What was the measurement principle behind the discontinued Coamatic® Plasminogen?

The plasminogen present in the sample is activated by the addition of an excess of streptokinase (Sk) forming a plasminogen-streptokinase (Plg/Sk) complex. Plg-depleted fibrinogen is included in the Sk reagent in order to avoid the risk of overestimation of Plg in the pathological plasmas containing elevated levels of fibrinogen (Fib) and/or fibrin degradation products (FDP). The PlgSk/Fib complex is determined by the rate of hydrolysis of the chromogenic substrate S-2403™. The pNA release measured at 405 nm is proportional to the plasminogen activity level of the plasma sample.