Gender-specific bioelectrical impedance reference values in healthy children

Bioimpedance parameters are important for assessing children's body composition and health status. However, interpreting these parameters is still challenging, especially without reference data and cut-off points.This study aimed to describe gender-specific reference phase angle (PhA) values and bioelectrical impedance vector analysis (BIVA) plots for healthy Brazilian children. Children aged 6–9 years were recruited from four public schools in Natal, Brazil. Anthropometric measurements and bioelectrical impedance (BIA) were performed. The values of age, weight (kg), height (cm), resistance (Ω), and reactance (Ω) were measured. Only eutrophic children were included according to body mass index (BMI)-for-age Z-score. BIVA 2002 software was used for the construction of BIVA plots. A P -value < 0.05 was accepted as statistically significant. The sample size was 108 children (boys, n= 49; girls, n= 59) with average age of 8.4 ± 0.77. The girls showed significantly higher values of resistance and resistance normalized by height (R/H) ( P  < 0.05) compared to the boys. Considering the 95% confidence ellipses for mean impedance vectors, there was no difference between boys and girls. Mean gender-specific reference values for PhA in our sample were traced. The 75th tertil for PhA were 5.79° and 5.40° for boys and girls, respectively. When comparing our sample with other ethnic groups was observed that we had higher values of R/H (582.4–620.7 versus 552.5–589.5) and lower values of Xc/H (53.8–54,7 versus 61.7–64,7) and PhA (5.3–5.1 versus 5.5–6.3) for boys and girls, respectively. The PhA values and the new tolerance ellipses provided by our data reflect the normal growth and development of the prepubertal children studied. These reference values have significant clinical utility since they can point out altered body composition in other children due to pathophysiological conditions. Verifying changes in nutritional prognosis and hydration status allow early clinical and nutritional interventions.