• Jon R Konradsen, Anna James, Björn Nordlund, Lovisa E Reinius, Cilla Söderhäll, Erik Melén, Asa M Wheelock, Asa Wheelock, Karin C Lödrup Carlsen, Marika Lidegran, Marri Verhoek, Rolf G Boot, Barbro Dahlén, Sven Erik Dahlén, and Gunilla Hedlin.
• Astrid Lindgren Children's Hospital, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden. jon.konradsen@karolinska.se
• J. Allergy Clin. Immunol. 2013 Aug 1;132(2):328-35.e5.

BackgroundProblematic severe childhood asthma includes a subgroup of patients who are resistant to therapy. The specific mechanisms involved are unknown, and novel biomarkers are required to facilitate treatment and diagnosis of therapy-resistant asthma. The chitinase-like protein YKL-40 has been related to asthma and airway remodeling.ObjectivesTo compare serum YKL-40 levels in children with severe, therapy-resistant asthma (n = 34), children with controlled persistent asthma (n = 39), and healthy controls (n = 27), and to investigate correlations with biomarkers of inflammation and airway remodeling.MethodsThe study protocol included questionnaires, measurement of exhaled nitric oxide in exhaled air, blood sampling for inflammatory biomarkers, and high-resolution computed tomography of the lungs to identify bronchial wall thickening (therapy-resistant only). Serum YKL-40 levels were measured by ELISA, and all asthmatic children were genotyped for a CHI3L1 promoter single nucleotide polymorphism (rs4950928).ResultsSerum YKL-40 levels were significantly higher in children with therapy-resistant asthma than in healthy children (19.2 ng/mL vs 13.8 ng/mL, P = .03). Among children with severe, therapy-resistant asthma, YKL-40 levels correlated with fraction of exhaled nitric oxide in exhaled air (r = 0.48, P = .004), blood neutrophils (r = 0.63, P < .001), and bronchial wall thickening on high-resolution computed tomography (r = 0.45, P = .01). Following adjustment for CHI3L1 genotype, significantly greater levels of YKL-40 were found in children with therapy-resistant asthma than in children with controlled asthma.ConclusionsYKL-40 levels are increased in children with severe, therapy-resistant asthma compared to healthy children, and also compared to children with controlled asthma following correction for genotype.Copyright © 2013 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.

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