Sensitivity of 125J-fibrinogen uptake test for diagnosis of established venous thrombosis in heparinized patients.

The sensitivity of the radiofibrinogen test was investigated to determine the accuracy of the test in diagnosis of venographically proven venous thrombosis in 70 heparinized patients. 125J-fibrinogen was administered between 2 h and 4 days (mean: 1.5 days) after initiating heparin therapy. There were two criteria for a positive test: if the difference between the counts for adjacent points on the same leg or equivalent sites on opposite legs was at least 15%; and/or if there were three adjacent points each with counts greater than 5% that of the same three points on the other leg. The fibrinogen uptake test was positive at the first examination in 67 of 70 patients, giving a sensitivity of 96%. The respective frequencies of truly abnormal results for the 3 X 5% and the 1 X 15% criteria were 94% and 71%. As far as localization and extension of thrombosis were concerned, the fibrinogen uptake test agreed with phlebography in 73% of the cases, when the counts in the groin and the upper third of the thigh were ignored. The 125J-fibrinogen uptake test is an accurate method for detecting established deep leg vein thrombosis even in anticoagulated patients.