VCAM1 and Creutzfeldt Jacob disease: Overall, in most CJD subtypes, systemic biomarkers such as NfL, GFAP, and VCAM‐1 appear to change almost in parallel with symptom onset, while early detection remains best achieved through seed amplification assays like RT‐QuIC, which can identify PrPSc years before neurodegenerative markers become abnormal [10, 12].