Validation of body composition assessment for unilateral amputees via BIA by comparison with DXA

Amputees suffer from metabolic diseases. Thus, for a healthy life, management through body composition (BC) tests is useful. We aimed to validate between the bioimpedance analysis (BIA(InBody_S10)) and dual-energy X-ray absorptiometry (DXA(Lunar Prodigy)) method for evaluating BC in amputees. 78 male (n = 66) and female (n = 12) unilateral amputees, with either trans femoral amputation (TFA) or trans tibial amputation (TTA), were recruited. Correlation, agreement, and differences between fat free mass (FFM) and percentage fat mass (PFM), computed with the two methods, were tested using methods such as Pearson's and Spearman's correlation, Lin's concordance correlation coefficient (CCC), Bland-Altman plot, bivariate linear regression, and %Diff = 100* (BIA-DXA)/DXA. In all groups, the FFM_BIA value was significantly overestimated compared to FFM_DXA; by contrast, the PFM_BIA value was significantly underestimated with respect to PFM_DXA. Additionally, differences between the results from the two methods were significantly higher for TFA than for TTA. In addition, a lower agreement between the two methods was observed in the TFA compared to the TTA group based on the correlation estimated through Lin's CCC. Moreover, body composition assessment with BIA needs to be carefully interpreted in amputees with some length of residual limb, especially regarding the TFA group.