Stability of plasma pTau217/Aβ42 ratio with delayed blood processing
Hana Mayfield, Casey S. John, Jenae Pennington, Riley E. Kemna, Maggie Kroeger, Amitava Dasgupta, Jeffrey M. Burns, Fanny M. Elahi, Melody Nelson, Jill K. MorrisAbstract
INTRODUCTION
Blood‐based biomarkers may improve access to Alzheimer's disease diagnosis, but use may be limited in clinics without on‐site processing capability. We evaluated the stability of the plasma phosphorylated tau 217 (pTau217)/amyloid beta 42 (Aβ42) ratio after delayed whole‐blood processing.
METHODS
We compared blood processed within 2 h or held at 4°C for approximately 24 or 48 h before centrifugation and analysis using the Fujirebio Lumipulse G1200. Stability was assessed using ordinary least squares regression, error index, Bland‐Altman analysis, and Deming regression.
RESULTS
Correlations with the 2‐h condition were high at both 24 and 48 h ( R = 0.998). Both delayed conditions met prespecified regression and error‐index criteria. Mean absolute percent error was 5.6% at 24 h and 9.8% at 48 h. Deming regression showed no constant bias, although proportional bias was observed at 48 h. No bias was observed for individual analytes for up to 48 h.
DISCUSSION
The pTau217/Aβ42 ratio in refrigerated whole blood remained stable for 24 h, with possible utility up to 48 h, supporting more flexible specimen‐transport workflows.