Development and validation of a novel patient-reported outcome measure in people with episodic migraine and chronic migraine: The Activity Impairment in Migraine Diary.

OBJECTIVE: To evaluate the content validity and psychometric properties of the Activity Impairment in Migraine Diary (AIM-D).

BACKGROUND: Measuring treatment effects on migraine impairment requires a psychometrically sound patient-reported outcome (PRO) measure developed consistent with U.S. Food and Drug Administration guidance.

METHODS: The AIM-D was created from concepts that emerged during qualitative interviews with five clinicians experienced in treating migraine and concept elicitation (CE) interviews with 40 adults with episodic migraine (EM) or chronic migraine (CM). The initial version was refined based on three waves of cognitive interviews with 38 adults with EM or CM and input from a panel of clinical and measurement experts. The AIM-D was psychometrically evaluated using data from 316 adults with EM or CM who participated in a 13-week prospective observational study. Study participants completed PRO assessments including the AIM-D and a daily headache diary. Exploratory and confirmatory factor analysis were used to determine the factor structure. The reliability, validity, and responsiveness of the AIM-D were assessed. Additional PRO measures including the Patient Global Impression - Severity (PGI-S), Migraine Specific Quality of Life Questionnaire, Version 2.1 Role Function-Restrictive domain, and Headache Impact Test were used for psychometric evaluation of the AIM-D.

RESULTS: Based on CE interviews with adults with migraine and input from an expert panel, activity impairment was identified as the target in the preliminary conceptual framework, which had two domains: performance of daily activities (PDAs) and physical impairment (PI). Revision of the draft AIM-D through multiple rounds of cognitive interviews and expert panel meetings resulted in a content valid 11-item version. Exploratory factor analysis supported both one- and two-domain structures for the AIM-D, which were further supported by confirmatory factor analysis (factor loadings all >0.90). The AIM-D domains (PDA and PI) and total score showed high internal consistency reliability (Cronbach's alpha 0.95-0.97), acceptable test-retest reliability for weekly average scores (intraclass correlation coefficient >0.60 for participants with no change in PGI-S between baseline and week 2), and good convergent and known-groups validity. There was evidence of responsiveness based on changes in PGI-S score and monthly migraine days.

CONCLUSION: The AIM-D is a content valid and psychometrically sound measure designed to evaluate activity impairment and is suitable for use in clinical trials of preventive treatments for EM or CM.