GFAP and neurodegenerative disease: As a result, Simoa achieves femtogram-level sensitivity, making it uniquely suited to detect low-abundance biomarkers such as neurofilament light chain (NfL), phosphorylated tau (p-tau) isoforms, glial fibrillary acidic protein (GFAP), and inflammatory cytokines—all highly relevant to the pathophysiology of neurodegenerative diseases.