Development and validation of bioelectrical impedance analysis in predicting total body water and adiposity in 6- to 8-year-old South African school children
Creators: name: Moeng-Mahlangu, Lynn
name: Monyeki, Makama
name: Reilly, John
name: Kruger, Herculina
Publisher: name: The Health & Fitness Journal of Canada
Year: 2022

description: Background: Limited information is available on studies validating prediction equations against criterion methods, determining total body water (TBW) and fat-free mass (FFM) in children from low to middle-income countries like South Africa. Purpose: To develop and validate bioelectrical impedance analysis (BIA) to predict TBW and FFM in 6- to 8-year-old South African school children. Methods: A cross-sectional study with 299 (149 development and 150 validation groups) 6- to 8-year children (mean age of 7.63±0.84) was used. TBW and FFM were determined with Deuterium Oxide Dilution, the reference method and predicted using BIA (Bodystat 1500®) with 50 kHz frequency. Paired t-tests compared the mean differences between BIA and Deuterium Dilution using the Statistical Package for Social Sciences (SPSS V26®). The new BIA equation was determined by multiple regression, and the accuracy of prediction equations for both TBW and FFM was assessed using Bland Altman plots. The level of significance was set at p≤0.05. Results: Some of the published TBW and FFM equations for BIA validated in the study demonstrated under- or over-estimations. The newly developed South African equation had higher accuracy for both TBW and FFM prediction. Significant associations (p&lt; 0.001) were found between TBW and impedance index for both development group (R2 = 74.3%) and cross-validation group (R2= 82.6%). The newly developed BIA prediction equation for the estimation of TBW was = 1.472 + 0.257*(Ht2/R) + 0.225*(weight) - 0.769*(sex) + 0.333*(age) with a regression coefficient R = 0.935 and SEE = 0.801; and FFM = 1.466 + 0.333 (Ht2/R) + 0.292*(weight) - 0.997*(sex) + 0.491* (age), with a regression coefficient R =0.934 and SEE =1.055. No significant differences (p&gt;0.05) were found between measured and predicted values for the validation group. Bland Altman plots showed a good level of agreement between TBW and FFM predicted by the new equations against reference measures of TBW and FFM. The bias expressed as the mean difference in TBW or FFM measured by isotope dilution and BIA was 0.0±0.69 l [95% CI:-1.352; 1.352] for TBW and 0.00±0.90 kg FFM [95% CI: -1.764; 1.764]. The limits of agreement were respectively; -1.352; 1.352 and -1.764; 1.764kg for TBW and FFM. The concordance correlation coefficients for the criterion values against the newly developed predicted BIA equations for TBW and FFM respectively were high (both r=0.91). Conclusion: It was evident that the published equations used for comparison in the current study are invalid to predict TBW and FFM in South African children. The newly developed equation demonstrates the potential for practical and accurate estimation of TBW and FFM for use in comparable groups of South African children aged 6 to 8 years. Funding: Research supported by the South African Medical Research Council (MRC) under the Self-Initiated Research Grants Programme. Additionally, funds received from the NRF for rated researchers are acknowledged. Financial support received from North-West University in the establishment of the stable isotope laboratory for the determination of body composition within the PhASRec research entity is greatly appreciated. Additionally, we would like to thank the IAEA for financial support (TC project SAF6020).
description: The Health &amp; Fitness Journal of Canada, Vol. 14 No. 3 (2021): Proceedings from the 8th International Society for Physical Activity and Health Congress