Colorimetric immunoassay process

A method for the qualitative and quantitative determination of antigenic materials in biological fluids and cells, said method comprising the steps of:

• (a) providing a sample containing a biological fluid or cell material to be tested for given antigenic material;
• (b) adding to said sample a colorimetric and immunoassay reagent, said reagent comprising an adduct of (i) an antibody for said antigenic material and (ii) a chromoprotein selected from the group consisting of ferritin, transferrin, cytochrome c, and ceruloplasmin, which chromoprotein is capable of being chemically coupled to said antibody by covalent bonding, said chromoprotein imparting to said adduct a characteristic absorbance spectrum in the visible light wavelength range;
• (c) reacting said colorimetric immunoassay reagent with said antigenic material to form a reagent-antigen complex;
• (d) separating the reaction mixture of step (c) into a reagent-antigen complex-containing fraction and an unreacted reagent-containing fraction;
• (e) measuring the absorbance of a solution of one of said fractions at the characteristic absorbance wavelength of said adduct;
• and
• (f) comparing the absorbance values measured in step (e) with an external standard sample of known adduct concentration.