RESUMO
OBJECTIVE: The main concern about measuring the concentration of rivaroxaban by anti-Xa assay in some laboratories is the lack of a commercial specific calibrator in emergencies. Therefore, this study aimed at providing a homemade anti-Xa calibrator and commercial low molecular weight heparin (LMWH) anti-Xa calibrator. METHODS: The anti-Xa plasma concentration of rivaroxaban was measured in 70 patients using a commercial specific anti-Xa calibrator, a commercial LMWH anti-Xa calibrator, and a homemade anti-Xa calibrator. RESULTS: We demonstrated a significant correlation and agreement (Pâ < .001) between LMWH-calibrated anti-Xa and the commercial specific calibrator. A significant correlation (Pâ < .001) was found between homemade calibrated anti-Xa made by normal pooled plasma and that calibrated with a commercial specific drug. The nonspecific homemade and LMWH calibrators had excellent agreement (Pâ < .001) and can be used interchangeably. CONCLUSION: Our data showed that for estimating rivaroxaban concentrations, the LMWH calibrator could be used as an alternative calibrator in the anti-Xa assay.
