A deteriorating effect of severe deficiency (ZZ genotype) on lung function has been known for many years; however, this effect may have been overestimated because mainly patients with COPD have been studied.
This is supported by the fact that, on average, the percentages of the predicted [FEV.sub.1] were 93% and 59% in nonsmokers and smokers with the ZZ genotype in our sample, whereas in a previous Danish study of ZZ individuals ascertained in patients with COPD, the equivalent values at the same age were 25% and <10%, respectively (25).
From the odds ratios for airway obstruction in SZ and ZZ individuals as well as genotype frequencies in this study, it can be calculated (26) that the fraction of airway obstruction attributable to the SZ or ZZ genotype in the general population is ~0.4% and 1.5%, respectively.
Individuals with SS, SZ, and ZZ genotypes were retested to confirm the diagnosis.
In the total general population sample, airway obstruction characterized by pulmonary function studies was more common in subjects with SZ and ZZ genotypes than in subject with the MM genotype, whereas frequency of airway obstruction was unaffected in subjects with the MZ genotype (Table 1).
Furthermore, we showed that both the SZ and ZZ genotypes, when identified in the population at large, are associated with airway obstruction and with reduced pulmonary function, especially in smokers.