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Updated: Oct 24, 2026
In Vitro Aggregation Assays Using Hyperphosphorylated Tau Protein
Published on: January 2, 2015
Stability of plasma pTau217/Aβ42 ratio with delayed blood processing
Hana Mayfield1,2, Casey S John1,2, Jenae Pennington1,2
1University of Kansas Medical Center Department of Neurology Kansas City Kansas USA.
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.
