Immunoelectrophoretic quantitation of antithrombin III. Electroimmunodiffusion in agarose gels containing heparin.

Antithrombin III (AT-III), being an alpha2-globulin, will have an electrophoretic mobility in the presence of heparin like prealbumin in agarose gels. This phenomenon was utilized to quantitate AT-III from serum and plasma by electroimmunodiffusion (EID) for 90 min agarose gels containing 75 USP units of heparin/ml gel. The method permits a rapid quantitation of AT-III from serum, citrated plasma and EDTA plasma, and a positive correlation was observed between these values and those obtained by single radial immunodiffusion (SRI). This is in contrast to quantitation of AT-III by EID in gels containing no heparin where the values for plasma showed poor correlation with those obtained by SRI.