Assessment of Adiposity in Neurofibromatosis Type 1: Comparison between Dual Energy X-ray Absorptiometry and Conventional Methods

Neurofibromatosis type 1 (NF1) is a genetic disease, characterized by multiple neural tumors as well as cutaneous symptoms. A simpler, non-invasive and cost-effective method for measuring adiposity would be useful in the care of individuals with NF1. Dual energy X-ray absorptiometry (DXA) is the standard method for this assessment but it is not widely accessible in daily clinical practice. This study aimed to compare body compositions measured using bioelectrical impedance analysis (BIA) and skinfold thickness (ST) predictive equations to those measured with DXA in twenty-six individuals with NF1. Body fat percentage (BF%) was predicted using DXA, five ST-equations and four BIA-equations. The BF% measured by DXA was 26.6 7.3 and 37.4 7.2 % for men and women, respectively. The best predictor of BF% was the Sun et al. BIA equation with a smaller difference compared to DXA (P=0.664), better median of adequacy (101.0%) and accuracy of 46.2%. For males, the Kyle et al. and Lohman BIA equations were the best predictors (accuracy: 78.6 and 64.3%, respectively). For females, all nine equations showed lower differences compared to DXA (P<0.001 for all equations). Among ST equations, Durnin and Womersley showed a smaller difference, greater median of adequacy and percentage of adequacy compared to DXA, even when stratified by sex. This study showed that BIA equations present better adequacy and accuracy compared to SK equations. Nevertheless, these equations should be used with caution in this population due to the variations observed in comparison to DXA.