CRP and chronic obstructive pulmonary disease: In order to identify patients of competent immunity who may develop refractory community-acquired pneumonia that is resistant to first-choice antimicrobial regimens, we designed this study, wherein clinical characteristics such as onset in warmer seasons, a history of COPD, and a longer TO-A, as well as changes in T lymphocyte subsets, inflammatory indicators, CRP, and metabolic indicators, i.e., LDL-C, Na+, and FCa2+, were regarded as risk factors for r-CAP.