Assessing Alzheimer's Disease Pathology

The presence of elevated cortical amyloid uptake and CSF pTau 181 levels was used to categorize participant’s AD-related neuropathology. Processed amyloid and CSF pTau values were provided by the Knight ADRC^{108 (link),109 (link)}. Mean cortical amyloid levels were measured with PiB, a PET imaging tracer that binds to fibrillar deposits of Aβ. A cutoff value of 1.42 SUVR using the cerebellar cortex as the reference region^{108 (link)} was used to identify participants with elevated levels of amyloid deposits (amyloid PiB⁺, n = 47; PiB⁻, n = 160). CSF pTau values were obtained by analyzing CSF samples using enzyme-linked immunosorbent assays (Innotest, Innogenetics^{110 (link)}). Participants with a value above 67 pg/ml were categorized as having elevated levels of pTau (pTau⁺, n = 61; pTau⁻, n = 176)^{109 (link)}. A large portion of the final sample had both of these variables available (n = 193 of 265 in the final sample); however, a subset was missing some form of AD-related pathology data (see Table 1 for missing data). Participants with one or more elevated AD-related pathology markers were categorized as positive for AD-related pathology.