HONOLULU – A patient comes to your office because of what sounds very much like a recent TIA. As a busy primary care physician on the health care front lines, you need to be able to quickly assess this individual’s near-term risk of a full-blown stroke. The ABCD2 score is the right tool for this task, according to Dr. S. Claiborne Johnston.
The ABCD2 score is a simple tool for predicting the risk of stroke within 2 days after a TIA. It requires no special training and takes just seconds to calculate based upon patient history. With a score of 3 or more on the 0-7 scale, tell the patient to go straight to the emergency department. No referral to the neurologist for a consultation is necessary, he said at the International Stroke Conference sponsored by the American Stroke Association.
Dr. S. Claiborne Johnston
"If you’re talking to the patient on the phone, she doesn’t need to come into the office at all. Have her go straight to the ED. With a score of 3 or more, her stroke risk in the next 2 days is pretty high – and, really, what are you going to do in the clinic to reduce that risk?" said Dr. Johnston, professor of neurology and epidemiology and director of the stroke center at the University of California, San Francisco.
In the emergency department, physicians can obtain a brain scan to further define the short-term risk. And it’s likely they will admit the patient for observation during that very high-risk 2-day period.
"If you look at the cost effectiveness of observing these people in the hospital, the cost of hospitalization is justified by the opportunity to treat promptly with IV TPA [tissue plasminogen activator] should a stroke occur," Dr. Johnston added.
He and his coworkers developed the ABCD2 score through analysis of large patient data sets (Lancet 2007;369:283-92). The score has since been validated in numerous studies in varied populations. And it is endorsed in various stroke guidelines. For example, the American Heart Association/American Stroke Association guidelines state: "It is reasonable to hospitalize patients with an ABCD2 score of 3 or more presenting within 72 hours of symptoms, or with lower scores if work-up cannot be done as an outpatient within 2 days or if there is other evidence for focused ischemia."
The ABCD2 score assesses five parameters: age, blood pressure, clinical features, duration, and diabetes. Each has been shown to be an independent risk factor for stroke within 2 days after a TIA, with an associated roughly twofold increased risk. A patient gets 1 point for being age 60 or more, 1 point for having a blood pressure above 140/90 mm Hg in the office at the time of the TIA evaluation, 2 points if focal weakness was a clinical feature of the TIA, 1 point for speech impairment without weakness, 1 point for a TIA duration of 10-59 minutes, and 2 points for a duration of 60 minutes or more.
Multiple studies by Dr. Johnston and others have established that roughly 34% of TIA patients have an ABCD2 score of 0-3, putting them in a low short-term risk category, with an associated 1% risk of stroke within the first 2 days after their TIA. Another 45% of patients will have a score of 4-5, with an associated 4% 2-day stroke risk. And 21% of TIA patients are very high risk, with a score of 6-7 and an 8% incidence of stroke within 2 days.
How does the ABCD2 score predict stroke risk? Most likely in part by identifying people who’ve had a true TIA rather than migraine or another TIA mimic. Neurologist-confirmed TIAs have been shown to have higher ABCD2 scores.
"We think ABCD2 scores are just a simple way of doing the complex work that neurologists try to do when they’re diagnosing a specific event," Dr. Johnston explained.
He presented the case of a 72-year-old diabetic woman who phones the office because she has just had a 90-minute episode of difficulty in speaking and arm weakness. She stresses that she feels completely normal now. But even without knowing her current blood pressure, her ABCD2 score is still 6, giving her an 8% risk of stroke within the next 2 days. She needs to go to the ED immediately.
"Some day there’s going to be a blood test for this risk assessment, and I hope it’s soon. It will be sort of a troponin for the brain, but even more sensitive so we can look at transient ischemia as opposed to infarction. There are groups working on this, and there are a couple of leads. It would be wonderful if we got that. Until then we have this – and it works. It’s not perfect. It’s not great. But it’s better than the other things we have now," the neurologist said.