Nutritional evaluation of hemodialysis patients using an impedance index

Malnutrition is frequent in chronic hemodialysis patients. Standard nutritional evaluation is based on anthropometric, laboratory and clinical parameters from which a malnutrition index can be derived. Bioelectrical impedance, more rapid and practical, can be used to evaluate body composition. The goals of our study were to: 1) evaluate the incidence of and some of the factors associated with malnutrition in hemodialysis patients; 2) assess the accuracy of a scoring system based on impedance results to identify malnourished patients as defined by the malnutrition index (based on anthropometric, laboratory and clinical parameters). Standard nutritional evaluation and impedance measurements were performed on 33 chronic hemodialysis patients. Using malnutrition index, 18 patients (54%) were severely or moderately malnourished. Dietary assessment revealed a high proportion of patients with insufficient protein or calorie intake. By multiple regression analysis, the only factor significantly correlated with the malnutrition index was calorie intake (r = 0.44); age, sex, years on hemodialysis, protein intake were not. Results obtained with impedance were strongly correlated to those obtained with anthropometry for the proportion of fat mass (r = 0.72) and lean body mass (r = 0.71) and for the malnutrition index (r = 0.78). The sensitivity of the scoring system based on impedance to identify moderately or severely malnourished patients as determined by standard nutritional evaluation was 100% and its specificity was 80%. The positive and negative predictive values were respectively 85% and 100%. In summary, malnutrition is frequent and associated with low caloric intake. Bioelectrical impedance, with the use of the scoring system we describe, can be used to correctly evaluate the nutritional status of hemodialysis patients.