Cerebrospinal fluid levels of amyloid-beta1-42 and brain amyloid-beta PET imaging with florbetapir-fluorine-18 had a limited association with each other as biomarkers for Alzheimer’s disease in a cross-sectional analysis of scans and CSF samples taken within 30 days of each other, according to Dr. Jon Toledo and his associates.

The associations between CSF amyloid-beta1-42 levels and florbetapir PET scans were not linear. The correlation between the two was strongest in the middle range. There was a larger range of florbetapir scan standardized uptake value ratios at the higher end of scores on the Alzheimer Disease Assessment Scale–cognitive subscale, compared with CSF amyloid-beta1-42 levels, indicating that florbetapir PET scans could better predict cognition. The association between the two biomarkers was significantly modified by APOE genotype, and no association was found in longitudinal CSF amyloid-beta1-42 levels and standardized uptake value ratios, the investigators reported.

The study “findings are significant for understanding how to interpret CSF amyloid-beta1-42 levels and florbetapir PET amyloid-beta measures for diagnosis and for understanding the mechanisms of amyloid-beta amyloidosis,” the researchers concluded.Find the full study in JAMA Neurology ( doi:10.1001/jamaneurol.2014.4829 ).