This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for BOTOX® Prophylaxis in Patients With Chronic Migraine (NCT01432379), a registered phase not stated study. The primary outcome is Incidence Rate of Dysphagia.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01432379 |
| Phase | Phase not stated |
| Condition | Migraine Disorders |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 1168 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Allergan |
| Results posted | Yes |
2. Clinical Question
Population
Adults with chronic migraine treated in clinical practice. The primary endpoint’s population is defined as patients who received at least 1 dose of botulinum toxin Type A. The registry lists 1168 participants enrolled overall and 1160 in the primary endpoint population.
Intervention
Botulinum toxin Type A, described as 155-195 U administered intramuscularly in the face, head, and neck areas as directed by a physician, approximately every 12 weeks for 1 year.
Comparator
No comparator group is described. This is a post-authorization observational study, and allocation is not stated. The registry record therefore does not establish a randomized or like-for-like comparison.
Primary question
What was the incidence rate of dysphagia, based on the first reported occurrence from study enrollment up to 64 weeks, among treated patients? The endpoint is expressed as events per 1,000 person-months. The estimate and its 95% confidence interval are not reported in the registry record.
The registry describes the study’s purpose as monitoring how BOTOX® was used and describing its safety profile in clinical practice for prophylactic treatment of headaches in adults with chronic migraine. That purpose is descriptive, rather than a stated test of whether treatment differs from an alternative. The secondary outcome listed is the incidence rate of intractable migraine, but its numerical result is also not reported in the registry record. Consequently, the posted information identifies what was to be measured but does not provide the endpoint estimates needed to quantify either outcome.
3. Trial Design
NCT01432379 is a completed post-authorization observational study sponsored by Allergan. The registry lists 1168 participants enrolled. Its brief summary describes monitoring utilization practices and describing the safety profile of BOTOX® in clinical practice among adults with chronic migraine receiving prophylactic treatment for headaches. The study start date is 2011-09-09 and the primary completion date is 2015-05-12.
The intervention is botulinum toxin Type A. The registry describes intramuscular administration of 155-195 U in the face, head, and neck areas as directed by a physician, approximately every 12 weeks for 1 year. This is a description of the intervention, not evidence that every participant received an identical schedule. Details of actual utilization patterns are not reported in the registry record.
The primary outcome is the incidence rate of dysphagia over 64 weeks, among patients who received at least 1 dose. The listed secondary outcome is the incidence rate of intractable migraine. The record identifies 2 outcome measures, but provides no numerical outcome estimates or analysis results; it lists 0 analyses. The study’s method for assigning participants is not stated. The registry specifically cautions that this is not a randomized comparison and that the arms are not a like-for-like control comparison.
The endpoint population contains 1160 treated patients, while overall enrollment is 1168. The registry does not explain this difference. It also does not report a separate untreated or active-control group for drawing comparative conclusions. For that reason, this design is best understood from the posted information as observational and descriptive. Details such as eligibility criteria beyond the adult chronic-migraine description, site procedures, follow-up completeness, and any protocol-defined statistical plan 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
| Stage | Botulinum Toxin Type A |
|---|---|
| STARTED | 1168 |
| COMPLETED | 783 |
| NOT COMPLETED | 385 |
Analysis population for the primary outcome, as defined in the registry: Treated Population: all patients who received at least 1 dose of botulinum toxin Type A
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.
Population: The Treated Population includes all patients who received at least 1 dose of botulinum toxin Type A and is used for baseline characteristics.
| Characteristic | Unit | Botulinum Toxin Type A |
|---|---|---|
| Participants analysed | 1160 | |
| Age, Continuous | Years | 46.6 (SD 11.75) |
| Sex: Female, Male: Female | Participants | 977 |
| Sex: Female, Male: Male | Participants | 183 |
6. Primary Endpoint
The registry lists the primary outcome as Incidence Rate of Dysphagia, measured over 64 weeks.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | 95% Confidence Interval |
| Unit | events per 1,000 person-months |
| Endpoint classification | Event-Rate Endpoint |
The primary endpoint is the incidence rate of dysphagia. Dysphagia is defined in the registry as difficulty or discomfort swallowing. The measure counts the first reported occurrence from study enrollment up to 64 weeks and expresses the rate as events per 1,000 person-months. The stated population is all patients who received at least 1 dose of botulinum toxin Type A.
A rate is used to relate the number of events to the amount of time participants contribute under observation. General statistical explanation: unlike a simple proportion, an incidence rate uses person-time in its denominator, so it can describe event occurrence when participants contribute different amounts of observation time. A rate is therefore interpretable only alongside clarity about the event definition and the time at risk. Here, the registry specifies the first reported occurrence and the rate unit, but does not provide the underlying number of events or person-months.
The registry lists a 95% confidence interval as the measure of dispersion. General statistical explanation: a confidence interval conveys the uncertainty around an estimated rate under the method used to construct it. Neither the primary rate nor its interval is reported in the registry record, and the method used to calculate the interval is not reported. The endpoint definition can therefore be described, but its magnitude and precision cannot be assessed from the posted results.
The registry also lists incidence rate of intractable migraine as a secondary outcome. Its definition and numerical result are not reported in the registry record. No conclusion about the frequency of either endpoint can be drawn from the outcome titles alone.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry identifies dysphagia incidence rate as the primary outcome and specifies the treated population, event definition, rate unit, and timeframe. Those details tell the reader what the endpoint was intended to represent. They do not disclose the actual rate. The primary estimate and its 95% confidence interval are not reported in the registry record, so the frequency of first reported dysphagia events and the precision of any estimate cannot be evaluated from the posted results.
The same limitation applies to the secondary outcome, incidence rate of intractable migraine. The outcome is named, but its numerical result is not reported in the registry record. The record lists 0 analyses. No p-value, model estimate, or comparative effect is available in the posted results. It would therefore be inappropriate to describe either outcome as increased, decreased, common, uncommon, or statistically distinguishable from another rate.
The registry gives 1168 as overall enrollment and defines the primary endpoint population as patients who received at least 1 dose; the adverse-event group lists 1160 at risk. The reason for the difference between enrollment and the treated population is not reported in the registry record. These figures describe different stated populations and should not be substituted for an event-rate estimate. In particular, a participant count by itself does not provide the person-time denominator required to interpret an incidence rate.
The study’s observational purpose also shapes interpretation. Its stated goal was to monitor utilization practices and describe safety in clinical practice. Allocation is not stated, and the registry cautions that this is not a randomized comparison and that the arms are not a like-for-like control comparison. The posted information therefore does not support a causal comparison with an alternative treatment or with no treatment.
General statistical explanation: estimates are most informative when their definitions, denominators, and uncertainty measures are all available. For an incidence rate, the event count and time at risk help clarify the scale of the estimate; the confidence interval indicates how much uncertainty remains under the chosen analysis. Neither the rate nor its interval is posted for the primary endpoint. Interpretation must consequently remain at the level of the study’s question and measurement plan, rather than claims about the magnitude or precision of its findings.
9. Statistical Methods Explained
The registry characterizes the primary outcome as an incidence rate, with events per 1,000 person-months as its unit. It defines the event as the first reported occurrence of dysphagia from enrollment up to 64 weeks. The endpoint population consists of patients who received at least 1 dose of botulinum toxin Type A. The registry states that the dispersion measure is a 95% confidence interval, but does not report the rate, interval limits, or calculation method.
What an incidence rate represents
General statistical explanation: an incidence rate relates event occurrence to accumulated time under observation. Person-time adds the time each eligible participant contributes while at risk, rather than treating all participants as if they necessarily had identical follow-up. The unit events per 1,000 person-months gives a standardized way to express that relationship. It does not mean that every participant was observed for the same duration, nor does the unit alone reveal how many events occurred.
For this endpoint, the event is the first reported occurrence of dysphagia. Focusing on a first occurrence differs from counting every episode a participant might experience. The description says the rate is based on the first reported occurrence, but the registry does not give the event count, the total person-months, or further rules for identifying and recording events. Those details are not reported in the registry record.
How to read a confidence interval
General statistical explanation: a confidence interval is an uncertainty range around an estimate, constructed using a statistical procedure. A narrower interval generally indicates greater precision under that procedure; a wider interval indicates less precision. The interval does not remove uncertainty or establish that an estimate is free from bias. Its interpretation depends on the analysis method and on the quality and completeness of the underlying observations.
The registry names a 95% confidence interval for the primary incidence rate. It does not provide the estimate or interval endpoints, and the method used to construct the interval is not reported in the registry record. Accordingly, readers cannot assess either the estimated rate or its statistical precision from the posted results. The stated confidence level alone is not a result.
What is not specified about the rate analysis
The registry does not report a model, distributional assumption, adjustment set, or detailed procedure for handling follow-up time. It also does not state how censoring, incomplete observation, or missing outcome information was handled. These omissions do not establish that such issues were ignored; they mean that the approach is not reported in the registry record.
General statistical explanation: rate data can show more variability than a simple model assumes, a concern often called over-dispersion. When present, over-dispersion can make uncertainty estimates too small if the analysis does not account for it. Whether it was assessed or addressed in this study is not reported in the registry record. This is a general methodological consideration, not a claim about the study’s data.
Planning illustrations are not trial results
The statistical material associated with this study includes sample-size planning illustrations based on an observed effect, with two-sided significance level 0.05, equal allocation between two hypothetical arms, and a normal approximation. The stated effect to detect is a fraction of the observed effect. The assumptions also distinguish total event counts for time-to-event settings from participants per arm in other settings. These are planning conventions, not evidence that the observational study used those design choices.
The registry does not report the sample-size justification or analysis plan for the study. It also does not report the observed effect needed to evaluate a numerical planning illustration. Any sample-size values derived under such assumptions are planning illustrations, not observed power and not a description of the study’s actual enrollment design. In this case, overall enrollment is listed as 1168, but that count does not establish how the study was planned or whether it had a particular probability of detecting an effect.
Because there is no randomized comparison described and no primary rate estimate posted, inferential procedures cannot be assessed from the available record. The registry does not report adjustment for covariates, tests of hypotheses, interim analyses, or a prespecified multiplicity procedure. General statistical explanation: these details matter because analysis choices affect the interpretation of estimates and uncertainty. Their absence from the record should be treated as missing documentation, not as evidence about what investigators did or did not do.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 2 outcome measures: the primary incidence rate of dysphagia and the secondary incidence rate of intractable migraine. It lists 0 analyses. Numerical results for these outcomes are not reported in the registry record. A multiplicity procedure, such as a rule for interpreting several outcome tests together, is also not reported in the registry record. Without reported estimates or tests, the extent to which multiplicity could affect interpretation cannot be evaluated.
General statistical explanation: when several outcomes or statistical tests are considered, the chance of at least one apparently notable finding can change, depending on how tests are conducted and interpreted. Prespecified outcome priorities and an analysis plan help readers understand how such results should be read. The record identifies a primary and a secondary outcome, but does not report an analysis plan or a method for addressing multiplicity. No claim about the investigators’ intended or actual procedure can be made from that absence.
The primary endpoint population is defined as patients who received at least 1 dose. The registry does not report how missing outcome information, incomplete follow-up, or participants without an observed endpoint were handled. It does not report imputation, censoring rules, or sensitivity analyses. These details are not reported in the registry record, so the potential influence of missing information cannot be assessed.
The registry reports 1168 participants enrolled, while the primary outcome population and adverse-event group each list 1160 at risk. The reason for this difference and the disposition of participants outside the treated population are not reported in the registry record. The record does not describe an intention-to-treat analysis population; the primary endpoint’s stated population is treated patients. The available information therefore supports describing that defined population, but not assuming how other participants entered or left analyses.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Botulinum Toxin Type A | 61 | 1160 | 5.3% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Botulinum Toxin Type A | 106 of 1160 |
Most frequent serious adverse event terms
| Event term | Organ system | Botulinum Toxin Type A |
|---|---|---|
| Migraine | Nervous system disorders | 11 of 1160 |
| Headache | Nervous system disorders | 3 of 1160 |
| Depression | Psychiatric disorders | 3 of 1160 |
| Abdominal pain upper | Gastrointestinal disorders | 2 of 1160 |
| Intracranial pressure increased | Nervous system disorders | 2 of 1160 |
| Anaemia | Blood and lymphatic system disorders | 1 of 1160 |
| Angina pectoris | Cardiac disorders | 1 of 1160 |
| Myocardial infarction | Cardiac disorders | 1 of 1160 |
| Pericarditis | Cardiac disorders | 1 of 1160 |
| Vertigo positional | Ear and labyrinth disorders | 1 of 1160 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Botulinum Toxin Type A |
|---|---|---|
| Migraine | Nervous system disorders | 106 of 1160 |
Serious events with the highest arm-level rate: migraine (0.9%), headache (0.3%), depression (0.3%), abdominal pain upper (0.2%), intracranial pressure increased (0.2%).
For the botulinum toxin Type A group, the registry lists 1160 participants at risk for serious adverse events and 61 affected. It also lists 1160 at risk for other adverse events and 106 affected. These are counts in the posted safety record; they are not the primary dysphagia incidence rate, and they do not include a reported person-time denominator. The registry’s death field contains no value, so deaths are not reported in the registry record.
The listed serious adverse-event terms and percentages are Migraine, 0.9%; Headache, 0.3%; Depression, 0.3%; Abdominal pain upper, 0.2%; Intracranial pressure increased, 0.2%; and Anaemia, 0.1%. The registry gives these as top serious terms. It does not report the event counts for each term or explain whether an individual could contribute more than one term. The percentages should therefore be read as listed, without summing them or treating them as mutually exclusive categories.
General statistical explanation: an affected-participant count, an event count, a percentage, and an incidence rate are different summaries. The relevant interpretation depends on how each is defined and on its denominator. The registry does not provide a control comparison suitable for estimating relative safety differences; allocation is not stated and the record cautions that the arms are not a like-for-like control comparison. These figures describe the posted safety information, not a causal effect.
12. What the Result Does, and Does Not, Mean
The posted record identifies a completed observational study intended to monitor use of botulinum toxin Type A and describe its safety profile in clinical practice for adults with chronic migraine. It specifies a primary safety endpoint: the incidence rate of first reported dysphagia events through 64 weeks among treated patients. It also identifies intractable migraine as a secondary outcome. Those definitions communicate what the registry intended to measure.
The registry does not report the numerical primary incidence rate or its 95% confidence interval. It also does not report the numerical secondary outcome. As a result, the posted results do not establish the frequency or precision of either outcome. The absence of estimates in the registry record is not evidence that no events occurred; it means the requested outcome results cannot be quantified from the record.
Safety counts are available: 61 of 1160 at risk are listed as affected for serious adverse events, and 106 of 1160 at risk are listed as affected for other adverse events. The record also lists several serious adverse-event terms with percentages. Those figures provide descriptive safety information, but they do not substitute for the primary dysphagia rate. The record’s death field has no reported value.
The observational design limits what the data can establish about causation. The registry does not state allocation, and it cautions against treating the arms as a like-for-like control comparison. No randomized comparison is described. Therefore, the posted information cannot establish whether an outcome was caused by the intervention or whether risk differed from that under another treatment.
General statistical explanation: a descriptive estimate can characterize what was observed in a defined population, while a causal claim requires a design and analysis that support comparisons and address alternative explanations. Precision is also important: an estimate without its uncertainty can be difficult to judge, and a defined endpoint without an estimate is not a quantitative finding. In this record, the endpoint definitions and selected safety counts can be described, but the missing outcome estimates, confidence intervals, and analysis details constrain interpretation.
13. Why This Trial Matters Statistically
This study is statistically relevant because it illustrates the distinction between specifying an endpoint and reporting an analyzable result. The registry defines dysphagia, identifies the treated population, gives a 64-week timeframe, and states the incidence-rate unit and confidence-interval type. Those elements establish the intended interpretation of the primary measure. Yet the rate and its interval are not reported in the registry record, so the measure’s actual value and precision remain unknown from the posted results.
The record also illustrates why the denominator matters. Overall enrollment is 1168, while the primary endpoint population and the safety group list 1160 at risk. An incidence rate depends on person-time, not simply on enrollment or the number at risk. Because the record does not provide total person-time or the primary event count, the endpoint cannot be reconstructed from the listed participant totals.
Another important issue is study design. The registry describes post-authorization observation in clinical practice and explicitly cautions that this is not a randomized comparison. The stated purpose is to monitor utilization and describe safety, rather than to report a controlled treatment contrast. Recognizing that distinction prevents descriptive safety information from being mistaken for evidence of a causal difference.
Finally, the record names a primary and a secondary outcome but reports 0 analyses. It does not report the statistical plan, missing-data handling, or multiplicity approach. General statistical explanation: transparent outcome reporting and analysis documentation help readers judge how estimates were generated and how much confidence to place in them. The available record is useful for identifying the study’s intended questions and some safety counts, while its missing endpoint estimates and analysis details sharply limit statistical interpretation.
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 the primary endpoint is that its incidence-rate estimate and 95% confidence interval are not reported in the registry record. The event definition, treated population, unit, and timeframe are described, but the event count and accumulated person-time are not. The rate cannot be checked or reconstructed from the participant totals alone.
The record lists 1168 participants enrolled and 1160 in the treated endpoint population and safety group. It does not explain the difference or report participant disposition. The handling of missing outcomes, incomplete follow-up, and censoring is not reported in the registry record. The registry also does not describe the procedure used to calculate rates or confidence intervals, or any adjustment for participant characteristics.
The observational design is another limitation for causal interpretation. Allocation is not stated, and the registry cautions that this is not a randomized comparison and that the arms are not a like-for-like control comparison. The record does not provide a suitable comparative estimate. The results therefore cannot be interpreted as an estimate of the effect of treatment relative to a control condition.
Safety results include affected-participant counts and selected serious adverse-event terms, but the death field has no reported value. Event-specific counts for the listed terms, rules for categorizing events, and details about overlapping terms are not reported in the registry record. The listed safety summaries should be interpreted as descriptive entries, not as a complete account of every possible safety outcome.
The record names a secondary outcome but does not report its numerical result, and it lists 0 analyses. Protocol details, sample-size justification, interim analyses, multiplicity handling, and the statistical analysis plan are not reported in the registry record. These limitations concern what can be established from the posted record; they do not imply that the unreported procedures or information were absent from the conduct of the study.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: BOTOX® Prophylaxis in Patients With Chronic Migraine — NCT01432379.
- Registry record last updated 2019-01-08; status last verified 2018-12.
- Results first posted 2016-12-12.
- 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.
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18. Record Summary
NCT01432379, titled “BOTOX® Prophylaxis in Patients With Chronic Migraine,” is a completed post-authorization observational study sponsored by Allergan. The registry lists 1168 enrolled participants, with a treated primary endpoint population of 1160. The intervention is botulinum toxin Type A, described as 155-195 U administered intramuscularly in the face, head, and neck areas approximately every 12 weeks for 1 year.
The primary outcome is the incidence rate of first reported dysphagia through 64 weeks, expressed per 1,000 person-months, with a 95% confidence interval specified. The secondary outcome is the incidence rate of intractable migraine. Neither numerical outcome result is reported in the registry record, which lists 0 analyses. Safety entries list 61 affected among 1160 at risk for serious adverse events and 106 affected among 1160 at risk for other adverse events. Allocation is not stated, and the registry cautions that this is not a randomized, like-for-like comparison.