Stroke Risk Calculator (ABCD2 Score)

The ABCD2 score was developed in 2007 to predict stroke risk after a transient ischemic attack (TIA). A TIA is a temporary episode of neurological dysfunction caused by reduced blood flow, with symptoms that resolve within 24 hours. Despite the temporary nature of symptoms, TIA is a medical emergency because the days immediately following carry the highest stroke risk.

ABCD2 stands for: Age, Blood pressure, Clinical features, Duration of symptoms, and Diabetes. Each factor adds points to a total score of 0 to 7.

Interpretation by score: Low risk (0-3): 2-day stroke risk approximately 1%. 7-day risk approximately 1.2%. Moderate risk (4-5): 2-day stroke risk approximately 4%. 7-day risk approximately 5.9%. High risk (6-7): 2-day stroke risk approximately 8%. 7-day risk approximately 11.7%.

These are population-level risks from the original validation studies. Individual risk depends on many additional factors: imaging findings, atrial fibrillation, carotid stenosis, and whether antiplatelet therapy was started immediately.

How much weight should this score carry? Less than its popularity suggests.

ABCD2 was widely adopted after 2007 and has aged poorly. Later validation work, including a large 2011 meta-analysis, found it discriminates weakly between patients who go on to have a stroke and those who do not, and that it misses a meaningful share of patients who turn out to have carotid stenosis or atrial fibrillation. Several national guidelines have since moved away from using it to triage.

So treat a low number as uninformative rather than reassuring. The score should not be used to decide whether to admit or discharge, and the American Heart Association recommends urgent evaluation and treatment of every TIA regardless of what it says. Workup includes brain imaging with MRI preferred, vascular imaging of the neck and intracranial vessels, cardiac monitoring, and blood tests.

Enter the measured age and blood pressure rather than deciding in advance whether each crosses its threshold. A reading of 138/88 scores zero where 140/88 scores one, and a single blood pressure taken in an emergency department is noisy enough that the difference is often measurement rather than physiology. The calculator flags a reading sitting close to the line.

The reason early treatment matters: antiplatelet therapy (aspirin, clopidogrel), statin initiation, and blood pressure control in the hours after TIA can reduce the subsequent stroke risk by 80% or more. Most of that risk reduction happens in the first 48 hours.