Enzyme linked fibrinolytic assay (ELFA). A new method for the measurement of t-PA in plasma using enzyme labelled fibrin

Abstract

We present an assay for components of the fibrinolytic system based on hydrolysis of solid-phase associated enzyme-labeled fibrin. This Enzyme-linked Fibrinolytic Assay, (ELFA) permits the measurement of less than 1 IU/ml of t-PA in 50 ul of plasma diluted to 1:80 within six hours, in a microtiter plate format, with a colorimetric endpoint. High levels (>10 IU/ml) of tissue plasminogen activator can be measured in less than 30 minutes. The assay was approximately 100 times more sensitive than a clot lysis assay performed in microtiter plates and used less reagents. By comparison with the parabolic rate, coupled assay using chromogenic substrates and soluble fibrin, ELFA performed assays with equal sensitivity and in less time. The ELFA assay uses solid phase fibrin as the substrate, activator and indicator for the assay. For this reason, it has the advantage of the clot lysis assays in that it is more analogous to the physiological hydrolysis of fibrin but with the sensitivity and convenience of the parabolic rate, coupled assay.