Stability of the thromboxane B2 biomarker of low-dose aspirin pharmacodynamics in human whole blood and in long-term stored serum samples

Background: Serum thromboxane B2 (sTXB2) is a validated biomarker of low-dose aspirin pharmacodynamics. In the original method, nonanticoagulated blood samples must be incubated at 37 °C immediately after withdrawal, centrifuged and serum supernatant should be frozen until assayed. Timely completion of all preanalytical steps may affect the feasibility and quality of sTXB2 measurements. The storage duration of frozen serum can also affect sTXB2 stability. Objectives: We assessed the stability of sTXB2 in clotted blood samples stored at 4 °C before further processing and in sera stored at −40 °C for over a decade. Methods: Venous whole blood withdrawn from individuals on chronic low-dose aspirin was dispensed in different tubes and immediately incubated at 37 °C for 1 hour. The reference tube was promptly processed following the original protocol; the remaining tubes were stored at 4 °C for 12 to 72 hours before further processing. Sera stored at a controlled −40 °C temperature for