TIA Stroke Risk ABCD² Score

ABCD² explained

After a transient ischemic attack, the patient is at risk of suffering from stroke. This is a risk prediction and stratification tool based on TIA characteristics and patient data:

This stratification method has been criticised in numerous studies, in one of the latest having recorded a poor performance (low sensitivity and low specificity in ER setting). Therefore, clinical judgment should prevail and the score can continue to be used in outpatient (non-emergency) settings.

There are other prediction tools, like this prognosis calculator for TIA patients, that consists of similar stroke risk factors.

Score interpretation

The five items in the ABCD² score are weighted depending on their contribution to stroke risk prediction.

The total score ranges between 0 and 7 and is associated with a risk group and stroke risk percentages at 2, 7 and 90 days after the transient ischemic attack:

Patients classified in the low risk group and who don’t have any other concurrent conditions (e.g. atrial fibrillation) may be treated ambulatory.

Patients in the moderate risk group are likely to require hospitalization, even if they don’t have any concurrent conditions that may increase risk of stroke.

Patients in the high risk group should be hospitalized and initiated on antithrombotic therapy.

One opinion about the model is that high scores, rather separate patients with clear diagnosis of TIA from patients with alternative diagnoses (e.g. seizure, migraine or other nonvascular spells), than predict high risk of stroke occurrence.

About the study

The 2007 study by Johnston et al. was aimed at validating existing California and ABCD scores and deriving a new prediction model for 2-day stroke risk.

A cohort of 2,893 patients, diagnosed with TIA in ER units and clinics across the US and the UK, was separated in four independent groups. Logistic regression was used to identify the relevant variables.

The new score performed well in validation with c statistics: 0.62 - 0.83 and was deemed to be likely the most predictive of the current prognosis scores.

TIA evaluation and management

Evaluation and appropriate management of patients who are diagnosed with transient ischemic attack is capital in reducing the risk of stroke.

According to the National Stroke Association Guidelines:

■ Initial evaluation should take place within 12 hours of ischemic episode occurring;

■ Laboratory tests that should be performed include full blood count, serum electrolytes, fasting blood glucose, creatinine, lipids;

■ EKG should take place within 48 hours of TIA;

■ Brain imaging study via computed tomography or MRI within 48 hours;

■ Vascular imaging via carotid imaging, CT or MR angiography, or transcranial Doppler.

In patients deemed at risk of stroke, antithrombotic therapy is to be initiated and depends on the type of TIA (atherothrombotic or cardioembolic). Hypertension also requires medication and the patient should be advised towards a physical activity schedule, smoking cessation and a healthy diet.

In the case of patients with TIA caused by high grade internal carotid artery stenosis, surgical endarterectomy is scheduled.

Original source

Johnston SC, Rothwell PM, Nguyen-Huynh MN, Giles MF, Elkins JS, Bernstein AL, Sidney S. Validation and refinement of scores to predict very early stroke risk after transient ischaemic attack. Lancet. 2007; 369(9558):283-92.

Validation

Josephson SA, Sidney S, Pham TN, Bernstein AL, Johnston SC. Higher ABCD2 score predicts patients most likely to have true transient ischemic attack. Stroke. 2008; 39(11):3096-8.

Other references

1. Rothwell PM, Giles MF, Flossmann E, Lovelock CE, Redgrave JN, Warlow CP, Mehta Z. A simple score (ABCD) to identify individuals at high early risk of stroke after transient ischaemic attack. Lancet. 2005; 366(9479):29-36.

2. Sanders LM, Srikanth VK, Blacker DJ, Jolley DJ, Cooper KA, Phan TG. Performance of the ABCD2 score for stroke risk post TIA: meta-analysis and probability modeling. Neurology. 2012; 79(10):971-80.