Granulocyte markers in hypertonic and isotonic saline-induced sputum of asthmatic subjects

The aim of this study was to assess whether hyperosmolarity affects granulocyte mediator levels in induced sputum of asthmatic subjects. A total of 32 mild-to-moderate asthmatics, who inhaled either hypertonic (HS; 4.5% NaCl) or isotonic (IS; 0.9% NaCl) solutions for 15 min, were studied. Selected sputum was used for analysis. Eosinophil cationic protein (ECP), eosinophil protein X (EPX), myeloperoxidase (MPO) and free neutrophil elastase (NE) were measured in sputum supernatant. Sample weight, total and differential cell counts, as well as viability and squamous cell percentage were no different after the two tests. No significant differences in ECP, EPX, MPO or NE levels were observed between HS- and IS-induced sputum. Repeatability of the two tests was good for macrophages, neutrophils, eosinophils, ECP, EPX and NE, but not for lymphocytes and MPO. In conclusion, hyperosmolarity does not affect sputum cell counts and the levels of most granulocyte degranulation markers examined in this study, confirming that both hypertonic and isotonic solutions can be reliably used to induce sputum in asthmatics.