Accuracy of the STA®-Liquid anti-Xa assay in clinical practice: results from a large cross-sectional study in Switzerland

Objective Rapid and accurate measurement of direct oral anticoagulant drug level is critical in emergency situations. The diagnostic performance of anti-Xa assays in routine clinical practice is however not well established. We aimed to study the accuracy of the STA®-Liquid anti-Xa assay for the determination of rivaroxaban, apixaban, and edoxban in a large prospective cross-sectional study in clinical practice.

Material and Methods Nine-hundred thirty-two consecutive patients which were referred for the determination of rivaroxaban, apixaban, and edoxaban drug levels to one of nine specialized hemostasis laboratories were included. The STA®-Liquid anti-Xa assay was conducted alongside liquid chromatography-tandem mass spectrometry (LC-MS/MS) as reference standard.

Results Sufficient sample material was available from 758 patients (median age 76 years, inter-quartile range 66-83, 43% female). The overall correlation (rs) of STA®-Liquid anti-Xa assay with LC-MS/MS was 0.98 for rivaroxaban (95% confidence interval 0.97 to 0.98), 0.98 for apixaban (0.97, 0.98), and 0.98 for edoxaban (0.96, 0.99). Bias of Bland & Altman difference plot was < +/- 5 µg/L for all drugs.

Conclusion The diagnostic accuracy of anti-Xa measurements as determined using the STA®-Liquid assay in clinical practice was high among all drugs and consistent throughout the spectrum of measurements. Implementation might facilitate fast and accurate measurement of DOAC levels in the emergency setting.

Publication History

Article published online:
18 June 2021