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PubMed2004

Access to bone densitometry increases general practitioners' prescribing for osteoporosis in steroid treated patients.

BACKGROUND: Availability of access to bone densitometry in the UK varies widely and there are concerns as to appropriate prescribing. Studies suggest inadequate use of osteoporosis prophylaxis in steroid users, despite recent guidelines. OBJECTIVE: To examine in a case-control study whether access to bone densitometry affects GPs' osteoporosis prescribing in high risk steroid users. METHOD: 10 general practices were included, five from primary care trusts (PCTs) with access to bone densitometry and five with limited access. Patients receiving prednisolone for >3 months were identified by database search. Patients receiving no prophylaxis other than calcium and vitamin D (Ca/D) were subsequently included. Appropriate patients in five practices were offered DXA scan (cases) and review. Patients in practices without access to scans (controls) were reviewed. GPs' opinions leading to treatment were sought by structured questionnaire. RESULTS: 132 (0.12%) patients were receiving prednisolone for >/=3 months, but no osteoporosis prophylaxis other than Ca/D. Pre-study prophylaxis ranged from 18 to 36%. Of 48 patients scanned, 21 (44%) were abnormal and 18 (38%) received new treatment. 13/44 (30%) controls received new treatment. 10/21 (48%) with abnormal scans started a bisphosphonate, compared with 7/44 (16%) controls (RR = 3, p = 0.004). No difference in risk factors for fracture was found in treated and untreated controls. CONCLUSIONS: GPs were three times more likely to start potent osteoporosis treatment after abnormal scans than GPs relying on clinical information. In practice, risk factors were not adequately assessed. Database searches may identify patients needing osteoporosis prophylaxis; however, DXA enables more appropriate patient treatment.

Adult↗
PubMed2003

Oral corticosteroid prescribing in women over 50, use of fracture prevention therapy, and bone densitometry service.

OBJECTIVE: To identify the most common diseases and age of corticosteroid use in women over 50, dosage in last year, duration of oral corticosteroid use, prescription for fracture prevention (drug used), and referrals for bone densitometry. METHODS: General practice records from 41 practices in Shropshire identified 62,230 women aged >50 from a population of 80,082. Data on fractures, duration of corticosteroid use, dose in the study year (1 April 1997-31 March 1998), use of fracture prevention therapy and bone densitometry were sampled from one out of three records. RESULTS: 3.2% were prescribed corticosteroids; 633 patients investigated in detail aged 70.1 (SD 10.5) years, had been prescribed 1526 (SD 1727) mg prednisolone (median 1040 mg) for 3.31 (SD 3.20) years (median 2.0 years). Patients with asthma/lung disease, most common in the younger group, had the lowest annual corticosteroid use; patients with rheumatoid arthritis (RA), polymyalgia rheumatica/temporal arteritis (PMR/TA), who were more likely to be elderly, had the highest annual use. Between the age of 70 and 79 years patients with RA had significantly more hip fractures than the other groups, and corticosteroid prescribing was most common. Bisphosphonates or hormone replacement therapy were prescribed for 48% aged 50-59 years but only 32% at 70-79 years (p<0.01); patients with asthma and RA being less likely recipients (p<0.01). Referrals for bone densitometry had occurred in 20.2%,with 60.2% having osteoporosis. Referrals were more common in those taking corticosteroids for longer periods (p<0.01). CONCLUSIONS: The elderly had the most prescriptions for corticosteroid treatment but the fewest for effective fracture prevention therapy. Patients with RA, PMR/TA had the greatest corticosteroid dosage, for the longest time. Patients with RA sustained more hip fractures than other groups but were least likely to have effective fracture prevention therapy prescribed.

Absorptiometry, Photon↗
PubMed1995

Scanner conformity in CT densitometry of the lungs.

PURPOSE: To quantify inter- and intrascanner conformity in computed tomographic (CT) densitometry of the lungs. MATERIALS AND METHODS: With six scanners from four manufacturers, a lung densitometry protocol with several variations was applied for performance comparison. Phantoms included water, air, and a humanoid thorax phantom equipped with a dog lung and exchangeable pseudolungs of polyethylene foam. RESULTS: All scanners produced acceptable CT numbers (Hounsfield units) for water, but some not for air. An incorrect calibration of air density affected all CT numbers at lung densities, but the error was easily correctable. Some systems were more sensitive to object size than others were. Sensitivity of CT numbers to section thickness, reconstruction filter, zoom factor, and table height was small, except for two scanners in relation to section thickness. CONCLUSION: After correction for poor air calibration, scanner conformity was acceptable when the reproducibility of lung densitometry in clinical practice was set as a reference.

Absorptiometry, Photon↗
PubMed1999

Pulmonary emphysema: subjective visual grading versus objective quantification with macroscopic morphometry and thin-section CT densitometry.

PURPOSE: To compare subjective visual grading of pulmonary emphysema with macroscopic morphometry and computed tomographic (CT) densitometry. MATERIALS AND METHODS: In 62 consecutive patients who underwent thinsection CT before surgical lung resection, emphysema was objectively quantified with computer-assisted macroscopic morphometry and CT densitometry. The percentage of lung macroscopically occupied by emphysema was compared with the percentage occupied on CT scans by pixels with attenuation values lower than a predefined threshold (CT densitometry). Three readers with varying degrees of expertise subjectively graded emphysema with visual assessment at two reading sessions. Data from objective quantification and subjective grading were analyzed with correlation coefficients, and interobserver and intraobserver agreement were calculated. RESULTS: Subjective grading of emphysema showed less agreement with the macroscopic reference standard results (r = 0.439-0.505; P < .05) than with objective CT densitometric results (r = 0.555-0.623; P < .001). The 95% CIs for the intercepts of the linear regression lines were suggestive of systematic subjective overestimation of emphysema by all three readers. Interobserver agreement was moderate (kappa = 0.431-0.589). Intraobserver agreement was good to excellent (kappa = 0.738-0.936). The expertise of individual readers did not substantially influence results. CONCLUSION: Systematic overestimation and moderate interobserver agreement may compromise subjective visual grading of emphysema, which suggests that subjective visual grading should be supplemented with objective methods to achieve precise, reader-independent quantification of emphysema.

Absorptiometry, Photon↗
PubMed1998

Diagnosis of osteoporosis by planar bone densitometry: can body size be disregarded?

Bone densitometry using dual energy X-ray absorptiometry (DXA) is frequently used to diagnose osteoporosis and to identify patients at risk of later fractures. The parameters of interest are bone mineral content (BMC) and bone mineral areal density (BMD). Bone densitometry results have a large overlap between normals and patient with fractures. This would suggest that other factors are important for the development of fractures or that bone densitometry is not used optimally. It is generally believed that the conversion of BMC to BMD by division of the former by the projected bone area is a good normalization procedure. Other normalization procedures have been attempted in the past with little success. We hypothesized that this might be due to a blurring effect of time since menopause, and that body size could be demonstrated to have an effect on measured BMC and BMD, if this time effect could be eliminated. The results of this study, comprising 1625 early post-menopausal women studied at virtually the same time since menopause, confirm that this is the case. Body surface area was the parameter among conventional body size variables showing the highest correlation with BMC and BMD. It was clearly shown that low values of BMD were seen more often in the lowest than in the highest body surface area quartile. The difference between quartiles was statistically significant. Simple division of BMC by actual body surface area or division of BMD by the square root of body surface removed the uneven distribution between the body surface area quartiles for lumbar spine and femoral neck measurements, and reduced it at peripheral measuring sites. It is suggested that BMC and BMD of the lumbar spine and the femoral neck should be normalized as described to avoid overdiagnosis of osteoporosis in persons of petite body stature and underdiagnosis in tall ones.

Absorptiometry, Photon↗
PubMed2003

Evaluation of calcaneus bone densitometry against hip and spine for diagnosis of osteoporosis.

Dual X-ray absorptiometry (DXA) is now widely available as a method for assessing bone density. However, the place of peripheral bone densitometry in clinical practice for diagnosis of osteoporosis is not yet clear. To examine the potential use in our district general hospital setting, we compared calcaneus measurements with conventional DXA of the hip and spine in 100 patients referred for assessment following identification of risk factors for osteoporosis. Measurements were made on both heels and the results were found to be similar but not completely interchangeable. Use of receiver operating characteristic curves confirmed that a threshold T-score of -1.6 could be used to identify many of the high risk subjects. However, there was only moderate agreement between fracture risk classifications derived from heel T-scores, and diagnostic classification (osteoporosis/osteopenia/normal) derived from axial DXA. The specificity of heel measurements was high, but sensitivity was poorer. Heel measurements could therefore be valuable in some circumstances for finding patients for whom treatment of osteoporosis would be appropriate, such as in a population with a low prevalence of osteoporosis. They may also be of value in a population with a high prevalence of disease, particularly if there were no alternative means of bone densitometry. However, with an intermediate prevalence, the relatively high risk of false negative values would mean that false reassurance could be given to many of those classed as "low risk". This could be a major drawback in clinical practice if heel densitometry were used as the initial investigation and axial measurements were also available, since they would give conflicting results for a substantial proportion of these patients.

Absorptiometry, Photon↗
PubMed2002

When should densitometry be repeated in healthy peri- and postmenopausal women: the Danish osteoporosis prevention study.

Intervention should be considered in postmenopausal women with bone mineral density (BMD) > or = 1 SD below the reference (T or Z score < -1). However, it is unclear when densitometry should be repeated. This study aimed at determining the need for repeat DXA within 5 years in untreated peri-/postmenopausal women to detect declines of T or Z score to below -1 with 85% confidence. A cohort of 925 healthy women (aged 51.2 +/- 2.9 years) were followed within the Danish Osteoporosis Prevention Study (DOPS) for 5 years without hormone-replacement therapy (HRT). DXA of spine, hip, and forearm was done at 0,1, 2, 3, and 5 years (Hologic QDR-1000/2000). The annual loss in SD units was 0.12 +/- 0.10 at the spine (1.3%), 0.10 +/- 0.09 at the femoral neck (1.2%), and 0.07 +/- 0.09 at the ultradistal (UD) forearm (1.0%). Accordingly, T scores below -1 developed earlier at the spine. The need for a future DXA scan to predict declines of T and Z scores below -1 depended strongly on baseline BMD. In subjects with a positive T score, the risk of developing T < -1 remained at <15% for 5 years at all measured sites. A new scan was needed after 1 year if the T score was below -0.5, and after 3 years if the T score was between 0 and -0.5. Slightly longer intervals apply if Z scores are used. Follow-up densitometry in untreated women should be individually targeted from baseline BMD rather than scheduled at fixed time intervals. An algorithm for planning repeat densitometry in perimenopausal women is provided.

Absorptiometry, Photon↗
PubMed2003

Precision and accuracy of DXA and pQCT for densitometry of the rat femur.

Measurements of bone mineral density and bone mineral content are key data in the study of osteoporosis and pathologic skeletal disease. Dual-energy X-ray absorptiometry and peripheral quantitative computed tomography are used in human and small animal studies. The purpose of this study was to evaluate the precision, accuracy, and systematic bias of measurement of the rat femur. Comparing machine-measured parameters with standard, nonradiographic measurements, we assessed validation of relative and absolute accuracy. Regression analysis and calculations of percent difference from standard values were used to determine the accuracy of each densitometry technique. Machine-specific and subject-specific precision was evaluated for each densitometer using repeated scans to calculate coefficients of variation. Each of the methods of densitometry examined in this study produced comparable results and was sensitive to small changes following experimental stimuli. Further, our assessment of the precision and accuracy observed between methods of scanning excised rat femurs validates our data acquisition method and serves as a foundation for future densitometry studies.

Absorptiometry, Photon↗
PubMed2004

Nomenclature and decimal places in bone densitometry.

There are inconsistencies in densitometry nomenclature and in the use of decimal places in reporting bone density results. These issues were discussed at the 2003 Position Development Conference (PDC) of the International Society for Clinical Densitometry (ISCD). Regarding nomenclature, there was agreement that DXA is the preferred designation for dual-energy X-ray absorptiometry. T-score (not T score, t score, or tscore) is the preferred designation for the standard deviation variance of bone mineral density (BMD) from the mean BMD of the young adult reference population. Z-score terminology should be consistent with that for T-score. For the reporting of bone densitometry results, BMD should be expressed to three decimal places, bone mineral content and area to two decimal places, T-scores and Z-scores to one decimal place, and percentages (percentage of reference population mean BMD) as integers.

Absorptiometry, Photon↗
PubMed2000

[Renal osteodystrophy in dialysis patients as estimated by three-point bone densitometry].

The aim of a study was to estimate the renal osteodystrophy status using bone densitometry in relation to selected biochemical parameters of calcium-phosphate metabolism. The study population consisted of 123 patients with end-stage renal disease, including 24 patients treated with continuous ambulatory peritoneal dialysis (CAPD), aged between 22 and 73 years (mean 49.9 years), on dialysis program for mean period of 14.9 months and 99 patients on maintenance hemodialysis for mean period of 58.8 months, aged between 19 and 72 years (mean 46.6 years). Densitometric measurements using DEXA technique were performed in three different skeletal points: distal ends of both radial bones, lumbar spinal region and femoral neck. Concomitantly, serum concentrations of total and ionized calcium, phosphates and parathormone as well as alkaline phosphatase serum activity were measured. Among male patients treated with CAPD significantly higher BMD values in right forearm were found as compared to women treated with this method (0.769 vs. 0.616; p < 0.001). Higher values of BMD were also found in both forearms in whole CAPD population as compared to those on hemodialysis. However, there was no difference in densitometry results between CAPD and HD patients as well as between men and women within these groups, when measured in femoral neck and lumbar spinal region. Among hemodialysis patients higher levels of phosphates and PTH were found as compared to CAPD, doses of drugs used for treatment of osteodystrophy--calcium carbonate, aluminum hydroxide and active vitamin D were also higher in individuals on HD. In addition, in CAPD patients statistically significant, positive correlations were found between BMD value in lumbar spinal area as well as in femoral neck and amount of ingested calcium carbonate, between BMD in lumbar spinal area and aluminum hydroxide dose taken by patients and between BMD in both forearms and dose of active vitamin D. We failed to demonstrate any relationship between obtained densitometric results as well as biochemical markers of calcium-phosphate metabolism and quantitative parameters of dialysis adequacy in both treatment modes. Obtained results let us to conclude that renal osteodystrophy is less advanced in patients treated with peritoneal dialysis, however this may be related only to markedly shorter renal replacement therapy period in this group. Lack of significant abnormalities in densitometry measurements taken in lumbar spinal area and femoral neck, while they are present in forearms, may suggest that the latter point of skeleton may be most useful for identification of bone mass deficiency in dialyzed patients.

Absorptiometry, Photon↗
PubMed2000

Different approaches to bone densitometry.

From 1990 to 2000, several effective new treatments were introduced for the prevention of osteoporotic fractures; these treatments were proven effective in large, international, clinical trials. At the same time, there was rapid technologic innovation, with the introduction of new radiologic methods for the noninvasive assessment of patients' bone density status. These developments led to the publication of guidelines for the clinical use of bone densitometry that include criteria for the referral of patients for investigation as well as recommendations for intervention thresholds for the initiation of preventive treatment of osteoporosis. Dual-energy x-ray absorptiometry scanning of the spine and hip remains the technique of choice for bone densitometry studies, although there is now a wider appreciation of the need for smaller, cheaper devices for scanning the peripheral skeleton if the millions of women most at risk of a fragility fracture are to be identified and treated. This article reviews these developments, concentrating in particular on the advantages and disadvantages of the different types of equipment available for performing bone densitometry investigations, the guidelines for the referral of patients, and the principles for the interpretation of the scan findings.

Absorptiometry, Photon↗
PubMed2000

[Dual-photon bone densitometry in dialyzed patients].

In non-invasive diagnosis of renal osteodystrophy the levels of bone minerals and the extent of bone turnover are evaluated. The contents of bone minerals are assessed quantitatively by different modalities of bone densitometry, among which the most accurate one is double-energy bone densitometry. So far no standard examination method was defined nor the most suitable portion of the skeleton for densitometric examination. In order to find such an area and also to assess the prevalence of bone demineralization, its severity and regional differences the authors made a cross-sectional study of bone density in dialyzed patients. The group comprised 45 patients, 24 men and 21 women subjected to regular dialyzation treatment for 20-24 months. In a lambda whole body bone densitometry was performed with evaluation of regional densities of the trunk, upper and lower extremities. At the same time the state of bone turnover was assessed arbitrarily using values of serum concentrations of intact parathormone; parathormone concentrations below 50 pg/ml were considered low, above 200 pg/ml high and concentrations within the mentioned range as the normal bone turnover. In the group of patients 62% had a high, 22% a normal and 16% a low bone turnover. The study provided evidence of a significant reduction of bone density (Z score <-1) in 58% of patients. In 92% of patients demineralization affected most and first the extremities. In 69% it affected the lower extremities and in 23% the upper ones. 8% of the patients had the most severe affections in the area of the trunk. This order of affliction was not influenced by bone turnover, sex and in women by age. The diaphysis of long bones seems to be a representative examination area of the skeleton for densitometric measurements in patients with regular dialyzation treatment.

Absorptiometry, Photon↗
PubMed2006

Position Development Conference of the International Society for Clinical Densitometry. Vancouver, BC, July 15-17, 2005.

Every 2 years the International Society for Clinical Densitometry (ISCD) organizes a position development conference at which a panel of experts reviews topics of interest in the field of bone densitometry and proposes Official Positions of the ISCD. In July 2005, the most recent conference was held in Vancouver, Canada, during which 4 topics were discussed: (1) Cross-calibration of dual energy x-ray absorptiometry (DXA) systems, (2) Vertebral fracture assessment, (3) World Health Organization (WHO) classification of bone density for populations other than postmenopausal women, and (4) WHO classification for varying skeletal sites. The Official Positions reached at this conference enumerated in this report have been published in The Journal of Clinical Densitometry, and can be found at www.iscd.org.

Absorptiometry, Photon↗
PubMed1994

[Computed X-ray densitometry].

Computed X-ray Densitometry (CXD) is a semi-automated method of radiographic densitometry. X-ray photographs of 2nd metacarpal bone, taken with a reference Aluminum phantom, are analyzed by a computed-densitometric machine (Bonalyzer). X-ray films are imaged by a CCD camera and displayed in a screen automatically. By pointing distal and proximal heads of the metacarpal bone, photodensity expressed as Aluminum concentration is computed. Parameters such as metacarpal cortical index (MCI) and cumulated photodensity (sigma Gs/D) at the mid-metacarpal bone are obtained. Precision determined by 5 photographs taken every 5 week, is 2%. Correlation with lumbar BMD assessed by DXA is 0.663 in elderly patients. Using this semi-automated method, radiographic densitometry can be used for clinical purpose, such as screening of patients with osteoporosis or observation of therapeutic effects. Especially, in patients over 70, this method has advantages, since lumbar BMD assessment with DXA at this age is hampered by degenerative diseases.

Absorptiometry, Photon↗
PubMed1993

[The usefulness of dual-energy radiographic densitometry (DO) in establishing the composition of calculi].

Dual-energy radiographic bone densitometry is utilized to determine the bone mineral content in patients with osteoporosis. The present in vitro experimental study investigated the usefulness of densitometry in determining stone composition and in evaluating the mineral and non mineral phases of the calculus. For the study we analyzed 114 calculi of 6 different chemical composition (calcium oxalate monohydrate, calcium oxalate dihydrate, magnesium ammonium phosphate, phosphate carbonate, uric acid and phosphate oxalate). The phosphate carbonate calculi had the highest mineral density, whereas the uric acid calculi had the lowest and contained more water. Although densitometry appears to be of little value in determining stone composition, it provides information on the mineral and non mineral phases of the calculus.

Absorptiometry, Photon↗
PubMed1993

Bone densitometry observations of osteopetrosis in response to bone marrow transplantation.

Spinal bone density was measured in eight patients with osteopetrosis to assess the natural history of the disease and to monitor the response to therapy. Quantitative computed tomographic scans of the lumbar vertebra were obtained in seven patients, and dual photon absorptiometric scans were obtained when the technique became available. Six children were afflicted with the infantile malignant recessive condition and two with the less severe dominant condition. In all cases, bone densitometry values ranged from four to five times higher than the mean for normal age and gender-matched controls. In four children with recessive osteopetrosis, quantitative computed tomographic and dual photon absorptiometric scans showed an excellent correlation (R = 0.93) between the methods. Quantitative computed tomographic values ranged from 597 to 730 mg/cm3 (mean = 655 mg/cm3) in children with osteopetrorickets and from 901 to 1000 mg/cm3 (mean = 980 mg/cm3) in the same children when the rickets was cured. In two children treated with bone marrow transplantation, bone densitometry values returned to normal within three years. Bone densitometry provides a safe and noninvasive method for observing the natural history and therapeutic response of the osteopetrotic syndromes.

Absorptiometry, Photon↗
PubMed1996

Bone densitometry: patients with end-stage renal disease.

Bone mass loss and osteoporosis are associated with various conditions, such as end-stage renal disease (ESRD), and treatments, such as prolonged steroid therapy. Bone densitometry is used to measure bone mass density to determine the degree of osteoporosis and to estimate fracture risk. Bone densitometers measure the radiation absorption by the skeleton to determine bone mass of the peripheral, axial, and total skeleton. Common techniques include single-photon absorptiometry (SPA) of the forearm and heel, dual-photon (DPA) and dual-energy x-ray absorptiometry (DXA) of the spine and hip, quantitative computed tomography (QCT) of the spine or forearm, and radiographic absorptiometry (RA) of the hand. Part I of this report addresses important technical considerations of bone densitometers, including radiation dose, site selection, and accuracy and precision, as well as cost and charges. Part II evaluates the clinical utility of bone densitometry in the management of patients with ESRD. End-stage renal disease affected more than 242,000 Americans in 1992, and each year 10,000 to 20,000 new cases are diagnosed. Although the survival rate of ESRD patients has improved, metabolic bone diseases that fall under the generic term "renal osteodystrophy" represent abnormal development of bone and major long-term complications. Issues addressed are the type and extent of bone loss associated with ESRD and whether these patients have an increased risk for fracture. The other assessments in this series address the clinical utility of bone densitometry for patients with asymptomatic primary hyperparathyroidism, steroid-dependent patients, estrogen-deficient women, and patients with vertebral abnormalities.

Absorptiometry, Photon↗
PubMed1996

Bone densitometry: patients receiving prolonged steroid therapy.

Bone mass loss and osteoporosis are associated with various conditions, such as asymptomatic primary hyperparathyroidism, and treatments, such as prolonged steroid therapy. Bone densitometry is used to measure bone mass density to determine the degree of osteoporosis and to estimate fracture risk. Bone densitometers measure the radiation absorption by the skeleton to determine bone mass of the peripheral, axial, and total skeleton. Common techniques include single-photon absorptiometry (SPA) of the forearm and heel, dual-photon (DPA) and dual-energy x-ray absorptiometry (DXA) of the spine and hip, quantitative computed tomography (QCT) of the spine or forearm, and radiographic absorptiometry (RA) of the hand. Part I of this report addresses important technical considerations of bone densitometers, including radiation dose, site selection, and accuracy and precision, as well as cost and charges. Part II evaluates the clinical utility of bone densitometry in the management of patients receiving prolonged steroid therapy. Steroids have broad effects on both immune and inflammatory processes and have been used to treat a wide variety of immunologically mediated diseases. Osteoporosis and vertebral compression fractures have been considered major complications of prolonged steroid therapy. Bone loss is also a direct result of many of the diseases treated with steroids. Issues addressed are the type and extent of bone loss associated with steroid therapy, risk for fracture, whether steroid dose reduction or alternative therapy is an option, and whether osteoporosis associated with prolonged steroid use can be prevented or treated. The other assessments in this series address the clinical utility of bone densitometry for patients with: asymptomatic primary hyperparathyroidism, end-stage renal disease, vertebral abnormalities, and estrogen-deficient women.

Absorptiometry, Photon↗