Is the diagnostic rate for the common subtypes of A1AT deficiency consistent across two Canadian Provinces?

Background: The diagnosis of alpha-1-antitrypsin (A1AT) deficiency has been hindered by obscurity concerning the testing process and treatment implications. In this study, we aimed to identify regional differences in the diagnostic rates for A1AT deficiency in the western Canadian provinces of British Columbia (BC) and Alberta (AB).

Methods: The number of A1AT deficiency variant genotype (ZZ, SZ, MZ, SS, and MS) diagnoses were reviewed for BC and AB. The regional diagnostic rates for A1AT deficiency variants in these two provinces, normalized for the predicted population prevalence of each variant genotype, was defined as the annual provincial diagnostic rate (APDR) for a given variant genotype. Sex specific variations in the mean age at diagnosis for the five variant genotypes were compared both within and between provinces.

Results: The SZ and MZ genotype APDRs were significantly increased in the AB population compared to the BC population. The SS and MS APDRs were similar between AB and BC. There was a significantly decreased mean age of diagnosis for AB males, as compared to BC males (for the SZ, MS, and MZ genotypes) and as compared to AB females (for the MS, MZ, and SS genotypes). There were no significant differences in the mean age of diagnosis between the females and males in BC, or between females in AB and BC, for any genotype.

Conclusion: The notably higher APDR for more severe A1AT deficiency genotypes, and lower mean age of diagnosis for most variant genotypes in AB males, deserves further investigation to determine the explanation(s) for these differences.