DOAC plasma levels measured by chromogenic anti‐Xa assays and HPLC‐UV in apixaban‐ and rivaroxaban‐treated patients from the START‐Register

Abstract

Introduction To measure direct factor Xa inhibitor (apixaban, edoxaban, rivaroxaban) concentrations, dedicated chromogenic anti‐Xa assays are recommended as suitable methods to provide rapid drug quantification. Moreover, the high‐performance liquid chromatography with ultraviolet detection (HPLC‐UV) is reported as a reliable quantitative technique. We investigated seven anti‐Xa assays and an HPLC‐UV method for measurement of apixaban and rivaroxaban levels in patients enrolled in the START‐Register. Methods A total of 127 apixaban and 124 rivaroxaban samples were tested by HPLC‐UV and the following anti‐Xa assays: Biophen DiXaI and Heparin LRT (Hyphen BioMed), Berichrom and Innovance Heparin (Siemens), STA‐Liquid Anti‐Xa (Stago Diagnostics), Technochrom anti‐Xa (Technoclone), and HemosIL Liquid Anti‐Xa (Werfen). Each method was performed in one of the participating laboratories: Bologna, Cremona, Florence, and Padua. Results Our data confirmed the overestimation of apixaban and rivaroxaban levels by the antithrombin‐supplemented anti‐Xa method (Berichrom). Performances and reproducibility of the six anti‐Xa assays not supplemented with antithrombin and the HPLC‐UV method were good, with limits of quantification from 8‐39 ng/mL (apixaban) and 15‐33 ng/mL (rivaroxaban). The six chromogenic methods showed good concordances with the quantitative HPLC‐UV [bias: −26.9‐22.3 ng/mL (apixaban), −11.3‐18.7 ng/mL (rivaroxaban)]. Higher bias and wider range between limits of agreement were observed at higher concentrations [<100 ng/mL: bias −21.3‐4.1 ng/mL (apixaban) and −6.2‐3.8 ng/mL (rivaroxaban); >200 ng/mL: bias −42.2‐36.8 ng/mL (apixaban) and −20.1‐68.9 ng/mL (rivaroxaban)]. Conclusion Overall, the anti‐Xa assays not supplemented with antithrombin and the HPLC‐UV method proved to be suitable for apixaban and rivaroxaban quantification.

Apixaban concentration variability and relation to clinical outcomes in real-life patients with atrial fibrillation

“…It appeared that apixaban concentrations measured with both anti-Xa assays were underestimated. This finding has already been reported for STA–Liquid anti-Xa 4 . The same study reported an overestimation of apixaban measured with the Berichrom Heparin assay, which is in contrast to our findings and could be attributed to different statistical calculations performed in both studies.…”

“…The AVERROES substudy showed 20% lower trough median anti-Xa levels in patients who fulfilled criteria for the reduced dose of apixaban 4 . Our patients receiving 2.5 mg apixaban twice daily had 25–28% lower median trough concentrations (with all methods) compared with those receiving 5 mg twice daily.…”

“…Apixaban concentration can be measured directly by liquid chromatography with tandem mass spectrometry (LC -MS/ MS), but the method is not widely available. Chromogenic anti-factor Xa assays calibrated with known concentrations of apixaban are suitable for quantifying a wide range of apixaban plasma concentrations 4 , 5 . Considerable inter-patient variability is observed in apixaban concentrations measured by both methods 3 , 5 – 7 , and scarce data on intra-individual variability are available 8 , 9 .…”

Biological Variation in Rotational Thromboelastometry in Patients with Atrial Fibrillation Receiving Rivaroxaban

“…There is no defined therapeutic range for rivaroxaban, but the rivaroxaban concentrations detected at both the trough and the peak in our study were similar to those observed in other studies in which the reference method (liquid chromatography with tandem mass spectrometry) was used [ 21 , 22 , 23 ]. A significant positive correlation between rivaroxaban concentration and Extem CT in patients receiving rivaroxaban has been reported by others [ 9 , 13 ], but in our study, this correlation was even higher, probably because of a much higher number of samples (n = 358).…”

Oral drug dosing following bariatric surgery: General concepts and specific dosing advice

“…103,104 Based on the above reports, it seems that until more data on DOAC use is available, VKAs or low molecular weight heparins are to be preferred over DOACs. Measuring DOAC [105][106][107] or anti-Xa 108,109 concentrations has been suggested when applied in special patient groups; however, as there is no hard evidence on the relation between peak, trough or AUC of these measures with outcome, it seems too early to use TDM as guidance for DOAC use in postbariatric surgery patients. In another special patient population (i.e., children), anti-Xa measurement for monitoring of the effect of rivaroxaban was regarded as inferior compared to measurement of rivaroxaban concentration.…”