A critical evaluation of a serum sermucoid assay and its replacement by a serum alpha 1 acid glycoprotein assay.

The composition of serum seromucoid, the protein fraction of serum not precipitated by 0.6 M perchloric acid, has been shown to vary with the technique of preparation. Immunochemical examination revealed that 91.5% of the protein present in the seromucoid fraction of serum was alpha 1 acid glycoprotein, the remainder consisting of alpha 1 antitrypsin, alpha 1 antichymotrypsin, beta 2 glycoprotein, haemopexin, albumin, and pre-albumin. Serum alpha 1 acid glycoprotein concentration determined by radial immunodiffusion correlated well with serum seromucoid concentration although the former was usually 0.4 g/l lower. The determination of serum alpha 1 acid glycoprotein by an immunological method is more precise than the seromucoid method and is not subject to interference from other proteins.