Validity Of A Pediatric-specific Equation To Predict Fat-free Mass In Children Ages 2-4 Years

Measures of body composition provide a better risk classification assessment than body mass index for sex and age percentiles in young children. The challenge is to identify a safe, non-invasive, economical (cost and time), and valid method of assessing body composition in young children. We previously created and cross-validated a pediatric specific, tetra-polar bioelectrical impedance analyses (BIA) equation for use in 5-11 year old White Non-Hispanic, Black Non-Hispanic, and biracial children. We recognized the need for a valid BIA equation in preschool-aged children. PURPOSE: To determine the validity of using our previously reported BIA equation to estimate body composition in 2-4 years old children. METHODS: Participants were 43 (21 boys) children 2-4 years (Mean ± SD: 3.7 ± 0.9 yrs) of age. Total body DXA scan fat-free mass (FFM) measures were used as the criterion measure, and a multi-frequency tetra-polar BIA device was employed using our previously published BIA equation (Clasey et al Obesity 19:1813-1817, 2011) of: DXA FFM (kg) = (−7655 + 297 (Ht) + 125 (BM) - 17.4 (Imp))/1000 where Ht, standing height (cm); BM, body mass (kg); and Imp, BIA impedance at a frequency of 50 khz (ohms). RESULTS: Our previously published BIA equation explained a significant (p < 0.01) amount (94.2%) of the variance in DXA FFM of our study participants. The FFM pure error of the BIA FFM calculated as the square root of the sum of the squared difference between the observed and predicted values divided by the number of study participants was 2.2 kg. A modified Bland-Altman plot demonstrated a mean difference of 1.8 kg with 98% of the measures falling within the 95% confidence intervals of -0.8 kg to 4.5 kg. CONCLUSIONS: We conclude that our previously published BIA equation is valid for use in 2-4 year old children. The use of this equation may assist in identifying effective strategies to prevent or combat childhood obesity in preschool-aged children in a variety of field, clinical and research settings. This study was supported in part by the University of Kentucky Pediatric Exercise Physiology Laboratory Endowment.