[Alpha-1 antitrypsin deficiency: correlation between biochemical tests and phenotypes in one family]

Phenotypes (Pi) for serum alpha-1 antitrypsin (AAT) were determined in a family of 19 members spanning three generations and presenting a deficiency in this protein. The standard Fagerhol crossed immunoelectrophoresis procedure was used for this purpose. The individual phenotypes consisted of seven MM, three ZZ, five MZ, one SZ and three MS. AAT levels were obtained by radial immunodiffusion, trypsininhibitory capacity measurements and from cellulose acetate electrophoresis. Good correlation was found between the phenotype and the three biochemical methods for demonstrating the normal phenotype MM and the severe deficiency state ZZ. Some discrepancies were observed for the heterozygotes. It is concluded that these various assays are inaccurate for the interpretation of intermediate AAT concentrations. Since Pi typing is not suitable for use on a routine basis, it is suggested that this analysis should be performed by a specialized laboratory if intermediate deficiency is suspected.