Prevalence of α1-antitrypsin PiZZ genotypes in patients with COPD in Europe: a systematic review

Abstract

The percentage of α₁-antitrypsin protease inhibitor ZZ (PiZZ) genotypes in patients with COPD is controversial, with large differences among various studies. We aimed to estimate the prevalence of PiZZ in COPD patients from 20 European countries with available data, according to the number of PiZZ and COPD individuals in each country.A systematic review was conducted to select European countries with reliable data on the prevalence of PiZZ and COPD. We created a database with the following data: 1) total population and population aged ≥40 years according to the Eurostat database; 2) number and 95% CI of PiZZ patients aged ≥40 years; 3) application of a conversion factor of genetic penetrance of 60%; 4) number of COPD individuals, with 95% CI, aged ≥40 years; and 5) calculation of the PiZZ/COPD ratio. Finally, results were presented using an Inverse Distance Weighted Interpolation map.We found 36 298 (95% CI 23 643-56 594) PiZZ individuals at high risk and 30 849 709 (95% CI 21 411 293-40 344 496) COPD patients, with a PiZZ/COPD ratio of 0.12% (range 0.08-0.24%), and a prevalence of 1 out of 408 in Northern, 1 out of 944 in Western, 1 out of 1051 in Central, 1 out of 711 in Southern, and 1 out of 1274 in Eastern Europe.These data may be useful to plan strategies for future research and diagnosis, and to rationalise the available therapeutic resources.

FIGURE 1

Map of inverse distance weighted interpolation showing the PiZZ/COPD ratio (1/x) in 20 European countries. PiZZ refers to the number of individuals aged ≥40 years, after applying a correction factor of 60% of genetic penetrance. COPD refers to the total number of patients aged ≥40 years from each country. The colour scale corresponds to the prevalence of PiZZ in the total COPD (1/x) of each country. Countries without data are shaded pale green. Unpopulated or sparsely populated regions (with less than two inhabitants per square kilometre) are shaded white. PiZZ: α₁-antitrypsin protease inhibitor ZZ. n=total number points with known values in IDW interpolation (12 for the current map); p=power parameter (p=2 for the current map); res=resolution (0.05 for the present map).