Measuring body composition in hemodialysis patients: before or after hemodialysis? before or after hemodialysis?

Background & Aims: Body composition and clinical outcomes such as mortality and quality of life are strongly correlated in patients with chronic kidney disease. Since body weight and body mass index do not reflect body composition, measuring body composition is essential. In hemodialysis patients, there is an equipoise about the best moment to measure body composition; before or after hemodialysis. Our aim was to explore the agreement between bio-impedance spectroscopy (BIS) derived body composition indices before and after hemodialysis. Methods: We performed BIS measurements in a cohort of hemodialysis patients. Patients were divided into group 1: measurements before and <30 min after the end of the hemodialysis session, and group 2: measurements before and ≥30 min after hemodialysis. Wilcoxon Signed Ranks Tests were performed to study differences. Bland–Altman procedure and two-way mixed intraclass correlation coefficients (single measures) were performed to study agreement. Results: We included 37 hemodialysis patients, with a median age of 58 (28) years, and 51% was male. The analysis includes 78 hemodialysis sessions. Body weight, overhydration, total body water, extracellular water, phase angle, and resistance were significantly different between measurements in both groups. Adipose tissue mass was significantly different in group 1 (P = 0.003), but not in group 2. All variables had very good agreement in both groups (ICC > 0.810, P < 0.001). Conclusions: These results suggest that BIS-derived body composition measurements can be performed both before and after hemodialysis. If body composition is measured after hemodialysis, then measurements should be performed ≥30 min after the end of the session.