A modified 125I-fibrinogen technique in suspected deep vein thrombosis. A comparison with plethysmography and phlebography.

The diagnostic efficiencies of a modified 125I-fibrinogen uptake test (FUT), venous strain gauge plethysmography, and the routine report on phlebography were compared in 301 consecutive patients with suspected deep vein thrombosis (DVT) in the leg. A keen, independent review of the phlebography films was used as the reference method. The FUT detected 62% of all thrombi after one hour, 71% after one day, and 98% after two days. False positive results were, however, found after two days in 52% of all patients without DVT. Plethysmography revealed 63% of the thrombi and was falsely positive in 23% of patients without DVT. The routine examination of phlebography films revealed only 86% of the thrombi seen at the final independent review. The routine report was falsely positive in 6% of patients without thrombi. Consequently, the modified FUT is a useful screening test; at one hour it was equally sensitive to DVT as plethysmography and after two days it excluded DVT with a significantly better sensitivity than the routine report on phlebography. Drawbacks of FUT are the delay of the diagnosis in some patients and the low specificity. In patients with a pathological FUT, further investigation is often required. Plethysmography is not recommended as a screening test, since it lacks both sensitivity and specificity.