A comparison of a peripheral DXA system with conventional densitometry of the spine and femur

Bone health in healthy Indian population aged 50 years and above

One thousand six hundred healthy subjects aged more than 50 years, residing in Delhi, were evaluated for bone mineral metabolic parameters. High prevalence of osteoporosis (35.1% subjects) was observed in this population. Bone mineral density (BMD) correlated positively with body mass index (BMI) and negatively with PTH levels. No correlation was observed with serum 25(OH)D levels.

INTRODUCTION

To assess the bone health status in elderly Indians and compare peripheral DXA (pDXA) with central DXA in evaluation of osteoporosis.

METHODS

The study involved 1,600 healthy subjects more than 50 years of age residing in Delhi, India, who underwent anthropometric, biochemical, and hormonal evaluation. BMD was measured by DXA at lumbar spine, hip, and distal radius; and by pDXA at forearm and calcaneum.

RESULTS

Seven hundred ninety-two males and 808 postmenopausal females, with a mean age of 57.67 ± 9.46 years were evaluated. Osteoporosis was present in 35.1% subjects (M-24.6%, F-42.5%) and osteopenia in 49.5% (M-54.3%, F-44.9%). Prevalence of osteoporosis increased with age in females, but not in males. BMD at all sites, except distal radius, was positively correlated with BMI (r=0.037, p=0.14). Total body BMD was negatively correlated with alkaline phosphatase (r= -0.184, p<0.00001) and PTH levels (r= -0.099, p<0.00001), respectively. No significant correlation was observed between serum 25(OH)D levels and BMD at any site. BMD at forearm and calcaneum, measured using pDXA, showed strong positive correlation with BMD measured by central DXA. pDXA had sensitivity of 88%, specificity of 55%, and negative and positive predictive values of 89% and 52%, respectively, at T-score -2.5 at peripheral sites compared to central DXA.

CONCLUSIONS

A high prevalence of osteoporosis was observed in elderly Indian subjects. pDXA has high negative predictive value, making it a useful tool in population screening for osteoporosis.

Comparative evaluation of local and international reference databases for forearm densitometry: different impacts on diagnostic decisions

Reference databases play a key role in the management of osteoporosis. The aim of this preliminary study was to compare the diagnostic consequences of using either an international or a local reference database in peripheral densitometry. For this purpose, standard curves for bone mineral density (measured by dual-energy X-ray absorptiometry at the distal and proximal forearm) were generated for healthy Hungarian men and women. In total, 303 healthy volunteers of both sexes (age range: 20-94 yr) were recruited from four osteoporosis centers. Subjects with medical conditions or taking medication affecting the bone metabolism were excluded. Bone densitometry was performed with pDEXA (Norland-Stratec, Fort Atkinson, WI) devices in each center after cross-calibration of the machines. The precision error of the forearm measurement was also determined (<1% in vitro, and 1.2-2.5% in vivo). In females, the peak forearm density was detected in the 30-39-yr group. The density decreased by 8% per 5 yr in early postmenopausal females, and by 10% per 10 yr in late postmenopausal females. In males, the highest bone mineral density was found in the 30-39-yr group for the distal forearm, but 1 decade later for the proximal site. Subsequently, a 5% decrease in density occurred per 10 yr, except in the 8th decade, in which a 20% decrease was demonstrated. One thousand four hundred thirty-four patients with suspected osteoporosis were classified according to the forearm density T-scores using both the new Hungarian reference database and the international database provided by the manufacturer. Comparison of the results measured at the distal forearm with the two different databases led to similar outcomes. However, at the proximal site, one fifth of the female patients were reclassified from the low-density group to the normal group using the domestic normative database. An opposite difference was observed for the males: use of the Hungarian reference data resulted in 40% more men being categorized in the low-density group than when the international normal database was applied. Our results suggest that not only geographic differences, but also the reference database used, can influence the prevalence of the diagnosis of osteoporosis. Further data are currently being collected to increase the statistical power of the study.

A frequent regulatory variant of the estrogen-related receptor alpha gene associated with BMD in French-Canadian premenopausal women

Genes are important BMD determinants. We studied the association of an ESRRA gene functional variant with BMD in 1335 premenopausal women. The ESRRA genotype was an independent predictor of L2-L4 BMD, with an effect similar to smoking and equivalent to a 10-kg difference in weight.

INTRODUCTION

Several genetic polymorphisms have been associated with osteoporosis or osteoporosis fractures, but no functional effect has been shown for most of these gene variants. Because functional studies have implicated estrogen-related receptor alpha (ESRRA) in bone metabolism, we evaluated whether a recently described regulatory variant of the ESRRA gene is associated with lumbar and hip BMD as measured by DXA and with heel bone parameters as measured by quantitative ultrasound (QUS).

MATERIALS AND METHODS

Heel bone parameters were measured by right calcaneal QUS in 1335 healthy French-Canadian premenopausal women, and one-half of these women also had their BMD evaluated at two sites: femoral neck and lumbar spine (L2-L4) by DXA. All bone measures were tested separately for association with the ESRRA genotype by analysis of covariance. The significance of the ESRRA contribution to the model was also assessed by two different permutation tests.

RESULTS

A statistically significant association between ESRRA genotype and lumbar spine BMD was observed: women carrying the long ESRRA genotype had a 3.9% (0.045 g/cm2) higher lumbar spine BMD than those carrying the short ESRRA genotype (p = 0.004), independently of other risk factors measured. This effect of ESRRA genotype is similar to the effect of smoking and equivalent to a 10-kg difference in weight. This association was confirmed by permutation tests (p = 0.004). The same trend was observed for femoral neck BMD (2.6%, p = 0.07). However, no association was observed between ESRRA and QUS heel bone measures.

CONCLUSION

These results support the genetic influence of this ESRRA regulatory variant on BMD.

Validity of bone mineral density measurements in distal sites as an indicator of total bone mineral density in a group of pre-adolescent and adolescent women

BACKGROUND

The study of bone mineral density (BMD) has received attention due to the importance of osteoporosis as a public health problem in Mexico. The objective of this study was to assess the validity of BMD measures in distal forearm and calcaneus with portable densitometers as indicators of BMD on other anatomic sites.

METHODS

We conducted a cross-sectional study with 219 women from 9 to 22 years of age in Cuernavaca, Morelos, Mexico. We measured BMD in central sites (the entire skeleton, excluding head, proximal femur, and lumbar spine) using dual X-ray absorptiometry (DXA) and in peripheral sites (distal forearm and calcaneus) using a portable densitometer with DXA technology. Measurements of height, weight, body composition, physical activity, and demographic characteristics were collected. Agreement of measurements of BMD was assessed using correlation and regression analysis, and the method proposed by Bland and Altman.

RESULTS

Higher levels of BMD were found in total skeleton (0.88 g/cm(2)) than in calcaneus (0.48 g/cm(2)) and distal forearm (0.38 g/cm(2)) (p <0.05). Moderate-to-high positive correlation coefficients (all significant) (p <0.05) were found between BMD in distal forearm and calcaneus vs. central anatomic sites, ranging from r = 0.49 to r = 0.78. BMD was higher in central sites compared with distal forearm and calcaneus.

CONCLUSIONS

Measurement of BMD in distal forearm and calcaneus with portable densitometers provided valid indicators of BMD in central anatomic sites among pre-adolescent and adolescent women in Mexico.

Discrepancy in results between spine and hip scans of a woman with end stage renal disease

Conditions and artifacts such as aortic calcifications, osteophytes, hip prostheses, and metallic objects can affect the results of dual X-ray absorptiometry scans of the spine and hip. Abdominal surgery often entails the use of metal sutures causing subtle artifacts near or over the lumbar spine resulting in inaccurate bone mineral density (BMD) measurements. We herein report a case of a woman whose spine BMD appeared normal while her hip BMD was > -3.5 SDs. Although the abdominal artifacts create some uncertainty in the diagnosis, renal osteodystrophy is suspect owing to the patient's renal history. This case demonstrates the importance of acquiring scans at two or more sites, closely evaluating scans for artifacts, and obtaining the patient's medical history.

Bone densitometry in the management of Colles' fractures: which site to measure?

This study assessed whether patients with Colles' fractures can be evaluated by measurement of peripheral bone mineral density (BMD) instead of the more established axial BMD technique. 205 consecutive patients who had sustained a recent Colles' fracture were invited to attend for BMD measurement at the lumbar spine, hip and forearm by dual energy X-ray absorptiometry (DXA) using a Hologic QDR4500C instrument. Hologic normal reference ranges were used for spine and ultradistal radius BMD, and the NHANES 111 reference range was used for the femoral neck. 158 patients attended, of whom only 61 had a T-score below -2.5 at one of the three measured sites (84 T<-2.0, 112 T<-1.5). 36 patients had bilateral forearm fractures and did not undergo a forearm measurement. After excluding these patients and using a T-score of -2.5 as a diagnostic threshold, a spine and hip measurement strategy missed 26% of osteoporotic patients and a forearm only strategy missed 33%. If a forearm strategy is adopted, with axial BMD performed only on those patients with an ultradistal radial T-score of <-1.5 and >-2.5, 27 further scans would be required and only four patients with T<-2.5 at the spine or hip would be undetected. Where axial BMD measurement is performed, this should be accompanied by forearm BMD measurement in some patients with Colles' fractures. A peripheral bone mineral densitometry strategy using forearm BMD alone will miss many individuals with osteoporosis. Therefore where forearm, and probably any peripheral scanning method, only is used for patient assessment there should be close liaison with an axial BMD centre with agreed joint protocols, as some patients should be advised to have an additional axial BMD measurement following their peripheral BMD measurement.

Increased hip bone mineral density in a woman with gluteal silicon implant

Conditions and artifacts such as aortic calcification, osteophytes, hip prostheses, and metallic objects can mislead the results of dual energy X-ray absorptiometry (DXA) scanning of the spine and hip. Gluteal silicon implants increasingly are being used for aesthetic purposes by women in Brazil, some of whom are at an age of high risk for the development of postmenopausal osteoporosis. We herein report a case of a woman whose hip bone mineral density by DXA clearly increased after the placement of bilateral gluteal implants of silicon. This case demonstrates the importance of inquiring about the presence of this artifact to avoid unnecessary evaluation of hip bone densitometry in these situations.

Prediction of the strength of the elderly proximal femur by bone mineral density and quantitative ultrasound measurements of the heel and tibia

Quantitative ultrasound (QUS) of the heel and tibia have recently been approved in the United States for diagnostic evaluation of low bone mass. The goal of this study was to use human cadaveric specimens to compare correlations among: a) strength of the proximal femur; b) bone mineral density of the femur, tibia, and heel; and c) QUS of the tibia and heel. We obtained 26 proximal femurs and intact lower limbs from 16 female and 10 male cadavers, with a mean age of 81+/-12 years. Bone mineral density (BMD, g/cm2) of the proximal femur and tibia were assessed using dual-energy x-ray absorptiometry, and BMD (g/cm) of the heel was measured using single-energy x-ray absorptiometry. Ultrasound velocity at the mid-tibia was determined using a contact, gel-coupled ultrasound device. Broadband ultrasound attenuation (BUA) and speed of sound (SOS) of the heel were determined using a transmission ultrasound device with water-based coupling. The femurs were tested to failure in a configuration designed to simulate a fall to the side with impact to the greater trochanter. As in previous studies, the strength of the proximal femur was very strongly correlated with femoral BMD and heel BMD (r2 = 0.78-0.92, p < .0001 for all). BUA and SOS of the heel were also strongly correlated to femoral strength (r2 = 0.70 and 0.67, respectively, p < 0.0001 for both), whereas tibia SOS was only weakly correlated (r2 = 0.19, p = 0.03). The average coefficient of variation for triplicate tibial SOS measurements was 0.50%. This study indicates that, although tibial SOS measurements are precise, they are not strongly correlated with femoral BMD or strength. In contrast, heel QUS measurements are strongly correlated with the strength of the proximal femur. These findings imply that tibial SOS may be of limited use for assessing hip fracture risk. Prospective fracture risk data are needed to define further the clinical utility of tibia ultrasound measurements.