BACKGROUND: Sporadic Creutzfeldt-Jakob disease (sCJD) is a fatal progressive neurodegenerative prion disease that affects the central nervous system. Although it has an heterogeneous clinical presentation, the principal and most frequent clinical features are progressive dementia, myoclonus or cerebellar manifestations as ataxia or nystagmus. It has a challenging diagnostic as it requires clinical compatibility with a positive result of another diagnostic tests such as real-time quaking-induced conversion (RT-QuIC) test, 14-3-3 protein cerebrospinal fluid (CSF) determination, magnetic resonance imaging (MRI) or electroencephalogram (EEG) in order to achieve a probable sCJD diagnosis. From all these tests, only RT-QuIC test and MRI can be abnormal at the beginning of the disease. For a definitive sCJD diagnosis, a brain biopsy or a brain autopsy is needed for its anatomopathological study. Nowadays, there is no curative available treatment for this disease. However, some clinical assays and other studies have suggested promising results for possible future curative treatments. OBJECTIVE: The aim of this study is to evaluate the diagnostic accuracy of total tau (t-tau) and phosphorylated-tau/total-tau (p-tau/t-tau) ratio combined with neurofilament light chain protein (NfL) CSF biomarkers for the early diagnosis of patients with sCJD

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