Serum Levels of Alpha1-antitrypsin and Their Relationship With COPD in the General Spanish Population

Background: Low plasma level of alpha1-antitrypsin (AAT) is an established risk factor for early-onset chronic obstructive lung disease (COPD). However, less attention is given to the levels of AAT in the general population.

Methods: This is a part of a multicentre, population-based study conducted at 11 sites throughout Spain. Plasma levels of AAT were available for 837 persons with a mean (SD) age of 58.05 (11.3) years: 328-smokers, 272-ex-smokers and 237 non-smokers. Out of 837, 303 (36.2%) had a diagnosis of COPD, 222 (26.5%) had respiratory symptoms but no COPD, and 312 (37.3%) were healthy controls.

Results: In the whole cohort, the mean level of plasma AAT was 1.51 (0.47)g/L. Levels were higher in COPD patients [1.55 (0.45)g/L] and individuals with respiratory symptoms [1.57 (0.47)g/L] than in controls [1.43 (0.47)g/L], p<0.001, a finding which persisted after correction for age and CRP. Plasma AAT levels were negatively associated with FEV1/FVC ratio, after adjustment for age, sex, smoking status, CRP, TNFα, fibrinogen and albumin. The risk for COPD was significantly associated with higher AAT levels in univariate and multivariate models, with odds ratios of 1.8 and 1.5, respectively. In the univariate and multivariate models smoking status, gender, and CRP levels were also associated with COPD probability, demonstrating that they act independently.

Conclusion: Increased circulating levels of AAT, similarly to CRP and other markers of systemic inflammation, is an important feature of COPD. Our results highlight a complex interrelationship between levels of AAT and health of respiratory system.