Evaluation of air-displacement plethysmography and bioelectrical impedance analysis vs dual-energy X-ray absorptiometry for the assessment of fat-free mass in elderly subjects

• Published in: European journal of clinical nutrition Vol. 62; no. 11; pp. 1282 - 1286
• Main Authors: Bertoli, S, Battezzati, A, Testolin, G, Bedogni, G
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.11.2008; Nature Publishing; Nature Publishing Group
• Subjects: Absorptiometry, Photon - methods; Adipose Tissue - metabolism; Aged; Aged, 80 and over; air-displacement plethysmography; Algorithms; anthropometric measurements; bioelectrical impedance; Bioelectricity; Biological and medical sciences; Body Composition - physiology; Body fat; Body Water - metabolism; body weight; Bone densitometry; Clinical Nutrition; Dual energy X-ray absorptiometry; elderly; elderly nutrition; Electric Impedance; Epidemiology; Evaluation; fat free mass; Fat-free body mass; Feeding. Feeding behavior; Female; Females; Fundamental and applied biological sciences. Psychology; Gender; gender differences; health status; Health status indicators; Humans; Impedance; Impedance, Bioelectric; Internal Medicine; Investigative techniques, diagnostic techniques (general aspects); Linear Models; Male; Males; Measurement; Measurement techniques; Medical examination; Medical imaging; Medical sciences; Medicine; Medicine & Public Health; Men; Metabolic Diseases; Middle Aged; Muscle, Skeletal - metabolism; Older people; original-article; Osteoarticular system. Muscles; Performance evaluation; Plethysmography; Plethysmography - methods; prediction; Public Health; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Regression analysis; Reproducibility of Results; Respiration; senescence; Sensitivity and Specificity; Sex differences; Sex Factors; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Weight; Whites; women; X-rays; Italy; dual-energy X-ray absorptiometry; body composition; bioelectrical impedance analysis; air-displacement plethysmography; elderly; Human; Dual energy absorptiometry; Lean body mass; Metabolic diseases; Impedance; Elderly; Body composition; Comparative study; Air plethysmography
• ISSN: 0954-3007; 1476-5640
• DOI: 10.1038/sj.ejcn.1602847

Objective: To evaluate air-displacement plethysmography (ADP) and bioelectrical impedance analysis (BIA) vs dual-energy X-ray absorptiometry (DXA) for the assessment of fat-free mass (FFM) in healthy elderly subjects. Subjects: Forty-two women and twenty-six men aged 60-84 years. Methods: FFM was measured by DXA and ADP. Body impedance (Z) was measured by four-polar BIA and the impedance index (ZI) was calculated as stature2/Z. Selection of predictors (gender, age, weight and ZI at 5, 50 and 100 kHz) for BIA algorithms was carried out using bootstrapped stepwise linear regression on 1000 samples of 68 subjects. Limits of agreement were used as measures of interchangeability of ADP and BIA with DXA. Results: The limits of agreement of ADP vs DXA were -11.0 to 2.4 kg in males and -4.8 to 2.2 kg in females. Gender, weight and ZI100 were selected as predictors of FFM by bootstrapped stepwise linear regression. In males, ZI100 (-12.2 to 12.2 kg) was much less accurate than weight (-6.0 to 6.0 kg) at predicting FFM and their combination did not improve the estimate (-6.0 to 6.0 kg). In females, ZI100 (-6.8 to 6.8 kg) was less accurate than weight (-5.6 to 5.6 kg) at predicting FFM and their combination improved the estimate only slightly (-5.0 to 5.0 kg). Conclusions: In healthy elderly subjects, (1) ADP and DXA are not interchangeable for the assessment of FFM, especially in males; and (2) ZI100 is not superior to weight for the prediction of FFM and their combination is of little advantage and only in females.