NPPB and chronic obstructive pulmonary disease: As shown in Table 2, multivariate analysis indicated that RDW, BNP, and PA : A were independent risk factors of PH secondary to COPD, with odds ratios of 1.521 (95% CI, 1.001–2.313; p=0.050), 1.007 (95% CI, 1.004–1.011; p < 0.001), and 5.365 (95% CI, 1.566–18.380; p=0.008), respectively.