Maggiore Q, Nigrelli S, Ciccarelli C, Grimaldi C,Rossi GA,
Nutritional and prognostic correlates of bioimpedance
indices in hemodialysis patients
(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
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)