INCREASED ACTIVATED PROTEIN-C PROTEIN-C INHIBITOR COMPLEX LEVEL IN PATIENTS POSITIVE FOR LUPUS ANTICOAGULANT

Activated protein C (APC)-protein C inhibitor (PCI) complex and APC-al pha(1)antitrypsin (alpha(1)AT) complex levels were measured in 29 pati ents positive for lupus anticoagulant (LA). LA was considered positive if two of the following three criteria were fulfilled: (1) prolongati on of the activated partial thromboplastin time, (2) prolongation of t he kaolin clotting time (KCT) and KCT mixing test, and (3) prolongatio n of the dilute Russell's viper venom time (DRVVT) and DRVVT/DRVVT wit h high lipid concentration. Plasma thrombin-antithrombin III (AT-III) complex and plasmin-alpha(2)-antiplasmin inhibitor complex levels in p atients positive for LA were increased slightly, but not significantly , and FDP-D-dimer and t-PA levels were not markedly increased. Plasma PAI-1 level in the LA-positive patients was significantly increased co mpared with normal volunteers. AT-III activity, protein C antigen, PCI antigen, and protein S antigen levels in the LA-positive patients wer e virtually normal, while protein C activity was slightly, but not sig nificantly, decreased. APC-PCI complex level was increased in all LA-p ositive patients, and was not detectable in patients with systemic lup us erythematosus and normal volunteers. APC-alpha(1)AT complex was inc reased slightly, in only two LA-positive patients; it was not detectab le in the other patients or in the normal volunteers. These findings s uggest that patients positive for LA are in a hypercoagulable state an d that protein C activity in such patients is decreased, due to the ac tivation of this protein.