Population-based study of ABCD2 score, carotid stenosis, and atrial fibrillation for early stroke prediction after transient ischemic attack: the North Dublin TIA study.

BACKGROUND AND
PURPOSE: Transient ischemic attack (TIA) etiologic data and the ABCD(2) score may improve early stroke risk prediction, but studies are required in population-based cohorts. We investigated the external validity of the ABCD(2) score, carotid stenosis, and atrial fibrillation for prediction of early recurrent stroke after TIA.
METHODS: Patients with TIA in the North Dublin city population (N=294 529) were ascertained by using overlapping hospital and community sources. The relations between individual ABCD(2) items, carotid stenosis, atrial fibrillation, and early stroke were examined.
RESULTS: In confirmed TIA cases (n=443), carotid stenosis predicted 90-day stroke (hazard ratio=2.56; 95% CI, 1.27 to 5.15, P=0.003). Stroke risk rose with increasing grade of carotid stenosis, ranging from 5.4% (95% CI, 3.3% to 8.7%) with <50% stenosis to 17.2% (95% CI, 9.7% to 29.7%) with severe stenosis/occlusion (hazard ratio=3.3; 95% CI, 1.5 to 7.4, P=0.002). In confirmed TIA cases (n=443), the ABCD(2) score performed no better than chance for prediction of 90-day stroke (c-statistic=0.55; 95% CI, 0.45 to 0.64), largely related to the 24.2% (8/33) of patients who experienced a recurrence and had low ABCD(2) scores (0-3). However, in nonspecialist-suspected TIA cases (n=700), the predictive utility improved for stroke at 28 (c-statistic=0.61; 95% CI, 0.50 to 0.72) and 90 (c-statistic=0.61; 95% CI, 0.52 to 0.71) days.
CONCLUSIONS: In a population-based TIA cohort, significant predictive information was provided by carotid stenosis. The ABCD(2) score had predictive utility in patients with TIA suspected by nonspecialists. Low scores occurred in several patients with stroke recurrences, suggesting that caution is needed before using the score in isolation.