Table 4.

Recommendations, advantages, and disadvantages of laboratory assays for measuring rivaroxaban exposure

Assay	Recommendations	Advantages	Disadvantages
Anti-Factor Xa chromogenic assay	• This assay is recommended (over PT measurement) and should always be used if possible	• Specific and sensitive quantitative measure • Determines plasma levels after all approved therapeutic doses of rivaroxaban have been administered • Rivaroxaban calibrators and controls are commercially available	• Requires rivaroxaban calibrators and controls • Assay is not available in many hospitals • Results need to be interpreted in relation to the timing of the tablet intake, in accordance with the pharmacokinetic profile
Prothrombin time	• Measurement of PT with a reagent sensitive to rivaroxaban (such as Neoplastin Plus; Roche Diagnostics, Mannheim, Germany) may be used for qualitative assessment only (measured in seconds)	• Assay is widely available • Simple assay • Quick results	• Gives a qualitative assessment expressed in seconds • Notable variations with different reagents • Conventional INR must not be used because INR does not correct for variations • The use of PT/INR or CoaguCheck tests (Roche Diagnostics, Mannheim, Germany) or PT with insensitive reagents (such as Innovin® [Siemens HealthCare Diagnostic Products GmBH, Marburg, Germany]) is not recommended

Note: Data from references 2, 19, 49, and 55.

Abbreviations: INR, international normalized ratio; PT, prothrombin time.