Plasminogen activator activity and plasma-coagulum lysis measured by use of optimized fibrin gel structure preformed in microtiter plates.

We introduce a new fibrin plate assay performed in microtiter plates. By means of spectroscopic studies we optimized the structure of the fibrin gel and then used the optimized fibrin gel to determine plasminogen activator activity. Plasminogen activator solutions were applied on top of the fibrin gel, and the absorbance of the gel was recorded at 405 nm. After incubation for 17 h at 25 degrees C, the absorbance was measured again. The difference in absorbance was proportional to the concentration of plasminogen activator, such that the dose-response curves were linear when the difference in absorbance was plotted as a function of the logarithmic concentration of plasminogen activator. We assayed both tissue-type and urokinase-type plasminogen activator activity. The intraassay CV was < 4.7% (n = 20); the interassay CV was < 3.1% (n = 15). Using the optimized procedure, we modified the assay for determination of plasma-coagulum lysis time in human plasma. We established a reference interval for lysis time in apparently healthy subjects of 75 to 201 ks. Patients with deep vein thrombosis showed significantly (P = 0.013) higher values.