Fig. 1

Plasma Aβ42, NT1 tau, and NfL levels are constant over a 5 day period. Plasma was collected from 10 healthy volunteers on three occasions at 2-day intervals (day 1, day 3, day 5). On each sample day, blood was collected at 2 time points: the first between 7 and 10 am (M), and the second between 4 and 7 pm (E). Specimens were analyzed using ultra-sensitive Simoa-based assays for a Aβ42, b NT1 tau, and c NfL. Shown are measurements for each of the analytes on day 1, day 3, and day 5. Each point represents a single measurement, and mean ± SEM are indicated. Values measured in morning samples (M) are in red circles, and evening specimens (E) are in blue squares. Mixed effect regression analysis revealed that plasma levels of a Aβ42, b NT1 tau, and c NfL were stable and not significantly influenced by time of day (morning vs. evening) and did not change over a 5-day interval (day 1 vs. day 3 vs. day 5)