A soluble fibrin standard: Comparable dose-response with immunologic and functional assays

A soluble fibrin (SF) preparation has been developed as a potential standar d by the Scientific and Standardization Committee for use in assays evaluat ing in vitro preparations and patient plasma samples. The SF standard was p repared by reaction of factor XIII-free fibrinogen with thrombin, followed by neutralization with hirudin and solubilization of the fibrin in acetic a cid. As characterized by SDS-PAGE, the polypeptide chain structure shows th e anticipated lass of fibrinopeptides and lack of gamma or alpha chain cros slinking. The standard was added to pooled normal plasma at concentrations from 12.5 mu g/ml to 340 mu g/ml and tested with four commercially availabl e assays based on immunologic reactions using ELISA or latex agglutination or on t-PA cofactor activity for plasminogen to plasmin conversion. Absolut e "soluble fibrin" concentrations were calculated using the manufacturers' calibrators and showed distinct dose-response relationships for each assay. Expression of the results following log-transformation produced a series o f parallel lines, indicating that this SF preparation can serve as a standa rd, effectively normalizing the disparate proprietary internal calibrators currently used for each assay.