045 Predicting risk of stroke following TIA: a systematic review of the validation of ABCD2 clinical prediction rule

Galvin, R., Geraghty, C., Motterlini, N., Dimitrov, B.D. and Fahey, T. (2010) 045 Predicting risk of stroke following TIA: a systematic review of the validation of ABCD2 clinical prediction rule. Journal of Epidemiology and Community Health, 64, supplement 1, A18-A18. (doi:10.1136/jech.2010.120956.45).

Abstract

Introduction: stroke is a leading cause of death and acquired disability in every society in which it has been studied. Stroke and transient ischaemic attack (TIA) arise from identical aetiologies and a number of studies have demonstrated that TIAs carry a significant risk of stroke. Several independent predictors of stroke have been incorporated into models such as the ABCD2 clinical prediction rule, which is used to predict risk of stroke following TIA. This systematic review assessed the predictive value of the ABCD2 rule in relation to 7 and 90?day risk of stroke.

Methods: a computerised systematic literature search was performed to retrieve articles that validated the ABCD2 rule. The original derivation study was used as a predictive model and applied to all validation studies, with observed and predicted number of strokes at 7 and 90?days stratified by risk group (0-3 low, 4-5 moderate, 6-7 high). Results from the studies were pooled and risk ratios (RR) with 95% CI produced. Forest plots were used to graphically display the data. A RR score of 1 represents correct prediction by the ABCD2 rule, <1 represents under-prediction and >1 over-prediction.

Results: nine validation studies (n=5626) predicted 7?day stroke risk. The ABCD2 rule correctly predicted occurrence of stroke at 7?days across all three risk strata: low risk (n=1933) — RR 1.12, 95% CI (0.61 to 2.05); moderate risk (n=2640)—RR 1.11, 95% CI (0.74 to 1.68); high risk (n=1053)—RR 0.98, 95% CI (0.69 to 1.41). There were 318 strokes predicted and 288 strokes observed at 7?days across all three risk strata. Data on five studies (n=4897) were pooled to predict 90?day stroke risk. The ABCD2 rule over-predicted the occurrence of stroke across all three risk strata — low risk (n=1660), RR 1.50, 95% CI (0.86 to 2.62); moderate risk (n=2214), RR 2.24, 95% CI (1.29 to 3.91); high risk (n=1033), RR 2.00, 95% CI (0.90 to 4.45). There were 268 strokes observed at 90?days in contrast to 404 predicted strokes. The chi-squared trend for analysis indicated that as the trichotomised ABCD2 score increased, the rate of stroke increased (p<0.0001).

Conclusion: the ABCD2 score correctly predicts 7?day risk of stroke across all risk strata but over-predicts 90?day risk of stroke in all groups. The variation in the study setting and design needs to be considered in the interpretation of these findings. ABCD2 is a useful CPR, particularly in relation to 7?day risk of stroke

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