Are segmental MF-BIA scales able to reliably assess fat mass and lean soft tissue in an elderly Swedish population?

BACKGROUND AND AIMS: The assessment of body composition is an important measure to monitor the process of healthy aging and detect early signs of disease. Dual X-ray absorptiometry (DXA) is considered a valid technique for the assessment of body composition but is confined to the clinical environment. Multi-frequency bio-electrical impedance analysis (MF-BIA) might be a versatile alternative to DXA. We aimed to assess whether a segmental MF-BIA scale can be an accurate and reliable tool for the monitoring of body composition in the elderly and whether the presence of metallic prostheses can influence the agreement between the two techniques. SUBJECTS AND METHODS: Weight and height were measured in 92 healthy subjects (53 women) aged 80-81 years from the H70 Gerontological and Geriatric study in Gothenburg. Total and segmental fat mass (FM) and lean soft tissue (LST) were estimated by DXA (Lunar Prodigy, Scanex, Sweden) and segmental MF-BIA (MC-180MA, Tanita, Japan). Bland-Altman analyses were performed to assess the agreement between the two techniques. The prediction of DXA-FM by MF-BIA was compared to that of the body mass index (BMI). RESULTS AND DISCUSSION: MF-BIA showed a significant underestimation of FM and an overestimation of LST that was larger in men than in women. Smaller but significant deviations were found for appendicular LST and SMM. MF-BIA was not superior to BMI at predicting DXA-FM. The lack of agreement between MF-BIA and DXA was not due to the presence of metal prostheses or diagnoses such as hypertension and edema. The prediction equations applied by the device used in this study should be adapted to the elderly population and details about the reference population(s) should be disclosed.