Neutrophils to Lymphocyte Ratio as a Biomarker in Bronchiectasis Exacerbation: A Retrospective Study

Introduction Bronchiectasis is a disorder resulting mainly from bronchial inflammation caused by recurrent or chronic infections. It is characterized by permanently dilated airways due to bronchial wall destruction. Exacerbations have a key role in bronchiectasis as they are associated with a negative impact on patient prognosis. Exacerbations are generally infectious events caused mostly by bacterial microorganisms. Infective or inflammatory agents cause neutrophil recruitment into the airways, which leads to proteolytic enzymes such as neutrophil elastase and matrix metalloproteinases release, resulting in airway matrix destruction. Neutrophil to lymphocyte ratio (NLR) is used as a biomarker of inflammation. It is calculated by dividing the number of neutrophils by the number of lymphocytes. Our aim is to evaluate Neutrophils to Lymphocyte Ratio in patients with bronchiectasis exacerbation and its correlation to microbiological data. Methods  The study involved patients with a diagnosis of bronchiectasis based on high-resolution computerised tomography (HRCT) of the chest who fulfilled the criteria of bronchiectasis exacerbation. Complete blood counts with differential counts, which included total white blood cells, neutrophils and lymphocytes, were obtained. NLR and C-reactive protein (CRP) levels were measured in patients with bronchiectasis exacerbation and in healthy controls. NLR was calculated as the ratio of the neutrophils to lymphocytes. The mean NLR values in patients with bronchiectasis exacerbation were compared to mean NLR values in healthy controls. The NLR values were compared to CRP levels in patients with bronchiectasis exacerbation. Sputum cultures were performed in all patients. The mean NLR values in patients with positive sputum cultures were compared with mean NLR values in patients with negative sputum cultures, and mean NLR values in patients with isolated Pseudomonas aeruginosa in sputum cultures were compared to mean NLR values in patients with other infectious agents isolated. Results The study population consisted of 80 patients with bronchiectasis exacerbation - 54 males and 26 females - with a mean age of 77.3±8.4 years, and 64 healthy controls - 36 males and 28 females - with a mean age of 62.9±15.3 years. The mean CRP levels in patients with bronchiectasis exacerbation were 75.03±73.87 mg/l. The mean NLR value in patients with bronchiectasis exacerbation was 9.2±7.8 and the mean NLR value of controls was 3.1±2.9 (p<0.001). The NLR values in patients with bronchiectasis exacerbation had no linear correlation with CRP values in these patients (r=0.002, p=0.992). Fifty-two patients had positive sputum cultures and 28 patients had negative sputum cultures. The mean NLR value in patients with positive sputum cultures was 10.5±9.1, and in patients with negative sputum cultures, it was 6.7±3.6 (p<0.012). The mean NLR value in patients with P.aeruginosa was 10.1±9.5, and in patients with other microorganisms isolated, it was 10.8±8.9 (p=0.784). Conclusions Neutrophil to lymphocyte ratio values are statistically greater in patients with bronchiectasis exacerbation compared to healthy controls. There is no linear correlation between NLR and CRP in these patients. NLR values are statistically greater in patients with positive sputum cultures compared to those with negative sputum cultures. Therefore, NLR can be used for predicting positive cultures in patients with bronchiectasis exacerbation.