Specific determination of plasmin inhibitor activity in plasma: documentation of specificity of manual and automated procedures.

Recently, a chromogenic kit for determination of plasmin inhibitor activity, Coamatic(R) Plasmin Inhibitor, has been developed with the aim to increase specificity and to allow application to a wide range of automates. The highly sensitive plasmin substrate S-2403 is used and, to further improve specificity, a low level of plasmin and a short incubation time is utilized as well as the incorporation of methylamine to quench alpha(2)-macroglobulin activity. The Coamatic(R) Plasmin Inhibitor kit has been evaluated regarding specificity and compared with six commercially available plasmin inhibitor (also denoted alpha(2)-antiplasmin) kits and with the manual Immediate Plasmin Inhibition Test (IPIT) method, the reference method within the framework of the European Concerted Action against Thrombosis and Disabilities. Analysis of plasmin inhibitor deficient plasma with Coamatic(R) Plasmin Inhibitor resulted in activities below 5% for all instrument applications, whereas all other commercial kits displayed unexpectedly higher values for this plasma (16-35%). There was a good agreement between the Coamatic(R) Plasmin Inhibitor method and the IPIT method for all tested instrument applications; slope=0.80-1.02 and r=0.92-0.97. No interference was detected from alpha(2)-macroglobulin, lysine, unfractionated and low-molecular weight heparin, and epsilon-amino caproic acid or from the non-plasminogen binding form of plasmin inhibitor. (C) 1999 Lippincott Williams & Wilkins.