SERPINA1 and alpha 1-antitrypsin deficiency: Similarly, effective concentrations of AAT were reported by two short-term studies43,44 and one 3-year study.51 A study investigating 18-fluorodeoxyglucose (18FDG) positron emission tomography–CT as a novel noninvasive biomarker49 had a subgroup of 10 patients with severe AATD.