ABCD2 Score Calculation and Application
Score Components and Point Assignment
The ABCD2 score is a 7-point clinical prediction tool that assigns points based on five key factors to stratify short-term stroke risk after TIA. 1
The scoring system allocates points as follows:
- Age: ≥60 years = 1 point 1
- Blood pressure: ≥140/90 mmHg at initial evaluation = 1 point 1
- Clinical features:
- Duration of symptoms:
- Diabetes mellitus: Present = 1 point 1
Risk Stratification Categories
The total score (0-7 points) stratifies patients into three distinct risk categories for stroke within 7 days:
- Low risk (0-3 points): 1.0-2.2% stroke risk at 7 days 1
- Moderate risk (4-5 points): 4.0-8.0% stroke risk at 7 days 1
- High risk (6-7 points): 8.0-12.5% stroke risk at 7 days 1
The critical threshold is a score ≥4, which defines high-risk patients requiring immediate hospitalization or specialized TIA clinic assessment within 24 hours. 2, 1 High-risk patients (ABCD2 ≥4) face an 8% stroke risk at 2 days compared to only 1% in low-risk patients (ABCD2 <4). 3
Clinical Application Algorithm
For High-Risk Patients (ABCD2 ≥4):
Immediate disposition: Admit to stroke unit or refer to specialized TIA clinic only if full assessment can be completed within 24-48 hours 2, 3
Urgent diagnostic workup (within 24 hours):
- Brain CT or MRI to exclude hemorrhage and identify acute infarction 2, 3
- Carotid duplex ultrasound for carotid territory symptoms 2, 1
- 12-lead ECG and continuous cardiac monitoring >24 hours 2
Immediate treatment:
- Dual antiplatelet therapy (aspirin plus clopidogrel) initiated within 12-24 hours, continued for 21 days 2, 3
- Urgent carotid revascularization within 2 weeks if stenosis >70% 2, 3
For Low-Risk Patients (ABCD2 <4):
Outpatient management: CT brain and carotid ultrasound within 48-72 hours, with assessment in rapid-access TIA clinic within 7-10 days 2, 1
Impact of Specialized Care
With urgent assessment and treatment in specialized settings, the 7-day stroke risk drops to only 0.9-2.1% across all ABCD2 categories, representing an approximately 80% relative risk reduction. 1 This dramatic improvement underscores that the ABCD2 score must be coupled with immediate action rather than used as a triage tool to delay care. 1
Long-Term Prognostic Value
Beyond short-term risk, an ABCD2 score >4 independently predicts long-term vascular events. 4, 5 In a Danish nationwide cohort, high-risk patients had a 3-year cumulative stroke incidence of 6.0% versus 4.2% in low-risk patients (HR 1.56). 6 Multivariate analysis confirmed ABCD2 >4 as an independent predictor of recurrent stroke (HR 2.27) and death (HR 1.68) over 40 months of follow-up. 4
Critical Pitfalls to Avoid
Do not use ABCD2 score alone to discharge low-risk patients from the emergency department. Even with a score <4, patients may harbor high-risk features such as diffusion-weighted imaging abnormalities, large artery stenosis, or atrial fibrillation that independently predict stroke. 7 The score's negative predictive value is not 100%—in one ED validation study, 3.4% of patients with ABCD2 <4 still had strokes within 7 days. 8
The majority of early recurrent strokes (approximately 50%) occur within the first 48 hours after TIA, making immediate evaluation and treatment imperative regardless of score. 2, 3 The American Heart Association recommends immediate ED referral for all patients presenting within 48 hours of symptom onset with motor weakness or speech disturbance, independent of calculated ABCD2 score. 2, 3