Stroke risk after transient ischemic attack in a Norwegian prospective cohort

Abstract

Background: Transient ischemic attack (TIA) is a risk factor of stroke. Modern treatment regimens and changing risk factors in the population justify new estimates of stroke risk after TIA, and evaluation of the recommended ABCD 2 stroke risk score. Methods: From October, 2012, to July, 2014, we performed a prospective, multicenter study in Central Norway, enrolling patients with a TIA within the previous 2 weeks. Our aim was to assess stroke risk at 1 week, 3 months and 1 year after TIA, and to determine the predictive value of the dichotomized ABCD 2 score (0-3 vs 4-7) at each time point. We used data obtained by telephone follow-up and registry data from the Norwegian Stroke Register. Results: Five hundred and seventy-seven patients with TIA were enrolled of which 85% were examined by a stroke specialist within 24 h after symptom onset. The cumulative incidence of stroke within 1 week, 3 months and 1 year of TIA was 0.9% (95% CI, 0.37-2.0), 3.3% (95% CI, 2.1-5.1) and 5.4% (95% CI, 3.9-7.6), respectively. The accuracy of the ABCD 2 score provided by c-statistics at 7 days, 3 months and 1 year was 0.62 (95% CI, 0.39-0.85), 0.62 (95% CI, 0.51-0.74) and 0.64 (95% CI, 0.54-0.75), respectively. Conclusions: We found a lower stroke risk after TIA than reported in earlier studies. The ABCD 2 score did not reliably discriminate between low and high risk patients, suggesting that it may be less useful in populations with a low risk of stroke after TIA. Trial registration: Unique identifier: NCT02038725 (retrospectively registered, January 16, 2014).