Comparison of commercially available radial immunodiffusion kits for the determination of serum alpha 1-antitrypsin concentrations

Six commercially available radial immunodiffusion kits for the determination of serum alpha1-antitrypsin concentrations were compared. Test samples were prepared by diluting purified human alpha1-antitrypsin to 2 different concentrations approximating heterozygous and homozygous deficiency concentrations. Significant variation in results was noted using the higher concentration of alpha1-antitrypsin. A greater degree of accuracy was demonstrated when testing the sample with the lower concentration. This further emphasizes the need for specific phenotyping in detecting patients with protease inhibitor types other than ZZ.