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Biomedical subjects

R B Mazess

Publications and source records attributed to R B Mazess.

At least 73 records · Page 4Linked to original sources
PubMed1990

Skeletal and body-composition effects of anorexia nervosa.

Eleven female patients (aged 18-46 y) with anorexia nervosa were measured by use of dual-photon absorptiometry for 1) bone mineral content (BMC, in g) and bone mineral density (BMD, in g/cm2) of the total skeleton and its regions, 2) BMD of the lumbar spine and the proximal femur, and 3) total body soft-tissue composition. The patients weighed 44.4 kg, approximately 15 kg less than normal peers (n = 22). The fat mass (3.35 kg) and content of soft tissue (7.8%) were four and three times lower (p less than 0.001) respectively, than those in normal women (15.1 kg and 26%, respectively). The total skeleton mineral (1921 g) was approximately 25% less than that of young normal women. The BMC as a fraction of the lean tissue mass was approximately 4.9% in the patients and 5.9% in normal women. Total body and femoral BMD averaged only 10% and 13% lower than those of normal women, respectively; however, spinal BMD was particularly reduced (approximately 25%, p less than 0.001).

Adipose Tissue↗
PubMed1990

Dual-energy radiographic absorptiometry of the lumbar spine: clinical experience with two different systems.

Dual-energy radiographic absorptiometry (DRA) of the lumbar spine was performed in 222 subjects (aged 17-92 years) of both sexes with use of two different systems. In a sub-group of 21 patients, results were compared with those obtained by means of dual-photon absorptiometry (DPA) of the lumbar spine. There was a high correlation among the results obtained with three instruments (r = .9, P less than .0001), and interconversion factors were calculated. Data conversion based on these regression equations may be useful for comparing results from one laboratory to another.

Absorptiometry, Photon↗
PubMed1990

Bone densitometry of the axial skeleton.

The role of bone densitometry used as a diagnostic tool is discussed as well as its role in monitoring both the disease process itself and therapy. The QCT method and the DPA/DEXA method are discussed separately, including their regions of interest, calibration, radiation dose, diagnostic sensitivity, precision, and the monitoring and accuracy of changes, and then these two methods are compared with each other.

Absorptiometry, Photon↗
PubMed1989

Advances in noninvasive bone measurement.

Several noninvasive measurement methods are used for evaluation of metabolic disease. Single-photon (125I) scans of the peripheral skeleton are useful in some diseases but are ineffective in osteoporosis (even on the distal radius or os calcis) because they cannot predict spinal or femoral density. Also, peripheral measurements show high percentages of false negatives, that is many patients with fractures have normal peripheral density. Dual-photon (153Gd) scans of the spine, femur, and total skeleton are precise and accurate (2% error) and provide direct measurements of bone strength at fracture sites. This gives the best discrimination of abnormality and the most sensitive monitoring. Quantitative computed computed tomography (QCT) allows measurement of the spine but not the critical proximal femur area. QCT has a large accuracy error because (a) the limited area measured (under 5 cm3) fails to represent the total vertebral body, (b) technical errors, and (c) variable fat and osteoid influence the results.

Bone and Bones↗
PubMed1989

Monitoring skeletal response to estrogen.

Estrogen replacement therapy at accepted doses is not fully effective in preventing bone loss and fractures in postmenopausal women. Bone densitometry is useful for monitoring estrogen replacement therapy to assess dose, foster compliance, and check for secondary bone loss. The most appropriate site for bone loss monitoring is probably the spine because it shows larger decreases at the menopause than appendicular sites, it shows larger increases with therapy, and it has clinical import in terms of fracture. Both dual-photon absorptiometry (or dual-energy x-ray absorptiometry) and computed tomography are the preferred monitoring methods. The precision of these densitometry methods is generally adequate to permit interim decisions with regard to continuing therapy, as well as conclusive decisions on therapeutic efficacy after 1 to 2 years of monitoring. Judicious use of densitometry in combination with biochemical determinations can enhance therapeutic control and provide both patient and physician confidence in long-term estrogen replacement therapy.

Absorptiometry, Photon↗
PubMed1989

Rapid determination of total hydroxyproline (HYP) in human urine by HPLC analysis of the phenylisothiocyonate (PITC)-derivative.

A recent development in the preparation for amino acid analysis is the use of phenylisothiocyanate (PITC) as a precolumn derivatizing agent prior to analysis to form a stable derivative. These derivatives can then be separated by reversed phase high pressure liquid chromatography (HPLC). Because of interest in the accurate measurement of urinary hydroxyproline (HYP), PITC was used for derivatization followed by HPLC analysis. Using an automated computer-controlled sampler system, up to 75 samples can be analyzed each 24 h. Technical details, specificity, and reliability of this method are provided. Duplicate measurements of HYP had a coefficient of variation (CV) of 5.5% and with a recovery of HYP in spiked urine samples of 94 to 104%. A sample frozen and thawed 10 times showed no change in the concentration of HYP. When total HYP was measured in 230 healthy women between 20 and 39 years of age, it was found to be 236.62 +/- 146.41 mumoles/L. These samples were researched in 3.5 days using this technique.

Adult↗
PubMed1988

Radial and spinal bone mineral density in a patient population.

Density of the radius (by single-photon absorptiometry) and the spine (by dual-photon absorptiometry) was measured in 281 normal young women and in a large heterogeneous group of 1,622 consecutive female patients. Both spinal and radial density were useful measurements when performed on patients with medical indications; spine and radius densities in these patients averaged 10-20% below those of age-matched controls. However, patients younger than 60 years of age had deficits of spine density that were twice as large as those in the radius, and twice as many of these patients had spinal osteopenia, compared with those with radial osteopenia. After age 70, loss of density in the radius approximated that in the spine and the prevalence of osteopenia was similar at both sites. The poorer sensitivity of the radius measurement reflected the fact that it did not predict spine density. The standard error of the estimate was 0.12 gm/cm2 in normal subjects and 0.15 gm/cm2 in patients. At any given radial density, the spinal density of patients averaged 0.18 gm/cm2 (15-20%) below that in normal subjects. Predictions of spinal density from body weight were as accurate as predictions from radial density. Preferential spinal osteopenia occurring without radial osteopenia precluded radial densitometry as a screening method for individuals with osteoporosis before age 60. However, measurement of the radius was more effective than body weight for defining groups at risk, even though the radius did not reliably predict individual spine density. A radius shaft density less than 0.55 gm/cm2 occurring with a body weight less than 55 kg was associated with a high prevalence of spinal osteopenia.

Adult↗
PubMed1988

Bone density of the radius, spine, and proximal femur in osteoporosis.

Bone mineral density (BMD) was measured in 140 normal young women (aged 20 to 39 years) and in 423 consecutive women over age 40 referred for evaluation of osteoporosis. Lumbar spine and proximal femur BMD was measured using dual-photon absorptiometry (153Gd), whereas the radius shaft measurement used single-photon absorptiometry (125I). There were 324 older women with no fractures, of which 278 aged 60 to 80 years served as age-matched controls. There were 99 women with fractures including 32 with vertebral and 22 with hip fractures. Subsequently, another 25 women with hip fractures had BMD measured in another laboratory; their mean BMD was within 2% of that of the original series. The mean age in both the nonfracture and fracture groups was 70 +/- 5 years. The BMD in the age-matched controls was 20% to 25% below that of normal young women for the radius, spine, and femur, but the Ward's triangle region of the femur showed even greater loss (35%). The mean BMD at all sites in the crush fracture cases was about 10% to 15% below that of age-matched controls. Spinal abnormality was best discriminated by spine and femoral measurements (Z score about 0.9). In women with hip fractures, the BMD was 10% below that of age-matched controls for the radius and the spine, and the BMD for the femoral sites was about 25% to 30% below that of age-matched control (Z score about 1.6). Femoral densities gave the best discrimination of hip fracture cases and even reflected spinal osteopenia. In contrast, neither the spine nor the radius reflected the full extent of femoral osteopenia in hip fracture.

Adult↗
PubMed1988

Bone mineral density in Australia compared with the United States.

Bone density measurements are currently being performed throughout the world in the diagnosis and management of osteoporosis as well as in research into this major health problem. However, it is not clear to what extent bone mineral density (BMD) values determined by dual-photon absorptiometry at one center can be applied to another. This is particularly relevant for the quantitative comparison of results from studies carried out in different laboratories. Furthermore, many centers now acquiring densitometers may not have the resources to determine their own normal range, relying instead on a "normal" range provided by the manufacturer. The question of the comparability of BMD data obtained in different centers was examined by comparing the normal range for the lumbar spine and proximal femur in 203 normal white Australian women and 892 normal white U.S. women, obtained using the same model densitometer. The two populations were compared according to decade. From superimposition of the Australian individual values on the North American normal ranges, only minor differences between the two populations were seen at any of the sites measured at any decade. None of these minor differences were statistically significant. This study shows a close similarity between BMD values in both the proximal femur and lumbar spine in normal white women in Australia and North America, provided the same model densitometer is used. Thus data obtained from different centers in populations with similar ethnic composition may be compared directly. These findings provide for the first time a sound basis for the quantitative comparison of the at times conflicting studies carried out in widely differing settings around the world.

Adult↗
PubMed1988

Long term follow-up of bone mineral status in children with renal disease.

Bone mineral content (BMC) was measured by photon absorptiometry in the non-dominant forearm of children with chronic renal failure followed for a total of 2472 months. From 48 children, 302 measurements were made, and changes which occurred in BMC over time were correlated with several factors. Patients were divided into those who had received glucocorticoids (group 1) and those who had not (group 2). Group 1 patients had a lower mean serum creatinine (Cr) (p less than 0.05), a lower growth velocity (p greater than 0.02) and were more demineralized than group 2 patients. There was no correlation between BMC and height velocity or estimated creatinine clearance. BMC and height Z-score (SDS) were highly correlated. Over the period of study, group 1 patients remained shorter, had a lower height velocity, a lower BMC Z-score and a lower BMC for each serum creatinine level. Long-term therapeutic intervention with oral 1,25(OH)2D improved bone mineral status in three children in the nonsteroid group, but none of those in the steroid group. This study demonstrates that steroid administration is probably the most important factor causing bone demineralization, possibly even more important than renal failure.

Adolescent↗
PubMed1988

Bone mineral density in women with breast cancer treated with adjuvant tamoxifen for at least two years.

While in limited animal studies tamoxifen is reported to protect against loss of bone mineral, data in humans are lacking. We measured bone mineral density (BMD) using single photon absorptiometry at the radius and dual photon absorptiometry at the lumbar spine in breast cancer patients treated with chemotherapy at our institution. In this group, 37 women were not treated with tamoxifen (NT) and 48 women were treated with tamoxifen (T) for at least two years. Younger age, greater weight and height, premenopausal status, and shorter time since menopause were found to be significant predictors of greater BMD. Tamoxifen-treated women had been postmenopausal for more years (p = 0.012). Regression analyses used to adjust for differences in risk of bone loss did not reveal significant differences in BMD between the two groups of women. For the postmenopausal women (27 NT and 34 T subjects), the adjusted mean BMD (g/cm2) at the spine was 1.11 (NT), 1.11 (T) (p = 0.93); and at the radius 0.63 (NT), 0.62 (T) (p = 0.30). This limited retrospective study suggests that tamoxifen does not have 'anti-estrogenic' effects on BMD.

Adult↗
PubMed1988

Bone densitometry in infants.

Bone mineral mass and density can be measured noninvasively by various absorptiometric procedures. Two methods, dual-photon absorptiometry (DPA) and quantitative computed tomography, have widespread application in adults but only limited use in children. One method, single-photon absorptiometry (SPA), has been used extensively in adults and children and has been modified for use in infants. The radius shaft has been used for most research on infants. However, the difficulty of using older SPA methods on this small bone (4 to 7 mm width) has led a few investigators to measure the shaft of the humerus. The typical precision of measurement in a newborn is about 5% with the use of computerized rectilinear scanners for the radius; older linear scanners have a precision error of 5% to 10% on the humerus. Linear scanners cannot measure precisely the radius in individual neonates. The SPA scans typically take about 5 minutes. The DPA technique using 153Gd has been modified for use on smaller animals (5 to 10 kg monkeys and dogs), but it has not been used on infants because DPA scans take 20 minutes. New methods using x-ray absorptiometry allow rapid (1 minute), precise (1%) measurements in the perinate. The need for a soft tissue bolus is eliminated, and both the axial and peripheral skeletons can be measured with dual-energy x-ray absorptiometry. Ultrasonic measurements do not yet offer adequate precision in the neonate, given the limited biologic range of values.

Bone and Bones↗
PubMed1988

Measurement of bone by dual-photon absorptiometry (DPA) and dual-energy X-ray absorptiometry (DEXA).

Bone densitometry is essential for (a) confirming a diagnosis of osteoporosis, (b) determining the degree of osteopenia and risk of fracture, and (c) monitoring the response of bone to therapeutic agents. Fracture risk at specific axial fracture sites (spine, proximal femur), is associated directly with bone mineral density (BMD) at these sites. ROC analysis demonstrates that the diagnostic sensitivity of spine and femur BMD for spine and/or femur fracture is substantially superior to BMD of appendicular sites in the immediate postmenopausal period. Femoral neck BMD affords high diagnostic sensitivity for proximal femur fracture even in the elderly. Recent prospective studies have shown that bone densitometry can predict future fractures in postmenopausal women. Conventional DPA with 153Gd provides high accuracy for total body, spine, and femur BMD with adequate clinical precision of 1%, 2% and 3%, respectively. Dual-energy x-ray absorptiometry (DEXA), using either switched kVp or by k-edge filtering, offers better precision; typically the precision error is halved. The higher flux available from x-ray sources provides other advantages over DPA, including: improved spatial resolution (2 vs 4 mm), reduced radiation exposure (1 vs 2 mrem), and decreased scan times (3 to 10X). Improved DPA systems, with automatic gain stabilization to minimize drift, could offer clinical precision comparable to DEXA but the scan time and spatial resolution remain as before. Both DPA and DEXA allow detection of therapeutic efficacy in individual patients over the first year or two of therapy.

Absorptiometry, Photon↗