Validity of bioelectrical impedance analysis to assess fat- free mass in patients with head and neck cancer: An exploratory study

BackgroundThe purpose of this study was to validate bioelectrical impedance analysis (BIA) using the Geneva equation for fat-free mass (FFM) in patients with head and neck cancer. MethodsIn 24 patients with head and neck cancer, agreement between BIA (FFMBIA) and dual energy x-ray absorptiometry (FFMDXA) 1 week before (T-0), 1 month (T-1), and 4 months (T-2) after cancer treatment was analyzed. ResultsFFM(BIA) did not differ from FFMDXA (mean difference 0.71 1.9, 0.30 +/- 1.9, and 0.02 +/- 2.1 kg) at any time point. Only at T-0, mean FFM correlated to the difference between FFMDXA and FFMBIA (r = 0.48; p = .017). Limits of agreement were 3.8, 3.7, and 4.1 kg, respectively. Concordance Correlation Coefficients were 0.98 at all time points. ConclusionBIA may be used to assess FFM with reasonable validity based on mean-level comparisons, but differences between BIA and DXA may vary by about 4 kg in an individual patient. These results require confirmation in a larger sample of patients with head and neck cancer. (c) 2013 Wiley Periodicals, Inc. Head Neck36: 585-591, 2014