This study specifically aimed to assess (i) to what extent plasma Aβ42/Aβ40, NfL and p-tau181 biomarkers detect the presence of AD Aβ pathology (i.e. Aβ-positivity); (ii) to what extent the addition of demographic data, APOE genotype and cognitive assessments and (iii) MRI can assist plasma biomarkers in detecting Aβ-positivity and (iv) to what extent the stage of clinical diagnosis affects these relationships. Here, APOE is linked to Alzheimer disease.