Neurology
ABCD² Score
Early stroke risk after TIA.
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Background
The ABCD² score estimates the short-term risk of stroke after a transient ischaemic attack (TIA) and was developed to help triage patients for urgent assessment. It combines five clinical features: Age ≥60 (1), Blood pressure ≥140/90 mmHg (1), Clinical features (unilateral weakness 2, speech disturbance without weakness 1), Duration (≥60 min 2, 10–59 min 1) and Diabetes (1), giving a total of 0–7. It was created by pooling and refining the earlier ABCD and California scores. The intention was to identify patients at highest early risk of completed stroke.
Interpreting the result
Scores are grouped as low (0–3), moderate (4–5) and high (6–7), with stroke risk in the first days after TIA rising as the score increases. Historically a score of 4 or more triggered urgent specialist review while lower scores were assessed less urgently. However, the score misses some early strokes in apparently low-risk patients, so current UK practice has moved away from using it to defer assessment. It is now best regarded as a descriptive risk indicator rather than a triage gate.
Advice
UK guidance (NICE) recommends urgent specialist assessment for everyone with a suspected TIA, irrespective of ABCD² score.
Worked example
A 68-year-old with hypertension presents after an hour of left arm weakness that has resolved: Age ≥60 (1) + BP ≥140/90 (1) + unilateral weakness (2) + duration ≥60 min (2) = 6, a high-risk score. Under current UK guidance they would be assessed urgently by a specialist regardless of this figure.
Pearls / pitfalls
- UK (NICE) guidance recommends urgent specialist assessment for everyone with a suspected TIA, so do not use a low ABCD² score to delay referral.
- The score does not account for atrial fibrillation, carotid stenosis or crescendo/recurrent TIAs, which independently demand urgent action.
- A "stroke mimic" (such as migraine aura or hypoglycaemia) can inflate the score — confirm the event was genuinely ischaemic.
- It predicts stroke risk, not the cause; aetiological work-up (imaging, ECG, carotids) is still required.
Evidence & validation
Derived and validated by Johnston et al. (2007) across multiple TIA cohorts; subsequent studies showed limited discrimination, and NICE now recommends urgent specialist assessment for all suspected TIAs irrespective of the score.
Frequently asked questions
Is the ABCD² score still used in the UK?
It is no longer used to decide who needs urgent assessment, because NICE recommends specialist review for all suspected TIAs. It may still appear as a descriptive risk indicator but should not be used to defer referral.
What ABCD² score is considered high risk?
A score of 6–7 is high risk and 4–5 moderate, with early stroke risk rising as the score increases. However, even low scores can be followed by stroke, which is why all patients are assessed urgently.
Why has guidance moved away from the score?
Validation studies found that the score missed a meaningful proportion of patients who went on to have an early stroke. Rapid specialist assessment for everyone proved safer than risk-stratifying with the score.
Does the score identify the cause of the TIA?
No — it only estimates stroke risk and does not detect causes such as carotid stenosis or atrial fibrillation. A full work-up including imaging, ECG and carotid assessment is still needed.
What counts towards the clinical features point?
Unilateral weakness scores two points and speech disturbance without weakness scores one point. Other transient symptoms score zero for that component.
References
- Johnston SC, Rothwell PM, Nguyen-Huynh MN, et al. Validation and refinement of scores to predict very early stroke risk after transient ischaemic attack (ABCD²). Lancet. 2007;369(9558):283–292.
- NICE NG128: Stroke and transient ischaemic attack in over 16s: diagnosis and initial management. 2019.
About the creator
Johnston SC et al.
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