Decreased Levels of Amyloid-β 1-42 in Cerebrospinal Fluid of Creutzfeldt–Jakob Disease Patients

Creutzfeldt–Jakob disease (CJD) is a rare neurodegenerative disease caused by the prion protein. In the search for biochemical markers for CJD, cerebrospinal fluid (CSF) of 101 patients was analysed for 14-3-3 protein, hTau-protein and amyloid-β 1-42 (Aβ_1-42). The 14-3-3 test had a specificity of 91.5% and a sensitivity of 84%. The hTau test resulted in 95% specificity and 74% sensitivity, when a cut-off of 1530 pg/ml was used. Aβ_1-42 detection in CSF of 29 probable or definite CJD patients revealed significantly decreased values (p = 0.01) compared to a group of 22 neurological controls. In the CJD patients a mean of 319 ± 102 pg/ml was found. In the neurological control group a mean of 553 ± 268 pg/ml was observed. In patients with a false positive 14-3-3 test (n = 5) a mean of 716 ± 441 pg/ml was found. We conclude that determination of Aβ_1-42 levels in CSF can be useful for identifying false positive 14-3-3 results in suspected CJD patients. We also compared the presence of senile plaques and the Aβ_1-42 levels in CSF of CJD patients. No clear correlation between them was found in this series. This signifies that the deceased Aβ_1-42 levels in CSF are not just due to plaque retention but that other mechanisms must also play a role.