The challenges of peripheral bone density testing: which patients need additional central density skeletal measurements?

Emerging Technologies in Osteoporosis Diagnosis

Osteoporosis is a disease defined by diminished bone mass, often resulting in debilitating fragility fractures. As hand surgeons who care for patients with fractures of the distal radius and proximal humerus often related to osteoporosis, it is critical to understand the diagnostic modalities used in the workup of decreased bone density. Although the current reference standard for diagnosing osteoporosis is dual x-ray absorptiometry, this technique has notable drawbacks such as the inability to provide a 3-dimensional image or information about bone microstructure. These limitations result in underdiagnosis of osteoporosis. Other emerging imaging technologies such as quantitative computed tomography, high-resolution peripheral quantitative computed tomography, and quantitative ultrasound offer distinct advantages over dual x-ray absorptiometry. Among these advantages are the production of 3-dimensional images, information about cortical and trabecular microstructure, and reduced radiation exposure. It is essential for hand surgeons to be aware of these evolving diagnostic modalities and the benefits that they offer to provide the best care for patients with osteoporosis.

Brazilin isolated from Caesalpinia sappan L. inhibits rheumatoid arthritis activity in a type-II collagen induced arthritis mouse model

BACKGROUND

Caesalpinia sappan L. extracts exhibit great therapeutic potential, and have been shown to have analgesic and anti-inflammatory properties. This study aimed to understand the anti-rheumatoid activity of brazilin that was isolated from ethyl acetate extract of C. sappan L. The evaluations were conducted in mice with type-II collagen-induced arthritis (CIA).

METHODS

Brazilin was purified via preparative HPLC and identified by mass spectrometry and 1H/13C NMR analysis. DBA/1J mice were divided into four groups (n=10). Three groups of mice received intradermal injections of inducer bovine type-II collagen (BTIIC; 2 mg/ml in 0.05 ml acetic acid) and 0.1 ml of booster complete Freund's adjuvant (CFA). A second injection of BTIIC with booster incomplete Freund's adjuvant (ICFA) was given subsequently after 21 days. On 22nd day, purified brazilin (10 mg/kg body weight) or the disease-modifying anti-rheumatic drug methotrexate (3 mg/kg body weight) was administered intraperitoneally daily or every three days for 21 days, respectively to two groups of mice. At the 42nd day, mice sera were collected, and the levels of pro-inflammatory cytokines and stress enzyme markers in serum were measured using standard immunoassay methods. The microstructure and morphometric analyses of the bones were assessed using high-resolution microfocal computed tomography.

RESULTS

Brazilin isolated from C. sappan reduced the arthritis index score and the extent of acute inflammatory paw edema in CIA-mice. The bone mineral density was significantly (p<0.05) lower in only-CIA mice, and appeared to increase commensurate with methotrexate and brazilin administration. Brazilin prevented joint destruction, surface erosion, and enhanced bone formation as revealed by microstructural examinations. Brazilin markedly attenuated mouse CIA and reduced the serum levels of inflammatory cytokines including TNF-α, IL-1β, and IL-6.

CONCLUSIONS

Brazilin purified from C. sappan L. shows protective efficacy in CIA mouse, and may be useful to treat chronic inflammatory disorders including rheumatoid arthritis.

Quantitative ultrasound measurements of the calcaneus and hand phalanges in elderly Spanish men: relationship with peripheral bone mineral density of the hand phalanges

OBJECTIVES

The aims of this pilot study were to describe quantitative ultrasound (US) measurements and peripheral bone mineral density (BMD) of the hand phalanges on dual-energy x-ray absorptiometry and to examine the correlations between them in elderly Spanish men.

METHODS

We studied 199 healthy men (mean age ± SD, 73.31 ± 5.10 years). The participants were not taking any medications, and they reported no diseases, including diseases that are associated with abnormalities in mineral metabolism. Phalangeal and calcaneal quantitative US measurements and phalangeal BMD measurements were performed in all participants.

RESULTS

A bivariate correlation analysis showed no association between quantitative US assessments at the phalanges or the calcaneus (P = .409). After adjustment for potential confounders, the correlation between phalangeal BMD and phalangeal quantitative US measurements was r = 0.417 (P < .0001), and the correlation for calcaneal quantitative US was r = 0.26 (P = .001). Further adjustment by percentage of body fat increased quantitative US correlations with phalangeal BMD: r = 0.450 (P < .0001) at the phalanges; r = 0.291 (P = .001) at the calcaneus.

CONCLUSIONS

There is a small correlation between quantitative US measurements at the calcaneus and phalangeal BMD that increases to a moderate level with quantitative US measurements at the phalanges in elderly Spanish men.

The measurement of broadband ultrasonic attenuation in cancellous bone--a review of the science and technology

The measurement of broadband ultrasonic attenuation (BUA) in cancellous bone at the calcaneus was first described in 1984. The assessment of osteoporosis by BUA has recently been recognized by Universities UK, within its EurekaUK book, as being one of the "100 discoveries and developments in UK Universities that have changed the world" over the past 50 years, covering the whole academic spectrum from the arts and humanities to science and technology. Indeed, BUA technique has been clinically validated and is utilized worldwide, with at least seven commercial systems providing calcaneal BUA measurement. However, a fundamental understanding of the dependence of BUA upon the material and structural properties of cancellous bone is still lacking. This review aims to provide a science- and technology-orientated perspective on the application of BUA to the medical disease of osteoporosis.

Serum osteoprotegerin concentration with strontium ranelate treatment for postmenopausal osteoporosis: an open, prospective study

BACKGROUND

Strontium ranelate (SR) is a new antiosteoporotic agent with antiresorptive and bone-forming properties. The exact mechanism by which SR exerts its effects is not clearly understood. Bone resorption requires interaction between osteoblasts and osteoclasts. Osteoblasts produce a ligand for receptor activator of nuclear factor-κB (RANK). They also secrete osteoprotegerin, a decoy protein that blocks the interaction of RANK with its ligand, thereby inhibiting the differentiation and activity of osteoclasts. SR also has been associated with osteoblast proliferation and decreased osteoblast-induced osteoclast differentiation via increased osteoprotegerin messenger RNA expression in human osteoblasts.

OBJECTIVE

The aim of this study was to investigate the relationship between SR treatment and serum osteoprotegerin concentration in women with post-menopausal osteoporosis (PMO).

METHODS

This open, prospective study was conducted in women admitted to the outpatient endocrinology clinic of Baskent University Faculty of Medicine, Adana Medical Center, Ankara, Turkey, for the evaluation of PMO. Women with PMO who enrolled were administered elemental calcium 1000 mg/d and vitamin D 800 IU/d for 1 month before the study period. After obtaining baseline serum samples for determining osteoprotegerin concentrations, patients were assigned to the treatment or control groups at a 5:2 ratio and SR 2 g/d was administered to the treatment group. The control group continued to receive only calcium and vitamin D. Serum osteoprotegerin concentration was measured again after 3 months of treatment.

RESULTS

Thirty-five women (treatment group: n = 25; mean [SD] age, 59.80 [7.38] years; control group: n = 10; mean [SD] age, 56.60 [5.06] years) enrolled in the study. A total of 32 women-24 in the treatment group and 8 in the control group-completed the study. Compared with baseline, mean [SD] serum osteoprotegerin concentration did not change significantly after 3 months in either the treatment group (4.91 [1.24] pmol/L vs 4.71 [1.19] pmol/L) or the control group (5.36 [2.82] pmol/L vs 5.10 [2.19] pmol/L).

CONCLUSION

The results of this small study found that serum osteoprotegerin concentrations were not significantly changed by SR treatment for 3 months among women with PMO.

Bone mineral density (BMD) assessment of central skeletal sites from peripheral BMD and ultrasonographic measurements: an improved solution employing age and weight in type 3 regression

The objective of this study was to develop a method whereby bone mineral density measurements of the heel and finger, as well as ultrasonographic measurements of calcaneal sound transmission, could identify individuals with a diagnosis of osteoporosis or osteopenia by the World Health Organization criteria for these diagnoses in the central skeleton (i.e., the lumbar spine (LS) and hip [femoral neck] [FN]). Two hundred and forty-four women in a university hospital laboratory setting had dual-energy X-ray absorptiometry measurements of bone mineral density (BMD) in the calcaneus, finger, hip, and spine, and quantitative ultrasound of the calcaneus. Regression equations were developed to predict central bone mineral T-scores from T-scores of peripheral measurements, adjusted by age and weight. Equations were validated by predicting the cut point for osteopenia at the lumbar spine and hip (T-score=-1.0). Ninety-five percent confidence intervals of the mean predicted LS or FN T-score from each peripheral site included -1.0. We conclude that our derived regression equations (taking into account interaction of peripheral BMD with patient age and weight) are useful for predicting T-scores in the central skeleton. This approach reduces the potential for misdiagnosis, which can result if one uses unadjusted peripheral T-scores, which are only moderately correlated with the central measurements of BMD.

Lebanese guidelines for osteoporosis assessment and treatment: who to test? What measures to use? When to treat?

With the demographic explosion of the population worldwide, the human, social, and economic costs of osteoporosis will continue to rise. It is estimated that the magnitude of the problem might be even larger in developing countries, including those in the Middle East. Although several organizations and countries have developed or adapted guidelines to their local needs, as of today there are no guidelines for osteoporosis assessment in the Middle East. In April 2002, a panel of osteoporosis experts met and discussed practice guidelines for osteoporosis assessment and treatment in Lebanon. The process, which involved an overview of international guidelines as well as local data on osteoporosis, resulted in a draft for Lebanese guidelines that addressed three main questions: "Who to test?" "What measures to use?" and "When to treat?". Representatives from five major Lebanese societies (Endocrinology, Rheumatology, Orthopedics, Obstetrics and Gynecology, and Radiology) subsequently reviewed, discussed, and officially endorsed the guidelines after revisions. The Lebanese guidelines were also endorsed by the Eastern Mediterranean branch of the World Health Organization.

Forearm single X-ray absorptiometry in the identification of postmenopausal women with osteoporosis at the hip and spine: a correlation study

The International Society for Clinical Densitometry (ISCD) has stated that forearm bone mineral density (BMD) testing combined with a thorough clinical evaluation may be an option for the diagnosis of osteoporosis when central bone density (CBD) testing is not available. This study assessed the performance of two different forearm sites in identifying subjects with spinal and femoral osteoporosis, and defined the 90% sensitivity point for the DTX-100 bone densitometer in the detection of central osteoporosis. Four hundred and two postmenopausal Bulgarian women between the ages of 50 and 81 yr (mean age 60.24 +/- 10.48 yr) participated in this study. Forearm BMD (distal and ultradistal forearm) was measured with a DTX-100 device (Osteometer Meditech, USA) and central BMD (lumbar spine and proximal femur) with a Hologic QDR 4500 A device. Linear T-score correlations among sites, sensitivity and specificity of the forearm site were analyzed. T-score correlations between the forearm and the central sites ranged from 0.32 to 0.69 (p < or = 0.05 for all correlations in age group 50-59). The forearm site sensitivity increased slightly with advancing age, but specificity decreased. When the distal forearm BMD cut point (0.340 g/cm2) was set to achieve 90% sensitivity to identify total hip osteoporosis, specificity was 40%; when the distal forearm BMD cut point (0.410 g/cm2) was set to achieve 90% sensitivity to identify spinal osteoporosis, specificity was 55.4%; when ultradistal forearm BMD cut points (0.280 and 0.320 g/cm2) were set to achieve 90% sensitivity to identify total hip and spinal osteoporosis, specificity was 40.8 and 59.2%, respectively. Forearm bone density measures may be useful to selectively screen for patients with central osteoporosis.

Heel ultrasonography is not a good screening tool for bone loss after kidney and pancreas transplantation

BACKGROUND

Solid organ transplant recipients, particularly simultaneous pancreas kidney recipients, are at high fracture risk. We tested whether quantitative ultrasonography (QUS) of the heel predicts bone mineral density (BMD) by dual energy X-ray absorptiometry (DXA) in solid organ transplant recipients.

METHODS

Thirty-eight transplant recipients (22 Female/16 Male) were studied. Spine and hip BMD was measured with a Hologic DXA scanner. 'Stiffness' of the heel was measured with a Lunar Ultrasound densitometer and compared with BMD by DXA. Contributing factors to bone loss were also assessed.

RESULTS

Mean age was 43.1 +/- 1.3 yr. Simultaneous pancreas-kidney, kidney, and pancreas alone transplant recipients were assessed. Mean time post-transplantation was 3.0 +/- 0.6 yr. Mean DXA spine T-score was -1.15 +/- 0.22 (mean +/- SEM) and hip T-score was -1.22 +/- 0.20. There was no difference in mean T-score between women and men at the hip or spine. Mean right heel stiffness T-score was -0.97 +/- 0.25. There was no correlation between QUS and DXA at either the hip or spine in women or men. QUS had a false negative rate for identifying osteopenia or osteoporosis of 17% compared with DXA. The false positive rate for identifying osteopenia was 61%.

CONCLUSIONS

The QUS is an unacceptable tool for identifying those at risk for bone loss after kidney or pancreas transplantation.

Relationship between low back pain in post-menopausal women and mineral content of lumbar vertebrae

Until recently, chronic low back pain in post-menopausal women was commonly attributed to osteoporosis. This opinion has since been challenged on many counts, but controversy persists. The objective of this study was to examine this relationship. In 67 post-menopausal women, the mineral content of the lumbar vertebrae was measured by dual-energy X-ray absorptiometry and the age-normalized bone mineral index (ANBMI), the Z-score, was determined. Mean ANBMI in 40 subjects who complained of chronic low back pain (Group 1) was compared with mean ANBMI in the 27 who did not (Group 2). Pain intensity and related disability were quantified using standard questionnaires. Their respective correlations with ANBMI index and age at onset of menopause were examined. Correlation coefficients and significance of group differences were examined by appropriate statistical methods. The results showed that the mean ANBMI in Group 1 subjects was 96.5 +/- 16.9%, in Group 2 subjects it was 88.6 +/- 10.0%. Neither pain intensity nor disability was correlated with ANBMI. A weak but significant positive correlation was noted between body mass index and intensity of low back pain (r = 0.37; P < 0.05). The occurrence and severity of chronic low back pain in post-menopausal women, and the disability thereof, appear to be unrelated to the mineral content of lumbar vertebrae.

Body composition changes with age have gender-specific impacts on bone mineral density

Body weight, smoking, alcohol, physical activity, and diet have been proven to affect bone mineral density (BMD) directly or indirectly. Of these, body weight is perhaps best known to affect BMD. However, there is some debate as to whether lean body mass (LBM) or fat mass (FM), the two components of body weight, most determines BMD. Recently, newer peripheral densitometry devices have been developed, which have the advantages of low cost and portability, and this has made field epidemiologic study of osteoporosis possible. As the number of studies that have focused on the contribution made by body composition to BMD is limited, we investigated the relative contribution of LBM and FM to BMD in healthy Korean subjects. 402 age- and weight-matched subjects over 45 years old were selected from a population-based cohort. The mean ages of men and women were 64.1 +/- 8.7 (mean +/- SD) and 64.2 +/- 12.7 years, and mean weights were 63.0 +/- 8.2 and 63.1 +/- 8.2 kg, respectively. BMD was measured by peripheral dual-energy X-ray absorptiometry (DEXA) and body composition by bioelectrical impedance. Sociodemographic characteristics and physical activities were investigated using a standard questionnaire delivered by face-to-face interview. BMDs were 0.48 +/- 0.01 and 0.37 +/- 0.11 g/cm2 in men and women, respectively. In men, age, weight, body mass index (BMI), LBM, FM, physical activity, smoking, alcohol, and education were significantly correlated with BMD. In women, age, weight, BMI, LBM, FM, education, years since menopause, number of deliveries, and number of children breast-fed were significantly correlated with BMD. By multiple regression, LBM, education, smoking, and alcohol in men, and age, LBM, FM, smoking, and number of delivery in women were independent determinants of BMD. LBM was an important contributor for BMD in men, but both LBM and FM were equally important contributors in female to BMD. This stems from the fact that body composition changes with age differ in men and women. Thus, the augmentation of muscle mass in men and the maintenance of an optimal weight in women act to prevent osteoporosis.

Pitfalls in bone mineral density measurements

Bone mineral density (BMD) measurements have been the single greatest advancement for osteoporosis. BMD measurements have helped define a prefracture diagnosis of osteoporosis, predict fracture risk in postmenopausal women and elderly men, and monitor the course of disease processes that negatively affect bone or therapeutic agents that can improve bone strength. Despite the large amount of clinical, epidemiologic, and basic science data that has advanced our understanding of BMD performance and interpretation, many pitfalls in BMD performance and interpretation pervade the practice of bone densitometry. However, all of these pitfalls can be overcome. Proper quality control and clinical interpretation of BMD computer printout reports are paramount for correct diagnosis, risk assessment, and serial BMD measurements. Though BMD application(s) are a clinical tool that can and should be used by many different primary care and specialty physicians, the performances and interpretations are not simple processes. Proper education and training in the use of BMD technologies provides the means of achieving the great intent that BMD measurements are capable of providing.

Discriminatory ability of quantitative ultrasound measurements is similar to dual-energy X-ray absorptiometry in a Brazilian women population with osteoporotic fracture

The discriminating ability and relevance of clinical risk factors, quantitative ultrasound (QUS) variables, X-ray-based bone mineral density (BMD) and hip axis length (HAL) measurements to evaluate the risk of osteoporotic fracture in elderly Brazilian women were examined in this study. QUS at the calcaneus (Achilles +, Lunar), HAL and BMD measurements (DPX-L, Lunar) at several anatomical sites were performed in 275 postmenopausal Caucasian women. Patients with suspected secondary osteoporosis were excluded. One hundred twenty-two (44.4%) women had had previous osteoporotic fracture. All of the subjects were over 50 years old (range 53-93) and answered a questionnaire that included details concerning aspects of lifestyle, diet, hormonal factors and drug use. Lateral thoracic and lumbar radiographs were taken and an independent radiologist reviewed the X-rays for the presence of vertebral fractures. After adjustments for age, the most relevant risk factors to discriminate patients with osteoporotic fracture from normal non-fracture controls were Stiffness index (OR 2.8 per standard deviation; 95% confidence interval 2.3, 8.7), familial history of hip fracture (OR 2.6 per standard deviation; 95% confidence interval 2.2, 5.4), femoral neck BMD (OR 2.3 per standard deviation; 95% confidence interval 1.9, 4.2), age (OR 2.1 per standard deviation; 95% confidence interval 1.6, 2.8) and weight (OR 1.9 per standard deviation; 95% confidence interval 1.5, 2.6). HAL measurements did not associate significantly with the risk of hip fracture in this population. The ability of QUS measurements discriminate between patients with fractures from those without was similar to, if not better, than X-ray-based BMD measurements. However, a combination of QUS and BMD measurements did not significantly improve fracture discrimination compared with either technique alone. Association of clinical risk factors with QUS or BMD measurements seems, on the other hand, to increase the sensibility to identify patients at risk of osteoporotic fractures.

Osteoporosis in pulmonary clinic patients: does point-of-care screening predict central dual-energy X-ray absorptiometry?

STUDY OBJECTIVES

Patients in a pulmonary clinic have disorders that predispose them to osteoporosis and may use glucocorticoid therapy, which has been associated with low bone mineral density (BMD) and increased fracture risk. Ideally, all patients at risk for osteoporosis would be screened using the best test available, which is central BMD by dual-energy x-ray absorptiometry (DXA). We proposed to stratify the risk for osteoporosis by the use of a simple questionnaire and point-of-care heel ultrasound BMD measurements.

DESIGN

Cross-sectional screening study.

SETTING

Pulmonary clinic in a single Veterans Affairs Medical Center.

PATIENTS

Approximately 200 male and female patients who had not had previous BMD testing were eligible for the study, and 107 gave consent.

INTERVENTIONS

One hundred seven men (white, 71 men; black, 35 men; and Asian, 1 man) underwent heel BMD testing and filled out a questionnaire. Ninety-eight men underwent a central DXA.

RESULTS

Of 98 subjects, 24.5% had a spine, total hip, or femoral neck (FN) T-score of <or= -2.5, which is the generally accepted definition of osteoporosis diagnosed using DXA, and 44.9% had a T-score of <or= -2.0. The best-fit models for predicting FN or total hip BMD included body weight, heel BMD, corticosteroid use for >or= 7 days, and race, which accounted for 52 to 57% of the variance. When a heel ultrasound T-score of -1.0 was tested to predict a central DXA T-score of -2.0, the sensitivity was 61% and the specificity 64%. Adding the questionnaire score and body mass index (BMI) to the heel T-score improved sensitivity but not specificity. Moreover, BMI and age predicted central BMD with similar sensitivity and specificity. Importantly, of 24 patients with a central DXA T-score of <or= -2.5, only 14 were identified by a heel T-score of <or= -1.0.

CONCLUSIONS

Although the findings from a heel ultrasound plus the answers to a questionnaire were reasonably good indicators for predicting the presence of low BMD, little predictability was gained over the use of BMI and age. In a group of pulmonary clinic patients, the prevalence of osteoporosis was clinically significant, and central DXA testing was the preferable technique for identifying patients who were at risk for fracture.

Bone mass measurements

The clinical application of bone densitometry is one of the advances in the field of osteoporosis that has led to the increased patient awareness of this increasingly prevalent disease. Bone densitometry has made it possible for clinicians to diagnose osteoporosis before the first fracture has occurred; predict risk for fracture in postmenopausal women, men, and in patients who are receiving glucocorticoids; and can be used as a surrogate marker to follow the efficacy of therapies and to examine those patients that might be osteoporosis-specific therapeutic nonresponders.

Bone mineral density--clinical use and application

Clinical application of bone densitometry has led to increased patient awareness of this increasingly prevalent disease. With bone densitometry, it is possible for clinicians to diagnose osteoporosis before the first fracture has occurred; predict risk for fracture in men, postmenopausal women, and in patients receiving glucocorticoids; and can be used as a surrogate marker to follow the efficacy of therapies and to examine those patients who might be osteoporosis-specific therapeutic non-responders.

Prediction of fracture risk in postmenopausal white women with peripheral bone densitometry: evidence from the National Osteoporosis Risk Assessment

Low bone mineral density (BMD) is a risk factor for fracture. Although the current "gold standard" test is DXA of the hip and spine, this method is not universally available. No large studies have evaluated the ability of new, less expensive peripheral technologies to predict fracture. We studied the association between BMD measurements at peripheral sites and subsequent fracture risk at the hip, wrist/forearm, spine, and rib in 149,524 postmenopausal white women, without prior diagnosis of osteoporosis. At enrollment, each participant completed a risk assessment questionnaire and had BMD testing at the heel, forearm, or finger. Main outcomes were new fractures of the hip, wrist/forearm, spine, or rib within the first 12 months after testing. After 1 year, 2259 women reported 2340 new fractures. Based on manufacturers' normative data and multivariable adjusted analyses, women who had T scores < or = -2.5 SD were 2.15 (finger) to 3.94 (heel ultrasound [US]) times more likely to fracture than women with normal BMD. All measurement sites/devices predicted fracture equally well, and risk prediction was similar whether calculated from the manufacturers' young normal values (T scores) or using SDs from the mean age of the National Osteoporosis Risk Assessment (NORA) population. The areas under receiver operating characteristic (ROC) curves for hip fracture were comparable with those published using measurements at hip sites. We conclude that low BMD found by peripheral technologies, regardless of the site measured, is associated with at least a twofold increased risk of fracture within 1 year, even at skeletal sites other than the one measured.

The use of ultrasound in the assessment of bone status

The assessment of skeletal status has wide clinical applications, especially in the management of osteoporosis. Osteoporosis, once thought of as an unpreventable and untreatable aging process, has revealed many of its secrets over the last decade, and the advent of successful drug therapy has changed our perception of the disease. Non-invasive techniques play a fundamental role in the diagnosis of osteoporosis and in the assessment of the efficacy of drug treatments. The primary technique used in osteoporosis is dual X-ray absorptiometry (DXA), that has been established as a reliable means of measuring bone density. Quantitative ultrasound (QUS), because of the relative portability of the equipment, ease of use, lack of ionizing radiation and low cost, has great potential for widespread use. Five devices for QUS assessment have recently been approved by the Food and Drug Administration and many more applications are in progress. QUS is a relatively new technology, at least in its application to bone fragility. Nevertheless, QUS has demonstrated that it is able to detect bone fragility as well as DXA. However, diagnosis of osteoporosis by QUS remains contentious, but the problems are due more to the limitations of the present T-scores rather than to the technique. A better option for QUS would be to report results in terms of remaining lifetime fracture risk, keeping in mind that a risk estimate needs not only the QUS or DXA measurement, but also the specific data, such as age, weight, gender, hormonal status and fracture history of the patient.

Using bone densitometry to monitor therapy in treating osteoporosis: pros and cons

Measurement of bone density is crucial for evaluating fracture risk. Low bone mass is a powerful predictor of fracture and is necessary to assess the need for treatment. Dual energy x-ray absorptiometry is accurate and precise. Use of bone density for monitoring therapy is an important tool for evaluating response to therapy, but an understanding of the limitations of the procedure are important for the practicing physician. Precision error of the technology and what change in density is clinically significant (least significant change) are important concepts to interpret results and make appropriate treatment decisions. This article reviews the use of bone densitometry as a tool for monitoring treatment in patients with low bone mass.

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.

Comparison of heel ultrasound and finger DXA to central DXA in the detection of osteoporosis. Implications for patient management

The goal of the study was to investigate the potential discordance in patient management when a clinician assumes that a peripheral device is a diagnostic surrogate for central DXA in the detection and treatment of osteoporosis. Over a period of 2 mo, asymptomatic women seeking conventional central DXA evaluation for osteoporosis at a diagnostic imaging center were also evaluated with heel ultrasound and finger DXA peripheral imaging devices. T-Scores of -2.5 or less in screening examinations were used to evaluate the discordance between the two peripheral devices and central DXA in the identification of patients with osteoporosis. Higher T-score cutoffs (>-2.5) were also evaluated. Using central DXA as the standard for comparison, the sensitivity of heel ultrasound for screening cases was 0.34 and specificity was 0.92. For finger DXA, sensitivity was 0.23 and specificity was 0.92. Overall discordance between the peripheral devices and central DXA was 21% (heel) and 23% (finger). Heel ultrasound identified 7 out of every 22 osteoporotic patients diagnosed with central DXA. Finger DXA identified 5 out of every 22 osteoporotic patients. Using lower T-scores for the peripheral devices increased sensitivity but markedly increased discordance with DXA. The peripheral devices we studied cannot be considered equivalent surrogates for central DXA in the screening of asymptomatic women for osteoporosis.

Classification of osteoporosis based on bone mineral densities

In this article we examine the role of bone mineral density (BMD) in the diagnosis of osteoporosis. Using information from 7671 women in the Study of Osteoporotic Fractures (SOF) with BMD measurements at the proximal femur, lumbar spine, forearm, and calcaneus, we examine three models with differing criteria for the diagnosis of osteoporosis. Model 1 is based on the World Health Organization (WHO) criteria using a T score of -2.5 relative to the manufacturers' young normative data aged 20-29 years, with modifications using information from the Third National Health and Nutrition Examination Survey (NHANES). Model 2 uses a T score of -1 relative to women aged 65 years at the baseline of the SOF population. Model 3 classifies women as osteoporotic if their estimated osteoporotic fracture risk (spine and/or hip) based on age and BMD is above 14.6%. We compare the agreement in osteoporosis classification according to the different BMD measurements for the three models. We also consider whether reporting additional BMD parameters at the femur or forearm improves risk assessment for osteoporotic fractures. We observe that using the WHO criteria with the manufacturers' normative data results in very inconsistent diagnoses. Only 25% of subjects are consistently diagnosed by all of the eight BMD variables. Such inconsistency is reduced by using a common elderly normative population as in model 2, in which case 50% of the subjects are consistently diagnosed as osteoporotic by all of the eight diagnostic methods. Risk-based diagnostic criteria as in model 3 improve consistency substantially to 68%. Combining the results of BMD assessments at more than one region of interest (ROI) from a single scan significantly increases prediction of hip and/or spine fracture risk and elevates the relative risk with increasing number of low BMD subregions. We conclude that standardization of normative data, perhaps referenced to an older population, may be necessary when applying T scores as diagnostic criteria in patient management. A risk-based osteoporosis classification does not depend on the manufacturers' reference data and may be more consistent and efficient for patient diagnosis.

Update on bone density measurement

Bone densitometry is a clinically accepted technique for assessing fracture risk and evaluating skeletal change. The proper clinical use of densitometry requires an understanding of the available techniques, their appropriate application, and the potential sources of measurement error. Recent clinical guidelines recommend that all women over the age of 65 years and all postmenopausal women with risk factors should have their bone density assessed. With the advent of smaller portable devices, bone density measurements are now widely available. In particular, ultrasound techniques, which do not use radiation, have particular promise for widespread screening applications. Peripheral densitometry alone cannot adequately address all clinical questions, particularly the question of monitoring subtle changes in bone density. For this purpose, central densitometers are still preferred. For any bone density measurement to be clinically useful, it must be performed with careful attention to detail, particularly with regard to instrument calibration, patient positioning, measurement analysis, and interpretation.

Utility of heel ultrasound bone density in men

In women, heel ultrasound (US) bone mineral density (BMD) has been shown to predict fracture risk, but the usefulness of this screening tool in men is not known. We measured the heel quantitative ultrasound index (QUI( in a convenience sample 185 of men (136 Caucasian, 1 Asian, and 48 African-American) with an average age of 63 yr (range of 25-85) undergoing BMD of the spine and hip by dual X-ray absorptiometry (DXA) to determine whether the heel measurement could predict central BMD. The average DXA T-score was -0.97, -1.20, and -1.61 for the spine, total hip, and femoral neck, respectively. The mean heel US BMD T-score (using the only available T-score, which was defined for Caucasian postmenopausal women) was -0.92. There were significant correlations among the various DXA measurements and the heel US BMD T-score (r = 0.373-0.483, p < 0.001). We defined arbitrarily osteopenia as a spine, total hip, or femoral neck T-score by DXA of < -1.5. We also made two different arbitrary definitions of osteoporosis by DXA: < -2.0 and < -2.5. Using these numbers as disease definitions, we determined the specificity, sensitivity, as well as positive and negative predictive values of using the heel US T-score to predict osteopenia or osteoporosis. Using various cutoffs for the heel T-score, we found that increasing the cutoff toward 0 increased the sensitivity but lowered the specificity. No cutoff was found that provided both good sensitivity and specificity. By analyzing the men by ethnic and age groups, we found that the best set of receiver operating characteristic (ROC) curves was derived from data using heel US to predict osteopenia and osteoporosis in men younger than age 65, although the areas under the ROC curve were approx 0.8. In conclusion, despite a strong correlation between the heel QUI and the spine and hip BMD by DXA, no heel T-score could predict osteopenia or osteoporosis with satisfactory sensitivity and specificity. It is possible that the use of risk factor assessment plus heel QUI might have better predictive value, and further studies are needed to determine whether heel QUI or other US determination is an independent risk factor for fracture in men.

Diagnostic discrepancies between two closely related forearm bone density measurement sites

At the present time the diagnosis of osteoporosis is based on the use of T-scores. Measurements at different skeletal sites or of different regions of interest may result in diagnostic discrepancies. In this study, we tried to demonstrate that bone mineral density (BMD)values at the closely related forearm sites may lead to diagnostic uncertainty, and to assess the degree of site heterogeneity across different age groups. The study consisted of 2348 women (age 20-83) referred for bone densitometry. Forearm BMD was measured at the distal and ultradistal sites by single X-ray absorptiometry (DTX-100 device). T-scores were calculated from Bulgarian reference data. Diagnostic disagreement between sites was found in 19.3% of all women. In 7.7% of all cases, the difference between T-scores at the two sites exceeded 1. The discrepancies were more pronounced after age 60. This corresponds well to the different onset and rates of trabecular and cortical bone losses as well as to their different distribution along the forearm. We encourage the separate assessment of cortical and trabecular bone densities or measurements at axial sites in case forearm sites yield conflicting results or low-normal BMD values.

Reconciling quantitative ultrasound of the calcaneus with X-ray-based measurements of the central skeleton

Osteoporosis is frequently undiagnosed before fracture because of the lack of availability of instruments to quantitate bone mass. To evaluate the utility of quantitative ultrasound (QUS) of the calcaneus to diagnose osteoporosis, we determined bone mineral density (BMD) of the posterior-arterior spine, total hip, and femoral neck by dual-energy X-ray absorptiometry (DXA) and QUS in 312 women aged 50 years and older. A risk factor assessment (simple calculated osteoporosis risk estimation [SCORE]) also was quantitated in all women. Ninety-four of the 312 women were diagnosed as osteoporotic based on T scores < or = -2.5 at the spine, total hip, and/or femoral neck. The sensitivity of the individual central sites for the diagnosis of osteoporosis was 49% at the spine (46 of 94 women), 32% at the total hip (30 of 94 women), and 81% at the femoral neck (76 of 94 women). At a QUS T score < or = -1, the peripheral technique had a sensitivity of 62% and a specificity of 72%. Combining a QUS T score of < or = -1 followed by a risk factor assessment of women with a QUS T score > or = -0.99 using a cut point of 11 increased sensitivity to 81% (comparable with femoral neck DXA) but decreased specificity to 58%. If peripheral QUS measurements and risk factor assessment are the only tools employed before initiation of therapy, the benefits of increased ease of diagnosis will need to be balanced against potentially unnecessary treatment in some normal patients and lack of treatment in some osteoporotic patients.

Classification of osteoporosis and osteopenia in men is dependent on site-specific analysis

To examine the diagnosis of osteoporosis and osteopenia in men based on bone density measurements at single or multiple sites using central and peripheral measurements, we studied 206 ambulatory, community-dwelling men over age 50. Bone mineral density of the hip, PA spine, forearm, and finger were assessed by dual-energy X-ray absorptiometry. The diagnosis of osteoporosis based on a single measurement ranged from 1% using the trochanter to 39% using Ward's triangle. Twenty-one percent of men had osteoporosis if the diagnosis was based on at least one osteoporotic value at three central sites (PA spine, total hip, femoral neck). Among these men using T-scores provided by the manufacturers, 51% of osteoporotic patients would be misclassified as normal using the accuDEXA((R)) (finger), and 37% of osteoporotic men would be misclassified as normal using the PA spine. We conclude depending on the number and selection of sites there is considerable variability in the classification and misclassification of osteoporosis and osteopenia in men.

How well do radiographic absorptiometry and quantitative ultrasound predict osteoporosis at spine or hip? A cost-effectiveness analysis

Dual energy X-ray absorptiometry (DXA) is widely accepted as the reference method for diagnosis and monitoring of osteoporosis and for assessment of fracture risk, especially at hip. However, axial-DXA is not suitable for mass screening, because it is usually confined to specialized centers. We propose a two-step diagnostic approach to postmenopausal osteoporosis: the first step, using an inexpensive, widely available screening technique, aims at risk stratification in postmenopausal women; the second step, DXA of spine and hip is applied only to potentially osteoporotic women preselected on the basis of the screening measurement. In a group of 110 healthy postmenopausal woman, the capability of various peripheral bone measurement techniques to predict osteoporosis at spine and/or hip (T-score < -2.5SD using DXA) was tested using receiver operating characteristic (ROC) curves: radiographic absorptiometry of phalanges (RA), ultrasonometry at calcaneus (QUS. CALC), tibia (SOS.TIB), and phalanges (SOS.PHAL). Thirty-three women had osteoporosis at spine and/or hip with DXA. Areas under the ROC curves were 0.84 for RA, 0.83 for QUS.CALC, 0.77 for SOS.PHAL (p < 0.04 vs RA) and 0.74 for SOS.TIB (p < 0.02 vs RA and p = 0.05 vs QUS.CALC). For levels of sensitivity of 90%, the respective specificities were 67% (RA), 64% (QUS.CALC), 48% (SOS.PHAL), and 39% (SOS.TIB). In a cost-effective two-step, the price of the first step should not exceed 54% (RA), 51% (QUS.CALC), 42% (SOS.PHAL), and 25% (SOS.TIB). In conclusion, RA, QUS.CALC, SOS.PHAL, and SOS.TIB may be useful to preselect postmenopausal women in whom axial DXA is indicated to confirm/exclude osteoporosis at spine or hip.

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.

Classification of osteoporosis and osteopenia in postmenopausal women is dependent on site-specific analysis

Despite the availability of guidelines from the World Health Organization study group for the classification of osteoporosis in postmenopausal Caucasian women, confusion still exists about the number of sites used for diagnosis and the clinical utility of peripheral bone mass assessments. To examine the diagnosis of osteoporosis and osteopenia based on bone density measurements at single or multiple sites using central and peripheral measurements, we studied 115 ambulatory, community-dwelling, Caucasian postmenopausal women. Bone mineral density of the hip, PA spine, forearm, and finger were assessed by dual X-ray absorptiometry. Bone mass of the calcaneus was obtained using ultrasound. The diagnosis of osteoporosis based on a single measurement varied from 4% using the trochanteric region to 34% using Ward's triangle, 17% using the calcaneus, and 13% using the finger. Twenty-eight percent of the women had osteoporosis if the diagnosis was based on at least one osteoporotic value at three standard central sites (PA spine, total hip, femoral neck). Among these women, using T-scores provided by the manufacturers, 16% of osteoporotic patients would be misclassified as normal using the Sahara Clinical Bone Sonometer (Hologic, Waltham, MA) (heel) and 34% misclassified using the accuDEXA (Schick, New York, NY) (finger). We conclude that there is significant variability in the classification of osteoporosis based on site selection, with significant potential for misdiagnosis.

Practical clinical application of biochemical markers of bone turnover: Consensus of an expert panel

Biochemical markers of bone turnover have emerged as powerful tools to aid in managing osteoporosis. The newer bone markers have been intensively studied for more than a decade. As a result, we can now confidently report their clinical utility in assessing risk of rapid bone loss and fracture, and monitoring therapy in postmenopausal women with or at risk of osteoporosis. In this review, we will provide a comprehensive foundation for this utility. While there are still questions remaining to be answered, bone marker technology has matured to play an essential role in patient management. We will describe, in practical terms, how bone markers can be appropriately incorporated into clinical practice today.