Factor XIII Deficiency and Measurement.

Factor XIII (FXIII) is a thrombin-activated coagulation factor that stabilizes the fibrin clot via covalent cross-linking of fibrin. Inherited and acquired FXIII deficiencies are important causes of bleeding, with acquired deficiencies being about 10 fold more prevalent. Acquired FXIII deficiency can arise in the setting of consumptive coagulopathies; massive blood loss; severe infections; hepatic dysfunction; acquired inhibitors of FXIII; and deficiencies of uncertain significance. FXIII deficiency is not detected by routine coagulation assays and requires evaluation by quantitative FXIII activity and antigen assays. Bethesda assay modifications of FXIII activity assays are helpful to diagnose acquired FXIII inhibitors.