A Single Health System Retrospective Qualitative Analysis of Inpatient Apixaban and Rivaroxaban Calibrated Anti-Xa...

The ability to obtain a quantitative drug level for apixaban and rivaroxaban exists using drug-specific calibrated anti-Xa assays; however, no standard exists defining when to obtain direct oral anticoagulant (DOAC) concentrations or how to adjust medication regimens based on the results.

Describe the incidence of DOAC levels obtained, identify trends in prescribing DOAC levels in clinical practice, and qualitatively assess level appropriateness and actions taken based on level results.

A qualitative, retrospective analysis was conducted using the electronic medical record to identify adult inpatients within a 10-hospital health system with a calibrated apixaban or rivaroxaban anti-Xa level result from April 1, 2020, to November 1, 2022. The primary endpoint was the incidence of DOAC levels drawn. Secondary outcomes included the percentage of DOAC concentrations that prompted a dose change, association between dose or agent change and concentrations outside the on-therapy range, and association between indication for obtaining DOAC levels and resultant concentrations.

One-hundred thirty-two calibrated anti-Xa levels were obtained in 101 inpatients during the study period, representing a level drawn in 0.48% of all apixaban and rivaroxaban orders. Eighty-three (63%) patients were on apixaban. Primary reasons to draw DOAC levels were extreme body weight (35%), treatment failure concerns (23%), bleeding concerns (18%), and drug interactions (14%). Only 42 (31.8%) of all levels were drawn appropriately as a peak. Seventeen (40.4%) of the peak levels were within the on-therapy range. Of the 25 levels outside the on-therapy range, 14 (56%) resulted in no change in therapy. For all levels drawn, 70 (53%) resulted in no change to therapy.

DOAC concentrations are often drawn at inappropriate times and seldom influence a dose or agent change. Future research is needed to determine if DOAC concentrations may be clinically meaningful in a select subgroup of patients.