P583 - RELIABILITY OF BIOELECTRICAL IMPEDANCE ANALYSIS IN SITTING AND STANDING POSITIONS COMPARED TO SUPINE POSITION

P583

RELIABILITY OF BIOELECTRICAL IMPEDANCE ANALYSIS IN SITTING AND STANDING POSITIONS COMPARED TO SUPINE POSITION

M. Hendriks¹, M. V. Lieshout¹, C. D. Klerk¹, J. A. Langius^1,*

¹Nutrition and Dietetics, The Hague University of Applied Sciences, The Hague, Netherlands

Rationale: Bioelectrical Impedance Analysis (BIA) is widely used for body composition assessment in the clinical and homecare setting. BIA provide the most accurate results when performed in a supine position. However, in daily practise this position is not always feasible. The aim of this study was to evaluate the reliability of seated and standing BIA measurements compared to the supine position.

Methods: BIA was performed in 20 adults (BMI 18.5–30.0 kg/m²) after an overnight fasting period of ≥8 hours and no intense physical activity before the measurements. The participants were measured four times in supine, seated, and standing positions, with one week between sessions. Position order was randomized within each session. Fat-free mass (FFM) was derived using the Kyle equation. Statistical analyses included paired samples t-tests, Bland-Altman plots, and Intraclass Correlation Coefficients (ICC).

Results: Included were 5 males and 15 females with a mean age of 28.3 (± 11.8) years. Baseline FFM in supine position was 47.9 ± 10.1 kg. FFM in the seated position was significantly higher than in the supine position at all 4 timepoints (0.66 ± 0.80 to 0.76 ± 1.04 kg, p < 0.05), while no significant difference was found between standing and supine (0.03 ± 0.48 to 0.32 ± 0.78 kg, p > 0.05). Over time, FFM trends were consistent across positions. Bland-Altman analysis showed a mean bias of 0.73 kg (limits of agreement: 0.55-0.90 kg) for seated vs. supine and 0.16 kg (limits of agreement: 0.00-0.31 kg) for standing vs. supine. ICC values (0.997-0.999, p < 0.001) indicated high measurement consistency.

Conclusion: The seated and standing positions provide reliable alternatives to the supine position in BIA measurements, with high consistency and clinically acceptable bias. These findings support the use of seated and standing position when supine positioning is not feasible.

Disclosure of Interest: None declared