In accordance with our study, Wang et al. showed higher YKL-40 levels in patients with severe CAP.[28] We described YKL-40 to be a good predictor for length of hospital stay and CAP mortality.[13] The correlation of high pulmonary marker levels with severity of pneumonia could be explained by the extent of inflammation and subsequent repair of pulmonary damage, which might explain the higher degree of pulmonary marker release to the blood in case of severe pneumonia. This evidence concerns the gene CHI3L1 and susceptibility to pneumonia measurement.