BACKGROUND: The ABCD2 score (Age, Blood pressure, Clinical features, Duration of 
symptoms and Diabetes) is used to identify patients having a transient ischemic 
attack who are at high risk for imminent stroke. However, despite its widespread 
implementation, the ABCD2 score has not yet been prospectively validated. We 
assessed the accuracy of the ABCD2 score for predicting stroke at 7 (primary 
outcome) and 90 days.
METHODS: This prospective cohort study enrolled adults from eight Canadian 
emergency departments who had received a diagnosis of transient ischemic attack. 
Physicians completed data forms with the ABCD2 score before disposition. The 
outcome criterion, stroke, was established by a treating neurologist or by an 
Adjudication Committee. We calculated the sensitivity and specificity for 
predicting stroke 7 and 90 days after visiting the emergency department using 
the original "high-risk" cutpoint of an ABCD2 score of more than 5, and the 
American Heart Association recommendation of a score of more than 2.
RESULTS: We enrolled 2056 patients (mean age 68.0 yr, 1046 (50.9%) women) who 
had a rate of stroke of 1.8% at 7 days and 3.2% at 90 days. An ABCD2 score of 
more than 5 had a sensitivity of 31.6% (95% confidence interval [CI] 19.1-47.5) 
for stroke at 7 days and 29.2% (95% CI 19.6-41.2) for stroke at 90 days. An 
ABCD2 score of more than 2 resulted in sensitivity of 94.7% (95% CI 82.7-98.5) 
for stroke at 7 days with a specificity of 12.5% (95% CI 11.2-14.1). The 
accuracy of the ABCD2 score as calculated by either the enrolling physician 
(area under the curve 0.56; 95% CI 0.47-0.65) or the coordinating centre (area 
under the curve 0.65; 95% CI 0.57-0.73) was poor.
INTERPRETATION: This multicentre prospective study involving patients in 
emergency departments with transient ischemic attack found the ABCD2 score to be 
inaccurate, at any cut-point, as a predictor of imminent stroke. Furthermore, 
the ABCD2 score of more than 2 that is recommended by the American Heart 
Association is nonspecific.