CRP and bacterial infectious disease: Serum C-reactive protein (CRP), a kind of acute phase protein, is a sensitive biomarker of systemic inflammation and tissue damage, and is not affected by anti-inflammatory drugs, immunosuppressants, hormones,[8] which can better reflect the bacterial infection of lower respiratory tract.[9] Evidence suggests that CRP is associated with the presence of potential bacterial pathogens in sputum.[10] However, due to the small sample size of current studies, there is insufficient evidence for the clinical value of CRP in guiding the use of AECOPD antibiotics.