双能X线吸收法测量身体成份精确度的研究

目的确定使用双能X线吸收法（DXA）在测定全身和局部身体成份短期精确度，以指导临床监测方案。方法对10名成年女性志愿者使用DXA（GE LUNAR PRODIGY型）骨密度仪进行了全身体成份测定。每名志愿者测量10次，每天重复5次分在2d（间隔不超过4d）中进行。志愿者测量期间饮食、运动等无明显改变，无腹泻等影响体重的疾病。每次测试需穿同样衣服，每次测量结束均离开骨密度仪，站到地面，下次测量再重新摆放体位。由同一名技师进行操作并分析。计算短期精确度。结果全身、上肢、大腿、躯干、男性区域及女性区域骨矿含量测定的变异系数（CV）分别为1．1％、1．5％、0．9％、2．8％、3．4％和1．7％，脂肪测定的CV分别为1．2％、3．5％、2．3％、2．7％、3．4％和1．8％，组织测定的CV分别为0．7％、1．4％、1．8％、1．6％、2．2％和1．4％，脂肪百分比的CV分别为1．2％、2．4％、1．1％、2．1％、2．3％和1．5％。结论全身体成份测定的CV在0．7％～1．2％，局部体成份测定的CV大部分在1％～2．5％之间。局部测定的精确度不如全身测定的精确度。全身测定和局部测定的精确度均可以满足临床和科研需要。     

Influence of patient's weight on dual-photon absorptiometry and dual-energy X-ray absorptiometry measurements of bone mineral density

Lumbar spine bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA) (Hologic QDR 1000) and by¹⁵³Gd dual-photon absorptiometry (DPA) (Novo Lab 22a) in 120 postmenopausal women. Though a high correlation existed between the two techniques, the ratio between DXA and DPA values was not constant. Using DXA we observed a higher dependence of BMD on weight than in the DPA measurements. To investigate the different behaviour of DXA and DPA machines with weight, we analysed the effects of increasing thickness of soft tissue equivalents on the BMD of the Hologic spine phantom and on the BMD equivalent of an aluminium standard tube. Increasing tissue-equivalent thickness caused the phantom BMD measured by DPA to decrease significantly but had not effect on the DXA measurements. The different behaviour of DPA and DXA equipment with regard to the phantoms could account for the differences observed in the relations between BMD and weight in the patients. Using multiple regression we studied the influence of weight and body mass index on the relation between BMD measured by the two techniques. The introduction of either of these variables into the regression resulted in an improvement of the prediction of the DXA values from the DPA values. However, the residual standard error of the estimate was still higher than the combined precision errors of the two methods, so that no simple relation allows a conversion of BMD_DPA into BMD_DXA. Our results confirm that BMD is positively correlated with weight in postmenopausal women; the influence of weight on BMD is blunted when the Novo Lab 22a DPA machine is used for measuring bone mineral.     

An evaluation of dual-energy X-ray absorptiometry and comparison with dual-photon absorptiometry

Dual-photon absorptiometry (DPA) is a well-established procedure for measuring bone mineral density (BMD). Recently, dual-energy X-ray absorptiomery (DXA) has become available, which has the ability to measure BMD both regionally and in the total body (TB). We have evaluated the in vivo and in vitro precision of a DXA instrument and compared it with a DPA instrument with similar software characteristics.The short-term precision of BMD measurements using DXA was assessed in 65 postmenopausal women who had duplicate scans performed, with repositioning between scans. Precision was 0.9% in the lumbar spine and 1.4% in the femoral neck.The midterm precision of DXA was compared with DPA by scanning 10 volunteers a mean of four times over 24 weeks, on both instruments. The precision of the bone mineral content (BMC) and area measurements was significantly better (P<0.05) with DXA than with DPA. Long-term in vitro precision was assessed by scanning an aluminium spine phantom over 42 weeks, and a cadaveric sample over 52 weeks, on both instruments. Precision was similar using the aluminium phantom, but was significantly improved (P<0.001) when using DXA for scanning the cadaveric sample.Highly significant correlations (allP<0.001) of BMD, BMC and area measurements were observed when 70 volunteers were scanned on both instruments. However, there was a systematic difference in BMD values between the instruments. The precision of TB composition measurements assessed in 16 volunteers, over a 16-week period, were TB BMD 0.65%, TB lean tissue 1.47%, and TB fat tissue 2.73%. The correlation between weight measured by electronic scales and TB mass as measured by DXA, which was assessed in 70 volunteers, was excellent (r=0.99,p<0.001).We conclude that DXA offers improvements in measuring BMD over DPA in terms of faster scanning times and improved resolution, resulting in better precision, with the additional advantage of the ability to measure TB composition with high precision.     

Accuracy and precision of lumbar bone mineral content by dual-energy X-ray absorptiometry in live female monkeys

Summary Dual-energy X-ray absorptiometry (DXA) was used to determine thein vivo bone mineral content (BMC) of lumbar vertebrae in 20 feral adult female cynomolgus macaques (Macaca fascicularis). The ash weight of the third lumbar vertebra (L3) was compared to the measured L3BMC of thein vivo DXA analyses. Correlation between the estimated L3BMC by DXA and the actual ash weight was significant (r=0.965,P<0.01); however, DXA methodology underestimated ash weight on the average of 6.2%. Correlation was significant between two sequentialin vivo DXA scans (r=0.988,P<0.001). Noninvasivein vivo DXA was a fast, precise, and effective method for measuring the lumbar BMC in female cynomolgus macaques.     

应用双能X线骨密度仪探讨糖尿病性骨质疏松症的影响因素

目的探讨2型糖尿病患者骨质疏松的影响因素。方法选择2011年9月至2013年3月在内分泌科住院的男性2型糖尿病患者209例为糖尿病组,选择同期体检的健康男性103例为对照组,应用双能X线骨密度仪(DXA)进行正位腰椎(L1-L4)及左侧股骨骨密度(BMD)测定,检测糖化血红蛋白(Hb A1C)、空腹血糖(FPG)及空腹C肽(CP),并进行统计学分析。结果糖尿病组骨量减少、骨质疏松发生率分别为14.35%、13.87%,明显高于对照组(P0.05)。两组检测者随着年龄增加,骨密度均呈下降趋势,50岁以上糖尿病患者腰椎及股骨颈骨密度均明显低于同龄对照组(P0.05)。糖尿病组骨密度多因素相关性分析显示,糖尿病患者骨密度与年龄、病程、Hb A1C呈显著负相关(P0.05),而与体重指数(BMI)、空腹C肽(CP)呈显著正相关(P0.05)。结论 2型糖尿病患者骨量减少及骨质疏松发生率较健康体检者明显升高;高龄、病程长及血糖控制不良是糖尿病患者BMD降低的危险因素。     

The determination of bone fracture properties by dual-energy X-ray absorptiometry and single-photon absorptiometry: A comparative study

Summary Dual-energy X-ray absorptiometry (DEXA) and single-photon absorptiometry (SPA) were used to quantitate the structural strength and local material properties of healing tibial osteotomies in 32 dogs. Dogs were divided into four equal groups, euthanatized at either 2, 4, 8, or 12 weeks, and imaged with DEXA and SPA. Invasive techniques were used to determine (1) the torsional properties of the bone, (2) the local stiffness properties and calcium content within the bone, and (3) new bone formation and porosity by histology. There were no differences between SPA and DEXA in their associations with the torsional properties of bone. SPA and DEXA had strong correlations with the ultimate torque (R²=0.76, 0.51) and the torsional stiffness (R²=0.68, 0.53) of bone. SPA and DEXA of periosteal callus, endosteal callus, and cortical bone had similar associations with indentation stiffness, calcium content, new bone formation, and porosity. SPA of gap tissue had significantly stronger associations with these four parameters than DEXA (P<0.05). Correlation coefficients (R²) with these local material properties ranged as high as 0.82 for SPA with new bone formation in the gap tissue and 0.73 for DEXA with indentation stiffness of periosteal callus.     

Vertebral bone mineral density measured laterally by dual-energy X-ray absorptiometry

The bone mineral density (BMD) of lumbar vertebrae in the anteroposterior (AP) view may be overestimated in osteoarthritis or with aortic calcification, which are common in elderly. Furthermore, the risk of spinal crush fracture should be more closely related inversely to the BMD of the vertebral body than to that of the posterior arch. Therefore, we measured BMD of lumbar vertebrae in lateral (LAT) view (L2–L3), using a standard dual-energy X-ray absorptiometer (DEXA), thus eliminating most of the posterior spinal elements. The precision of BMD LAT measurement was determined both in vitro and in healthy volunteers. Then, we compared the capability of BMD LAT and BMD AP scans for monitoring bone loss related to age and for discriminating the BMD of postmenopausal women with nontraumatic vertebral fractures from that of young subjects. In vitro, when a spine phantom was placed in lateral position in the middle of 26 cm of water in order to simulate both soft-tissue thickness and X-ray source remoteness, the coefficient of variation (CV) of six repeated determinations of BMD was 1.0%. In vivo, the CV of paired BMD LAT measurements obtained in 20 healthy volunteers after repositioning was 2.8%. The age-related difference between a peak bone mass group estimated in a group of 27 healthy women aged 20 to 35 years and a group of 50 women aged 60 to 75 years, in whom neither vertebral fracture nor osteoporosis risk factors could be detected, were 21.7% and 37.6% in AP and LAT view, respectively. An arbitrary BMD fracture threshold was defined in AP and LAT views as the 90th percentile of the BMD value of a group of 22 osteoporotic women with vertebral fractures. The distribution of BMD AP and LAT above and below this threshold in 169 consecutively screened women without vertebral fracture was then analysed. In both AP and LAT views, 39.1% and 31.3% had BMD values above and below this threshold, respectively. Of the remaining, 16.0% had a BMD below this threshold only in AP and 13.6% only in LAT view. Thus, if BMD LAT was a better reflection of vertebral body bone mass than BMD AP, and thereby a better predictor of the resistance to crush fracture, our results would suggest that only the use of the standard AP view could under- or overestimate spinal fracture risk in about 30% of women screened for osteoporosis. In conclusion, our results indicate that BMD measurement in lateral view is feasible with a standard DEXA instrument. This mode of scanning, besides overcoming artefacts due to osteoarthritis of the posterior arch and aortic calcifications, appears to provide a greater sensitivity for assessing bone mass loss of the vertebral body than the standard anteroposterior scan.     

Optimizing data acquisition and analysis of morphometric X-ray absorptiometry

Morphometric X-ray absorptiometry (MXA) uses dual-energy X-ray absorptiometry (DXA) scanners to perform vertebral morphometric measurements of the vertebrae. In this study we evaluated the four available MXA scan modes - single-energy (SE) and dual-energy fast (F), array (A) and high definition (HD) - on a commercial bone densitometer (Hologic QDR-4500A). Sixty postmenopausal women (mean age 59 years, range 40–73 years) were recruited and split into two groups matched for body mass index (BMI, kg/m²). Three MXA scans, covering 13 vertebrae from T4 to L4, were acquired on each subject; all subjects were scanned in SE and A modes, while the third scan was performed in F mode in group 1 and in HD mode in group 2. Subjects were invited to return 6 months after the commencement of the study to repeat their scans. The HD mode produced the most reliable image, with 97% of all scans analyzable to T7 and the fewest vertebrae being lost to analysis (1.5/13 vertebrae lost per scan). A SE + HD combination (using whichever image allows the analysis of more vertebrae) further decreased the number of vertebrae lost to 0.8 of 13 vertebrae, i.e. a typical scan was analyzable up to and including T5. BMI had a noticeable and scan-mode-dependent effect on MXA image quality, an increase in the number of vertebrae lost to analysis occurring once BMI exceeded 30. BMD had a far smaller effect on image quality and no effect at all using the SE+HD combination. Precision (CV%) was similar for all three dual-energy modes at around 3.5% without the scan ‘compare’ facility and 2.6% with it. The best precision was obtained with SE scan (2.7%/2.2%). BMI and BMD had little or no effect on precision. We conclude that optimal results are obtained by the acquisition of both SE and HD scans. However, for rapid assessment by trained operators SE scans alone offer almost equal utility.     

Bone mineral density measured by dual-energy X-ray absorptiometry in healthy finnish women

Summary A cross-sectional study of 351 healthy Finnish women aged 20–76 years was done to establish reference values of bone mineral density (BMD) using dual-energy X-ray absorptiometry (DEXA). The effects of age and of several physical and lifestyle factors on BMD of the lumbar spine and proximal femur (femoral neck, trochanter, and Ward's triangle area) were investigated. Altogether 58 women were excluded from the final analysis due to significant spinal osteoarthritis or other diseases or drugs known to influence calcium or bone metabolism. The precision of the method was 0.9, 1.2, 2.7, and 2.4% in the lumbar, femoral neck, Ward's triangle and trochanter area, respectively. Lumbar BMD was increased by 30% (P<0.001) in 15 patients with osteoarthritis (21% of women 50 years or older), but it was apparently unaffected in 5 cases with aortic calcification. Except for the trochanter area, BMD diminished along with age, and this was significant after the menopause. The peak of mean BMD was observed at the age of 31–35 years in the spine and at the age of 20–25 years in the femoral neck and Ward's triangle. BMD was in a positive relationship to weight both in premenopausal and postmenopausal women and to the use of oral contraceptives in premenopausal women and to that of estrogen replacement therapy in postmenopausal women. Labors and pregnancies had a weak positive effect on BMD in premenopausal women. As compared with nonusers premenopausal women who had used alcohol showed a slightly decreased BMD of Ward's triangle. In postmenopausal women there was a positive correlation between alcohol intake and BMD.     

Bone loss around failed femoral implant measured by dual-energy X-ray absorptiometry

Periprosthetic bone mineral density (BMD) and its changes after primary total hip arthroplasty (THA) have been studied extensively, but quantitative data on BMD around loosened prostheses are still lacking. In this study, using dual-energy X-ray absorptiometry (DXA), we determined periprosthetic BMD in 19 patients with failed primary THA. There was a decrease in BMD (8.8%–25.5%) in every Gruen zone as compared with the patient's non-operated (control) side. Although the bone loss was most significant in the proximal femur, as in primary THA, the pattern of bone loss around the failed THA differred from the typical remodeling seen after successful THA. We suggest that quantitation of bone mass around the failed femoral stem is possible. Remarkable generalized bone loss around the stem is associated with a loosened prosthesis. Received: November 12, 1999 / Accepted: December 24, 1999     

股骨近端骨密度的测量

双能X线骨密度仪检测骨密度是诊断骨质疏松症和疗效随访的金标准,特别是髋部骨密度的测量对于骨折的预测尤其测定部位本身骨折的预测作用较大.由于脊柱部位的骨密度测量值易受到脊柱退行性疾病的病理改变如退行性侧凸、骨赘增生、腰椎间盘突出等影响,测量的准确性下降.因而近年来欧美国家临床试验也好或者骨质疏松诊疗也好,大都以股骨近端的BMD测定为标准.本文就股骨近端解剖特点、骨密度测量的意义、方法以及测量的注意点作一个综述,以期帮助临床医生或技术员全面评估股骨近端骨密度测定的意义.     

Spurious dual-energy X-ray absorptiometry images in a patient exposed to the contrast agent thorotrast

A 69-year-old woman presented with a 20-year history of back pain and a 10 cm height loss. She had received an injection of the contrast agent, Thorotrast, at age 23. There was no history of fluoride exposure. Multiple vertebral compression fractures were seen on radiographs. Dual-energy X-ray absorptiometry (DXA) scans revealed high normal bone mineral content on the spine and, on whole body scan, visualization of the liver and spleen regions. Given the attenuation coefficient of thorium and the thorium concentrations reported for liver, spleen and vertebral bodies, it is likely that thorium was visualized in the liver and spleen and that it caused spurious elevation in her DXA bone mineral content values.     

Hologic和Norland骨密度仪的精确度比较和数据换算

目的应用Hologic椎体体模和欧洲体模对不同骨密度仪进行横向及纵向评估,并应用 Shewhart规则进行仪器质量控制,同时比较Hologic及Norland骨密度仪活体精确度差异,探讨两者的数据换算关系。方法 Norland XR-36和Hologic Delphi A骨密度仪分别用欧洲体模连续扫描10次,每次扫描均应重新放置体模,用Shewhart规则对两台机器每日校准值进行质控。另外分别采用两套系统对30名志愿者的脊椎骨和左股骨的骨密度进行了两次重定位测量,计算精确度误差,通过F-检验比较差异。两台骨密度仪分别用Hologic腰椎体模每天测5 次,连续8 d,建立两仪器之间的数据换算关系。结果①Norland XR-36和Hologic Delphi A 骨密度仪用Shewhart规则监控均符合,Norhand XR-36连续3 m变异系数百分比为0．38％～ 0．53％,Hologic Delphi A连续3 m变异系数百分比为0．37％～0．41％,Norland-XR-36所测欧洲体模高、中、低为1．355,0．944,0．582,与真值相差9．6％,5．6％,16．4％;Hologic Delphi A高、中、低均值为1．423,0．940,0．534,与真值相差5．1％,6％,6．8％。②Hologic Delphi A的活体精密度高于Norland XR-36骨密度仪。③两仪器间BMD,BMC,Brea绝对值差异明显,但可用线性回归方程进行数据换算:BMD Hologic=0．970 Norland 0．026(r= 0．980;P<0．01);BMC Hologic=1．005 Norland 0．128(r=0．989;P<0．01);Brea Hologic=1．056 Norland-0．592(r=0．978;P<0．01)。结论以欧洲体模评估Norland XR-36和 Hologic Delphi A骨密度仪均有良好的精确度,但两仪器之间的数据不能直接互用,可用回归方程进行数据校正。质量控制是确保骨密度仪理想的精确度的必要措施。     

Bone densitometry of the forearm: Comparison of single-photon and dual-energy X-ray absorptiometry

Forearm bone mineral densitometry was performed initially by single-photon absorptiometry (SPA), but is now achievable by dual-energy X-ray absorptiometry (DXA) as well, with a good correlation between both measurements. However, it is still unknown whether: (1) short-term precision of DXA is superior to SPA and (2) identical regions of interest (ROT) are mandatory to correlate SPA with DXA. The aim of this study was to answer these questions using a commercial system for DXA (DXA-FAS) and to test an in-house system using spine DXA and a soft-tissue compensator (DXA-STC). In ten subjects, four measurements on the same day showed significantly lower (p < 0.05) coefficients of variation (CV) for bone mineral density (BMD) by DXA-FAS (proximal site: 0.74%; ultradistal site: 1.20%) than by SPA (1.26% and 2.25%). However, the CV for bone mineral content (BMC) were similar for DXA-FAS (0.73% and 1.58%) and SPA (0.79% and 1.34%). The significant difference (p < 0.05) for surface calculation by DXA-FAS (1.24% and 0.93%) compared with SPA (2.36% and 1.28%) explains all the advantages of DXA-FAS for short-term precision. The measurements taken on the same day on the ulna and the radius or on the radius alone by SPA, DXA-FAS, and DXA-STC on 108 subjects aged 18–80 years were highly correlated [r ranging from 0.925 to 0.995 (p < 0.0001) and standard error of the estimate from 3.15% to 8.89%]. The need for a manual adjustment of the ROT was found to be mandatory for BMC but not BMD assessment. The use of DXA-STC is a fast method for forearm bone densitometry and its correlation with SPA is very high. However, its short-term precision for BMC (3.00% and 1.54%), BMD (2.15% and 1.12%), and surfaces (1.99% and 1.12%) is significantly higher (p < 0.05) than that of DXA-FAS. We conclude that short-term precision of DXA is better than that of SPA only for BMD and surface measurement but not for BMC. ROT should be adjusted manually for the assessment of BMC but not for that of BMD.     

Comparison of antero-posterior and lateral measurements of the vertebral mineral contents by dual-energy x-ray absorptiometry

Bone mineral measurements of the 2nd and 3rd vertebrae were made using dual energy x-ray absorptiometry (DEXA) in both antero-posterior (AP) and lateral (Lat) projections in 49 women (Group I; 24 young controls, II; 11 elderly controls, III; 14 osteoporotics). The coefficients of variation of the AP and Lat measurements of BMC in 3 young women were 2.2% and 8.4% of the respective mean values. In Group I, BMCs obtained by the Lat measurement were 11.6±15.7% below BMC_AP (p<0.05). In Group II and III, on the other hands, BMC_Lat was as low as below 34.2±11.9% (Group II) and 40.1±21.5% (Group III) of respective AP contents (p<0.01). This discrepancy between BM C_Lat and BMC_AP in Group II and III could not be acounted by the measurement error of Lat determination alone. Furthermore, the difference of bone mineral density (BMD) between Group I and II (or III) appeared to be much more pronounced when compared by the data obtained from the Lat measurements than the comparison using BMD_AP. Extra-skeltal calcification projected on the AP plane, including calcified aorta and ligaments, may attribute such a difference between AP and Lat measurements. Our observation indicated the possibility of an overestimation of BMC and BMD by the AP determination of the spine. Therfore, an improvement of the reproducibility to measure the spine by the Lat determination with DEXA is mandatory for the detection of subclinical osteoporosis.     

A comparison of two dual-energy X-ray absorptiometry systems for spinal bone mineral measurement

Summary Two dual-energy X-ray absorptiometry (DEXA) systems—the Hologic QDR-1000 and the Norland XR-26 bone densitometers—were evaluated in terms of precision, accuracy, linearity of response, X-ray exposure, and correlation of in vivo spinal measurements. In vitro precision and accuracy studies were performed using the Hologic anthropomorphic spine phantom; linearity of response was determined with increasing thicknesses of aluminum slabs and concentrations of Tums E-X in a constant-level water bath. Both systems were comparable in precision, achieving coefficients of variation (CVs) of less than 1% in bone mineral content (BMC, g), bone area (cm²), and bone mineral density (BMD, g/cm²). Both were accurate in their determination of BMC, bone area, and BMD with reference to the Hologic spine phantom. Both systems also showed good BMC and BMD linearity of response. Measured X-ray skin surface exposures for the Hologic and the Norland systems were 3.11 and 3.02 mR, respectively. In vivo spinal measurements (n=65) on the systems were highly correlated (BMC: r=0.993, SEE=1.770 g; area: r=0.984, SEE=1.713 cm²; BMD: r=0.990, SEE=0.028 g/cm²). In conclusion, both systems are comparable in terms of precision, accuracy, linearity of response, and exposure efficiency.     

Specific evaluation of localized bone mass and bone loss in the rat using dual-energy X-ray absorptiometry subregional analysis

Dual-energy X-ray absorptiometry (DXA), together with the use of ultra-high resolution software, recently appeared as an accurate method for determining bone mineral density (BMD) in the rat. In order to assess the ability of this technique to detect changes in bone mass in the rat rapidly and precisely, we measured BMD at various sites of the femur using DXA subregional analysis. In particular, we studied the BMD of the metaphyseal part of the femur (M-BMD) rich in trabecular bone, and compared the values obtained with the cancellous bone volume measured by histomorphometry. In short-term ovariectomized animals (experiment 1), M-BMD was the only parameter to differentiate statistically between 10 ovariectomized (OVX) and 10 SHAM-operated (SHAM) rats (–11.2%,p<0.01) 9 days after surgery. M-BMD still expressed the greatest variation between OVX and SHAM rats 42 days following ovariectomy (experiment 2) (–16.1%,p<0.001 v –6.2%,p<0.01 for the total femur BMD) and confirmed previous data demonstrating a greater loss of cancellous than cortical bone after cessation of ovarian activity. M-BMD was highly correlated with cancellous bone volume (BV) in normal (r=0.82,p<0.001,n=30), OVX (r=0.77,p<0.001,n=22) and SHAM (r=0.88,p<0.001,n=21) rats. Furthermore, subcutaneous treatment with rat parathyroid hormone fragment (1–34) (r-PTH(1-34)) partially and significantly protected animals from trabecular osteopenia induced by OVX; there was a similar degree of protection of BV and M-BMD (50% and 61% respectively), while BMD of the entire femur achieved complete protection. This M-BMD measurement, specifically reflecting cancellous bone mass as confirmed by the correlation study and the response to PTH treatment, is a sensitve and simple method which can be used to assess any precocious modifications of bone density under physiopathological or therapeutic conditions in experimental rat models of bone loss.     

The effects of standardization and reference values on patient classification for spine and femur dual-energy X-ray absorptiometry

The effect of two methods for standardizing dual-energy X-ray absorptiometry (DXA) measurements on patient classification by theT-score has been determined for a group of over 2000 patients. The methods proposed by the International DXA Standardization Committee and the European Community's COMAC-BME group were used in conjunction with young reference data from the major DXA manufacturers, the COMAC-BME group and the third US National Health and Nutrition Examination Survey (NHANES III). The two standardization techniques produced dissimilar classifications as measured by the kappa statistic (=0.34–0.90), especially for the femoral neck, with up to 24.3% of patients reclassified from osteopenic to normal and 18.6% reclassified from osteoporotic to osteopenic when the standardization method was changed. Considering the effects of both reference data and standardization techniques together, there was a wide variation of patient classification, with the number of patients classified as osteoporotic varying from 9.6% to 21.1% for the postero-anterior spine L2–4 region and from 2.3% to 27.6% for the femoral neck. The agreement between different classifications ranged widely, from very poor to excellent (=0.02–0.98). The creation of standardized reference data must be an important priority in order to harmonize patient management using standardized BMD measurements. The choice of standardization technique, however, must be addressed in light of the results presented here.     

Correlations of dual-energy X-ray absorptiometry,quantitative computed tomography,and single photon absorptiometry with spinal and non-spinal fractures

Controversy continues as to which method of measuring bone mineral density (BMD) best detects osteoporosis and best correlates with fractures of the spine, hip and elsewhere. To answer these questions the prevalence of fractures was carefully determined among 90 subjects (70 with osteoporosis, 6 with mild primary hyperparathyroidism, 1 with osteomalacia and 13 normals) and simultaneous measurements were made using spinal computed tomography (QCT), spinal anteroposterior (AP) and supine lateral dual X-ray absorptiometry (DXA), femoral neck and total hip DXA, and distal third radial DXA and single photon absorptiometry (SPA). The DXA measurements which had the greatest sensitivity in detecting osteoporosis (defined as a BMD lower than –2.5 SD of peak bone mass at age 30 years) were the supine lateral spine DXA (84%) and femoral neck DXA (75%); less sensitive were the DXA measurements of the distal third of the radius (61%) and AP spine (51%). DXA measurements of the femoral neck and distal third of the radius were more useful than spinal measurements in detecting the osteopenia of mild primary hyperparathyroidism. Vertebral compression fractures (VCF) correlated well with spinal QCT (r=–0.38) and lateral spine DXA (r=–0.41), but poorly with AP spine DXA (r=–0.17) and distal third radial DXA (r=–0.02). Non-spinal fractures correlated best with the distal third radial DXA (r=–0.42). In conclusion, spinal QCT, supine lateral spine DXA and femoral neck DXA are the best BMD methods to screen for osteoporosis, whereas AP spine DXA is a poor screening method in women over 60 years of age. Spinal QCT and lateral spine DXA correlate well with VCFs, whereas correlations of VCFs with AP spine DXA, femoral neck DXA and distal third radial DXA are poor.     

Implementation of an osteoporosis research program with a mobile dual-energy X-ray absorptiometry unit: The Montana/Wyoming experience

To expedite recruitment, and subject participation, for a large clinical osteoporosis therapy trial utilizing the bisphosphonate ibandronate, an integrated network of 13 satellite clinical sites was developed, linked by a mobile clinic vehicle transporting a dual-energy X-ray absorptiometry (DXA) unit. A predominantly rural area of the United States (Montana, northern Wyoming) was accessed for the project, due to the large pool of potential subjects living in this area who were not yet involved in osteoporosis clinical studies. The results of the project to date (through 10 months) confirm the feasibility of such a study design, with 1774 subjects screened by DXA for the study, and 280 (15.8%) accepted. The mobile DXA unit has functioned according to specifications for a stationary DXA machine, with the stability of spine phantom measurements over 10 months assessed as a coefficient of variation of 0.46%. The success of the project validates the concept of performing clinical osteoporosis therapy trials in previously underutilized rural community settings, facilitated by a satellite site network and mobile clinic.