Develepment and validation of a BIA prediction equation for 11-13 year old Sri Lankan girls

Abstract

INTRODUCTION AND OBJECTIVES: Population-specific measures of body composition are important in management of childhood obesity. This study aimed to develop and validate a bioelectrical impedance analysis (BIA) equation to assess total body water (TBW) and fat mass (FM) in Sri Lankan girls aged 11-13 years. METHODS: Forty-six 11-13 year-old healthy school girls were purposively selected and randomly divided into model development (n=30) and model validation (n=l6) sub-samples. Weight, height and impedance using BIA were measured. TBW was determined and FM was derived through the criterion Deuterium-dilution technique. Prediction equations for TBW and FM were developed using impedance index (heightvimpedance; cm2/Q), weight and height as independent variables. Final equations were developed combining the two sub-samples. Validity was assessed using correlation coefficients, paired-samples T-test and Bland-Altman plots. RESULTS: In the validation sample, predicted TBW and FM showed significant correlations and did not significantly differ from reference values, Final prediction equation for TBW had a R2 of 92.3% and RMSE of l.035 while FM prediction equation had a R2 of 94.3% and RMSE of 1.38. TBW predicted from new equation (19.48± 3.45kg) was not significantly different from reference TBW (19.52±3.65kg) and the two measures were significantly correlated (r=0.975, p<0.001). Similarly, predicted FM (10.41±4.39kg) was not significantly different from reference FM (10.38±4.74kg) and predicted and reference values were significantly correlated (r=0.974, p<0.001). In both prediction equations, the majority ofresiduals were within mean± l.96SD. CONCLUSION: Newly developed prediction equations for BIA assessment of TBW and FM show high validity compared to reference technique.