Abstract: Objective To explore the combined diagnostic value of red blood cell distribution width(RDW) and serum cystatin C(Cys-C) for pulmonary hypertension secondary to chronic obstructive pulmonary disease (COPD), and to provide new diagnostic indexes and methods for the early diagnosis of COPD secondary pulmonary hypertension.
Methods A total of 122 patients with COPD were selected to measure the pulmonary arterial pressure by Doppler echocardiography (the systolic pressure of pulmonary artery>40 mmHg was pulmonary arterial pressure). The patients were divided into two groups: the normal group and the increased group. Taking 3-5 mL of venous blood from patients, ethylene diamine tetraacetic acid anticoagulation, RDW and Cys-C values were detected respectively, receiver operator characteristic curve (ROC curve) of RDW and Cys-C in diagnosing COPD secondary pulmonary hypertension was drawn, diagnostic value was calculated, and then the probability of RDW and Cys-C in diagnosing COPD secondary pulmonary hypertension was predicted by logistic regression. Finally, the ROC curve of RDW and Cys-C in COPD secondary pulmonary hypertension was drawn, and its diagnostic value was calculated.
Results The AUC of RDW and Cys-C was 0.844 and 0.849 respectively. The sensitivity was 75.9% and 84.1% respectively, the specificity was 85.9% and 75.6% respectively, the AUC of RDW and Cys-C was 0.926, the sensitivity and specificity were 90.9% and 87.2%, respectively.
Conclusion RDW and Cys-C have certain value in the diagnosis of COPD secondary pulmonary hypertension. The combination of RDW and Cys-C can improve the sensitivity and specificity of COPD secondary pulmonary hypertension diagnosis, and reduce the misdiagnosis rate and missed diagnosis rate.

Key words: pulmonary disease, hypertension, red blood cell distribution width, serum cystatin C