Exhaled nitric oxide levels in alpha-1-antitrypsin PiMZ subjects

Although the likelihood of intermediate alpha-1-antitrypsin deficiency (PiMZ) patients developing chronic obstructive pulmonary disease (COPD) remains uncertain, several investigators have suggested that a lack of antiprotease inhibitor activity may favour the development of airway inflammation with subsequent pulmonary tissue damage. The levels of exhaled nitric oxide (FeNO) in PiMZ subjects are unknown and polymorphisms in nitric oxide synthase have been linked to lung disease susceptibility in subjects with alpha-1-antitrypsin (AAT) deficiency. This study was aimed at assessing FeNO levels in a group of PiMZ subjects and comparing it with the concentrations found amongst groups of COPD and control patients.

A group of 31 PiMZ subjects, 31 COPD patients and 30 controls underwent pulmonary function tests, AAT assay and phenotyping, and FeNO measurement in an ambulatory setting.

FeNO values observed in the group of PiMZ subjects (21.6 +/- 8.9 ppb) showed a significant increase compared with COPD (14.5 +/- 8.7 ppb; P < 0.01) and the control groups (9.1 +/- 2.9 ppb; P < 0.01). Within the PiMZ population, a significant, negative correlation was observed between plasma AAT levels and FeNO readings.

Not only did PiMZ subjects show increased FeNO levels compared with COPD patients and controls; FeNO levels proved to be related to the reduced concentration of plasma AAT. Such findings seem to suggest the importance of FeNO measurements on PiMZ subjects for monitoring a possible progression of airway inflammation to obstructive lung disease as observed in some of these patients.