ABCD2 is a 0–7 point bedside score for adults with time-defined TIA, intended to estimate very early stroke risk after initial assessment for stroke mimics and intracranial haemorrhage.

The 2007 Lancet study derived and validated the unified score in pooled emergency department and TIA clinic cohorts in the USA and UK (about 4,800 patients with time-defined TIA) to predict stroke at 2, 7 and 90 days, with the model optimised for 2-day stroke risk.

ABCD2 score	Original risk category	2‑day stroke risk	90‑day stroke risk
0–3	Low	≈1%	≈3%
4–5	Moderate	≈4%	≈10%
6–7	High	≈8%	≈18%

Subsequent systematic reviews and modern rapid-access TIA services report lower absolute event rates and only moderate predictive performance, particularly in TIA mimics and very low-risk settings.

Contemporary guidelines (for example NICE NG128) advise against using ABCD2 alone to determine urgency of referral or imaging after suspected TIA. Treat the score as a rough short-term risk signal to support, not replace, clinical assessment, vascular imaging and cardiac work-up.

ABCD2 Score for Transient Ischaemic Attack (TIA)