Sample characteristics.

For samples from the Knight Alzheimer's Disease Research Center and Alzheimer's Disease Neuroimaging Initiative the number of samples, percent female, percent of APOE e4 carriers, percent of non-demented (CDR = 0) samples, percent amyloid positive, percent of CDR = 0 samples that are amyloid positive, percent of CDR> = 0.5 samples that were amyloid positive) and mean and standard deviation of the key analytes from this study are shown. *Amyloid positivity is inferred from CSF AB42 levels (KADRC AB42<500 pg/ml; ADNI AB42<192 pg/ml). **ADNI phenotypes were obtained from ADNI after transformation to approximate a normal distribution. Sample characteristics.