Current status of immunoscintigraphy in the detection of thrombosis and thromboembolism

Abstract

This review describes the use of monoclonal antibodies (MoAbs) for immunoscintigraphic detection of thrombosis and thromboembolism. Two major groups of MoAbs have been tested: Antibodies directed against platelets and antibodies directed against fibrin. Several antiplatelet antibodies have been developed that are directed against either the platelet membrane glycoprotein complex, IIb/IIIa, which binds fibrinogen, or against two different proteins, alpha granule membrane protein GMP-140 and thrombospondin (TSP) that are expressed during platelet activation. Platelets labeled with radioactive antibody or antibody fragments have characteristics similar to platelets labeled in vitro with lipophilic complexes. Studies in animal models indicate that antiplatelet antibody and antiactivated platelet factor antibody imaging have a high sensitivity for clots less than 24 hours old and that images can be positive as early as one to two hours after antibody administration. A limited number of antiplatelet antibody studies have been performed in patients. This technique appears to yield accurate results provided that active platelet deposition is occurring at the time of the study. Several antifibrin MoAbs, specific for fibrin monomers, have been developed. Compared with antiplatelet antibodies, antifibrin antibodies and antibody fragments appear to be capable of detecting older experimental clots (up to five days old). Images in experimental thrombosis models are routinely positive within two hours of antibody administration. Recently reported clinical trials indicate a high sensitivity in all anatomic locations within the extremities whether or not patients were receiving heparin.