The inflammatory biomarker YKL-40 is elevated in the serum, but not the sputum, of E-cigarette users

Exp Lung Res. 2021 Feb-Mar;47(2):55-66. doi: 10.1080/01902148.2020.1847216. Epub 2020 Nov 17.


Methods: We conducted a cross-sectional study of adults between 18 and 55 years old. Inclusion criteria were: exclusive e-cigarette use or cigarette smoking for ≥ 1 year or no history of tobacco use. Participants with a history of pulmonary illness, atopy, medications (except birth control pills), marijuana, and illegal substance use were excluded. Custom Multiplex ELISA was used to measure YKL-40 and other biomarker levels in the serum and induced sputum of the participants. Multivariable linear regression was used to compare the levels of YLK-40 in healthy participants, e-cigarette, and cigarette users after adjusting for age, sex, and BMI.

Results: We recruited 20 healthy controls, 23 cigarette smokers, and 22 exclusive e-cigarette users. Serum YKL-40 (ng/ml) was significantly higher in e-cigarette users (Median 21.2 [IQR 12.1-24.0] ng/ml) when compared to controls (12.2 [IQR 8.7-18.1] ng/ml, p = 0.016) but comparable to cigarette smokers (21.6 [IQR 11.62-51.7] ng/ml, p = 0.31). No significant differences were found in the serum or sputum of the other biomarkers tested.

Conclusion: The inflammatory biomarker, YKL-40 is elevated in the serum but not the sputum of e-cigarette users with no reported pulmonary disease. Further research is necessary to characterize this association.

Keywords: E-cigarette; YKl-40; serum; sputum.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adolescent
  • Adult
  • Biomarkers
  • Chitinase-3-Like Protein 1 / blood*
  • Cross-Sectional Studies
  • Electronic Nicotine Delivery Systems*
  • Humans
  • Middle Aged
  • Smokers
  • Sputum / chemistry
  • Young Adult


  • Biomarkers
  • Chitinase-3-Like Protein 1