Immunoscintigraphic detection of venous thrombosis of the lower extremities by means of human antifibrin monoclonal antibodies labeled with 111In.

A new monoclonal antibody specific for the beta-chain of human fibrin (C22A) and labeled with 111In has been obtained and successfully used in rabbits and dogs for the in vivo detection of venous thrombosis. Studies in humans are currently ongoing. In order to assess the diagnostic value of 111In-antifibrin for the detection of venous thrombosis of the lower extremities, the authors investigated 25 consecutive patients. Ten patients had clinical and instrumental (contrast phlebography and duplex scanning) evidence of acute deep venous thrombosis (DVT), 3 had a long-standing DVT with relapsing episodes of swelling and pain, 5 had superficial venous thrombosis, and the remaining 7 had no signs of thrombosis at all. Twenty patients were being treated with heparin. All patients received 111In-antifibrin at the dose of 74 MBq IV and were scanned with a large field of view gamma camera coupled with a high-energy, parallel-hole collimator at 30 minutes and three, six, and twenty-four hours postinjection. Only the persistence of an abnormal uptake at twenty-four hours confirmed by two observers at visual inspection was considered as positive. A positive result was obtained in 9 of 10 DVT patients (90% sensitivity) and in all SVT patients. The single DVT patient with a negative 111In-antifibrin test had the longest interval between scintigraphy and onset of symptoms (fifty-five days). Thus, the age of thrombi represented a substantial limitation for the test. A false-positive result was obtained in a single SVT patient, in whom also a deep involvement, unconfirmed by phlebography, was suspected (91.6% specificity).(ABSTRACT TRUNCATED AT 250 WORDS)