Body composition following stem cell transplant: comparison of bioimpedance and air-displacement plethysmography.

Objective: The aim of this study was to assess the agreement between detected changes in body composition determined by bioimpedance spectroscopy (BIS) and air-displacement plethysmography (ADP) among patients with cancer undergoing peripheral blood stem cell transplantation (PBSCT); and to assess the agreement of absolute values of BIS with ADP and dual energy x-ray (DXA).
Methods: Forty-four adult hematologic cancer patients undergoing PBSCT completed both BIS and ADP assessment at preadmission and at 3 mo after transplantation. A subsample (n = 11) was assessed by DXA at 3 mo after transplantation. Results were examined for the BIS instrument's default setting and three alternative predictive equations from the literature. Agreement was assessed by the Bland-Altman limits of agreement analysis while correlation was examined using the Lin's concordance correlation.
Results: Changes in body composition parameters assessed by BIS were comparable with those determined by ADP regardless of the predictive equations used. Bias of change in fat-free mass was clinically acceptable (all <1 kg), although limits of agreement were wide (more than ±6 kg). Overall, the BIS predictive equation accounting for body mass index performed the best. Absolute body composition parameters predicted by the alternative predictive equations agreed with DXA and ADP better than the BIS instrument's default setting.
Conclusion: Changes predicted by BIS were similar to those determined by ADP on a group level; however, agreement of predicted changes at an individual level should be interpreted with caution due to wide limits of agreement.
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