RESULTS: Among a total of 18,783 patients screened, 136 (0.72%) had at least one F allele. Of 14,735 patients screened for the I allele, 24 (0.16%) had at least one I allele. One patient had both alleles (PI*FI). The majority of the total F and I population (n=159) were PI*MF heterozygotes (n=123), followed by PI*MI (n=21) and PI*ZF (n=12), and the overall mean (SD) serum AAT level was normal at 141.2 (34.1) mg/dL. However, 13/159 patients (8.2%; mostly PI*ZF) had AAT <90 mg/dL. Mean serum AAT for PI*ZF was 75.0 (10.4) mg/dL. A further 11 patients (mostly PI*MF) had low-normal AAT between 90-110 mg/dL. Prevalence of F and I alleles in large populations has been reported at 0.40% and 0.21%, respectively.