The Hart Biologicals Fiix™ Test Kit* is a modified Thromboplastin reagent for use in the in vitro control of patient anticoagulant therapy by venous blood Fiix™ Prothrombin times. Mixing whole blood sample/plasma sample with The Fiix™ Test Kit, results in the formation of a clot. The time taken for the clot to form is measured and used to determine the anticoagulant status of the patient.