Clinical or biological features that defined COPD, such as previous diagnosed chronic bronchitis, symptoms of cough and sputum production, effort-induced dyspnea, and increased CRP, had a negative probability for risk factors of asthma (OR = −17.0, P < 0.001; OR = −27.2, P < 0.001; OR = −16.4, P < 0.001; OR = −11.5, P < 0.001, resp.; Table 4 and Figures 2(a) and 2(b)). Here, CRP is linked to asthma.