Interpreting blood‐based biomarker results in heterogeneous populations with multiple co‐morbidities

A major benefit of the use of blood‐based biomarkers in screening for Alzheimer’s disease (AD) pathology, or diagnosing AD dementia, is that the collection of blood is less invasive and costly than cerebrospinal fluid or neuroimaging markers. Blood biomarkers are also more feasible and available at the primary care levels, where most individuals will present with cognitive symptoms. However, most studies examining blood‐based biomarkers of amyloid, phosphorylated tau, or neurodegeneration for screening or diagnosis have been conducted in neurology or memory clinics. Patients that reach these clinics often have less comorbidities and are younger than those seen and followed in primary care. Thus, there is a need to assess the utility of these blood‐biomarkers in diverse, community‐based cohorts of older ages, with multiple comorbidities, and with brain co‐pathologies (i.e., cerebrovascular disease).