Does the body adiposity index (BAI) apply to paediatric populations?

Objective: Validation of body adiposity index (BAI) in a paediatrics sample; and to develop, if necessary, a valid BAI for paediatrics (i.e. BAIp). Methods: A total of 1615 children (52% boys) aged 5-12 years underwent anthropometry. Their body composition was assessed using a foot-to-foot bioimpedance. The validity of BAI=(Hip circumference/Height^1.5)-18 was tested by combining correlation and agreement statistics. Then, the sample was split into two sub-samples for the construction of BAIp. A regression was used to compute the prediction equation for BAIp-based percentage of body fat (%BF). Results: The initial BAI over-estimated the %BF of children by 49% (29.6±4.2% versus 19.8±6.8%; p<0.0001). The original methodology led to a BAIp=(Hip circumference/Height^0.8) - 38 in children. When compared to BAI, BAIp showed both better correlation (r=0.57; p<0.01 versus r=0.74; p<0.0001) and agreement (ICC=0.34; [95% CI=-0.19-0.65] versus ICC=0.83; [95% CI=0.81-0.84]). However, there were some systematic biases between the two values of %BF as exemplified by the large 95% limit of agreement [-9.1%; 8.8%] obtained. Conclusion: BAI over-estimates the %BF in children. In contrast, BAIp appears as a new index for children's body fatness, with acceptable accuracy. In its current form, this index is valid only for large-scale studies.