The phase angle of the electrical impedance is a predictor of long-term survival in dialysis patients.

INTRODUCTION: Protein-energy malnutrition is a risk factor for mortality in dialysis patients; however, its clinical assessment has not been well defined. Electrical bioimpedance (EBI) is a non-invasive and objective procedure, which is increasingly being used for this assessment.
OBJECTIVE: The aim of this study is to analyse the relationship between the phase angle determined by EBI at a frequency of 50kHz (AF50) and other nutritional parameters, and prospectively evaluate its ability as a marker for long-term mortality. PATIENTS AND METHODS: We included 164 patients (127 on haemodialysis and 37 on peritoneal dialysis) who underwent an EBI analysis while simultaneously determining inflammation and nutrition parameters. The Charlson comorbidity index was then calculated.
RESULTS: In the linear correlation analysis, we found that the AF50 had a direct association with lean mass, intracellular water, extracellular water and interdialytic weight gain, while having an inverse association with age and fat mass. Patients with AF50 >8&ordm; had a better nutritional status, were younger and had significantly longer survival at the six-year follow-up. Among the patients studied, both the AF50 and the other body composition parameters were better in peritoneal dialysis than in haemodialysis, but these differences may be attributable to the fact that the first patients were younger. In the multivariate analysis, only the AF50 <8&ordm; and comorbidity adjusted for age persisted as independent risk factors for mortality.
CONCLUSIONS: We conclude that AF50 has a good correlation with nutritional parameters and is a good marker of survival in dialysis patients. Nevertheless, intervention studies are needed to demonstrate if the improvement in EBI parameters is associated with better survival.