Fibrinogen is a heterohexamer of molecular mass 340 kDa, made up of two sets of alpha, beta, gamma polypeptide chains, and synthesized in the parenchymal cell of the hepatocyte and in the megakaryocyte. On cleavage by thrombin in the initial stages of coagulation activation, Fibrinogen self-assembles to yield a fibrin clot matrix that subsequently is crosslinked by factor XIIIa to form an insoluble network. It also binds to the platelet glycoprotein IIb and IIIa receptor so as to form bridges between platelets, thus facilitating aggregation.
You can perform the sandwich ELISA for detection of Fib. B. There are so many kits available but you have to look for their specificity and sensitivity.