Sputum processing for evaluation of inflammatory mediators

Neutrophil‐dominated inflammation is prominent in the cystic fibrosis (CF) and chronic bronchitis (CB) airways. We assessed the degree of airway inflammation by measuring the sputum concentrations of interleukin (IL)‐8, myeloperoxidase (MPO), and deoxyribonucleic acid (DNA). We determined the relationship among the concentrations of these mediators and investigated methodological problems that may be responsible for reported variability in measurements. Sputa obtained from 31 patients were solubilized with phosphate‐buffered saline, dithiothreitol (DTT) (0.1% or 1%), or dornase alfa (0.2 mg/mL). The sputum concentration of IL‐8 and MPO was measured by enzyme‐linked immunosorbent assay (ELISA), and DNA was measured using microfluorimetry. There was a significant relationship among sputum IL‐8, MPO, and DNA. For MPO (means ± SD), CF was 1,392 ± 771 vs. CB at 75 ± 65 mcg/mL; P