Increased circulating levels of alpha(1)-antitrypsin and calprotectin are associated with reduced gas diffusion in the lungs

The aim was to examine the relationship of serum inflammatory markers to th e level of single-breath diffusing capacity of carbon monoxide (TL,CO), A stratified sample (n = 1,121) of a Norwegian general population aged 18-7 3 yrs was examined, The inflammatory markers measured were calprotectin, a prominent protein in the cytosol fraction of neutrophil granulocytes, and a l-antitrypsin (al-AT), the major inhibitor of neutrophil elastase in the lo wer respiratory system, Both markers have increased circulating levels in t he course of an acute inflammatory reaction. Subjects with a TL,CO < 80% of predicted value had a higher level of both a l-AT (p = 0.003) and calprotectin (p < 0.03) than those with a TL,co > 100% . In multiple linear regression analyses, al-AT was still significantly ass ociated with TL,CO after adjusting for sex, age, smoking habits, haemoglobi n, carboxyhaemoglobin, forced expiratory, volume in one second and alveolar volume. In a similar analysis, no significant overall association was foun d between calprotectin and TL,CO, hut in a stratified analysis, calprotecti n was significantly related to TL,CO in females. However, no significant se x interaction in the relationship between the inflammatory markers and TL,C O was found. The findings suggest that increased levels of al-antitrypsin and of calprot ectin are risk factors for decreased diffusing capacity of carbon monoxide.