ABCD2 scores and prediction of noncerebrovascular diagnoses in an outpatient population: a case-control study.

BACKGROUND AND PURPOSE Among patients with transient ischemic attack, the ABCD2 score predicts short-term stroke risk. Use of the ABCD2 score assumes the underlying diagnosis to be transient ischemic attack; however, most transient ischemic attack services assess a variety of diagnoses. We hypothesized that patients with low ABCD2 score predominantly have noncerebrovascular diagnoses. METHODS Our transient ischemic attack clinics assess all suspected cerebrovascular events referred. Comprehensive clinical and investigation details are prospectively recorded. We collated data for patients seen between August 1992 and January 2005 inclusive. We calculated ABCD2 scores and compared proportions of noncerebrovascular diagnoses for each ABCD2 grade using chi(2) analysis. We ran similar analyses for atrial fibrillation, vascular lesions on brain imaging, and carotid stenosis. We calculated positive predictive value of low (0 to 1) ABCD2 score for noncerebrovascular diagnosis and described properties of ABCD2 as a diagnostic tool using receiver operating characteristic curves. RESULTS We derived ABCD2 scores for 3646 patients of whom 1769 had a noncerebrovascular diagnosis. There was a positive association between increasing ABCD2 score and cerebrovascular diagnosis (P<0.001). Higher ABCD2 score was associated with vascular lesions on brain imaging (P<0.001) and moderate-severe carotid disease (P<0.001) but not atrial fibrillation (P=0.097). The positive predictive value of low ABCD score was 0.81 for noncerebrovascular diagnosis and 0.93 for negative imaging. Receiver operating characteristic curve analysis suggested reasonable accuracy (area under the curve, 0.745). CONCLUSIONS For low scores, ABCD2 may assist in selecting out noncerebrovascular diagnoses. However, this approach will potentially misclassify many true transient ischemic attacks. Further refinement would be needed before clinical application.