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Harmonizing the preclinical Alzheimer cognitive composite for multi‐cohort studies

Versions of the Preclinical Alzheimer Cognitive Composite (PACC) and within cohort standardization models have been implemented in multiple observational and clinical trials. Harmonizing PACC data across studies, however, requires modern psychometric approaches to reflect the psychometric, testing, and demographic nuances between cohorts and enable meta‐analyses. We present a method for harmonizing PACC across four cohorts: the Alzheimer’s Disease Neuroimaging Initiative (ADNI), the Anti‐Amyloid Treatment in Asymptomatic Alzheimer’s disease (A4), Harvard Aging Brain Study (HABS), and Australian Imaging, Biomarker & Lifestyle Study of Ageing (AIBL).