CHI3L1 and asthma: A previous study in pediatric patients with asthma indicated that those with elevated serum YKL-40 levels also exhibited elevated FeNO levels.[34] However, another study suggested a lack of direct relationship between serum YKL-40 and FeNO.[35] The inconsistencies in these outcomes might have stemmed from multifactorial influences on FeNO and the variability in serum YKL-40 levels.