Research PaperComparison of bioelectrical impedance and DXA for measuring body composition among adults with Down syndrome

BackgroundIndividuals with Down syndrome (DS) have been shown to display high levels of adiposity and a unique body shape. Laboratory methods used to evaluate body composition might be too cumbersome for this special population. Therefore, field methods are desired due to their non-invasive nature.Objective: to determine the agreement between dual energy x-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA) for measuring body fat percentage BF% and fat-free mass (FFM) among adults with DS.MethodsTwenty-one adults (male: n = 10; female: n = 11) with DS participated in this study. BF% and FFM were determined by DXA and BIA.ResultsThere was a significant mean difference between DXA and BIA for BF% (41.33 ± 8.98% and 34.23 ± 9.22%, respectively) and FFM (41.80 ± 8.74 kg and 46.95 ± 9.92 kg, respectively). The correlation between the two devices for BF% and FFM were significant (r = 0.89 and r = 0.94, respectively, p < 0.001 for both). The standard error of estimate and total error values were 4.38% and 8.27%, respectively, for BF% and 3.04 kg and 6.13 kg, respectively, for FFM. The 95% limits of agreement ranged from −15.64% below to 1.46% above the constant error (CE) of −7.09% for BF% and from −1.52 kg below to 11.83 kg above the CE of 5.15 kg for FFM.ConclusionsThe significant mean differences and large amount of individual error suggest that BIA may not be an appropriate surrogate body composition measure compared to DXA in adults with DS.