Comparison between Bioimpedance Analysis and Dual-Energy X-ray Absorptiometry in assessment of body composition in a cohort of elderly patients aged 65-90 years.

We compare bioimpedance analysis (BIA) with dual-energy X-ray absorptiometry (DXA) in the assessment of free fat mass (FFM), fat mass (FM) and percentage of body fat under different conditions in relation to age categories, hydration parameters, body mass index (BMI) and sarcopenia. A cross-sectional analysis of body composition was estimated by BIA and DXA in 379 hospitalized elderly patients. In addition, estimates of FFM, FM and percentage of body fat were investigated across different conditions. Paired t-tests, Bland-Altman plot and intraclass correlation coefficient analysis were used to compare methods. Data showed an underestimation of means (BIA versus DXA) of FFM (women: 0,97 kg, p<0,01; men: 1,99 kg; p<0,01), and an overestimation of both the FM (women: +1,11 kg; p<0,01; men: +1,67 kg; p<0,01) and percentage of body fat (women: +2,07 %, p<0,01; men: +2,82 %, p<0,01). BIA underestimated FFM and overestimated FM and percentage of body fat in patients from the age group of 75 to 85 years, in patients with a total body water content <60%, in underweight and normal weight patients and in patients with sarcopenia (p<0,01). The intraclass coefficient results were indicative of poor reproducibility between BIA and DXA for FFM (women: +0,197; men: +0,250) and FM (women: +0,141; men +0,144). BIA is a good alternative for estimation of FFM and FM only in overweight or obese patients or in patients with good hydration status. BIA, on the other hand, is not an accurate method for assessing FFM in sarcopenic patients.