D-dimer, Magnetic Resonance Imaging Diffusion-weighted Imaging, and ABCD2 Score for Transient Ischemic Attack Risk Stratification

Background: We sought to determine whether measurement of D-dimer (DD) would improve risk stratification after transient ischemic attack (TIA). Methods: We enrolled 167 patients with acute TIA in a prospective observational study. DD was measured using rapid enzyme-linked immunosorbent assay. The primary outcome measure was a composite end point consisting of stroke or death within 90 days or the identification of a high-risk stroke mechanism requiring specific early intervention (defined as >= 50% stenosis in a vessel referable to symptoms or a cardioembolic source warranting anticoagulation). Results: The composite end point occurred in 41 patients (25%). A 50% or greater stenosis was found in 25 patients (15%), a cardioembolic source in 14 (8%), and clinical events in 8 (5 strokes, 3 deaths), 6 of whom also had a high-risk cause of TIA. ABCD(2) score was associated with outcome (P for trend = .017, c-statistic 0.63). DD levels did not differ based on outcome status (geometric mean 0.75 v 0.82 mu g fibrinogen equivalent unit/mL, P = .56), and DD had little use for predicting outcome (c-statistic 0.57), even when combined with ABCD(2) score. Of 96 patients with early magnetic resonance imaging (MRI), 23% had diffusion-weighted imaging (DWI) abnormalities, and MRI DWI was predictive of outcome (c-statistic 0.76). The addition of MRI DWI to ABCD(2) improved predictive accuracy (c-statistic 0.83) compared with either alone. Conclusions: Many patients with TIA have a high-risk mechanism (large vessel stenosis or cardioembolism) or will experience stroke/death within 90 days. Increasing ABCD(2) scores were associated with this composite end point. Measurement of DD did not provide additional prognostic information.