Search PubMed⌕ Search

Biomedical subjects

H K Genant

Publications and source records attributed to H K Genant.

At least 217 records · Page 12Linked to original sources
PubMed1995

Radiographic osteoarthritis of the hip and bone mineral density. The Study of Osteoporotic Fractures Research Group.

OBJECTIVE: To examine the cross-sectional association between radiographic features of hip osteoarthritis (OA) and bone mineral density (BMD) of the hip, spine, and appendicular skeleton among Caucasian women ages 65 and older who were participating in the Study of Osteoporotic Fractures. METHODS: Pelvis radiographs of 4,855 subjects were assessed for individual radiographic features of hip OA: osteophytes, joint space narrowing, subchondral sclerosis, cysts, and femoral head deformity. Hips were graded on a summary scale of 0 (no OA) to 4 (severe OA) based on the number of radiographic features present. Appendicular BMD was measured in all subjects, and hip and spine BMD in 84% of the group. We used linear regression to examine the association of BMD with hip OA, and to adjust for age, weight, and other determinants of bone mass. RESULTS: Three hundred fifty-one women (7.2%) had mild (grade 2) and 228 (4.7%) had moderate to severe (grade 3-4) radiographic evidence of hip OA. Women with grade 3-4 hip OA had a higher age-adjusted BMD at the femoral neck and Ward's triangle (9-10%; P < 0.0001), trochanter (4%; P < 0.01), lumbar spine (8%; P < 0.0001), and distal radius and calcaneus (5%; P < 0.0001 [for each comparison]) compared with those with grade 0-1 OA in the worse hip. Elevations in BMD were greatest in the femoral neck of hips with OA, in women with bilateral hip OA, and in women with hip osteophytes. These findings were essentially unchanged by adjustment for determinants of bone mass. CONCLUSION: Elderly Caucasian women with moderate to severe radiographic hip OA had higher BMD in the hip, spine, and appendicular skeleton than did women without hip OA. Our findings are consistent with a role of elevated BMD in the pathogenesis of hip OA.

Aged↗
PubMed1995

Quantitative ultrasound and vertebral fracture in postmenopausal women. Fracture Intervention Trial Research Group.

Quantitative ultrasound is a promising technique to evaluate fracture risk. To test the hypothesis that reduction of one ultrasound measurement, broadband ultrasound attenuation (BUA), is associated with an increased risk of vertebral fracture in postmenopausal women, we performed a cross-sectional analysis of 442 women aged 55-80 years enrolling in a clinical trial of alendronate. Prior to randomization, we obtained bone mineral density (BMD) measurements of the hip, spine, and whole body, radiographs of lateral lumbar and thoracic spine, and duplicate measurements of calcaneal BUA with a Walker Sonix UBA575. Vertebral fractures were defined by morphometry and semiquantitative reading by a radiologist. After adjustment for potential confounders, the relative risk of vertebral fracture was 1.8 (95% CI 1.4-2.3) for each standard deviation reduction in BUA; for each standard deviation reduction in BMD, the relative risk was 1.7 (95% CI 1.3-2.1) at the femoral neck, and 2.2 (95% CI 1.7-2.9) at the spine. Adjustment for hip, spine, or whole body BMD did not significantly alter the relation between BUA and vertebral fracture. For example, after adjusting for spine BMD, the relative risk of vertebral fracture was 1.5 (95% CI 1.1-2.0) for each standard deviation reduction in BUA. We conclude that low BUA is associated with the presence of vertebral fractures in postmenopausal women. The relation between BUA and vertebral fracture is similar to that observed for BMD and vertebral fractures. Furthermore, the relation between BUA and vertebral fracture persists after adjustment for BMD.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

A two-year program of aerobics and weight training enhances bone mineral density of young women.

Previous research suggests that physical activity may have a beneficial effect on bone mineral density (BMD) in women. This relationship was explored in a 2-year, randomized, intervention trial investigating the efficacy of exercise and calcium supplementation on increasing peak bone mass in young women. One hundred and twenty-seven subjects (ages of 20-35 years) were randomly assigned either to an exercise program that contained both aerobics and weight training components or to a stretching program. Calcium supplementation (up to 1500 mg/day including dietary intake) or placebo was given in a double-blinded design to all subjects. Spinal trabecular BMD was determined using quantitative computed tomography (QCT). Spinal integral, femoral neck, and trochanteric BMD were measured by dual X-ray absorptiometry (DXA) and calcaneal BMD by single photon absorptiometry (SPA). Fitness variables included maximal aerobic capacity (VO2max), and isokinetic muscle performance of the trunk and thigh. Measurements were made at baseline, 1 year, and 2 years. Sixty-three subjects (32 exercise, 31 stretching) completed the study, and all the measured bone parameters indicated a positive influence of the exercise intervention. There were significant positive differences in BMD between the exercise and stretching groups for spinal trabecular (2.5%), femoral neck (2.4%), femoral trochanteric (2.3%), and calcaneal (6.4%) measurements. The exercise group demonstrated a significant gain in BMD for spinal integral (1.3 +/- 2.8%, p < 0.02), femoral trochanteric (2.6 +/- 6.1%, p < 0.05), and calcaneal (5.6 +/- 5.1, p < 0.01) measurements. In contrast to exercise, the calcium intervention had no positive effect on any of the bone parameters. In regard to fitness parameters, the exercise group completed the study with significant gains in VO2max and isokinetic (peak torque) values for the knee flexion and extension and trunk extension. This study indicates that over a 2-year period, a combined regimen of aerobics and weight training has beneficial effects on BMD and fitness parameters in young women. However, the addition of daily calcium supplementation does not add significant benefit to the intervention.

Absorptiometry, Photon↗
PubMed1995

Comparison of methods for defining prevalent vertebral deformities: the Study of Osteoporotic Fractures.

Women with vertebral deformities caused by osteoporosis have more back pain and disability and are at higher risk for subsequent vertebral deformities than women without deformities. Despite the importance of vertebral deformities, there has been a great deal of controversy about how to identify or define them. In order to compare methods for defining vertebral deformities, we studied spinal radiographs from women in the Study of Osteoporotic Fractures (SOF), a cohort study of 9704 non-black women over age 65 recruited from population-based listings in four clinical centers. Using radiographs obtained at the baseline exam, we compared five methods for defining vertebral deformities: one based on a semiquantitative reading by a radiologist and four using vertebral morphometry. The semiquantitative method was compared with the other methods in a random sample of 503 films, while the morphometric methods were compared with each other in a larger sample of 9575 films. We tested a system of "triage" in which only those films with evidence of deformity were assessed by morphometry. We compared the relationship between deformity, defined by each method, and a variety of clinical criteria including bone mineral density at the lumbar spine, height loss since age 25, back pain, and incidence of subsequent deformity. Semiquantitative reading and three of the four morphometry-based methods provided similar relationships to clinical criteria. The fourth morphometry method (based on ratios of each vertebral height to the corresponding height at T4) produced significantly weaker relationships for several of the clinical validation criteria. Triage of radiographs rarely resulted in missed deformities and did not reduce the performance of any of the methods. We conclude that use of any of the similar methods, with or without triage, provides a valid approach to defining vertebral deformities.

Aged↗
PubMed1995

Estimates of volumetric bone density from projectional measurements improve the discriminatory capability of dual X-ray absorptiometry.

To determine whether estimates of volumetric bone density from projectional scans of the lumbar spine have weaker associations with height and weight and stronger associations with prevalent vertebral fractures than standard projectional bone mineral density (BMD) and bone mineral content (BMC), we obtained posteroanterior (PA) dual X-ray absorptiometry (DXA), lateral supine DXA (Hologic QDR 2000), and quantitative computed tomography (QCT, GE 9800 scanner) in 260 postmenopausal women enrolled in two trials of treatment for osteoporosis. In 223 women, all vertebral levels, i.e., L2-L4 in the DXA scan and L1-L3 in the QCT scan, could be evaluated. Fifty-five women were diagnosed as having at least one mild fracture (age 67.9 +/- 6.5 years) and 168 women did not have any fractures (age 62.3 +/- 6.9 years). We derived three estimates of "volumetric bone density" from PA DXA (BMAD, BMAD*, and BMD*) and three from paired PA and lateral DXA (WA BMD, WA BMDHol, and eVBMD). While PA BMC and PA BMD were significantly correlated with height (r = 0.49 and r = 0.28) or weight (r = 0.38 and r = 0.37), QCT and the volumetric bone density estimates from paired PA and lateral scans were not (r = -0.083 to r = 0.050). BMAD, BMAD*, and BMD* correlated with weight but not height. The associations with vertebral fracture were stronger for QCT (odds ratio [QR] = 3.17; 95% confidence interval [CI] = 1.90-5.27), eVBMD (OR = 2.87; CI 1.80-4.57), WA BMDHol (OR = 2.86; CI 1.80-4.55) and WA-BMD (OR = 2.77; CI 1.75-4.39) than for BMAD*/BMD* (OR = 2.03; CI 1.32-3.12), BMAD (OR = 1.68; CI 1.14-2.48), lateral BMD (OR = 1.88; CI 1.28-2.77), standard PA BMD (OR = 1.47; CI 1.02-2.13) or PA BMC (OR = 1.22; CI 0.86-1.74). The areas under the receiver operating characteristic (ROC) curves for QCT and all estimates of volumetric BMD were significantly higher compared with standard PA BMD and PA BMC. We conclude that, like QCT, estimates of volumetric bone density from paired PA and lateral scans are unaffected by height and weight and are more strongly associated with vertebral fracture than standard PA BMD or BMC, or estimates of volumetric density that are solely based on PA DXA scans.

Absorptiometry, Photon↗
PubMed1995

Assessment of the skeletal status by peripheral quantitative computed tomography of the forearm: short-term precision in vivo and comparison to dual X-ray absorptiometry.

In order to assess precision of peripheral quantitative computed tomography (pQCT), duplicate bone mineral density (BMD) measurements at the radius were performed in 20 healthy premenopausal, 20 healthy postmenopausal, and 20 osteoporotic postmenopausal women using a Stratec XCT-960 system. The short-term reproductibility in vivo for the total, trabecular, and cortical regions of interest (ROI) was expressed as the absolute precision error (standard deviation, SD) and as the relative precision error (SD/mean x 100, or coefficient of variation, CV, in %). Reproducibility in vivo was good in all volunteers but was influenced by the study group and the ROI. The precision error for trabecular BMD was 3 mg/cm3, or about 1.6%. This is large relative to the aging decrease of 0.22%/year, or to the difference (12 mg/cm3, or 7%) between osteoporotic women and postmenopausal controls. In order to compare pQCT to dual X-ray absorptiometry (DXA) at the forearm and at the lumbar spine (L1-L4), 40 premenopausal healthy controls, 40 postmenopausal healthy controls, and 35 postmenopausal osteoporotic women were assessed. DXA measurements performed at the ultradistal, middistal, 1/3, and total ROI of the radius showed only moderate correlations between r = 0.38--0.75, r = 0.27--0.64, and r = 0.38--0.53 for the comparison versus pQCT total BMD, versus pQCT trabecular BMD, and versus pQCT cortical BMD, respectively. Correlations of DXA at the lumbar spine and pQCT were between r = 0.18 and 0.44. DXA at radius and spine was able to discriminate between post- menopausal controls and osteoporotic women (p = 0.001--.004),but BMD measurements by pQCT did not show this ability (p = 0.15--0.52). However, two nonstandard pQCT parameters, namely the surface area of the cortical bone and the cortical BMC were factors that discriminated well between these two groups (p = 0.002, p = 0.005, respectively). These pQCT parameters also yielded the highest relative annual changes in pre- and post-menopausal control subjects. The measurement of cortical bone in the distal radius proved to be a good predictor of vertebral fracture status and was a good indicator of age-related skeletal change. Our data emphasize the importance of cortical measurements when using pQCT of the radius to assess osteoporosis.

Absorptiometry, Photon↗
PubMed1995

MRI of bone marrow in the distal radius: in vivo precision of effective transverse relaxation times.

The effective transverse relaxation time T2* is influenced by the presence of trabecular bone, and can potentially provide a measure of bone density as well as bone structure. We determined the in vivo precision of T2* in repeated bone marrow measurements. The T2* measurements of the bone marrow of the distal radius were performed twice within 2 weeks in six healthy young volunteers using a modified water-presaturated 3D Gradient-Recalled Acquisition at Steady State (GRASS) sequence with TE 7, 10, 12, 20, and 30; TR 67; flip angle (FA) 90 degrees. An axial volume covering a length of 5.6 cm in the distal radius was measured. Regions of interest (ROIs) were determined manually and consisted of the entire trabecular bone cross-section extending proximally from the radial subchondral endplate. Reproducibility of T2* and area measurements was expressed as the absolute precision error (standard deviation [SD] in ms or mm2) or as the relative precision error (SD/mean x 100, or coefficient of variation [CV] in %) between the two-point measurements. Short-term precision of T2* and area measurements varied depending on section thickness and location of the ROI in the distal radius. Absolute precision errors for T2* times were between 1.3 and 2.9 ms (relative precision errors 3.8-9.5 %) and for area measurements between 20 and 55 mm2 (relative precision errors 5.1-16.4%). This MR technique for quantitative assessment of trabecular bone density showed reasonable reproducibility in vivo and is a promising future tool for the assessment of osteoporosis.

Adult↗
PubMed1995

Factors influencing short-term precision of dual X-ray bone absorptiometry (DXA) of spine and femur.

In this study we analyzed the effect of variations in bone area size, baseline soft tissue composition represented by the R-value, and bone region of interest positioning on the precision in vivo of bone mineral density (BMD) and content (BMC) as measured by dual X-ray absorptiometry (DXA). The posterior-anterior (PA) spine, decubitus lateral, and femur modes were evaluated. Eleven (PA-spine), 9 (dec-lat), and 14 (femur) postmenopausal women were scanned twice on a Norland XR-26 with repositioning to determine short-term precision of BMD, BMC, AREA, and the R-value. Phantom precisions (CV[%] of 10 consecutive scans) for BMD (BMC) were PA spine: 0.66% (0.57%), neck: 1.1% (1.2%), and trochanter: 0.55% (1.0%). Precisions in vivo (CV[%]; two consecutive scans averaged over all patients) were PA spine: 0.9% (1.0%), dec-lat: 7.1% (18%), neck: 1.3% (1.9%), and trochanter: 2.5% (4.9%). BMD precision could be fully explained by BMC and AREA variations. However, BMC alone was a particularly poor predictor of BMD in the dec-lat (r2 = 0.05) and in the neck (r2 = 0.13) modes. AREA was a strong predictor for BMC precision explaining between 41% and 88% of the BMC changes. Changes in soft tissue composition contributed significantly in explaining the BMC changes in the dec-lat projection. A higher dependence of BMC changes on AREA changes resulted in a larger difference between BMC and BMD precision.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1995

Bilateral comparison of femoral bone density and hip axis length from single and fan beam DXA scans.

Dominant/nondominant differences in bone mineral density (BMD) have been observed in the upper extremities. However for the proximal femur, the distinction between dominant and nondominant hips is not clear. The purpose of this study is to evaluate left/right variations in femoral BMD and hip axis length (HAL) in both single beam and fan beam dual x-ray absorptiometry (DXA) scans. A total of 36 women aged 41-76 years (average age 60 +/- 10 years) received single beam and fan beam DXA scans of both proximal femora with a Hologic QDR-2000 scanner. Femoral BMD and hip axis length were determined for each scan. Left/right and single beam/fan beam correlations were determined and differences were evaluated using a two-way analysis of variance. Femoral BMD at corresponding measurement regions in opposing femora were highly correlated (r = 0.81-0.96). No significant left/right differences were detected. At the femoral neck, the mean BMD difference (+/- standard deviation) was 1.5% +/- 4.7% in a single beam mode and -0.6% +/- 6.3% in fan beam mode. Though mean values of femoral BMD were equivalent, the observed individual left/right differences were occasionally large (as high as 26% in the femoral neck). The hip axis length of the left and right hips were highly correlated and statistically equivalent. However, hip axis length using fan beam was significantly larger (7.5%) than the single beam measurement with a larger observed variation. We conclude that measurement of a single proximal femur will usually be sufficient for clinical evaluation of BMD and/or hip axis length.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1995

Influence of degenerative joint disease on spinal bone mineral measurements in postmenopausal women.

We assessed the impact of various forms of spinal degenerative joint disease (DJD) on bone mineral density (BMD) measured by quantitative computed tomography (QCT) and dual X-ray absorptiometry (DXA) in a group of postmenopausal women. Lateral (T4-L4) and AP (L1-L4) spinal radiographs were reviewed for fracture and DJD in 209 women (mean age 62.6 +/- 6.7). The severity of DJD findings was graded as 0, 1, or 2 on the lumbar films, except for vertebral osteophytes which were graded from 0 to 3. Vertebral fractures were defined semiquantitatively as approximately 20% reduction in anterior, middle, or posterior vertebral height. BMD was measured in all subjects by QCT and DXA, including posteroanterior DXA (PA-DXA), lateral DXA (L-DXA) and midlateral DXA (mL-DXA). When BMD was measured by QCT and mL-DXA in the 168 women without fractures, no significant differences were found between women with and those without DJD. However, BMD by PA-DXA was significantly higher in women with DJD changes, particularly when osteophytes were present at the vertebral bodies or facet joints. BMD by L-DXA was less affected by DJD. For this measurement a significant increase in BMD was only noted in subjects with vertebral osteophytes. Multivariate analysis of variance (MANOVA) showed that BMD by QCT and mL-DXA was not affected by DJD. In contrast, for all women, BMD by PA- and L-DXA was affected more by DJD than by fracture status. Chi-square testing demonstrated no significant relationships between vertebral fractures and any of the DJD changes. We conclude that QCT and mL-DXA are superior to PA-DXA and L-DXA in detecting bone loss in patients with DJD. Thus, for these patients, BMD assessment by QCT or mL-DXA may be advisable.

Absorptiometry, Photon↗
PubMed1995

Comparison of semiquantitative and quantitative techniques for the assessment of prevalent and incident vertebral fractures.

To compare visual semiquantitative (SQ) reading and quantitative morphometry (QM) for assessing prevalent and incident vertebral fractures, radiographs of the thoracolumbar spine were evaluated in 400 (only baseline films) and 335 (baseline and follow-up films) postmenopausal women with osteopenia as defined by a T-score of less than 2 SD below young normals. QM was performed using different cutoff thresholds, and the SQ reading was performed by three radiologists independently. A joint consensus reading of the radiographs by all participating radiologists was used as a reference standard. Our results indicate that the concordance within SQ methods is excellent, and it is higher than that between SQ and QM regardless of the cutoff criteria used. This finding was consistent for the diagnosis of prevalent as well as incident vertebral fractures. For prevalent fractures the use of the 2.5 SD cutoff criterion provided the highest concordance with the consensus reading and with the radiologists' reading, thereby providing high sensitivity (70.23%) with moderate specificity (98.76%) relative to the consensus reading when compared with the 3 SD or 4 SD cutoff criteria. For the diagnosis of incident vertebral fractures the best agreement between our consensus reading and QM was found for an absolute reduction of 6 mm and for a combination of relative and absolute reduction of 15% and 3 mm in vertebral height. The respective sensitivities and specificities for the two criteria were 51%/99.9% and 75.4%/98.9%, respectively. Even though the consensus reading may favor the reader's evaluation over QM, the assessment of prevalent and incident fractures using QM alone may not be sufficiently reliable for detection of vertebral fractures in epidemiological studies and clinical trials. It should be performed principally in conjunction with a trained radiologist or a highly experienced clinician.

Bone Diseases, Metabolic↗
PubMed1995

A review of the recent advances in magnetic resonance imaging in the assessment of osteoporosis.

Osteoporosis is a common metabolic disorder with considerable associated morbidity and mortality. The loss of bone mineral integrity and the resultant occurrence of atraumatic fractures are typically symptomatic of the disease. Currently skeletal status is commonly assessed using non-invasive conventional radiography and scintigraphy as well as densitometric techniques such as quantitative computed tomography and dual-energy X-ray absorptiometry. But, apart from gross bone mineral density, the fine structure of trabecular bone also plays an important role in defining the biomechanical competence of the skeleton. Recently attention has been focused on deriving measures that provide information about not only trabecular bone density but also microstructure. Magnetic resonance imaging (MRI) is one such new technique which potentially may provide information pertaining to bone density and structure as well as to occult fracture detection. Cortical bone produces a signal void in MR images, due to the fact that it contains very few mobile protons that give rise to a signal in MRI; also the MR relaxation time T2 of these protons is very short which produces a very fast decay of the MR signal during image acquisition. However, the trabecular bone network affects the MR properties of bone marrow. The difference in the magnetic properties of trabecular bone and bone marrow generates local imperfections in the magnetic field. The MR signal from bone marrow is modified due to these imperfections and the MR relaxation time T2 of marrow is shortened. The extent of relaxation time shortening and hence loss of signal intensity is proportional to the density of trabecular bone and marrow interfaces and their spatial architecture. Recent investigation in this area include studies aimed at quantifying marrow relaxation times and establishing their relationship to trabecular bone density and structure. In addition, with advances in imaging software and hardware, MR images at in-plane resolutions of 78-200 microns may be obtained. The trabecular bone structure is clearly revealed in such images and studies aimed at the development of high-resolution MRI techniques combined with quantitative image analysis techniques are currently under way. These potentially useful techniques for assessing osteoporosis and predicting fracture risk are reviewed in this paper.

Bone Density↗
PubMed1995

Spinal bone mineral assessment in postmenopausal women: a comparison between dual X-ray absorptiometry and quantitative computed tomography.

We compared quantitative computed tomography (QCT) and dual X-ray absorptiometry (DXA) with respect to their ability to discriminate subjects with and without prevalent vertebral fractures. In 240 post-menopausal women (mean age 63.7 +/- 6.9 years) lateral spine radiographs (T4-L4) were reviewed for the presence of vertebral fracture. Using a semiquantitative technique to grade the severity of vertebral deformities, we classified fractures as mild, moderate or severe (grade 1 to 3, respectively). Postero-anterior DXA (PA-DXA) and lateral DXA (L-DXA) measurements (L2-4) as well as QCT measurements of the lumbar spine (T12-L3 or L1-14) were obtained in all women. Seventy-two women were diagnosed with at least one fracture, and of these 40 were graded as mild. Comparing normal women with fractured women, we found the area under the receiver operating characteristics (ROC) curves to be greatest for QCT (0.81), followed by L-DXA (0.72) and PA-DXA (0.65). The differences among all three techniques were significant. Comparing the normal women with women having only mild fractures, the areas under the ROC curves were 0.79, 0.73 and 0.63 for QCT, L-DXA and PA-DXA, respectively. Significant differences existed between QCT and PA-DXA as well as between L-DXA and PA-DXA. Logistic regression analysis also revealed the highest age-adjusted odds ratios for QCT (3.67; 2.25-5.97) while L-DXA and PA-DXA showed substantially lower odds ratios (2.00; 1.39-2.87, and 1.54; 1.11-2.15, respectively). We conclude that low bone density as measured by QCT, PA-DXA or L-DXA is significantly associated with the prevalence of vertebral fractures. Of the methods studied, QCT of trabecular bone offered the best discriminatory capability. L-DXA proved to be superior to PA-DXA in its diagnostic sensitivity, particularly in women with mild fracture. Mild vertebral fractures are associated with decreased spinal bone density and may be regarded as osteoporotic deformities.

Absorptiometry, Photon↗
PubMed1995

Spinal bone mineral loss in estrogen-replete, calcium-replete premenopausal women.

After peak bone mass in women is attained, the benefits of increased dietary calcium or supplemental calcium are uncertain. In a longitudinal, 4-year study we have investigated the effect of calcium intake on bone mineral in a group of 41 premenopausal women, aged 38-42 years at entry. Skeletal density was measured four times during the 4-year follow-up; spinal trabecular bone density (STBD) was measured by quantitative computed tomography, and midradius bone mineral density (RBMD) was measured by single photon absorptiometry. At baseline, no differences in bone density were observed among subjects in the highest and lowest quartiles of habitual dietary intake. Overall, STBD declined -0.86 +/- 0.15% per year (p < 0.001), but RBMD did not decline. Total calcium intake (dietary calcium plus supplemental calcium) did not correlate with the rate of STBD loss. Serum estradiol level did not decrease during the study, and bone loss did not correlate with the mean estradiol level. We conclude that premenopausal women in the fifth decade lose about 1% of spinal trabecular mineral yearly, in spite of a normal serum estradiol level and ample calcium intake.

Adult↗
PubMed1995

Accurate assessment of precision errors: how to measure the reproducibility of bone densitometry techniques.

Assessment of precision errors in bone mineral densitometry is important for characterization of a technique's ability to detect longitudinal skeletal changes. Short-term and long-term precision errors should be calculated as root-mean-square (RMS) averages of standard deviations of repeated measurements (SD) and standard errors of the estimate of changes in bone density with time (SEE), respectively. Inadequate adjustment for degrees of freedom and use of arithmetic means instead of RMS averages may cause underestimation of true imprecision by up to 41% and 25% (for duplicate measurements), respectively. Calculation of confidence intervals of precision errors based on the number of repeated measurements and the number of subjects assessed serves to characterize limitations of precision error assessments. Provided that precision error are comparable across subjects, examinations with a total of 27 degrees of freedom result in an upper 90% confidence limit of +30% of the mean precision error, a level considered sufficient for characterizing technique imprecision. We recommend three (or four) repeated measurements per individual in a subject group of at least 14 individuals to characterize short-term (or long-term) precision of a technique.

Absorptiometry, Photon↗
PubMed1995

Which vertebrae should be assessed using lateral dual-energy X-ray absorptiometry of the lumbar spine.

The purpose of this study was to determine precision and diagnostic capability of bone mineral density measurements using lateral dual-energy X-ray absorptiometry (DXA) of the lumbar spine in supine position. Duplicate postero-anterior (PA) and lateral DXA measurements were performed in 60 women. Precision errors of the single vertebral levels using lateral DXA ranged from 3.3% to 4.9%. The combination of all levels improved the precision errors to 2.0%. Paired PA and lateral DXA measurements (Hologic QDR 2000) including the vertebral levels L2 to L4 were performed in 331 postmenopausal women. In 42 women an overlap of L4 by the pelvis was suspected on the lateral DXA images. Vertebral fractures were assessed as a fracture/non-fracture dichotomy. L4 and combinations of vertebrae including L4 showed the best discriminatory capabilities with respect to vertebral fractures in receiver operating characteristic (ROC) analyses, t-tests and Z-scores, with smaller variability of the results when multiple vertebral levels were used. The areas under the ROC curves were 0.662 and 0.639 for lateral and PA measurements of L2 to L4, respectively when all women were included. Excluding the women with pelvic overlap on lateral DXA scans improved the ROC area for lateral scans to 0.686 while that for PA scans remained almost constant (0.641). The differences between PA and lateral measurements were not statistically significant. In 162 women of our study cohort an additional quantitative computed tomography (QCT) measurement of the vertebral levels L2 to L4 was performed and overlapping bony structures at the three levels were studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗