Blood-based biomarkers for Alzheimer’s disease diagnosis: a joint position paper from the Italian Societies of Neurology (SIN) and of Clinical Biochemistry and Clinical Molecular Biology - Laboratory Medicine(SIBioC) and from the Autonomous Association affiliated with SIN for dementia (SINdem)

Background Blood-based biomarkers are reshaping the diagnostic paradigm of Alzheimer's disease (AD), offering a minimally invasive alternative to cerebrospinal fluid (CSF) and positron emission tomography (PET). However, their clinical implementation requires harmonized analytical validation, standardized procedures, and clear guidance on appropriate use and interpretation. Methods This joint position paper was developed by the Study Groups on Biomarkers in Neurology of the Italian Society of Neurology (SIN) and the Italian Society of Clinical Biochemistry and Clinical Molecular Biology-Laboratory Medicine (SIBioC), together with the Autonomous Association affiliated with SIN for Dementia (SINdem). A multidisciplinary panel of neurologists and laboratory experts systematically reviewed current evidence, international guidelines, and regulatory frameworks to formulate consensus recommendations for clinical adoption in Italy. Results Among available plasma biomarkers, phosphorylated tau at threonine 217 (p-tau217), alone or as a ratio with amyloid-(342, shows the highest diagnostic accuracy, approaching CSF and PET performance. Fully automated platforms ensure analytical robustness and reproducibility. The document provides detailed guidance on pre-analytical handling, test selection, and reporting standards, emphasizing appropriate clinical indications and the need for contextual interpretation considering confounders such as advanced age or renal dysfunction. Conclusions This position paper defines a unified framework for integrating plasma biomarkers into AD diagnostic pathways, bridging neurology and laboratory medicine. It highlights key steps toward regulatory inclusion in the Italian healthcare system and quality-assured clinical practice.