The assessment involved brushing pre-specified sites on the head, neck and forearms, followed by a participant rating of discomfort on a 100 mm visual analog scale. The intended timing was within 4 hours from onset of migraine head pain.

A count endpoint can describe how many people in the assessed group met an outcome definition. It is useful for a descriptive question about whether the phenomenon was observed among participants tested during an attack. For interpretation, however, the count needs a clearly defined outcome classification and the number of participants assessed. The record does not state the rule for converting the ratings into a yes-or-no allodynia classification, and it does not report the number who completed the test.

The registry lists the endpoint unit as participants and the parameter as a number. It does not post the observed count. Consequently, neither the number classified with allodynia nor the number classified without it can be read from the registry record. A numerical estimate of the frequency, or its precision, cannot be described from the posted results. The planned measurement is clear in broad outline, but the endpoint result is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a planned binary outcome: participants are counted according to whether they had allodynia during a migraine attack. The statistical ideas below are general explanations of how such an outcome can be analyzed; the registry record does not report that these analyses were performed for this study.

What does a participant count represent?

For a binary outcome, each assessed participant is classified into one of two categories, such as meeting or not meeting an outcome definition. The event count is interpreted alongside the number assessed. That denominator matters because the same count can imply different frequencies in groups of different sizes. In this record, the outcome population is identified as participants who completed the test, but neither the completed-test denominator nor the event count is reported. Enrollment of 28 cannot substitute for that missing denominator.

Why does the classification rule matter?

A visual analog scale produces a rating of discomfort, while a binary participant count requires a rule for classifying the rating or set of ratings. For example, a protocol might specify which sites or ratings determine a participant-level classification. This is a general methodological point, not a description of the rule used in this study: that rule is not reported in the registry record. If it is unclear how ratings become a yes-or-no outcome, readers cannot reproduce or fully interpret the count.

The record says that brushes were applied at pre-specified sites on the head, neck and forearms, and that discomfort was rated from “normal sensation” to “extremely painful or unpleasant” on a 100 mm visual analog scale. It does not report the scoring threshold, whether ratings were combined across sites, or how inconsistent site responses were handled. These details affect the operational meaning of the endpoint. They are not statistical results and should not be inferred from the scale description alone.

What would an uncertainty interval show?

In general, a confidence interval describes the uncertainty around an estimated quantity under a specified statistical method. For a binary outcome, an interval around a proportion can communicate how precisely the observed data estimate the frequency in the population represented by the study. The interval depends on the event count, denominator, and method. No interval or event count is reported, so precision cannot be evaluated. An interval would not remedy a missing or ambiguous outcome definition, and it would not by itself resolve concerns about who completed testing.

What can be learned from this design?

A single-group descriptive assessment can characterize the observations in the group tested, provided outcome data and an adequate description of measurement are available. It does not estimate a contrast against a control group when no comparator is reported. It also does not isolate the effect of a treatment, since the intervention entry states that there was no intervention and the purpose was to test for allodynia. This is a general interpretation of the listed design, not a claim about an unreported analysis.

General statistical reasoning also distinguishes a study's observed result from its design assumptions. The record notes that planning illustrations use a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect specified as a fraction of an observed effect. Those are assumptions attached to planning illustrations, not reported features of this one-group study's design. The record does not report an observed effect or two-arm comparison for this endpoint. Any such illustration cannot be treated as evidence from the study, a study-specific sample-size justification, or observed power.

Why does over-dispersion matter?

Over-dispersion is a general concern when count data vary more than a statistical model expects. It is most relevant to count outcomes that can take a range of values; this endpoint is described as a participant count for a binary outcome, and no count model is reported. The record supplies no analysis from which dispersion or model fit could be assessed. It would therefore be inappropriate to claim that over-dispersion was present or that a particular adjustment was used.

What analysis details are absent?

The registry reports zero analyses. It does not report a statistical plan, a confidence-interval method, a hypothesis test, a missing-data method, or adjustments for covariates. It also does not report whether analyses were planned by body site or by any participant subgroup. These items are not interchangeable: a statistical method specifies how data are summarized or compared, while a measurement rule specifies how the endpoint is formed. Both types of detail would be needed to assess a posted estimate fully. In their absence, the responsible interpretation is limited to the design and outcome definition that the registry does state, with no reconstructed analysis or presumed protocol.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Episodic Migraineurs")
n      <- c(25)
events <- c(15)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Episodic Migraineurs  25  15  60.0  38.7  78.9  40.7  76.6  40.6  76.6

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure and zero analyses. It does not report a statistical analysis plan, so it is not possible to determine whether additional outcomes, subgroup analyses, or repeated assessments were planned outside the registry listing. No multiplicity adjustment is reported. Multiplicity is a general issue that can arise when many hypotheses are tested: the chance of a chance-positive finding can increase as tests accumulate. That concern cannot be quantified for this study from the registry record because the analysis set and testing strategy are not reported.

The registry defines the primary outcome population as participants who completed the allodynia test. It reports enrollment of 28 but does not report the number who completed the test, the number with usable ratings, or the number included in an analysis. It also does not describe missing-data handling, reasons for incomplete assessments, or whether participants with partial site measurements were included. These details are important because excluding participants with incomplete outcomes can affect how representative the analyzed group is of those enrolled.

There is no reported analysis population definition beyond the reference to test completers. The record does not state whether the analysis included every enrolled participant, only those with complete measurements, or another group. Nor does it report how an incomplete rating would affect the participant-level classification. These matters are not reported in the registry record and should not be inferred from the completed status or enrollment count. With no posted outcome count or analysis, the impact of missing data and multiplicity cannot be evaluated.

12. 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 2% reporting threshold.

The registry lists 28 episodic migraineurs at risk for serious adverse events and reports 0 affected. For other adverse events, it likewise lists 28 at risk and 0 affected. These figures describe the posted safety entries; they do not provide detail about how events were defined, collected, or adjudicated.

The death field is not populated with a number, so deaths are not reported in the registry record. A zero in the serious-event or other-event count should be read as the registry's reported count for that category, not as proof that every possible event was assessed in every circumstance. The record does not provide event narratives, severity breakdowns, timing, or a separate safety analysis.

This study is listed as having no intervention and is described as testing for the presence of allodynia. The safety counts therefore are not a comparison of treatment-related risks between groups. There is no comparator group listed. The figures should not be used to infer comparative safety or to make claims beyond the adverse-event categories and counts posted in the registry record.

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

The study's central question is descriptive: how many participants completing a brush test during an acute episodic migraine attack had allodynia? The registry outlines the planned assessment and reports enrollment of 28. It does not report the primary outcome count or how many participants completed the test. As a result, the posted results do not answer the central question with an observed estimate.

This absence should not be confused with a finding of no allodynia. The registry does not report a zero outcome count. Nor does it establish that all participants enrolled were tested or that any specific proportion had the condition. The completion status describes the study's registry status, while the missing outcome result leaves the descriptive finding unknown in this record.

Even a reported count would have a limited interpretation. With no comparator and no intervention listed, the study is not presented as a treatment comparison. A count among participants tested would describe that group under the stated assessment conditions; it would not show that an intervention caused or prevented allodynia. Generalization beyond participants meeting the listed eligibility description would also require information about recruitment and representativeness, which is not reported in the registry record.

The endpoint description gives the reader some basis for understanding the measurement: brush discomfort was rated at specified body sites on a 100 mm visual analog scale, within 4 hours from onset of migraine head pain. But the registry does not state the rule for deriving a participant-level binary classification from those ratings. Without the classification method, denominator, and observed count, neither the result nor its precision can be assessed.

The responsible conclusion is therefore about reporting, not about the presence or absence of allodynia in the study group. The registry record identifies the research question and intended measurement but does not provide the numerical primary result or an analysis. No treatment benefit, lack of benefit, or comparative safety conclusion follows from this record.

14. Why This Trial Matters Statistically

This study highlights a basic statistical distinction between enrolling participants and reporting an analyzable endpoint. The registry records enrollment of 28, but the intended outcome population consists of participants who completed the test. Because the number of completers is not reported, the enrollment figure alone cannot serve as the denominator for the primary result. A clear denominator is essential to interpreting any participant count.

It also illustrates the distinction between measurement and classification. A visual analog scale records ratings, while the endpoint is a number of participants with allodynia. Moving from ratings at several body sites to a binary participant-level count requires a defined rule. The record describes the scale and assessment locations but does not report that rule. Statistical interpretation depends on transparent outcome definitions as well as on numerical summaries.

The design matters, too. A descriptive assessment without a listed comparator has a different inferential purpose from a randomized treatment comparison. It can characterize a group if results are reported, but it cannot estimate a treatment contrast. The absence of a primary result means that even the descriptive aim cannot be evaluated from the registry record.

Finally, a completed status and a registered outcome do not guarantee that numerical results or analysis methods are available in the record. Readers need outcome counts, analysis populations, missing-data information, and methods to judge what was estimated and how precisely. Their absence limits interpretation, regardless of the clinical motivation for studying the phenomenon.

15. Limitations

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

The primary limitation is that the registry record does not report the primary outcome result, despite listing one primary outcome measure. It also reports zero analyses. The number of participants who completed the allodynia test is not reported, so the outcome denominator cannot be established from the record. Enrollment of 28 should not be taken as proof that all 28 contributed to the endpoint.

The endpoint definition is incomplete for statistical interpretation. The record describes brush ratings at pre-specified sites on the head, neck and forearms, but does not report how those ratings were converted into a participant-level classification of allodynia. It does not report a threshold, a rule for combining site results, or handling of partial assessments. Without this information, reproducibility and interpretation are limited.

The registry lists one group and no intervention, and allocation is not stated. It does not list a comparator, so there is no basis for a control-group contrast. The record also does not report recruitment details, participant characteristics beyond episodic migraine with or without aura, or the representativeness of the enrolled group. These omissions limit assessment of how broadly any eventual descriptive result might apply.

Statistical planning and analysis details are not reported in the registry record. There is no stated analysis plan, sample-size justification, missing-data method, or confidence-interval method. The planning assumptions associated with illustrative calculations do not establish the study's own design rationale or analysis. Finally, death counts are not reported, and the adverse-event entries provide counts without further event detail.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Research Study to Determine Sensitivity to Gentle Touch and Pressure During an Active Migraine Attack. — NCT00329771.
• Registry record last updated 2024-03-27; status last verified 2024-03.
• Results first posted 2014-04-21.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

The registry describes a completed, single-group assessment study of brush allodynia during an acute episodic migraine attack, sponsored by Thomas Jefferson University. It reports enrollment of 28, a start of 2006-03, and primary completion in 2006-12. No intervention or comparator group is listed.

The primary outcome was the number of participants with allodynia, assessed within 4 hours from onset of migraine head pain using brush stimulation and a 100 mm visual analog scale. The number completing the test and the primary outcome result are not reported in the registry record. The record lists one outcome measure and zero analyses.

Safety entries report 0 serious adverse events and 0 other adverse events among 28 at risk; deaths are not reported in the registry record. The posted information identifies the question and planned measurement but does not permit an estimate of the observed frequency or its precision.