FAN BEAM DUAL X-RAY ABSORPTIOMETRY UNDERESTIMATES FATNESS IN ADULTS.

Authors: SCHOELLER, D - UNIV OF WISCONSIN MADISON; TYLAVSKY, F - UNIV OF TENNESSEE MEMPHIS; Baer, David; BORRUD, L - NAT CTR FOR HEALTH STATIS; CHUMLEA, W - WRIGHT STATE UNIV; EARTHMAN, C - VA POLYTECHNIC INST; FUERST, T - UNIV OF CA SAN FRAN; HARRIS, T - NAT INST ON AGING NIH; HEYMSFIELD, S - ST. LUKE'S ROOSEVELT HOSP; HORLICK, M - ST. LUKE'S ROOSEVELT HOSP; Lukaski, Henry

Submitted to: The American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2004
Publication Date: 5/1/2005
Citation: Schoeller, D.A., Tylavsky, F., Baer, D.J., Borrud, L., Chumlea, W.C., Earthman, C., Fuerst, T., Harris, T., Heymsfield, S., Horlick, M., Lohman, T.G., Lukaski, H.C., Shepherd, J., Siervogel, R.M., Borrud, L.G. 2005. QDR 4500A dual-energy X-ray absorptiometer underestimates fat mass in comparison with criterion methods in adults. American Journal of Clinical Nutrition. 81:1018-1025.

Interpretive Summary: The accurate assessment of body composition is critical. Dual energy X-ray absorptiometry (DXA) has become one of the most frequently used methods for estimating human body composition. Although the DXA technique has been validated for the measurement of fat-free mass and fat mass, it has been reported that there are differences in the results obtained from instruments produced by different manufacturers, as well as different models produced by the same manufacturer. DXA-derived body composition data were obtained from seven research centers. Six data sets were provided by the investigators and one was a published data set. There were 1198 subjects aged from 19-82 years with a body mass index from 17 to 65 kg/m2. The fan beam DXA over estimated fat-free mass in all data sets (p<0.05). The difference (mean+SE) was 5+1% when averaged across data sets. It is recommended that the fat-free mass estimate from a fan beam QDR4500A should be reduced by 5% and fat mass be increased to weight from the DXA - 0.95*FFM from the DXA. These data are important to individuals who have body composition assessed with this technique, to scientists working in the field of obesity and weight management and to several federal government agencies (particularly the Department of Health and Human Services who is responsible for national health surveys using this technique.) Data from these surveys are used by the federal government to establish national health policies regarding body weight and obesity.

Technical Abstract: Dual Energy X-ray Absorptiometry (DXA) has become one of the most frequently used methods for estimating human body composition. Although the DXA technique has been validated for the measurement of fat-free mass and fat mass, it has been reported that there are differences in the results obtained from instruments produced by different manufacturers, as well as different models produced by the same manufacturer. Based on review of available data, it appears that Fan Beam DXA overestimates fat-free mass (FFM). DXA-derived body composition data were obtained from seven research centers. Six data sets were provided by the investigators and one was a published data set. The data included fat mass and fat-free mass measured on a QDR4500A and criteria measurements of body composition from total body water by dilution at four centers, densitometry from one center, and four-compartment analysis at two centers. There were 1198 subjects aged from 19-82 years with a body mass index from 17 to 65 kg/m2. The fan beam DXA over estimated fat-free mass in all data sets (p<0.05). The difference (mean+SE) was 5+1% when averaged across data sets. It is recommended that the fat-free mass estimate from a fan beam QDR4500A should be reduced by 5% and fat mass be increased to weight from the DXA - 0.95*FFM from the DXA accordingly. This is particularly important because the National Health and Nutrition Survey is using the QDR4500A to assess body composition in a nationally representative sample of individuals in the United States.