HDCN Article Review/Hyperlink

Maggiore Q, Nigrelli S, Ciccarelli C, Grimaldi C,Rossi GA, Michelassi C

Nutritional and prognostic correlates of bioimpedance indices in hemodialysis patients

Kidney Int (Dec) 50:2103-2108 1996

Bioimpedance analysis (BIA) is being used to assess nutritional status in ESRD patients. Maggiore et al measured bioimpedance measures in 131 ESRD patients and 272 controls to determine how well BIA analysis can predict malnutrition. The bioimpedance measures assessed were the resistance (Rz), the reactance (Xc) and their geometric ratio (Xc/Rz = PA or phase angle). The study was strengthened by the fact that it was not only cross- sectional, but had a longitudinal component, with patients being followed for up to 41 months.

Rz, Xc and PA all increased significantly during a dialysis session. Rz was higher, and Xc and PA were lower in ESRD patients predialysis vs. values in control patients. Postdialysis, values in RZ and PA were still different from controls. A variety of nutritional indices did correlate with the bioimpedance parameters, but the latter missed a substantial portion of severely malnourished patients. On serial analysis simply weighing the patient was a much better way of picking up developing malnutrition than bioimpedance measures. Interestingly the phase angle (PA) was a good predictor of mortality (as it is in patients with AIDS), and the PA was a more reliable predictor of mortality than standard nutritional variables such as the Subjective Global Assessment score.

Comment: So the bad news is that BIA fails to correlate very well with nutritional indices, and the good news is that at least one index of the BIA, the phase angle (PA) may be a very important predictor of subsequent mortality. It is unclear, however, exactly what the PA is measuring or why it should correlate with clinical outcome. (John T. Daugirdas, M.D., University of Illinois at Chicago)