NIA-AA Staging of Preclinical Alzheimer Disease: Discordance and Concordance of CSF and Imaging Biomarkers

Abstract The National Institute of Aging and Alzheimer’s Association (NIA-AA) criteria for Alzheimer disease (AD) treat neuroimaging and cerebrospinal fluid (CSF) markers of AD pathology as if they would be interchangeable. We tested this assumption in 212 cognitively normal participants who have both neuroimaging and CSF measures of β-amyloid (CSF Aβ1-42 and PET imaging with Pittsburgh Compound B) and neuronal injury (CSF t-tau and p-tau and structural MRI) with longitudinal clinical follow-up. Participants were classified in preclinical AD Stage 1 (β-amyloidosis) or preclinical AD Stage 2+ (β-amyloidosis and neuronal injury) using the NIA-AA criteria, or in the normal or suspected non-Alzheimer pathophysiology group (SNAP; neuronal injury without β-amyloidosis). At baseline, 21% of participants had preclinical AD based on CSF and 28% based upon neuroimaging. Between modalities, staging was concordant in only 47% of participants. Disagreement resulted from low concordance between biomarkers of neuronal injury. Still, individuals in Stage 2+ using either criterion had an increased risk for clinical decline. This highlights the heterogeneity of the definition of neuronal injury, and has important implications for clinical trials utilizing biomarkers for enrollment or as surrogate endpoint measures.