Validity of the body adiposity index in adults with Down syndrome

• Individuals with Down syndrome display unique body composition profiles.
• Determining valid predictors of body fat is important in this population.
• The body adiposity index (BAI) is a non-threatening method that has potential.
• However, we showed that it provided large errors compared to DXA.
• Caution should be employed when using BAI for this population.

The purpose of this investigation was to determine the agreement between the body adiposity index (BAI) and dual energy X-ray absorptiometry (DXA) for measuring BF% in adults with Down syndrome (DS). Twenty adults (male: n = 10; female: n = 10) with Down syndrome volunteered to participate in this study. Criterion BF% was determined by DXA and predicted BF% was estimated by the BAI method. There was a significant mean difference (p < 0.001) between DXA BF% (39.94 ± 10.80%) and the BAI BF% (42.60 ± 8.19%). The correlation between the two BF% variables was large and significant (r = 0.73, p < 0.001). However, the standard error of the estimate and total error was 7.79% and 7.86%, respectively. Additionally, the 95% limits of agreement ranged from 12.21% below to 17.52% above the constant error of 2.65%. Our findings suggest that on average, the BAI significantly overestimated BF% when compared to DXA values. Though there was a strong correlation between both methods, the wide limits of agreement suggest there is large amount of individual error when estimating BF% via the BAI. Therefore, the use of the BAI for individuals with DS does not appear to be accurate for estimating BF%.