FXIII antigen assays are used to determine the FXIII deficiency subtype: FXIII-A or FXIII-B deficiency.
Factor (F) XIII antigen assays are recommended by the Factor XIII and Fibrinogen SSC Subcommittee of the International Society on Thrombosis and Haemostasis (ISTH) as a second step to determine the subtype of FXIII deficiency (FXIII-A or FXIII-B deficiency) subsequent to having detected a decrease in FXIII activity.1 If plasma FXIII-A2B2 concentration is decreased, detection of FXIII-A and FXIII-B antigens should follow.1-3 FXIII antigen concentrations can be measured using a sandwich enzyme-linked immunosorbent assay (ELISA) or latex immunoassay.2,4,5
Enzyme-linked immunosorbent assay (ELISA)
In quantitative sandwich ELISA systems, an antibody specific for FXIII is pre-coated onto a microplate. FXIII in a sample is sandwiched by the immobilised antibody and a second polyclonal antibody specific for FXIII, which is labelled with an enzyme that induces a colour reaction upon addition of substrate.
To detect plasma FXIII-A2B2, for example, a biotinylated monoclonal capture antibody against FXIII-B that is immobilised in streptavidin-coated wells and a horseradish peroxidase (HRP)-labelled monoclonal detection antibody against FXIII-A are used.6 To detect FXIII-A or FXIII-B subunits, both the biotinylated capture and the HRP-labelled detection antibodies react with only one of the two subunits (FXIII-A or FXIII-B), but are directed against different epitopes of the same antigen molecule.6
Example that demonstrates the principle of an ELISA system detecting FXIII antigen.7
Latex particles coated with antibody specific to human FXIII agglutinate in the presence of FXIII. The degree of agglutination is directly proportional to the concentration of FXIII antigen in the sample and is determined by measurement of transmitted light or light scattering (see product information of respective assays). Commercially available latex immunoassays include HemosIL® Factor XIII Antigen (Werfen, Instrumentation Laboratory, Bedford, MA, USA) specific for FXIIIA and K-Assay Factor XIII (Stago, Asnières sur Seine, France; Kamiya Biomedical Company, Seattle, WA, USA).
1. Kohler HP, Ichinose A, Seitz R, et al. Diagnosis and classification of factor XIII deficiencies. J Thromb Haemost 2011;9:1404-6.
2. Biswas A, Ivaskevicius V, Thomas A, Oldenburg J. Coagulation factor XIII deficiency. Diagnosis, prevalence and management of inherited and acquired forms. Hamostaseologie 2014;34:160-6.
3. Bolton-Maggs PH, Favaloro EJ, Hillarp A, Jennings I, Kohler HP. Difficulties and pitfalls in the laboratory diagnosis of bleeding disorders. Haemophilia 2012;18 Suppl 4:66-72.
4. Schroeder V, Kohler HP. Factor XIII deficiency: an update. Semin Thromb Hemost 2013;39:632-41.
5. Opat S, Butler J, Malan E, Duncan E, Tran HA. Factor XIII assays. Methods Mol Biol 2013;992:171-80.
6. Orosz ZZ, Katona E, Facsko A, Berta A, Muszbek L. A highly sensitive chemiluminescence immunoassay for the measurement of coagulation factor XIII subunits and their complex in tears. J Immunol Methods 2010;353:87-92.
7. Katona E, Haramura G, Karpati L, Fachet J, Muszbek L. A simple, quick one-step ELISA assay for the determination of complex plasma factor XIII (A2B2). Thromb Haemost 2000;83:268-73.