Utility of Urinalysis in Discriminating Cardioembolic Stroke Mechanism

Abstract

To determine whether elevated urine erythrocyte (red blood cell) and leukocyte (white blood cell) counts, reflecting concomitant renal and cerebral emboli of cardiac origin, would be useful in discriminating cardioembolic (CE) from non-CE stroke in acute ischemic stroke. Consecutive patients presenting within 24 hours of ischemic stroke over 3(3/4) years were studied. Patient medical history and urinalysis data, including white blood cell count, red blood cell count, specific gravity, and glucose and protein levels at admission, were analyzed and compared with the final determination of stroke subtype. Multivariate analysis (CE vs non-CE stroke) was performed using a classification and regression tree that included all 5 urine variables as potential predictors. Additional predictors entered into the classification and regression tree model were age, presence of urinary tract infection at admission, history of hypertension, history of diabetes mellitus, and serum creatinine level. A total of 341 individuals met the study criteria. Their mean age was 68.6 years; 49.8% were female, 70.9% were white, and 38.7% had the CE stroke subtype. In bivariate analysis, age (P = .009), urine white blood cell count (P = .02), urine red blood cell count (P = .005), urine specific gravity (P = .02), and serum creatinine level (P = .02) were significantly higher in those with the CE vs the non-CE stroke subtype. In the classification and regression tree, 58.3% of those with CE stroke were correctly classified and 84.7% of those with non-CE stroke were correctly classified, for an overall accuracy of 71.5%. The best single predictor for the CE stroke subtype was a white blood cell count of greater than 14.5/microL, followed by a red blood cell count of greater than 41.7/microL and a serum creatinine level greater than 1.08 mg/dL (>95.5 micromol/L). Based on the distribution in the first 2 divisions in the tree, a patient could be placed into 1 of 4 categories that corresponded to 3 levels of CE stroke likelihood: low (25%), moderate (50%), and high (80%). Urinalysis may have utility in the early identification of the CE stroke subtype in patients with acute ischemic stroke.