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Table 4 Fat-free mass determined by dual-energy x-ray absorptiometry and derived equations based on different resistance indices (RI)

From: Bioelectrical impedance analysis to estimate body composition, and change in adiposity, in overweight and obese adolescents: comparison with dual-energy x-ray absorptiometry

Method Group A (n = 33) Group B (n = 33) P
DXA Mean ± SD (kg) 47.9 ± 12.6 46.9 ± 10.9 0.682
H2/R50  
Mean ± SD (kg) 48.3 ± 11.4 46.5 ± 10.8 0.519
Bias (kg) 0.4 -0.5  
Limits of agreement (kg) -6.8 to 7.6 -7.9 to 7.0  
r c (95% CI) 0.95 (0.91 – 0.97) 0.94 (0.88 – 0.97)  
H2/R  
Mean ± SD (kg) 48.3 ± 11.4 46.5 ± 10.6 0.516
Bias (kg) 0.4 -0.4  
Limits of agreement (kg) -7.5 to 8.2 -7.5 to 6.6  
r c (95% CI) 0.94 (0.89 – 0.97) 0.94 (0.89 – 0.97)  
H2/Zc  
Mean ± SD (kg) 48.1 ± 11.3 46.7 ± 11.2 0.612
Bias (kg) 0.2 -0.2  
Limits of agreement (kg) -6.9 to 7.2 -8.6 to 8.1  
r c (95% CI) 0.95 (0.91 – 0.98) 0.93 (0.85 – 0.96)  
  1. RI examined were height2/resistance 50 kHz (H2/R50), height2/estimated resistance at infinity (H2/R) and height2/impedance at characteristic frequency (H2/Zc).