Clinical and diagnostic value of YKL-40 and NGAL in patients with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is one of the most common diseases of the bronchopulmonary system. A search of novel inflammatory markers for early diagnosis, optimization and monitoring of therapy is a promising direction of modern studies. Our objective was to evaluate the levels of YKL-40 and NGAL in serum and induced sputum and to determine their significance as inflammation markers in patients with COPD. The study included 50 patients with COPD, 60 patients with asthma. The control group consisted of 30 ageand sex-matched volunteers without allergic and broncho-obstructive diseases. Clinical and anamnestic data, indices of external respiratory function were evaluated. Induced sputum was collected with subsequent assessment of cellular composition. Immunophenotyping of lymphocytes by flow cytometry was performed. The concentration of YKL-40 and NGAL in serum was determined using an enzyme immunoassay test system (R&D Systems). The obtained data were processed using STATISTICA and SPSS Statistics software systems. A significant increase in the absolute number of T lymphocytes in patients of the studied groups compared to the control group was found. The highest number of T cytotoxic lymphocytes and NK-cells was registered in the COPD group. Cell population analysis in the induced sputum from COPD patients revealed the predominance of neutrophilic inflammation pattern. The maximum YKL-40 concentration in blood serum was registered in COPD patients. The levels of NGAL in serum of COPD patients were not significantly different from those in asthma group. NGAL level in induced sputum was significantly higher in COPD group. Correlation analysis confirmed a correlation between YKL-40 and NGAL levels in serum and neutrophilic inflammation indices, smoking index, number of hospitalizations due to COPD exacerbation during a calendar year. YKL-40 and NGAL levels were found to be significantly increased in patients with common COPD exacerbations compared to the group with infrequent exacerbations. YKL-40 and NGAL are promising markers of neutrophilic airway inflammation in COPD patients. The obtained data allow us to consider YKL-40 and NGAL as markers of non-T2-endotype COPD with neutrophilic inflammation pattern and high risk of exacerbations.