Storage-dependent variability in Alzheimer disease-related plasma biomarker results using the Fujirebio Lumipulse G1200 platform.

Alzheimer disease plasma biomarkers have emerged as minimally invasive, cost-effective tools for early diagnosis and disease monitoring yet their stability under common "real world" pre-analytical conditions remains incompletely characterized. We evaluated the stability of six plasma biomarkers, Aβ40, Aβ42, pTau181, pTau217, NfL, and glial fibrillary acidic protein (GFAP) using the Fujirebio Lumipulse G1200 platform. Plasma samples were initially collected from four healthy and cognitively unimpaired volunteers. Samples were stored under four conditions: room temperature (0-4 h), +4 °C (1-10 days), -20 °C (1-3 weeks), and -80 °C (4-8 weeks). In this pilot study, Aβ40 and Aβ42 remained generally stable. In contrast, pTau181 readings exhibited marked elevations in frozen samples, while pTau217 showed modest early fluctuations followed by significant decreases with prolonged storage. Next, we recruited 12 additional participants (six cognitively normal and six with mild cognitive impairment [MCI]), and their plasma samples were analyzed both fresh and after 4 weeks of storage at -80 °C. Among these participants, pTau181 readouts were significantly higher, and pTau217 were lower, in -80 °C frozen in comparison to never-frozen samples. These findings underscore the critical need for biomarker-specific sample workup and handling protocols and indicate that results for fresh plasma cannot be assumed to be the same as for frozen samples.