Concentration Estimation of Apixaban and Rivaroxaban in Plasma From Patients Through Heparin-Calibrated Anti-Xa Assay...

Area of Science:

• Clinical Chemistry
• Pharmacology
• Thrombosis Management

Background:

• Direct oral anti-Xa inhibitors (DOACs) like apixaban and rivaroxaban are crucial for treating and preventing thrombosis.
• While generally safe, measuring plasma drug concentrations is sometimes clinically necessary for these anticoagulants.

Purpose of the Study:

• To compare the performance of three different Heparin Calibrated Anti Xa (HC-Anti Xa) assay systems.
• To evaluate these systems for measuring apixaban (APIXA) and rivaroxaban (RIVA) concentrations in patient plasma samples.

Main Methods:

• Analyzed 49 apixaban and 40 rivaroxaban patient plasma samples using peak or trough concentrations.
• Measured drug concentrations using specific anti-Xa assays (Werfen, Stago) and compared results with three HC-Anti Xa systems (Werfen, Siemens, Stago).

Main Results:

• Significant differences in HC-Anti Xa values were observed across the three systems, with the Stago system yielding the highest results.
• High correlation (r² > 0.94) was found between Werfen and Siemens assays for both drugs, but Stago showed a plateau effect at high concentrations.
• Agreement improved for concentrations ≤ 200 ng/mL, but inter-system differences persisted at various clinical decision points.

Conclusions:

• Heparin Calibrated Anti Xa assays can estimate apixaban and rivaroxaban concentrations, but results are system-dependent.
• Laboratories must establish and understand the specific HC-Anti Xa values corresponding to critical anticoagulant concentrations for accurate clinical use.