Summary
A soluble fibrin (SF) preparation has been developed as a potential standard by the
Scientific and Standardization Committee for use in assays evaluating in vitro preparations and patient plasma samples. The SF standard was prepared by reaction
of factor XIII-free fibrinogen with thrombin, followed by neutralization with hirudin
and solubilization of the fibrin in acetic acid. As characterized by SDS-PAGE, the
polypeptide chain structure shows the anticipated loss of fibrinopep-tides and lack
of sγ or α chain crosslinking. The standard was added to pooled normal plasma at concentrations
from 12.5 μg/ml to 340 μg/ml and tested with four commercially available assays based
on immunologic reactions using ELISA or latex agglutination or on t-PA cofactor activity
for plasminogen to plasmin conversion. Absolute “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 of parallel lines, indicating that this SF preparation can serve
as a standard, effectively normalizing the disparate proprietary internal calibrators
currently used for each assay.
