The proposed method of alpha-1-antitrypsin (AAT) deficiency screening is based on the assessment of AAT biological activity and exploits the principle introduced by Guthrie, in agar plate with discs punched from native dried blood spots on filter paper cards used for phenylketonuria screening. The essence of the method is to place blood discs on the agar layer containing trypsin and to pour an agar layer with dissolved fat-free milk over them. As trypsin from the lower layer diffuses upwards and digests the milk casein, the upper layer will clear up together with the milky zone above blood discs with AAT-dificiency, while the milky zone above blood discs where the trypsin-AAT complex is formed, remains cloudy. The diagnostic specifity of this test is 99.816% and diagnostic sensitivity 99.16%. The following incidences in the Moravian population of 183 617 newborns were found: for PiZZ 1:18.362, PiSZ 1:12.241, PiMZ 1:2550, PiMS 1:91.809, and for total AAT deficiency 1.1855. The test costs 0.0138 USD per sample and from the 22 hours of one plate assay only about 3 h require manual work.

        Key words: alpha-1-antitrypsin deficiency,newborn mass screening, agar plate principle, dried blood spot, filter paper cards.