Table 3 Instruments used as external validators

Migraine Disability Assessment (MIDAS) scale [29]

5 items counting days of lost productivity (complete or by > 50%) from paid or household work and missed family, social or leisure activities during the preceding 3 months

Sum of responses (the MIDAS score) quantifies impact in days lost per 3 months

Headache Impact Test (HIT-6) [30]

6 items assessing lost time at work, school or social activities, pain severity, fatigue, frustration and difficulty in concentration, each with 5 frequency response options (never, rarely, sometimes, very often, always)

Response options scored 6, 8, 10, 11 and 13 respectively, with higher summed scores (range 36–78) indicating greater impact

Migraine Specific Quality of Life (MSQ) questionnaire, version 2.1 [32]

14 items assessing QoL in the preceding 4 weeks in 3 migraine-specific dimensions (role function-restrictive; role function-preventive; emotional function), each item having 6 Likert-type response options.

On a scale 0–100 (higher being better QoL) through transformation involving 3 steps

PRIME-MD Patient Health Questionnaire – depression module (PHQ-9) [31]

Depressive symptoms over the preceding 2 weeks assessed in the 9 domains of DSM-IV, each with 4 frequency response options (not at all, on several days, on more than half of days, nearly every day)

Response options scored 0–3, with higher summed scores (range 0–27) indicating more severe depression

Migraine Prevention Questionnaire (MPQ) [33]

5 items (regarding headache frequency, acute medication use and headache-related impairment, worry and anxiety) identify need for, and guide, preventative pharmacological treatment of migraine based on consensus guidelines

Responses summed into a total score, which falls into one of 3 categories: preventative treatment not indicated, should be considered or should be offered