Establishing content validity for the migraine Global Impression Item (mGI-I) assessment: a modified single-item migraine symptom severity questionnaire

Abstract

Abstract Objective To establish content validity of a single-item, migraine-specific symptom severity questionnaire for completion by migraine patients, key family members (KFMs) of migraine patients, and Healthcare Professionals (HCPs) who treat migraine patients. Background Migraine is a common disabling primary headache disorder with high prevalence and significant socioeconomic burden and personal impacts. There is a need for a global assessment of migraine symptom severity to evaluate potential new therapies from multiple perspectives. Methods The migraine Global Impression Item (mGI-I) was drafted and tested in a non-interventional, qualitative study comprising telephone interviews with 15 migraine patients, 15 KFMs of migraine patients, and 15 migraine treating HCPs. The mGI-I was drafted with two different item stem options and two different response scale options to ask about the patient’s migraine from the perspective of each respondent. Cognitive interviews were conducted to test comprehensiveness, clarity and ease of completion of the different versions of the mGI-I iteratively in three sequential waves of respondents. Results Revisions were made to the draft mGI-I after Wave 1 and Wave 2 of the interviews. Changes were made to simplify the item stem (removing unnecessary text), make language more patient-friendly (e.g. use of “migraine attack”), and add clarity to the item stem for consistent interpretation (include descriptive language of migraine attacks). Across both waves there was a preference for a 5-point response scale compared to a 7-point scale. In Wave 3, all respondents found the revised instructions, item stem, and 5-point response scale comprehensive, easy to understand and to answer. No further changes to the mGI-I were made after Wave 3. Conclusions This qualitative study of 45 total respondents across 3 subpopulations, established the content validity and appropriateness of the mGI-I in migraine patients, KFMs, and migraine-treating HCPs. The study specifically confirmed that the mGI-I is comprehensive, easily understood and answered for each respondent population.