F2 and deep vein thrombosis: The aim of our study was to determine rivaroxaban concentrations in real-world Chinese patients with deep vein thrombosis (DVT) by an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method to initially explore the correlation of the plasma concentration range and PT, aPTT, and anti-factor Xa activities and to determine a method for clinical monitoring of rivaroxaban.