173 Longitudinal change in biomarkers cognitively normal individuals. Additionally, the relatively small sample size resulted in even smaller numbers when dividing the sample into eight ATN profiles. Strengths include the longitudinal nature of the study with the availability of biomarkers, diagnoses and cognition with substantial duration of follow-up. Furthermore, we used dynamic scan protocols which enabled us to calculate BPND, which is a more accurate measure of amyloid and tau load than the semi-quantitative SUVr. Concluding, we showed biomarker status changes in cognitively normal individuals with SCD. There was considerable variability in the sequence of ATN biomarkers becoming abnormal, suggesting that there is not one (causal) order of events. Changing from a negative to positive amyloid status was associated with APOE ε4 carriership and predicted subtle cognitive decline, suggesting the potential clinical relevance of amyloid burden in the negative range. 7
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