Interobserver agreement in the classification of stroke in the Women's Health Study

Background and Purpose-Accurate classification of stroke events is essential in large cohort studies of risk factor assessment and in treatment trials such as the Women's Health Study (WHS). Methods-Based on medical record review, we assessed interrater reliability in stroke classification and disability status in the WHS using the K statistic. Results-During 7.0 years of follow-up, 271 incident strokes occurred, of which 133 were reclassified. There was excellent interrater agreement in the diagnosis of major stroke types, hemorrhagic subtypes, and degree of disability, as well as substantial agreement in the definition of the vascular territory involved. Only moderate agreement was reached in the classification of ischemic subtypes. Conclusions-Major stroke types, degree of disability, and vascular territory involved can be reliably classified on the basis of a review of medical records in the WHS, whereas classification of ischemic stroke subtypes needs further refinement of diagnostic criteria.