Factor XIII immunoassay

A method of detecting factor XIII activity in a biological sample, comprising the steps of:

• a) immobilizing or having obtained a capture antibody on a solid support, wherein the capture antibody comprises an antibody or antibody fragment that specifically binds to fibrinogen;
• b) incubating the biological sample with the capture antibody;
• c) washing the immobilized capture antibody to remove unbound protein;
• d) contacting the immobilized capture antibody with a-thrombin, calcium, and a2-antiplasmin (AP);
• e) washing the immobilized capture antibody to remove unreacted a2-AP;
• f) contacting the immobilized capture antibody with a detection antibody or antibody fragment that specifically binds to a2-AP, wherein the detection antibody or antibody fragment includes a detection label;
• g) washing the immobilized capture antibody to remove unbound protein;
• and
• h) determining that factor XIII activity is present if the detection label is detected, wherein the biological sample is whole blood or plasma.