β‐amyloid peptides in cerebrospinal fluid of patients with Creutzfeldt–Jakob disease

Decreased levels of β‐amyloid peptide 1‐42 (Aβ1‐42) in cerebrospinal fluid (CSF) are a characteristic feature of Alzheimer's disease (AD) but recently were also observed in Creutzfeldt–Jakob disease (CJD). We analyzed the CSF of patients with CJD, and AD and nondemented controls using a quantitative urea‐based Aβ sodium dodecyl sulfate polyacrylamide gel electrophoresis immunoblot. Like in AD and nondemented controls, we found a highly conserved pattern of carboxyterminally truncated Aβ1‐37/38/39 in addition to Aβ1‐40/42 also in CJD patients. By the introduction of the ratio Aβ1‐39 to Aβ1‐42, CJD and AD can effectively be differentiated. We conclude that the immunoblot shows disease‐specific CSF Aβ peptide patterns in CJD and AD and suppose that measurement of the Aβ peptide pattern seems to be a promising diagnostic tool in the differential diagnosis of dementias. Ann Neurol 2003;54:263–267