Objectives.—To identify items that serve to assess the severity of migraine with a high level of clinical and psychometric relevance and to combine these into a unitary severity scale.
Background.—Severity of migraine is an important determinant of patient quality of life and of health care resource utilization. Despite this, no validated method exists for measuring migraine severity.
Methods.—After selection from the medical literature items of potential relevance to the severity of migraine, consensus meetings led to a choice of items which subsequently were refined further on the basis of patient interviews. The psychometric properties of those items then were assessed in a survey involving 287 migraineurs. The methods used to test reliability and validity included test-retest, calculation of Cronbach α coefficient, analysis of factorial structure using principal components analysis, a comparison of the agreement between doctors' and patients' assessments, and correlation with a validated quality-of-life questionnaire. The most pertinent items revealed by the factorial analysis were combined in a unitary scale.
Results.—Seven items reflecting severity were identified by expert consensus. These were intensity of pain, tolerability, disability in daily activities, presence of nausea or vomiting, resistance to treatment, duration of attacks, and frequency of attacks. Principal components analysis identified 3 dimensions accounting for 65% of the overall variance related to intensity of attacks, resistance to treatment, and frequency of attacks. The internal consistency and the reproducibility of the items appeared quite satisfactory, and variations in these items were correlated with quality-of-life scores. The 4 items related to intensity of attacks were combined into a single scale with 3 response modalities.
Conclusions.—The 3 dimensions identified by this investigation appeared medically relevant and to have good psychometric properties. The items on the intensity dimension can be used to generate a simple scale for assessing migraine attack severity.