Red Cell Distribution Width Correlates With Nt-Probnp in Pulmonary Hypertension

Abstract

N-terminal pro-brain-type natriuretic peptide (NT-proBNP) is an established biomarker for pulmonary hypertension (PH), as an indicator of disease severity, and a predictor of mortality and morbidity. Red Cell Distribution Width (RDW), the measure of anisocytosis amongst red cells, is increasingly being realized to be a biomarker for various conditions. The purpose of this study was to assess the correlation between RDW and NT-proBNP in the setting of the new definition of PH as per the 6th World Symposium, which includes all patients with a mean pulmonary artery pressure (mPAP) of over 20 mm Hg. METHODS: Patients who underwent right heart catheterization (RHC) at our hospital system between November 2014 and November 2019 were included in this retrospective study. Exclusion criteria included patients under the age of 18, active malignancy, known hemoglobinopathy, blood transfusion within one month of laboratory testing, and a lack of RDW or NT-proBNP measured within 3 months of RHC. Hemodynamic parameters obtained on RHC were documented. The closest RDW and NT-proBNP values obtained within 3 months of the RHC were noted. Student's t-test was used to compare NT-proBNP between patients with elevated RDW (> 14.5%) and normal RDW (# 14.5%). Secondly, mean RDW was compared between elevated BNP ($ 300 pg/mL) and normal BNP (< 300 pg/mL). RESULTS: 231 patients were included in this study. 176 of them had RHC-proven PH. Amongst PH patients, there was a statistically significant significant difference in the mean NT-proBNP between the elevated RDW (> 14.5%, n ¼ 90) and the nonelevated RDW (# 14.5%, n ¼ 86) groups (7401.57 vs 3663.83 pg/mL, p ¼ 0.0076). Patients with elevated NT-proBNP ($ 300 pg/ mL, n ¼ 142) tended to have a higher RDW than those with normal BNP (< 300 pg/mL, n ¼ 34) (15.03 vs 14.36%, p ¼ 0.0264). These relationships held true when generalized to include patients without PH. The elevated RDW group (n ¼ 100) had a significantly higher NT-proBNP than the normal RDW group (n ¼ 131) (6866.19 vs 3136.6 pg/mL, p ¼ 0.002). The elevated NT-proBNP group (n ¼ 172) also had a higher RDW than the normal NT-proBNP group (n ¼ 69) (14.84 vs 13.96%, p ¼ 0.0003). CONCLUSIONS: NT-proBNP has previously been shown to be a valid biomarker for assessing disease severity, and to predict mortality and morbidity in patients with PH. The correlation between RDW and NT-proBNP in the setting of PH implies that RDW may also be a useful surrogate marker for disease severity in PH. CLINICAL IMPLICATIONS: RDW is a relatively cheap marker that could be used alongside other biomarkers such as NT-proBNP to measure the severity of disease in PH. Further studies are required to directly validate this relationship.