Warfarin monitoring in patients with anticardiolipin antibodies, but without lupus anticoagulants.

Misleading international normalized ratios (INR) may be obtained from anticoagulated patients with lupus anticoagulants (LA). As a result, special precautions have been suggested for oral anticoagulant dosing. It is possible that plasma from subjects with an anticardiolipin antibody (ACA) without an LA could also affect the INR. We have studied nine such subjects who were anticoagulated and compared them with 11subjects who had neither antibody. The INR was performed, using local specific ISIs, with 11 different thromboplastins. No substantial difference was seen between the ACA-positive and ACA-negative patients, for either individual thromboplastins or patients. We similarly measured INRs in eight nonanticoagulated patients with ACAs. No effect on the INR results was observed. Thus, in these anticoagulated and nonanticoagulated patients we detected no evidence of any effect of an ACA on the INR.