Fig. 3

Quantification of neutrophils and NETs. a, b Evaluation in categories, bars represent percentages of total individuals sampled per study group (a) and per COPD severity stage (b). c, d Percentages of NET coverage in sputum preparations. c Bar chart showing means ± standard errors. d Boxplots with medians and interquartile ranges, whiskers have maximum 1.5 interquartile range. Supercript asterisks indicate significant differences between groups (P < 0.05). e Scatter plot illustrating the relation between FEV1 and the percentage of NET coverage, study groups represented by different symbols (Spearman’s rank correlation coefficient ρ = −0.562, P < 0.001)