Glial fibrillary acidic protein as a biomarker for diagnosis of Alzheimer’s disease in cerebrospinal fluid, plasma and saliva measured with Lumipulse technology: a narrative review
Josef Marksteiner, Christian Humpel
Abstract
Glial fibrillary acidic protein is an intermediate filament protein released primarily by astrocytes in the central nervous system, providing structural and functional support to neurons. Glial fibrillary acidic protein is a key biomarker of neuroinflammation and astrocyte activation. Recent research advances have highlighted the potential of glial fibrillary acidic protein as a diagnostic and prognostic marker for Alzheimer's disease. Traditionally, cerebrospinal fluid has been the primary medium for analyzing biomarkers of neurodegeneration; however, the detection of biomarkers in plasma and saliva may offer new possibilities for non-invasive diagnostic methods, thus providing practical advantages for routine monitoring and early detection. The aim of this narrative review is to describe the differences and significance of the biomarker glial fibrillary acidic protein in plasma, cerebrospinal fluid, and saliva of patients with Alzheimer's disease. Using a novel luminescence-based method, the Lumipulse technology, the article detects and analyzes possible differences in the concentration of glial fibrillary acidic protein in cerebrospinal fluid, blood, and saliva of healthy individuals and patients with Alzheimer's disease. Although elevated glial fibrillary acidic protein levels in the cerebrospinal fluid of patients with Alzheimer's disease may reflect neuroinflammation, the high variability of the samples and the nonsignificant differences in glial fibrillary acidic protein levels, when compared with those of healthy individuals, limit its utility as a diagnostic marker. In contrast, plasma glial fibrillary acidic protein levels were higher in patients with Alzheimer's disease than in healthy subjects, showing a potential as a noninvasive diagnostic marker. Notably, plasma glial fibrillary acidic protein was stable at room temperature for at least 7 days. Salivary glial fibrillary acidic protein levels were close to the detection level, making it unsuitable for use as a biomarker of Alzheimer's disease. The results of this article confirm that plasma glial fibrillary acidic protein can be used as a potential biomarker for the diagnosis of Alzheimer's disease, is stable, and can effectively differentiate between Alzheimer's disease and healthy individuals.