Clinical predictive value of the ABCD2 score for early risk of stroke in patients who have had transient ischaemic attack and who present to an Australian tertiary hospital

OBJECTIVE: To determine the predictive value of the ABCD(2) score for early risk of stroke in Australian patients who have had transient ischaemic attack (TIA). DESIGN, PARTICIPANTS AND SETTING: Cohort study of 512 consecutive patients with suspected TIA referred by the emergency department to the acute stroke unit (in accordance with the TIA pathway) of an urban tertiary hospital in Melbourne, Victoria, between 1 June 2004 and 30 November 2007. MAIN OUTCOME MEASURES: Overall accuracy, estimated by the area under the curve (AUC) of receiver operating characteristic plots (of true positive rate v false positive rate), and sensitivity, specificity, predictive values and likelihood ratios at prespecified cut-off ABCD(2) scores for stroke within 2, 7 and 90 days. RESULTS: 24 patients were excluded because their symptoms lasted more than 24 hours. All included patients were reviewed by a stroke physician; TIA was confirmed in 301/488 (61.7%). Most (289/301; 96.0%) had complete follow-up. Stroke occurred in 4/292 patients (1.37%; 95% CI, 0.37%-3.47%) within 2 days and 7/289 (2.42%; 95% CI, 0.98%-4.93%) within 90 days; no patient had a stroke between 2 and 7 days. The AUCs for stroke in patients with confirmed TIA were 0.80 (95% CI, 0.68-0.91) and 0.62 (95% CI, 0.40-0.83) for stroke within 2 days and 90 days, respectively. At a cut-off of ≥ 5, the ABCD(2) score had modest specificity for stroke within 2 days (0.58) and 90 days (0.58), but positive predictive values (2 days, 0.03; 90 days, 0.04) and positive likelihood ratios (2 days, 2.40; 90 days, 1.71) were both poor. The score performed similarly poorly at other prespecified cut-off scores. CONCLUSIONS: Given its poor predictive value, the use of the ABCD(2) score alone may not be dependable for guiding clinical treatment decisions or service organisation in an Australian tertiary setting. Validation in other Australian settings is recommended before it can be applied with confidence.