Clinical Education Center

Question 1. What are the reference citations for the peak and trough ranges?

Peak and trough ranges provided on the patient report are from the published literature, as specified in the table below.

Question 2. What methodology is used for the rivaroxaban assay?

The method is a modified, chromogenic anti-Xa assay in which optical density is directly proportional to the rivaroxaban concentration. The optical density derived from the patient sample is compared to that of calibrators with known rivaroxaban concentration. The resulting concentration is reported in µg/L.

Question 3. What is the coefficient of variation (CV) of the rivaroxaban assay?

The CV of the rivaroxaban assay is ≤5.8%.

Question 4. What is the lower limit of detection?

The lower limit of detection for this rivaroxaban assay is 30 µg/L. Rivaroxaban trough levels may be below this value. For this reason, it is suggested that samples be collected at the peak (2-4 hours after the last dose).

Question 5. What are the known assay interferences?

Other anti-Xa anticoagulants including unfractionated heparin, low molecular weight heparin (enoxaparin, tinzaparin, dalteparin), and fondaparinux may interfere with the results. This is because the assay does not include a heparin neutralizer.

Gross lipemia, hemolysis >375 mg/dL, and gross icterus also interfere.