Validation of dual x-ray absorptiometry for body-composition assessment ofrats exposed to dietary stressors

Evidence of the validity and accuracy of dual x-ray absorptiometry (DXA) to measure soft-tissue composition of laboratory rats with altered body compo sition associated with nutritional perturbations is lacking. We compared DX A determinations made in prone and supine positions with measurements of ch emical composition of 49 male, weanling Sprague-Dawley rats that were fed t he basal AIN-93 growth diet, were fed the basal diet modified to contain 30 % fat, were fasted for 2 d, were limit fed 6 g of the basal diet daily for 1 wk, or were treated with furosemide (10 mg/kg intraperitoneally 2 h befor e DXA). DXA produced similar estimates of body mass and soft-tissue composi tion in the prone and supine positions. DXA estimates of body composition w ere significantly correlated with reference composition values (R-2 = 0.371 -0.999). DXA discriminated treatment effects on body mass, fat-free and bon e-free mass, fat mass, and body fatness; it significantly underestimated bo dy mass (1% to 2%) and fat-free and bone-free mass (3%) and significantly o verestimated fat mass and body fatness (3% to 25%). The greatest errors occ urred in treatment groups in which body mass was diminished and body hydrat ion was decreased. These findings suggest that DXA can determine small chan ges in fat-free, bone-free mass in response to obesity and weight loss. Err ors in DXA determination of fat mass and body fatness associated with extra corporeal fluid and dehydration indicate the need for revision of calculat ion algorithms for soft-tissue determination. (C) Elsevier Science Inc. 200 1.