Alpha-1-acid glycoprotein as a potential serum biomarker for cerebral amyloid angiopathy

Background Cerebral amyloid angiopathy (CAA) is a form of cerebral small vessel disease (SVD) associated with Alzheimer's disease, intracerebral hemorrhage, and cognitive decline. Despite its clinical significance, no reliable serum biomarker exists for early diagnosis or monitoring of disease progression. Objective This study hypothesizes that α1-acid glycoprotein (α1-AGP) and other serum biomarkers can aid CAA diagnosis and assessment using gel-based mass spectrometry. A comparative analysis was performed to investigate associations between serum biomarkers and radiological scores. Methods Serum proteins from individuals with probable or possible CAA (n = 10), classified using the modified Boston criteria, and age-matched controls (n = 10) were analyzed via two-dimensional differential gel electrophoresis (2D-DIGE) and matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI-TOF/TOF-MS). Candidate proteins were validated using enzyme-linked immunosorbent assay (ELISA). Outcome measures included biomarker diagnostic accuracy, assessed by receiver operating characteristic (ROC) curve analysis, and correlations between α1-AGP levels and CAA-SVD scores. Results Four proteins—hemopexin, complement C3, complement C9, and α1-AGP—were significantly elevated, while apolipoprotein A-1 was reduced in the CAA group. ELISA confirmed higher α1-AGP levels in individuals with CAA (p < 0.0001). ROC analysis demonstrated that α1-AGP could indicate the presence of CAA with a sensitivity and specificity of 1.00 (95%CI: 1.000, 1.000). Additionally, α1-AGP levels correlated with the CAA-SVD score (R² = 0.783). Conclusions α1-AGP may serve as a novel serum biomarker for CAA. Larger cohorts and external validation are required to substantiate these findings and determine their clinical relevance.