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Abnormal clotting of the intrinsic/contact pathway in Alzheimer disease patients is related to cognitive ability.

Alzheimer disease (AD) is a neurodegenerative disorder characterized by extracellular β-amyloid (Aβ) deposition. Although peripheral inflammation and cerebrovascular pathology are reported in AD, there is a lack of plasma biomarkers in this field. Because the contact system is triggered in patient plasma, we hypothesized that the hemostasis profile could be a novel biomarker in AD. Here, we assessed the clotting profile in plasma from AD patients and age-matched controls. Utilizing clinically relevant assays, thromboelastography and activated partial thromboplastin time, we found impaired clot initiation and formation rate in AD patient plasma. These coagulation end points correlated with cerebrospinal fluid neurofilament-light levels and cognition and were more profound in younger AD patients. Ex vivo intrinsic clotting of plasma from AD mice expressing human amyloid precursor protein (APP) was also delayed in an age-dependent manner, suggesting that this phenotype is related to APP, the parent protein of Aβ. Further analysis of coagulation factors in human plasma indicated that endogenous inhibitor(s) of factors XII and XI in AD plasma contribute to this delayed clotting. Together, these data suggest that delayed clotting in young AD patients is a novel biomarker and that therapies aimed to correct this phenotype might be beneficial in this patient population. Follow-up studies in additional AD patient cohorts are warranted to further evaluate these findings.