The association between blood eosinophil percent and bacterial infection in acute exacerbation of chronic obstructive pulmonary disease

Choi, Juwhan; Oh, Jee Youn; Lee, Young Seok; Hur, Gyu Young; Lee, Sung Yong; Shim, Jae Jeong; Kang, Kyung Ho; Min, Kyung Hoon

Chronic obstructive pulmonary disease (COPD) is an airway and lung disease that impairs the immune lung defense system making it susceptible to bacterial infections. 1,2 COPD patients may experience acute exacerbations due to these bacterial infections. 3 The global initiatives for chronic obstructive lung disease (GOLD) guideline recommend the use of antibiotics when a bacterial infection is suspected in events of acute exacerbations of chronic obstructive pulmonary disease (AECOPD). 4 The GOLD guideline also suggests that symptoms such as increase in dyspnea, sputum volume, and sputum purulence are the criteria for antibiotic usage. 5 Since these symptoms are not presented as absolute numerical values, the use of antibiotics is based on clinical experience and judgment. Hence, antibiotics are often overused and stray from the GOLD guidelines, as reported by a study conducted in Europe. 6 To solve this problem, various biomarkers that distinguish bacterial infections have been studied, which include C-reactive protein (CRP) and procalcitonin. However, CRP commonly elevates in viral infections and hence cannot specifically distinguish bacterial infections. 7, 8 Procalcitonin is useful for distinguishing bacterial infections but is expensive and less accessible. 9 Therefore, we need a biomarker that can specifically distinguish bacterial infections, while being cost-effective and user-friendly.