title: A longitudinal assessment of circulating YKL-40 levels in preschool children with wheeze.
abstract: The chitinase-like protein YKL-40 (CHI3L1) is elevated in the circulation of adults and schoolchildren with chronic severe asthma. It is unknown whether YKL-40 is altered in younger, preschool children with wheeze, acute or chronic. We therefore examined YKL-40 in preschool children during an acute episode of wheeze and during remission, in comparison with healthy controls.
  
  
  
  Blood was obtained from 128 children (aged 6-44 months) at the emergency department during an acute episode of wheeze, and at two follow-up visits (approximately 3 months and 1 year later), as well as from 100 age-matched healthy controls on one occasion. Plasma YKL-40 levels were examined in relation to CHI3L1 rs4950928 genotype and clinical characteristics including Asthma Predictive Index, medication use, time spent with respiratory symptoms, atopic status, and blood leukocytes.
  
  
  
  Children with wheeze had higher median YKL-40 levels at the acute visit (14.7 (11.5-22.6) ng/ml, p < 0.001) and 3-month follow-up (15.9 (11.5-20.2), p < 0.001) compared to the 1-year follow-up (11.9 (9.5-17.3)). YKL-40 levels in healthy controls (13.6 (11.0-17.0)) tended to be lower than those during acute wheeze (p = 0.07) and 3-month follow-up (p = 0.04), but were no different at the 1-year follow-up. CHI3L1 rs4950928 affected YKL-40 in all subjects, with highest levels present in those with the CC genotype (p < 0.001). Genotype frequency was similar in the two subject groups. YKL-40 levels showed a positive correlation with blood neutrophil counts but no consistent relationships with clinical characteristics of relevance to continuous wheeze.
  
  
  
  YKL-40 levels were elevated during acute wheeze in preschool children, a finding which may be related to current neutrophilic inflammation, but YKL-40 was not associated with characteristics of persistent wheeze in this young cohort.
authors.affiliation: Experimental Asthma and Allergy Research, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: James
authors.affiliation: Astrid Lindgren Children's Hospital, Karolinska University Hospital, Stockholm, Sweden.|Department of Women's and Children's Health, Immunology and Allergy Unit, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Katarina
authors.initials: K
authors.lastname: Stenberg Hammar
authors.affiliation: Department of Biosciences and Nutrition, Immunology and Allergy Unit, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Lovisa
authors.initials: L
authors.lastname: Reinius
authors.affiliation: Astrid Lindgren Children's Hospital, Karolinska University Hospital, Stockholm, Sweden.|Department of Women's and Children's Health, Immunology and Allergy Unit, Karolinska Institutet, Stockholm, Sweden.|Department of Medicine, Immunology and Allergy Unit, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Jon R
authors.initials: JR
authors.lastname: Konradsen
authors.affiliation: Experimental Asthma and Allergy Research, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Sven-Erik
authors.initials: SE
authors.lastname: Dahlén
authors.affiliation: Department of Women's and Children's Health, Immunology and Allergy Unit, Karolinska Institutet, Stockholm, Sweden.|Department of Biosciences and Nutrition, Immunology and Allergy Unit, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Cilla
authors.initials: C
authors.lastname: Söderhäll
authors.affiliation: Astrid Lindgren Children's Hospital, Karolinska University Hospital, Stockholm, Sweden.|Department of Women's and Children's Health, Immunology and Allergy Unit, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Gunilla
authors.initials: G
authors.lastname: Hedlin
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D000071451:Chitinase-3-Like Protein 1 / Q000097:blood* / Q000235:genetics; D018450:Disease Progression; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D008137:Longitudinal Studies; D008297:Male; D009504:Neutrophils / Q000276:immunology*; D020641:Polymorphism, Single Nucleotide; D011153:Population; D012135:Respiratory Sounds / Q000276:immunology*
chemical_list: C084533:CHI3L1 protein, human; D000071451:Chitinase-3-Like Protein 1
keywords: YKL-40; asthma; chitinase; infants; wheeze