Sputum YKL-40 levels correlated moderately with sputum neutrophil counts (rs = 0.484, P < .0001; Fig 4, G) and were increased more in patients with neutrophilic versus eosinophilic disease (see Fig E6, A, in this article's Online Repository at www.jacionline.org). Here, CHI3L1 is linked to eosinophil disorder.