Introduction:Alpha1 antitrypsin deficiency(AATD) is an underdiagnosed condition despite the initiatives to increase the awareness.Methods: Population-based study with data from the Information System for Development in Research in Primary Care (SIDIAP) database that contains information of 5.8 million people. We collected the number and values of AAT determinations performed in Primary Care in two periods(2007-08;2010-11), and described the characteristics of the tested individuals and the management of the subjects with deficient values(AAT<100 mg/dl).Results: During these 2 periods,12409 determinations were performed(10.8% in children), with no significant differences between years. Mean age was 52.6(16.3) years in adults and 4.6(SD=4.1) in children. Up to 28.9% of adults and 29.4% of children had a previous diagnosis of a disease related to AATD (in adults:COPD 13.7%, liver disease 8.4%, in children:asthma 22.3%, liver disease 0.5%).In total, 663(5.3%) individuals had an intermediate AAT deficiency(50-100 mg/dl), and 24(0.2%) had a severe deficiency(<50 mg/dl, 2 children). Nine(41%) of the adults with severe deficiency had a previous diagnosis of COPD and 4 were diagnosed of COPD in the 6 months after the test. During the 6 month follow-up, 2 patients with severe deficiency had a spirometry performed and were diagnosed of COPD.Only 3 patients(12.5%) were referred to a pneumologist.Conclusion:The number of AAT determinations in Primary Care is low and it has not increased. AAT is requested 10 times more in adults and the reason to perform the test is not always clear. After the determination, not all detected severe AATD patients are referred to a specialist.Funded by an unrestricted grant by Grifols,FUCAP and SEPAR.