Subclassification of non-specific circulating anticoagulants

Abstract

Until recently all non-specific circulating anticoagulants (NSCA) were described as "lupus inhibitors". The adoption of phospholipid or platelet correction tests to distinguish non-haemorrhagic inhibitors (which dissplay positive PL correction) from haemorrhagio inhibitors, which fail to correct with PI and the use of various other tests has led to an appreci-aion of heterogeneity among VSCA. We now describe two NSCA which display phospholipid correction but which are associated with minor bleeding problems, clinically unlike typical iupus anticoagulants OLA. Furthermore such haemorrhagio LA can be clearly distinguished from more typical LA by giving negative results in a dilute Russell's viper venom time test (DRVVT). The first anticoagulant was detected in plasma from an 85 year old man requiring skin grafts after removal of superficial cancers from his legs. It was shown to be an IgM antibody which bound factor VIII weakly in vivo. The second anticoagulant was found in a 55 year old lady with a very long history of minor bleeding episodes associated with "LA". Neither patient's plasma displayed antiphospho-lipid antibodies in El.ISA tests. These inhibitors appear to function by interfering with the "tenase" complex rather than with the assembly of the "prothrombinase" comp1ex which is believed to be the target of more-typical "LA".