252 Accuracy of simple methods to estimate body composition in cystic fibrosis patients

Abstract

Background: Fat free mass (FFM) depletion was reported in CF pts and is associated with worse pulmonary function. These findings suggest that monitoring of body composition (BC) should be introduced in clinical practice. However, the accuracy of simple methods to predict BC, such as skinfold thickness (SFT) measurements and bioimpedance (BIA), has been poorly investigated in CF. Aims: To evaluate the accuracy of equations based on SFT and BIA parameters for estimation of 2-compartment BC model (FFM&FM). Methods: Dual energy X-ray absorptiometry (DXA), 50 kHz BIA (Akern 101) and SFT measurements were performed on 138 CF pts (median age = 16 yrs, range = 8−47 yrs, 62 males). DXA was used as the criterion method for the estimation of FFM and FM. The equations developed by Slaughter (pts <17 yrs) and by Durnin (pts 17 yrs) based on SFT and the equations provided by the manufacter of BIA device (Bodygram PRO 3.0) were used to estimate percentage of fat mass (%FM). The difference between estimated and measured values by DEXA (bias), and the limits of agreement (Bland–Altman 95% limits of agreement) (LA) were calculated to compare accuracy of estimations. Results: In pts aged <17 yrs Slaughter equation significantly underestimated %FM (p< 0.0001). Mean bias was −3.7% (−10.9, 3.4) using Slaughter equation and −0.2% (−9.3, 8.9) using BIA. In pts aged 17 yrs, mean bias was −0.5% (−6.9, 5.9) using Durnin equation and −1.0% (−9.1, 7.2) using BIA. Conclusions: The estimation of BC by simple methods should be used with caution in CF patients, due to wide intra-individual differences. Population specific equations should be provided to make these methods of clinical usefulness.