New Scale Assesses Interictal Migraine Burden

BY DIANA MAHONEY
Elsevier Global Medical News

BOSTON (EGMN) - A new scale that measures the interictal burden of migraine has good internal consistency and reliability within and across multiple domains, according to a study presented May 1 at the annual meeting of the American Academy of Neurology.

Above and beyond the pain and disability caused by an acute migraine attack, migraine sufferers experience feelings of frustration, guilt, and helplessness during interictal periods, which can have a substantial impact on quality of life, said Dawn C. Buse, Ph.D., director of psychology at Montefiore Medical Center in Bronx, New York. And while the majority of migraineurs' time is spent interictally, current instruments designed to assess migraine burden look only at the ictal burden, she said.

To address the lack of a global measure for evaluating the ictal and interictal burden of migraine, Dr. Buse and her colleagues created the self-administered Migraine Interictal Burden Scale (MIBS), which measures between-attack migraine burden across four domains: disruption at work and school, diminished family and social life, difficulty planning, and emotional difficulty.

To develop the tool, the investigators reviewed existing instruments, clinical experience, and focus group input to identify 30 candidate items. The 30 items were then included in a questionnaire mailed to 2,500 preidentified migraineurs. Responses in the 1,691 completed and returned surveys found that 1,362 respondents (81%) met the International Classification of Headache Disorders, second edition (ICHD-2) criteria for migraine, according to the investigators. With use of categorical confirmatory factor analyses and Markov Chain Monte Carlo graded item response therapy models, a five-factor structure was extracted from the qualifying responses from which the weakest items were discarded, ultimately yielding a 12-item scale.

In regard to the validity of the scale, each of the domains correlated significantly with severity level on the Migraine Disability Assessment Questionnaire (MIDAS), which measures ictal burden, said Dr. Buse. With control for headache frequency, prescription medication use, and gender, the total MIBS score significantly predicted MIDAS disability. Additionally, the interictal model accounted for 38% of the variance in ictal burden as measured by MIDAS, suggesting that the areas are correlated but distinct.

Additional studies are underway to further assess the reliability and validity of the interictal scale as a prelude to intervention studies to reduce interictal burden, said Dr. Buse.

"Our primary goal in developing this instrument is to disseminate the message among clinicians that patients' perceived interictal burden can substantially impact their quality of life," said Dr. Buse. "Whether or not physicians choose to use this instrument, we want them to be aware of it and to get the word out that they should be asking patients not only about their headache pain and treatment efficacy, but also about other lifestyle factors that are affected in between attacks."

The instrument could also have an important clinical impact when counseling patients about preventive migraine treatment, Dr. Buse noted. "Patients are sometimes hesitant about starting preventive therapy. Showing them exactly how much their migraine experience is affecting their every day life could be a useful starting point in this discussion."

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