National Health and Nutrition Examination Survey whole-body dual-energy X-ray absorptiometry reference data for GE Lunar systems.

The National Health and Nutrition Examination Survey (NHANES 1999-2004) includes adult and pediatric comparisons for total body bone and body composition results. Because dual-energy x-ray absorptiometry (DXA) measurements from different manufacturers are not standardized, NHANES reference values currently are applicable only to a single make and model of Hologic DXA system. The purpose of this study was to derive body composition reference curves for GE Healthcare Lunar DXA systems. Published values from the NHANES 1999-2004 survey were acquired from the Centers for Disease Control and Prevention website. Using previously reported cross-calibration equations between Hologic and GE-Lunar, we converted the total body and regional bone and soft-tissue measurements from NHANES 1999-2004 to GE-Lunar values. The LMS (LmsChartMaker Pro Version 3.5) curve fitting method was used to generate GE-Lunar reference curves. Separate curves were generated for each sex and ethnicity. The reference curves were also divided into pediatric (≤20 years old) and adult (>20 years old) groups. Adult reference curves were derived as a function of age. Additional relationships of pediatric DXA values were derived as a function of height, lean mass, and bone area. Robustness was tested between Hologic and GE-Lunar Z-score values. The NHANES 1999-2004 survey included a sample of 20,672 participants' (9630 female) DXA scans. A total of 8056 participants were younger than 20 yr and were included in the pediatric reference data set. Participants enrolled in the study who weighed more than 136 kg (over scanner table limit) were excluded. The average Z-scores comparing the new GE-Lunar reference curves are close to zero, and the standard deviation of the Z-scores are close to one for all variables. As expected, all measurements on the GE-Lunar reference curves for participants younger than 20 yr increase monotonically with age. In the adult population, most of the curves are constant at younger age and drop moderately as age increases. We have presented NHANES reference curves applicable to DXA whole-body scans acquired on GE Healthcare Lunar systems by age, sex and ethnicity. Users of GE Healthcare GE-Lunar DXA systems can now benefit from the large body composition reference data set collected in the NHANES 1999-2004 study.

Can forearm bone mineral density be measured with dxa in the supine position? A study in Chinese population.

The purpose of our study was to confirm that forearm bone mineral density (BMD) results obtained with the patient in the supine position are equivalent to results obtained with patient in the sitting position. The subjects were a Chinese sample of 82 healthy adults (35 males and 47 females; age: 22.5-59.8 yr; body mass index: 17.6-32.4). Forearm BMD was measured by dual-energy X-ray absorptiometry, with the forearm positioned in the sitting and supine positions. Repeated measurements were available for some subjects, and the average of the repeats for those subjects were used in the analysis. The standard enCORE software (GE Lunar, Madison, WI) adjustment for supine position was applied to the BMD values obtained in the supine position for 33% radius, ultradistal (UD) radius, and radius total regions of interest (ROIs) to give sitting-equivalent values. The supine sitting-equivalent results were regressed on the sitting values through the origin. There were statistically significant differences in the UD and total-radius forearm results between supine sitting-equivalent BMD and sitting BMD. The correlation coefficients of UD and total radius were 0.967 and 0.976, respectively. There was no significant difference between supine sitting-equivalent BMD and sitting BMD in the 33% radius forearm BMD. The correlation coefficient of 33% radius was 0.956. For Chinese subjects, there was no significant difference in BMD for the 33% radius, the only ROI recommended for diagnosis by ISCD. Forearm scans could be accomplished with the patient suitably positioned for the routine lumbar spine and proximal femur scans.

Age-related bone mineral density, bone loss rate, prevalence of osteoporosis, and reference database of women at multiple centers in China.

Our study surveyed age-related bone mineral density (BMD), bone loss rate, and prevalence of osteoporosis in women at multiple research centers in China. Survey results were used to establish a BMD reference database for the diagnosis of osteoporosis in Chinese women nationwide. We used dual-energy X-ray absorptiometry bone densitometers to measure BMD at posteroanterior (PA) lumbar spine (L1-L4; n=8142) and proximal femur (n=7290) in female subjects of age 20-89 yr from Beijing, Shanghai, Guangzhou, Chengdu, Nanjing, and Jiaxing. A cubic regression-fitting model was used to describe the change of BMD with age at various skeletal sites. Peak BMD occurred between 30 and 34 yr of age for femur neck and total femur, and between 40 and 44 yr for spine and trochanter measurement sites. Young adult (YA) BMD values (mean and standard deviation [SD], calculated as the average BMD in the age range of 20-39, were 1.116+/-0.12, 0.927+/-0.12, 0.756+/-0.11, and 0.963+/-0.13 g/cm2 at PA spine, femoral neck, trochanter, and total femur, respectively. The BMD of 85-yr-old women reflected a loss of 32% at the spine and 30-35% at femur measurement sites. The prevalence of osteoporosis, defined as a BMD of

Automated assessment of exclusion criteria for DXA lumbar spine scans.

Modern bone densitometry systems using dual-energy X-ray absorptiometry (DXA) automatically analyze lumbar spine scans and provide clinically important information concerning spine bone mineral density (BMD) and fracture risk. Lumbar spine BMD accurately reflects skeletal health and fracture risk in most cases, but degenerative diseases associated with aging may lead to the formation of reactive bone (osteophytes) and other confounding conditions that elevate BMD without a concomitant increase in bone strength or decrease in fracture risk. Automated densitometry software known as computer-aided densitometry (CAD) (GE Medical Systems Lunar) assists the user in identifying scans with common acquisition and analysis irregularities known to influence BMD values. Visual examination of 231 female spine scans measured with DXA found abnormal conditions that could influence BMD results in 29% of scans. The sensitivity and specificity of several criteria for identifying scans with conditions that could influence BMD were determined. A good criterion for identifying scans with abnormal conditions was a T-score difference of greater than 0.9 or 1.0 between L1-L4 mean and individual vertebrae. Criteria for excluding affected vertebrae were determined. Exclusion of affected vertebrae resulted in a mean BMD decrease of nearly 0.6 SD (T-score) among affected scans.