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.