To Monitor Precisions Of The DXA Measurements At Total And Regional Bone Mineral Density And Body Composition

Objective To monitor precisions of the DXA measurements at total and regional bone mineral density and body composition.Materials and methods To scan the GE-Lunar phantom daily by DXA, and to set up a Shewhart chart for monitoring the machine's performance and stability. Thirty volunteers were recruited; each subject was scanned twice by DXA in the same day. Measurement sites included lumbar spine, proximal femur and whole body. Precision errors were expressed as root mean square of CV (RMS-CV).Results The average values of phantom is 1.196g/cm2, according to the±1.5% control principles of Shewhart, the range of normal value is 1.178 g/cm2?1.214 g/cm2. If the value exceeds the range, we should contact engineers for service. Mean precision errors of bone mineral density measurements at lumbar spine, femoral neck, Ward's triangle, great trochanter and total femur ranged from 0.6%?1.2%, with the lowest of 0.6% at total femur, as well as with the highest of 1.2% at Ward's triangle; Mean precision error of bone mineral density measurements at total body and regional sites ranged from 0.7% to 2.0%, with the lowest of 0.7% for the total body measurement. Mean precision errors of lean measurements at total and regional sites ranged from 0.6% to 2.1%, with the lowest of o.6% for the total lean measurement. Mean precision errors of fat measurements at total and regional sites ranged from 1.0% to 3.2%, with the lowest of 1.0% for the whole body fat measurement.Conclusion High precisions of DXA measurement at total and regional bone mineral density and body composition could meet clinical and research needs. Objective To evaluate HIV-infected patient's body composition changes by Dual X-ray absorptiometry (DXA) and to analyze factors associated with lipodystrophy (LD).Materials and methods Total body composition was measured by DXA in HIV-infected patients and healthy people. The age of 66 cases of HIV-infected adult people who were on HAART was 20-71 years, mean age was 40.1±9.5 years. Control group was 35 cases of healthy people, mean age was 41.0±9.4 years, aged 28-69 year. Patients were divided into LD and Non-LD groups according to whether they were complicated with lipodystrophy. Healthy people were selected as controls.Results Fat mass (FM) of HIV-infected men was correlated negatively with the duration of HIV infection and with the duration of HAART regimen (?S=-0.448,-0.563; P=0.032, 0.000, respectively); Multiple linear regression results showed that FM had positive correlation with weight and bone mineral content (BMC), and had negative correlation with lean mass(LM). Total and regional FM were found significant differences between LD patients, Non-LD patients and controls, the lowest in LD patients and the highest in controls (P<0.05). Total, trunk and legs BMC of LD patients were lower than that of controls (P<0.05). Lumbar bone mineral density (BMD) of LD patients was lower than that of Non-LD patients and controls (P=0.021,0.007). LM of LD patients was higher than that of Non-LD patients, and trunk LM had statistical difference between the two groups (P=0.003). Premenopausal women'FM was uncorrelated with the duration of HIV infection and with the duration of HAART therapy (?S=0.218,-0.252, P=0.384, 0.224). Multiple linear regression results showed that FM had positive correlation with weight and negative correlation with lean mass (LM). FM was significantly lower in LD patients and Non-LD patients than that in controls (P<0.05).Total, trunk and legs BMC of LD patients were statistically lower than that of controls. Lumbar BMD of LD patients were lower than that of Non-LD patients and controls (P=0.011,0.004). LM of LD patients was higher than that of Non-LD patients, legs LM had significant difference between LD patients and Non-LD patients P<0.05.Conclusions Fat mass decreased with the time of HIV infection and/or HAART regimen. Significant peripheral and central fat loss were seen in HIV-LD patients, meanwhile, decreased BMC and increased LM were also found in them. Therefore, applying DXA to assess HIV-infected patient's body composition changes could provide objective information for physicians to prevent lipodystrophy and osteoporosis.