The psychometric properties of the Migraine-Specific Quality of Life Questionnaire version 2.1 (MSQ) in chronic migraine patients

The Migraine-Specific Quality of Life Questionnaire version 2.1 (MSQ) has been shown to have good psychometric performance
in measuring headache impact in migraine patients, but its properties specifically in chronic migraine (CM) patients are unknown.
The objective of this study was to evaluate the psychometric properties of the MSQ in a group of CM patients undergoing prophylactic
treatment.

Measurement properties of the MSQ were examined using two international, multicenter, randomized clinical trials evaluating
onabotulinumtoxinA as headache prophylaxis in CM patients (N = 1,376). Confirmatory factor analysis (CFA) was used to test the latent structure of the MSQ in CM patients. The reliability,
convergent and discriminant validity, and responsiveness of the MSQ were assessed.

CFA confirmed the currently proposed three-factor MSQ latent structure across the two studies. Good reliability was observed
for all three MSQ scales, across studies and time points. MSQ scale scores strongly correlated with the scores of the Headache
Impact Test-6 (HIT-6). Analysis of known-groups validity indicated that MSQ scale scores discriminated between groups of patients
differing in their 28-day headache frequency were as follows <10, 10–14, and ≥15 days, and the sample-derived quartiles of
the total cumulative hours of headache were as follows <140, 140 to <280, 280 to <420, and ≥420 h (p < 0.0001), across both studies and time points. MSQ change scores were higher in magnitude in groups experiencing greater
decline in headache frequency (p < 0.001).

The MSQ is a psychometrically valid tool that can be used to reliably measure the impact of migraine among CM patients.