Validation of ABCD2 scores ascertained by referring clinicians: a retrospective transient ischaemic attack clinic cohort study.

INTRODUCTION: Transient ischaemic attack (TIA) services routinely use ABCD2 scores ascertained by referring clinicians to triage patients. Most ABCD2 validation studies have used ABCD2 scores calculated by stroke-specialist investigators and not referring clinicians. This study aimed to assess the usefulness of referring clinicians' ABCD2 scores in predicting strokes.

METHODS: A retrospective study of a TIA clinic cohort from Gloucester, UK, followed up for 4 years from 2010 to 2012. ABCD2 scores were dichotomised to high risk-ABCD2≥4 and low risk-ABCD2<4. Outcomes of interest were subsequent stroke and stroke or TIA. Survival analysis was used determine the cumulative probability of these outcomes and to identify if ABCD2 risk category was associated with stroke.

RESULTS: Of 1067 (284 high risk, 783 low risk) patients, 49.6% were classified by the clinic stroke physicians as TIA/minor stroke and 50.4% as mimics. Follow-up was for a median of 34.9 (IQR 27.7-41.6) months with 56 strokes and 106 strokes/TIA. The number of strokes by 7 days, 90 days and 48 months, respectively, were: high risk 0, 2 and 20 and low risk 2, 6 and 36 (p=0.21). Unadjusted HR for subsequent stroke was 1.41 (95% CI 0.82 to 2.46) in the high-risk group compared with the low-risk group and HR adjusted for the diagnosis of TIA/stroke was 1.2 (95% CI 0.69 to 2.08).

CONCLUSIONS: ABCD2 scores recorded by referring clinicians did not identify patients at high risk of subsequent stroke, suggesting that the score should not be used for TIA clinic triage.