Serum YKL-40 and assessment of severity of bronchial asthma in Egyptian children

Background: Serum and lung tissue levels of a chitinase-like protein YKL-40 have recently been found to be increased in patients with bronchial asthma. Furthermore, serum YKL-40 levels correlated positively with thickening of the lung sub-epithelial basement membrane, frequency of rescue inhaler use, and deterioration in pulmonary function in European asthmatic subjects. Objectives: to assess the role of YKL-40 measurement in evaluating asthma severity, compared to clinical assessment and the related pulmonary function tests. Methods: We quantified serum YKL-40 levels in two groups of Egyptian asthmatics: One group with mild to moderate asthma, and one with severe asthma. Serum YKL-40 was measured by enzyme-linked immunosorbent assay (ELISA) kits (Quidel). Clinical scoring of asthma severity by Pediatric Asthma Score (PAS) and pulmonary functions were performed. Results: The serum levels of YKL-40 were significantly elevated in severely asthmatic Egyptian children compared with the other group (151ng/ml-72ng/ml; p<.05). YKL-40 levels were correlated positively to PAS (r=0.34, p<0.05), and inversely to FEV1 (r=-0.32, p<0.5). Best cut off value of YKL-40 for asthma prognosis was 90 ng/ml, sensitivity 86.5%, specificity 81%, and diagnostic accuracy of 85%. Conclusions: YKL-40 is found in increased quantities in the sera of severe asthmatics, and correlated significantly to PAS and pulmonary function deterioration. YKL-40 is considered a promising biomarker for asthma severity and pulmonary remodeling warranting further study as a potential novel pathway to disease management.