Impact of fasting status and storage time on plasma Amyloid-β 42 and 40, p-tau181, p-tau231, GFAP and NfL measurements

BACKGROUND : Pre-analytical factors may influence plasma biomarker levels reflecting Alzheimer’s disease (AD) pathology and neurodegeneration. We evaluated the impact of fasting and long-term storage at -80ºC on plasma biomarkers (Amyloid-β[Aβ]40, Aβ42, phospho-tau181, p-tau231, GFAP and NfL). METHODS : Biomarkers were measured in ALFA cohort using Simoa technology. Fasting effects were assessed using 16 paired samples. Long-term storage at -80ºC was evaluated in 623 samples stored up to 10 years. RESULTS : Fasting lowered Aβ peptides levels, but it was mitigated with the Aβ42/40 ratio. Long-term storage showed no effect on Aβ42/40 or NfL. However, Aβ peptides, p-tau181, p-tau231 and GFAP levels were higher in samples stored longer than 6 years. CONCLUSION : Fasting only influences Aβ peptides levels. The variability created by long-term storage in Aβs, p-tau181, p-tau231 and GFAP was below 6%. The results suggest that fasting does not influence biomarkers measurements and storage time might be considered, especially in longitudinal studies.