Relationships of high mean corpuscular volume, low total iron binding capacity and protein-energy wasting in patients on maintenance hemodialysis

BACKGROUND: Recent studies have reported that high mean corpuscular volume (MCV) may be associated with mortality in chronic kidney disease patients. A high MCV is caused by erythropoietin-stimulating agent (ESA). Most patients with protein-energy wasting (PEW) have functional iron deficiency (FID) and need a high ESA dose. FID is associated with low total iron binding capacity (TIBC), which is a marker of iron status, malnutrition, and inflammation, and it may be a predictor of muscle loss. The relationships between high MCV and iron status markers in patients on hemodialysis (HD) are not well known. The aim of this study was to assess the relationships between high MCV and iron status markers in a cross-sectional and longitudinal study considering nutritional status, inflammation, muscle mass, and hydration status. METHODS: A prospective cohort of 39 HD patients was examined for 12 months. The relationships between MCV and iron status markers (TIBC, ferritin, hepcidin-25, iron) were examined using multivariate linear regression analysis and multivariate repeated measures analysis. RESULTS: At baseline, a high MCV (≥ 100 fL) was significantly related to low TIBC and low muscle mass. Multiple regression analysis showed that MCV was associated with low TIBC. On multivariate repeated measures analysis, MCV was associated with a sustained low TIBC, and proportion of PEW and ERI were associated with a sustained high MCV. CONCLUSION: High MCV was associated with low TIBC. Furthermore, a sustained high MCV suggested ESA hypo-responsiveness and tendency to iron use disorder and may be a useful marker of PEW.