Study objective: Several clinical prediction rules have been created to help physicians stratify the risk of future stroke for a patient diagnosed with transient ischemic attack. We performed an evidence-based emergency medicine shortcut review of available prognostic scores to determine which clinical prediction rules are valid and useful. Can emergency physicians reliably use a clinical prediction rule to predict which transient ischemic attack patients assessed in the emergency department have a low enough risk of acute stroke (1% to 2%) to be discharged home and which have a sufficiently high risk so that hospitalization is the safest disposition?

Methods: We searched PubMed, EMBASE, and DARE database for articles that derived or validated a clinical prediction rule to stratify the risk of stroke up to 7 days among patients with transient ischemic attack. We used standard criteria to determine the level of development of the rule and to appraise the quality of various prognostic studies.

Results: Five studies met the inclusion criteria. Three clinical prediction rules were derived, the "California rule," the "ABCD rule," and the "ABCD(2) rule." The ABCD rule has been validated in multiple studies (level 2), with a consistent 7-day risk of stroke less than 2% for patients with scores of less than 4. The California rule has been validated in only 1 independent cohort (level 3). The ABCD(2) rule has only been internally validated using a split sample technique (level 4). In all 3 clinical prediction rules, a higher prognostic score correlates with increased risk in all the derivation and validation studies.

Conclusion: There is a clear and predictable increase in stroke risk with an increased number of risk factors in all 3 clinical prediction rules. The ABCD rule has been well validated and is most likely to be predictive and clinically useful. Patients with an ABCD score of less than 4 are clearly at lower risk of stroke within 2 and 7 days of presentation (<2%) and may be candidates for discharge home with urgent outpatient evaluation. Future research in this area should involve impact analysis of the ABCD rule and further validation of the California and ABCD(2) rules in other populations.