Inclusion of Regional Body Composition Parameters Improves Bone Mineral Density Cross-Calibration Between GE Lunar Prodigy and iDXA Densitometers.

Since 1989, the Kuopio Osteoporosis Risk Factor and Prevention (OSTPRE, n = 14220) Study has followed long-term changes of bone mineral density (BMD) and body composition in women with GE Lunar devices. During the course of OSTPRE, the dual-energy X-ray absorptiometry device had to be replaced by a newer model. Then, it was essential to determine whether systematic measurement differences in BMD and body composition will occur. As a part of the OSTPRE study, BMD was measured in 54 women, whereas body composition was determined in 55 women, aged 27-71, by using both the GE Healthcare Lunar Prodigy and iDXA narrow-angle fan beam densitometers during the same visit. The total body fat mass (FM) and lean body mass (LBM) results of these scanners showed a high linear correlation (r = 0.981-0.994, p < 0.0001). However, the mean total body FM and LBM values measured by iDXA were on average 2.3% (0.5 kg, 95% confidence interval: 0.3-0.7 kg) higher and 0.8% (0.3 kg, 95% confidence interval: 0.1-0.6 kg) lower, respectively, than those measured by Prodigy. Inclusion of local soft tissue measurements (total body LBM, legs/android FM) improved the agreement of total body, total hip, and lumbar spine BMD values between the devices but not femoral neck BMD agreement. Equations, based on linear regression analyses, were derived to minimize differences between the instruments. Then, the differences in BMD and body composition measurements were negligible between Prodigy and iDXA. Using correction equations enables an objective comparison of longitudinal BMD and body composition measurements.

Cross-Calibration of GE Healthcare Lunar Prodigy and iDXA Dual-Energy X-Ray Densitometers for Bone Mineral Measurements.

In long-term prospective studies, dual-energy X-ray absorptiometry (DXA) devices need to be inevitably changed. It is essential to assess whether systematic differences will exist between measurements with the new and old device. A group of female volunteers (21-72 years) underwent anteroposterior lumbar spine L2-L4 (n = 72), proximal femur (n = 72), and total body (n = 62) measurements with the Prodigy and the iDXA scanners at the same visit. The bone mineral density (BMD) measurements with these two scanners showed a high linear association at all tested sites (r = 0.962-0.995; p < 0.0001). The average iDXA BMD values were 1.5%, 0.5%, and 0.9% higher than those of Prodigy for lumbar spine (L2-L4) (p < 0.0001), femoral neck (p = 0.048), and total hip (p < 0.0001), respectively. Total body BMD values measured with the iDXA were -1.3% lower (p < 0.0001) than those measured with the Prodigy. For total body, lumbar spine, and femoral neck, the BMD differences as measured with these two devices were independent of subject height and weight. Linear correction equations were developed to ensure comparability of BMD measurements obtained with both DXA scanners. Importantly, use of equations from previous studies would have increased the discrepancy between these particular DXA scanners, especially at hip and at spine.

Body fat distribution is associated with lumbar spine bone density independently of body weight in postmenopausal women.

OBJECTIVE: To assess the association between the body fat distribution and axial bone mineral density (BMD) in postmenopausal women with or without hormone replacement therapy (HRT). DESIGN: Cross-sectional population-based study. SETTING: University of Eastern Finland, Bone and Cartilage Research Unit, Kuopio, Finland. POPULATION: 198 postmenopausal women, mean age 67.5 (1.9 SD), mean BMI 27.1 (3.9 SD). METHODS: Regional body composition and BMD assessed by dual X-ray absorptiometry (DXA, Prodigy). MAIN OUTCOME MEASURES: Spinal and Femoral BMD. RESULTS: Out of the body composition parameters, FM was the main determinant of postmenopausal bone mass. Only the lumbar spine (L2-L4) BMD, not the femoral neck BMD, was positively associated with the trunk FM. Positive trends for association were revealed between the spinal BMD and the trunk FM regardless of the use of HRT. Adjustments did not change the results. CONCLUSIONS: Higher trunk fat mass was associated with the spinal BMD, but not with the hip BMD in postmenopausal women, irrespective of the HRT use. In addition to biological factors, uncertainties related to DXA measurements in patients with varying body mass may contribute to this phenomenon.

Is discordance in bone measurements affected by body composition or anthropometry? A comparative study between peripheral and central devices.

Screening of osteoporosis using peripheral bone measurements has become more common, even though diagnostic discrepancies are known to exist between peripheral dual-energy X-ray (pDXA) or quantitative ultrasound (QUS) and central DXA measurements. Values of diagnostic parameters such as bone mineral density, speed of (ultra)sound, and broadband ultrasound attenuation are affected by bone size and soft tissue composition. However, their significance for the discordance between peripheral and central techniques is unclear. In this study, bone status and total body composition of 139 women (mean age 68.3 yr [1.7 SD], mean body mass index 26.5 kg/m2 [3.6 SD]) were assessed by 3 GE Lunar devices. Heel pDXA and heel QUS were conducted using peripheral instantaneous X-ray imaging (PIXI) and Achilles, respectively, and central DXA measurements were taken at the posterior-anterior lumbar spine (L2-L4) and at the left femoral neck using Prodigy. Positive significant associations were found between body height or fat (%) and most DXA or QUS parameters. The discordance between the site-dependent DXA or QUS T-score values typically increased (p<0.05) as a function of body weight or fat (%), but not with body height. On an average, body adiposity accounted for less than 11% of the differences between the techniques; however, increase of total body fat from 20% to 45% led to a discrepancy of one T-score between DXA(HEEL) and QUS(HEEL). To avoid diagnostic bias, comparative assessment of the devices using the same population is recommended.

Cross-calibration of Lunar DPX-IQ and DPX dual-energy x-ray densitometers for bone mineral measurements in women: effect of body anthropometry.

When dual-energy X-ray absorptiometry (DXA) instruments are replaced, it is essential to determine if systematic differences in measurements occur. As a part of the Kuopio Osteoporosis Risk Factor and Prevention study (N=14,220), a group of women, aged 36 to 69 yr underwent anteroposterior lumbar spine L2 to L4 (n=89) and proximal femur scans (n=88) by the Lunar DPX and DPX-IQ, respectively, during the same visit. A high linear association (r from 0.944 to 0.989, p<0.001) between the two scanners was established for lumbar spine and proximal femur bone mineral density (BMD). The average DPX values for BMD were 1.1% and 2.0% higher than those of DPX-IQ for the lumbar spine (p<0.001) and Ward's triangle (p=0.001), respectively. Femoral neck BMD values by the DPX were 1.4% lower (p<0.001) compared to DPX-IQ. The difference between trochanter BMD results (0.1%) was not significant (p=0.809). In the femoral neck and trochanter, but not in the lumbar spine or Ward's triangle, the differences in BMD values of the two machines were found to depend on body mass index. After linear formulas based on simple and multivariate linear regression analyses were calculated, the differences were negligible, enabling objective comparison of longitudinal measurements.

Changes in body weight and onset of hypertension in perimenopausal women.

We assessed the determinants of onset of hypertension in a large, prospective population-based study of perimenopausal women from the Kuopio Osteoporosis Risk Factor and Prevention (OSTPRE) study. The data collection started in 1989, when a baseline postal inquiry was sent to all women aged 47-56 years (n=14 220) residing in the Kuopio Province in Eastern Finland. Names, social security numbers and addresses were obtained from the Population Register Centre of Finland. A total of 11 798 women responded at baseline and at 5-year follow-up in 1994. After the exclusion of 1777 women with prevalent hypertension at baseline and women with missing height or weight information, the study population consisted of 9485 without established hypertension at baseline. New cases of established hypertension during the follow-up (n=908) were ascertained with the Registry of Specially Refunded Drugs of the Finnish Social Insurance Institution (SII). According to the National Health Insurance, the SII granted 90% reimbursement for drug costs in defined chronic illnesses necessitating continuous medication, like arterial hypertension. Weight and weight gain both raised the risk by 5% per kg (P<0.001). Weight gain of 4-6 kg increased the risk of hypertension 1.25 times and a gain of more than 7 kg 1.65 times compared with the control (zero) group. To conclude, the onset of hypertension in peri- and early postmenopausal women was related to an increase in body weight despite controlling for initial body weight, reported physical activity and use of HRT. Therefore, preventing weight gain by dietary means and exercise is of great importance at menopausal age.