Value of copeptin and the S-100b protein assay in ruling out the diagnosis of stroke-induced dizziness pattern in emergency departments

Dizziness is a frequent reason for visiting emergency departments (EDs). Differentiating stroke from other causes is challenging for physicians. The role of biomarkers has been poorly assessed. We evaluated whether copeptin and S100b protein (PS100b) assessment, alone or in combination, could rule out stroke in patients visiting EDs for dizziness. We included patients 18 years of age or older, visiting the adult ED of a French university hospital for a new episode of dizziness evolving for less than 72 h. All patients underwent standardized physical examination (HINT [Head Impulse test, Nystagmus, test of skew deviation] maneuvers), copeptin and S-100b protein (PS100) measurement and injected brain imaging. Stroke diagnosis involved diffusion-weighted magnetic resonance imaging or, if not available, neurological examination and contrast brain CT scan compatible with the diagnosis. Of the 135 patients participating in the study, 13 (10%) had stroke. The sensitivity, specificity and positive and negative predictive values of copeptin/PS100 combination were 100% (95%CI, 77-100%), 48% (40-57%), 14% (11-27%) and 100% (94-100%), respectively. Values for copeptin alone were 77% (CI95% 0.50-0.91), 50% (CI95% 0.49-0.58), 14% (CI95% 0.08-0.24), 93% (CI95% 0.87-0.98), and for PS100 alone were 54% (CI95% 0.29-0.77), 97% (CI95% 0.92-0.99), 64% (CI95% 0.35-0.84), 95% (CI95% 0.90-0.98). Absence of copeptin and PS100 elevation seems to ruling out the diagnosis of stroke in patients visiting the ED for a new episode of dizziness. These results need to be confirmed in a large-scale study.