Which Statement Is True Regarding Monitoring Anticoagulant Therapy in Patients

Which statement is true regarding monitoring anticoagulant therapy in patients with a LA?

A) If the patient's PT and international normalized ratio (INR) were within normal range before starting warfarin, then the INR can be used for therapeutic monitoring.
B) Because the APTT is prolonged in people with LA, the PT has to be used to monitor heparin therapy.
C) Because the patient has an LA, if he or she is receiving warfarin therapy, an INR of no more than 2.0 is adequate.
D) If the patient is receiving warfarin, then a chromogenic factor X assay may be needed. If the patient is receiving heparin, then a chromogenic anti-factor Xa (heparin assay) should be used if monitoring is required.
E) The physician should use his or her best judgment regarding dosing of anticoagulants because it is impossible to monitor anticoagulant therapy in people with LA.