Role of a Bioelectrical Impedance Analysis in Predicting Anemia among Cardiovascular Disease Patients

Objective Anemia frequently complicates cardiovascular disease (CVD) and is associated with high mortality rates. A bioelectrical impedance analysis (BIA) is a noninvasive method for measuring human body composition. A direct association between serum hemoglobin (Hb) levels and the extracellular water-to-total body water (ECW/TBW) ratio, as measured by a BIA in patients with diabetes, has been reported. However, the predictive value of the ECW/TBW ratio for detecting anemia in patients with CVD has not been fully elucidated. Methods We conducted a study involving consecutive patients admitted to our cardiology department from January 1, 2021, to December 31, 2022. A BIA was performed once during hospitalization for all patients, whenever possible. The correlation between the Hb level and ECW/TBW ratio was assessed. The predictive accuracy for anemia was evaluated using a receiver operating characteristic (ROC) curve analysis. Results The ECW/TBW ratio was significantly higher in the anemia group than in the non-anemia group [0.41 (0.40, 0.41) vs. 0.39 (0.38, 0.40), p<0.001]. The ECW/TBW ratio exhibited a significant negative correlation with Hb, with an R value of 0.57 and a p value of <0.01. However, this correlation coefficient decreased to 0.45 among subjects with B-type natriuretic peptide (BNP) levels ≥200 pg/mL. The area under the ROC curve (AUC) for the ECW/TBW ratio for detecting anemia was 0.83. However, its predictive performance decreased in patients with BNP levels exceeding 200 pg/mL, with an AUC of 0.71. Conclusion The BIA-derived ECW/TBW ratio is a valuable predictor of anemia in patients with CVD, provided BNP levels are not elevated.