Bioelectrical impedance analysis versus quantitative computer tomography and anthropometry for the assessment of body composition parameters in China

Obesity, especially abdominal obesity, is correlated to increased risk of cardiovascular morbidity and mortality. It is urgent to search a simply method to predict visceral fat area (VFA). Herein, we evaluated the correlation of waist circumference (WC) measured by anthropometry and bioelectrical impedance analysis (BIA), and VFA estimated by BIA or measured by quantitative computed tomography (QCT) in China. The mean body mass index (BMI) was 25.09 +/- 3.31 kg/m(2) and the mean age was 49.16 +/- 9.19 years in 2754 subjects. VFA-BIA were significantly smaller than VFA-QCT in both BMI and age subgroups between male and female (p<0.001). High correlation was observed for WC between BIA and manually (r=0.874 for all, r=0.865 for male and r=0.806 for female) and for VFA between BIA and QCT (r=0.512 for all). The intraclass correlation coefficient (ICC) showed the perfect agreement between BIA and manually to measure WC (ICC=0.832 for all, 0.845 for male and 0.697 for female) and implied a good reliability for VFA between BIA and QCT with women among subgroups (ICC=0.623 for all, ICC=0.634 for age<50 years and ICC=0.432 for BMI>24 kg/m(2)), whereas the good reliability was lost in men (ICC=0.174). The kappa analysis showed a moderate consistency for VFA measured by BIA and QCT (Kappa=0.522 with age<50 years, 0.565 with age<greater than or equal to>50 years in male; Kappa=0.472 with age<50 years, 0.486 with age<greater than or equal to>50 years in female). In addition, BIA to estimate VFA (r=0.758 in male, r=0.727 in female, P<0.001) has a stronger correlation with VFA measured by QCT than BMI and WC according to gender categories. Furthermore, ROC analysis showed the cut-off point of VFA measured by BIA for predicting visceral obesity was: 101.90 cm(2), 119.96 cm(2) and 118.83 cm(2) and the Youden's index was 0.577, 0.577 and 0.651, respectively and the Kappa value was 0.532, 0.536 and 0.611 in unadjusted model, model 1 and model 2. In conclusion, being non-invasive and free of radiation, BIA can be used as a safe and convenient tool to estimate VFA in female; especially for monitoring the VFA of the same person, the BIA has superiority to a certain extent. However, the consistency is not most ideal between BIA and QCT. When using BIA to assess whether a person is visceral obesity, we must take into consideration age, BMI and WC. Therefore, we established a regression formula to reflect VFA-QCT by VFA-BIA, age, BMI, and WC. In addition, a more accurate formula is needed to match the CT data in China.