Optimizing the screening of alpha-1 antitrypsin deficiency using serum protein electrophoresis

Abstract

Abstract Objectives Alpha-1 antitrypsin (A1AT) deficiency was first identified in patients with emphysema by the absence of the α1 band on serum protein electrophoresis (SPE). Today, capillary zone electrophoresis is widely performed in laboratories. Here, we compared two SPE systems to detect decreased A1AT concentrations to optimize their use as a screening tool for A1AT deficiency. Methods Serum protein electrophoresis was performed on 200 samples on the Capillarys 2 and the V8 Nexus. The latter presents two α1 bands (α1 band 1 and 2) while the Capillarys 2 has only one (Capillarys 2 total α1). The measures of A1AT and α1 acid glycoprotein (AAG) were performed as well as the phenotyping of M, S and Z alleles. Results At a A1AT cutoff of 0.80 g/L, a cutoff of 1.21 g/L using the V8 Nexus α1 band 2 corresponded to a 100% sensitivity and a 92.4% specificity while a 1.69% cutoff corresponded to a 100% sensitivity and a 92.4% specificity. The performance of the α1 band 1 was suboptimal and rather corresponded to AAG. On the Capillarys 2, a cutoff of 2.0 g/L corresponded to a 75.0% sensitivity and a 86.6% specificity, while a 3.2% cutoff showed a 96.4% sensitivity and a 67.4% specificity. The V8 Nexus α1 band 2 was the method the most correlated with A1AT (r=0.90–0.94). Conclusions The V8 Nexus α1 band 2 was the best predictor of A1AT deficiency, probably owing to a better resolution. The use of SPE was however unable to predict each phenotype. Phenotype or genotype studies are therefore still advisable in case of A1AT deficiency.