Background: Population studies indicate that alpha-1-antitrypsin (AAT) deficiency is an under diagnosed disease. Although alpha-1 serum protein is widely known to accompany AAT deficiency, the diagnostic utility of measuring the alpha-1 band to screen for this condition has not been assessed in the literature.
Subjects and method: Electropherograms with alpha-1 band widths under the reference values were collected over a period of 3 months. The Pi phenotype of AAT was identified for these sera by isoelectric point determination. The phenotypes were compared to those obtained for the population of the same geographic area (n = 440). The alpha-1 band reference values were obtained from 73 healthy individuals with no Pi phenotype deficiency. Moreover, the alpha-1 band was also measured for a group of 17 PiZZ deficient patients.
Results: We analyzed 7,305 electropherograms. One hundred four individuals (1.4%) without hypoproteinemia had alpha-1 readings below reference (set at 2.3%). The phenotypes in this group were 25 PiMM (24%), 52 PiMS (54%), 13 PiMZ (12.5%) and 5 PiSS 5 (5%). The odds ratios (CI 95%) in comparison with the normal population were, respectively, 0.10 (0.16-0.06); 4.58 (2.97-7.04); 4.35 (2.09-9.04) and 5.51 (1.66-18.16) (p < 10-5 in all cases except PiSS, which was p < 0.05). The levels for PiZZ patients were 1.4% +/- 0.3% (range 1.0%-2.1%).
Conclusions: Three times fewer subjects with a normal PiMM phenotypes are found among individuals with low alpha-1 band serum protein levels, and many more of such individuals are carriers of Z allele heterozygotes. Alpha-1 band readings in patients with AAT deficiency (PiZZ phenotype) have alpha-1 values below reference. Measuring alpha-1 protein is an easy technique, within the expertise of any laboratory, and may be very useful for screening for AAT deficiency in patients with chronic respiratory diseases.