Reference: BMJ. 2021 Feb 4
When patients present with neurologic symptoms consistent with a transient ischemic attack (TIA), accurate prediction of future stroke risk is critical to deciding between hospital admission and discharge to home. The ABCD2/ABCD2i scores are often used in an attempt to distinguish patients at high risk of stroke in the next seven days from those at low risk, but the poor predictive accuracy of these scores has been repeatedly demonstrated. To address the need for a better tool, researchers developed the Canadian TIA Score in a prior study and set out to externally validate this score in a recent multicenter prospective cohort study. The score results range from -3 to 23, and are based in part on clinical presentation, laboratory values, ECG, and head CT results.
Investigators enrolled 7,607 adults (mean age 68 years) with TIA or minor stroke defined by discharge diagnosis. At time of assessment, physicians calculated the Canadian TIA Score, ABCD2 score, and ABCD2i score. Patients were stratified as low (< 1%), medium (1-5%), and high (> 5%) risk for stroke using each of the clinical decision tools. Primary outcomes were new stroke or carotid revascularization within seven days of initial assessment. Most patients had hypertension and nearly 20% had diabetes. The Canadian TIA Score classified 16.3% of patients as low-risk and 11.6% as high-risk. Patients in the medium- and high-risk categories were older, more likely to have multiple comorbidities, and more likely to be taking antiplatelet agents at baseline. A total of 182 primary outcomes occurred, with 108 patients diagnosed with subsequent stroke and 83 undergoing revascularization. Thirty-four patients were lost to follow-up at seven days. The estimated event rate for the primary outcome in the low-risk group was 0.7% with an observed event rate of 0.5% (interval likelihood ratio 0.20, 95% CI 0.09-0.44). The ABCD2 and ABCD2i scores classified no patients as low-risk for the primary outcomes.
In current practice, no clinical decision rule accurately predicts the risk of stroke in the ensuing 7-30 days after TIA symptoms. Importantly, in this study, the 34 patients lost to follow-up were not accounted for in the analysis; if we assume the worst-case scenario, this could significantly impact prognostic value. However, this external validation study of the Canadian TIA Score demonstrates this clinical decision rule may effectively stratify the risk of stroke or need for revascularization in the subsequent seven days. Depending on the clinician’s level of comfort and the local availability of resources, low-risk patients could be evaluated in the outpatient setting and high-risk patients could be managed with urgent neurology consultation in emergency departments. If nothing else, the data support abandoning the ABCD2 and ABCD2i scores.
For more information, see the topic Transient Ischemic Attack (TIA) in DynaMed.
DynaMed EBM Focus Editorial Team
This EBM Focus was written by Carina Brown, MD, Assistant Professor at Cone Health Family Medicine Residency. Edited by Alan Ehrlich, MD, Executive Editor at DynaMed and Associate Professor in Family Medicine at the University of Massachusetts Medical School, Dan Randall, MD, Deputy Editor for Internal Medicine at DynaMed, and Katharine DeGeorge, MD, MS, Associate Professor of Family Medicine at the University of Virginia and Clinical Editor at DynaMed.