New prognostic instrument improves prediction of stroke risk after TIA

The existing prognostic scores for early-risk stroke prediction after transient ischaemic attack (TIA)* have been validated and refined to develop a unified score that is more predictive than previous methods, according to an Article published in this week's issue of The Lancet.

About 240,000 TIAs are diagnosed every year in the USA, and about 70,000 in the UK. Recent studies have shown that 4-20% of these patients will have a stroke within 90 days of a TIA, and half within the first two days. Identification of those at highest and lowest risk of stroke in the first days and weeks after a TIA would allow appropriate use of costly secondary prevention strategies, including hospital admission. However, it has not been possible to estimate individual risk with sufficient accuracy to guide clinical decisions. Two prognostic scores for estimating short-term risk of stroke after TIA have been proposed - ABCD score and the California score - they estimate the risk for stroke within 7 days or 90 days, respectively, after presentation with TIA. However, the 2-day risk is often most relevant for decisions about necessity of urgent evaluation and observation.

Claiborne Johnston (Department of Neurology, University of California, San Francisco, USA) and colleagues validated the two existing prognostic scores in large independent groups from different populations, comparing predictions of stroke risk at 2, 7, and 90 days. Since both previous prognostic scores predicted stroke risk reliably across a wide range of populations and contained several similar components, the researchers generated a new unified score for optimum 2-day risk. The new score, ABCD² (ABCD squared) was a more accurate predictor of risk of stroke than either of the two previous scores in the two derivation groups, and generally performed better in the four validation cohorts, thus creating a sole single standard for use in clinical care and public education.

Professor Johnston states: "We did the study because there continues to be a lot of confusion and inconsistency among physicians treating patients with TIA. Some admit nearly all such patients to the hospital while others monitor in the outpatient setting. This new score should be very useful in deciding who should come into the hospital right away."