PURPOSE: To make it possible to quantitatively detect the quantity of soluble fibrin in blood sample by using specific composition containing fibrinogen in enzyme immunoassay(EIA).

CONSTITUTION: The composition containing fibrinogen, sugar alcohol, preservative, metal halogenide, amino acid and fibrinopeptide A discharge compound inverts whole fibrinogen in plasma having known fibrinogen concentration into fibrin under the condition of retaining the fibrin in the solution. When this composition is used for the EIA, the sugar alcohol is preferably mannitol, the preservative is sodium azide, the metal halogenide is sodium bromide, and the amino acid is glycin. The quantity of the soluble fibrin in the blood sample can be quantitatively detected by the EIA using the compositions.