CST3 and chronic obstructive pulmonary disease: Univariate logistic regression analysis revealed that older age, DLCO% predicted < 80%, FVC/DLCO ≥ 0.44 l/mmol/min/kPa, coexistence with coronary heart disease, PaO2 < 60 mmHg, PaCO2 ≥ 50 mmHg, and elevated levels of neutrophil count, BUN and cystatin C all significantly increased the odds of combining PH in COPD patients.