Role of Osteopontin and NGAL in Differential Diagnosis of Acute Exacerbations of COPD and Pneumonia

Objective: Chronic Obstructive Pulmonary Diesase (COPD) is an inflammatory lung disease that progresses with attacks. Pneumonia is an infectious lung disease that progresses with lung infiltrations. Osteopontin (OP) is a cytokine which participates in inflammation. Neutrophil Gelatinase Associated Lipocalin (NGAL) is an antimicrobial peptide with neutrophil activation and antibacterial properties. In this study, serum OP and NGAL levels were assayed in COPD exacerbation, stabile COPD and pneumonia. The aim of our study is to assess the importance of NGAL and OP levels as biomarkers in the differential diagnosis of COPD and pneumonia. Material and Methods: One hundred twenty consecutive patients who were admitted to our department between May 2011 and August 2013 were included in the study. Serum OP and NGAL levels were measured with ELISA method within 24 hours following the determination of diagnosis. COPD acute exacerbation (AE-COPD) group was comprised of 95 patients (87 male and mean age 69.0±10.6), and the pneumonia group was comprised of 25 patients (16 male and mean age 57.5±22.9). Serum OP and NGAL levels of the patients in the AE-COPD group were re-measured within 30-45 days following acute exacerbation in stabile period. Results: Serum OP levels were higher in the pneumonia group compared to the AE-COPD group (93.47 ng/ml vs 53.10 ng/ml; p<0.001). Multivariate regression analyses indicated that OP levels to be >84 ng/ml is an independent predictor that increases risk for pneumonia more than 8-fold (95% CI, 2.43-26.59). Sensitivity and specificity of OP in the differentiation of pneumonias from AE-COPD were determined to 80% and 92%, respectively. Serum NGAL levels also increased as COPD severity increased and was found to be statistically significant (p: 0.032). Conclusion: It has been indicated that serum osteopontin level can be an independent predictor in differentiating COPD exacerbation from pneumonia. Additionally, as COPD severity (stage) increases, serum NGAL levels also increase, which may be helpful in assessing the severity of COPD.