Evaluation of Blood-Based Diagnostic Biomarkers for Canine Cognitive Dysfunction Syndrome

Canine cognitive dysfunction syndrome (CDS) is a progressive neurodegenerative disorder in aging dogs and serves as a natural model for Alzheimer's disease in humans. This study evaluated blood biomarkers-amyloid-beta (Aβ40, Aβ42), neurofilament light chain (NfL), and glial fibrillary acidic protein (GFAP)-for diagnosing and staging CDS and assessed whether combining biomarkers with behavioral questionnaires improves diagnostic reliability. Seventy-seven dogs, including healthy controls and CDS cases, were assessed using the Canine Cognitive Dysfunction Rating Scale (CCDR), Canine Dementia Scale (CADES), and Canine Cognitive Assessment Scale (CCAS). Plasma Aβ40, Aβ42, GFAP, and serum NfL levels were measured via ELISA. While Aβ40, Aβ42, and GFAP were not significantly associated with CDS stage, serum NfL levels were elevated (p < 0.05) across all questionnaires. Receiver operating characteristic (ROC) analyses showed areas under the curve (AUCs) of 0.763 (CCDR), 0.722 (CADES), and 0.777 (CCAS), with cut-off values around 18.28-43.13 pg/mL. NfL shows promise as a blood biomarker correlated with CDS severity. Combining serum NfL measurements with questionnaire assessments may enhance diagnostic accuracy for CDS in veterinary practice.