COMPARISON OF DUAL-ENERGY X-RAY ABSORPTIOMETRY AND MEASUREMENT OF TOTAL-BODY WATER-CONTENT BY DEUTERIUM-OXIDE DILUTION FOR ESTIMATING BODY-COMPOSITION IN DOGS

Objective-To compare percentage of body fat (%BF) estimates from dual- energy x-ray absorptiometry (DEXA) with those derived from total body water (TBW) determination by deuterium oxide (D2O) dilution. Animals-3 1 healthy, adult, purebred dogs of various ages and breeds (body weigh t, 15 to 39 kg). Procedure-The TBW was measured by D2O dilution and su bsequent analysis via nuclear magnetic resonance (NMR). Blood was coll ected before and 2 hours after IV administration of 275 mg of D2O/kg o f body weight. Plasma was separated and stored at -30 C until analysis by deuterium NMR. The DEXA scans were obtained immediately after bloo d collection from dogs under general anesthesia. Results-Measurements of %BF by DEXA averaged 15.8% higher than calculated estimates of TEW content by D2O dilution. The linear regression of %BF by TEW content o n %BF by DEXA had a slope of 1.04 and a correlation coefficient of 0.8 4, indicating excellent relative agreement between methods despite the significant difference in absolute agreement between the 2 methods. T he average difference between methods did not differ by breed, sex, bo dy condition score, body weight, or %BF, as measured by DEXA. Conclusi on-Comparability of our data with those of previous studies suggest th at DEXA is useful for in vivo estimation of body composition in health y dogs. Body fat estimated by D2O dilution will be less than that dete rmined by DEXA, despite excellent relative agreement between methods.