Title: Evaluation of anthropometry as an alternative to DXA as predictor of low bone mineral density in children and adolescents with cystic fibrosis

Abstract

Background & Aims: Low bone mineral density (BMD) for age in people with Cystic Fibrosis (CF) is associated with worse nutritional status. The aim of this study is to assess body composition by anthropometry as a predictor of BMD in people with CF. Methods: Multicenter cross-sectional study with 39 people aged 5 and 20 years with CF. BMD was assessed by dual energy x-ray emission (DXA) in the incidence of the total body less head (TBLH) and the TBLH Z-score (Z-TBLH) was calculated, adjusted by sex, age, height and ethnicity. Anthropometry was assessed by weight, height, mid-upper arm circumference (MUAC) and triceps skinfold (TSF). Arm muscle area (AMA) and Body Mass Index (BMI) were calculated. Lean mass (LM), fat mass (FM) and free-fat mass (FFM) were identified by DXA. Statistical models of simple and multiple linear regression were created to establish the predictive power of Z-TBLH in the variables. Results: Average age of the participants was 13.31 ± 3.86 years, 59% of whom were male. They showed more LM (30.97 Kg ± 11.29) than females (23 Kg ± 6.73). 20 of 30 participants (66.7%) had at least copy of F508del. Among the multiple models, adjusted by height, age and sex, it found BMI (R² = 0.367), Weight (R² = 0.220), AMA (R² = 0.338) as significant predictors of Z-TBLH. The final model composed of AMA, TSF and Age (p = 0.001; R² = 0.381) had AMA and Age as significant predictors. AMA was associated with an increase in the BMD Z-score in the participants studied. Conclusion: A statistical model composed of the values of AMA, TSF and Age can predict Z-TBLH, as well as anthropometric variables Weight, or BMI, or AMA associated with height, age and sex, in children and adolescents aged 5 to 20 years old, of both sexes.