Prognostic value of the ABCD² clinical prediction rule: A systematic review and meta-analysis

Objective: The purpose of this systematic review with meta-analysis is to determine the predictive value of the ABCD² at 7 and 90 days across three strata of risk. Background: The risk of stroke after transient ischaemic attack (TIA) is significant. The ABCD² clinical prediction rule is designed to predict early risk of stroke after TIA. A number of independent validation studies have been conducted since the rule was derived. Methods: A systematic literature search was conducted to identify studies that validated the ABCD². The derived rule was used as a predictive model and applied to subsequent validation studies. Comparisons were made between observed and predicted number of strokes stratified by risk group: low (0-3 points), moderate (4-5 points) and high (6-7 points). Pooled results are presented as risk ratios (RRs) with 95% confidence intervals (CIs), in terms of over-prediction (RR > 1) or under-prediction (RR < 1) of stroke at 7 and 90 days. Results: We include 16 validation studies. Fourteen studies report 7-day stroke risk (n = 6282, 388 strokes). The ABCD² rule correctly predicts occurrence of stroke at 7 days across all three risk strata: low [RR 0.86, 95% CI (0.47-1.58), I² = 16%], moderate [RR 0.99, 95% CI (0.67-1.47), I² = 68%] and high [RR 0.84, 95% CI (0.6-1.19), I² = 46%]. Eleven studies report 90-day stroke risk (n = 6304). There is a non-significant trend towards over-prediction of stroke in all risk categories at 90 days. There are 426 strokes observed in contrast to a predicted 626 strokes. As the trichotomized ABCD² score increases, the risk of stroke increases (P < 0.01). There is no evidence of publication bias in these studies (P > 0.05). Conclusion: The ABCD² is a useful CPR, particularly in relation to 7-day risk of stroke.