title: YKL-40 and genetic status of CHI3L1 in a large group of asthmatics.
abstract: BACKGROUND
  Studies have shown a relationship between asthma, serum YKL-40, and the single nucleotide polymorphism (SNP) (-131 C/G, rs4950928) in the CHI3L1 gene that codes for YKL-40. However, the findings differ. We studied the relationship between clinical asthma phenotypes, serum YKL-40, and SNP (-131 C/G, rs4950928).
  
  
  METHODS
  In this study, 1,137 patients with asthma, 415 with rhinitis only, and 275 non-asthmatic controls were included. Assessment included a clinical interview concerning the diagnosis of asthma, severity of asthma, and asthma treatment as well as clinical tests to assess asthma and rhinitis. Serum YKL-40 was measured, and genotyping for the SNP (-131 C/G) was conducted.
  
  
  RESULTS
  No significant difference in the serum concentration of YKL-40 was found between patients with asthma, patients with rhinitis, and non-asthmatic controls; however, YKL-40 was increased in patients with severe asthma. No association was found between the SNP (-131 C/G rs4950982) and the risk of having asthma (odds ratio = 0.90, p=0.4). Higher levels of serum YKL-40 were found in all subjects when comparing CC genotype to CG and GG genotypes (45 µg/L vs. 32 µg/L and 19 µg/L, p<0.0001).
  
  
  CONCLUSIONS
  There was no association between polymorphisms of SNP (-131 C/G) and asthma. The highest serum YKL-40 concentrations were seen in severe asthmatics. Individuals with less severe asthma showed a smaller difference against controls, limiting its clinical usefulness. More research is needed to clarify the relationship between different asthma phenotypes, YKL-40, and CHI3L1.
authors.affiliation: Department of Respiratory Medicine, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark; jakobwerner@gmail.com.
authors.forename: Jakob W
authors.initials: JW
authors.lastname: Hansen
authors.affiliation: Department of Respiratory Medicine, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Simon F
authors.initials: SF
authors.lastname: Thomsen
authors.affiliation: Department of Respiratory Medicine, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Celeste
authors.initials: C
authors.lastname: Porsbjerg
authors.affiliation: Department of Respiratory Medicine, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Linda M
authors.initials: LM
authors.lastname: Rasmussen
authors.affiliation: Department of Respiratory Medicine, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Lotte
authors.initials: L
authors.lastname: Harmsen
authors.affiliation: Department of Medicine, Herlev Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Julia S
authors.initials: JS
authors.lastname: Johansen
authors.affiliation: Department of Respiratory Medicine, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Vibeke
authors.initials: V
authors.lastname: Backer
keywords: CHI3L1; YKL-40; asthma; biomarker; rhinitis