Measurement of factor XIII activity in plasma

Coagulation factor XIII (FXIII) is converted by thrombin and Ca 2 + into an active transglutaminase (FXIIIa) in the fi nal phase of coagulation cascade. Its main function is the mechanical stabilization of fi brin clot and its protection from fi brinolysis by cross-linking of fi brin chains and α 2 -plasmin inhibitor to fi brin. In non-substituted patients FXIII defi ciency is a severe hemorrhagic diathesis, not infrequently with fatal consequences. The main reason for using FXIII assays is the diagnosis of FXIII defi ciency. The aim of this review is to provide a comprehensive critical evaluation of the methods reported for the determination of FXIII activity in the plasma. Such methods are based on two principles: 1) measurement of labeled amines incorporated by FXIIIa into a glutamine residue of a substrate protein, 2) monitoring ammonia released from a peptide bound glutamine residue by FXIIIa using NAD(P)H dependent glutamate dehydrogenase indicator reaction. The incorporation assays are sensitive, but cumbersome and time-consuming, they are diffi cult to standardize and cannot be automated. The ammonia release assays are less sensitive, but quick, well standardized, and can be automated; this type of assay is recommended for the screening of FXIII defi ciency. The traditional clot solubility assay should not be used for this purpose.