Criteria for detection of deep venous thrombosis by 99Tcm-plasmin test.

Criteria for the interpretation of 99Tcm-plasmin test results were systematically investigated in 353 patients with suspected deep venous thrombosis (DVT). Scintillation detector measurements were made at 12 points on each leg after intravenous injection of 99Tcm-porcine plasmin. Phlebography was used as a reference method. The criteria were chosen to obtain the highest possible sensitivity (98 to 100%). On this assumption, the specificity reached 66 to 69%, when using the two most efficient criteria. These criteria involved a comparison between count rates at three adjacent points of the leg suspected of having DVT, and count rates at the three corresponding points of the other leg. Comparison between measurements performed at 5 and 30 min after the injection showed a higher sensitivity of the test at the 30 min measurement. The specificity decreased when the results from both 5 and 30 min measurements were combined. Further increase in specificity could only be achieved at the cost of decreased sensitivity. The suggested criteria seem to be the most efficient for this kind of radionuclide test and improved test-efficiency has to await more thrombus-specific radiopharmaceuticals.