Indications for Using an Alternative Method to the PT or INR for Monitoring Warfarin Therapy in a Patient with a Lupus Anticoagulant

Patient selection: presence of a lupus anticoagulant

Indications for monitoring the patient with an alternative method:

(1) prolongation of the PT in the absence of oral anticoagulation and Factor VII deficiency (some patients with a lupus anticoagulant will show an elevation in the PT in addition to the usual increase in the PTT)

(2) variation in the INR reported by different laboratories while on stable warfarin therapy (due to differing sensitivities to the anticoagulant shown by the different thromboplastins)

(3) discordance between clinical status and reported INR (bleeding with low INR, thrombosis with high INR)

Alternative methods that are less affected by the anticoagulant:

(1) chromogenic Factor X

(2) prothrombin-proconvertin time