Does the precision of dual-energy X-ray absorptiometry for bone mineral density differ by sex?

Given larger bone size in men, bone mineral density (BMD) precision might differ between sexes. This study compared dual-energy X-ray absorptiometry BMD precision of 3 International Society for Clinical Densitometry-certified technologists in older men and women. Each technologist scanned a cohort of 30 men and 30 women (total n = 180) by using a Lunar iDXA densitometer (GE Healthcare, Madison, WI). Each volunteer had 2 lumbar spine and bilateral hip scans with repositioning between examinations. BMD least significant change was calculated. Age and body mass index did not differ between men and women. Mean height and weight were greater in men, 174.6 cm ± 6.9 and 81.6 kg ± 11.1 respectively, (p < 0.0001) than in women, 161.5 cm ± 5.9/69.1 kg ± 14.2, respectively. Bone area was greater in men (p < 0.0001) at all sites. BMD least significant change was statistically better (p < 0.05) in women at the mean total femur (0.014 vs 0.018 g/cm(2)) and left femoral neck (0.025 vs 0.038 g/cm(2)), but not different at either total femur, the right femoral neck, or lumbar spine (all p > 0.05). In conclusion, statistically significant male/female differences in BMD precision were observed at the mean total femur and left femoral neck. Given the small magnitude of difference in g/cm(2) and inconsistent pattern, that is, no right femoral neck difference, there is virtually no clinical difference in BMD precision between sexes. These data do not support a need for sex-specific precision analyses.

Positioner and clothing artifact can affect one-third radius bone mineral density measurement.

This report identifies a radius dual-energy X-ray absorptiometry (DXA) confounder and technical approach to avoid this inaccuracy. Initially, a precision study revealed substantial differences (p<0.001) in radius bone mineral density (BMD) least significant change ranging from 0.038 to 0.073g/cm(2) between 3 technologists that each performed assessments in 30 men and 30 women. Subsequently, visual examination of all 360 forearm DXA images, including bone, soft tissue, neutral, and air point-typing was performed. Errors in automated "soft tissue" identification were observed; compared with the manufacturer's ideal depiction, suboptimal soft tissue point-typing was present in 30/360 scans (8.3%) involving 27 individuals. These point-typing deviations appeared to result from inclusion of forearm positioner slots at the scan field edges or clothing covering the forearm. Twenty-four individuals had a paired scan appropriately point-typed, thus allowing evaluation of the effect on BMD measurement. In those with incorrect point-typing associated with positioner slots, the mean one-third radius BMD was ∼7% higher. In conclusion, positioner slots at the edges of the distal scan field can lead to automated soft tissue identification inaccuracies and consequent erroneous one-third radius BMD measurement. DXA technologists should avoid slot inclusion in forearm scans and evaluate point-typing as part of routine analysis.

BMD measurement and precision: a comparison of GE Lunar Prodigy and iDXA densitometers.

This study assessed bone mineral density (BMD) comparability and precision using Lunar Prodigy and iDXA densitometers (GE Healthcare, Madison, WI) in adults. Additionally, the utility of supine forearm measurement with iDXA was investigated. Lumbar spine and bilateral proximal femur measurements were obtained in routine clinical manner in 345 volunteers, 202 women and 143 men of mean age 52.5 (range: 20.1-91.6)yr. Seated and supine distal forearm scans were obtained in a subset (n=50). Lumbar spine and proximal femur precision assessments were performed on each instrument following International Society for Clinical Densitometry recommendations in 30 postmenopausal women. BMD at the L1-L4 spine, total proximal femur, and femoral neck was very highly correlated (r(2)≥0.98) between densitometers, as was the one-third radius site (r(2)=0.96). Bland-Altman analyses demonstrated no clinically significant bias at all evaluated sites. BMD precision was similar between instruments at the L1-L4 spine, mean total proximal femur, and femoral neck. Finally, one-third radius BMD measurements in the supine vs seated position on the iDXA were highly correlated (r(2)=0.96). In conclusion, there is excellent BMD correlation between iDXA and Prodigy densitometers. Similarly, BMD precision is comparable with these two instruments.

Vitamin K treatment reduces undercarboxylated osteocalcin but does not alter bone turnover, density, or geometry in healthy postmenopausal North American women.

Low vitamin K status is associated with low BMD and increased fracture risk. Additionally, a specific menaquinone, menatetrenone (MK4), may reduce fracture risk. However, whether vitamin K plays a role in the skeletal health of North American women remains unclear. Moreover, various K vitamers (e.g., phylloquinone and MK4) may have differing skeletal effects. The objective of this study was to evaluate the impact of phylloquinone or MK4 treatment on markers of skeletal turnover and BMD in nonosteoporotic, postmenopausal, North American women. In this double-blind, placebo-controlled study, 381 postmenopausal women received phylloquinone (1 mg daily), MK4 (45 mg daily), or placebo for 12 mo. All participants received daily calcium and vitamin D(3) supplementation. Serum bone-specific alkaline phosphatase (BSALP) and n-telopeptide of type 1 collagen (NTX) were measured at baseline and 1, 3, 6, and 12 mo. Lumbar spine and proximal femur BMD and proximal femur geometry were measured by DXA at baseline and 6 and 12 mo. At baseline, the three treatment groups did not differ in demographics or study endpoints. Compliance with calcium, phylloquinone, and MK4 treatment was 93%, 93%, and 87%, respectively. Phylloquinone and MK4 treatment reduced serum undercarboxylated osteocalcin but did not alter BSALP or NTX. No effect of phylloquinone or MK4 on lumbar spine or proximal femur BMD or proximal femur geometric parameters was observed. This study does not support a role for vitamin K supplementation in osteoporosis prevention among healthy, postmenopausal, North American women receiving calcium and vitamin D supplementation.

Effect of female database use for T-score derivation in men.

Whether to use male or female databases to obtain T-scores in men remains controversial. This study evaluated the impact of deriving male T-scores using female databases in 350 men aged 22.8-93.5 (mean 67.5+/-12.2) yr who were referred for clinically indicated dual-energy X-ray absorptiometry exams. Spine, femur, and nondominant radius scans were obtained in routine clinical manner using a GE Healthcare Lunar Prodigy densitometer. Analyses were performed using software version 9.30. Initially, the GE Healthcare Lunar male normative database was used to calculate T-scores. Subsequently, scans were reanalyzed using female databases; GE for the spine and radius, and NHANES III for the femur. Using the manufacturer's male database, T-scores (mean [range]) of the L1-4 spine, femur neck, total femur, and .3 radius were 0.0 [-4.6 to +8.5], -1.6 [-4.3 to +2.3], -1.1 [-4.0 to +3.3], and -0.7 [-5.3 to +2.9], respectively. On reanalysis with female databases, T-scores "improved" (p<0.0001) with a positive bias of 0.34, 0.33, 0.58, and 1.20, respectively at the above 4 sites. Using female databases, the proportion of men classified as having normal bone mass increased from 22% to 33% and those identified as osteoporotic decreased from 29% to 17%. If pharmacologic treatment were prescribed at a T-score <-2.0, use of the female databases would reduce those treated for low bone mass from 46% to 32%. In conclusion, using female databases to derive male T-scores results in "improvement" of diagnostic classification for a substantial number of men with fewer being classified as having low bone mass.

Addition of right lateral decubitus positioning improves vertebral visualization with VFA in selected patients.

Densitometric vertebral fracture assessment (VFA) allows detection of clinically unappreciated vertebral fracture. However, vertebral visualization using VFA can be suboptimal. In such individuals, alternative spine positioning may enhance visualization. Consistent with this, we observed that reversal of positioning (right lateral decubitus rather than standard left lateral decubitus, subsequently referred to as "reverse" positioning) improved visualization in patients with suboptimal vertebral visualization. This report describes 33 such individuals (i.e., 30 men and 3 women); their mean age and their lowest T-score (L1-L4 spine, proximal femur or 0.3 radius) was 69.9 yr and 2.2, respectively. All images were acquired using a GE Healthcare Lunar Prodigy densitometer (GE Healthcare, Madison, WI). Reverse VFA increased the number of visualized vertebrae in 82% of these patients (27 of 33; p<0.0001). Specifically, only 62% of vertebrae from T4-L5 were visualized using the standard left lateral position. Addition of either full or partial reverse VFA increased (p<0.0001) the number of visualized vertebrae to 83% (384 of 462). In this cohort, reverse positioning allowed detection of 4 additional vertebral fractures, including two in patients without previously identified fractures. We conclude that in selected patients with suboptimal vertebral visualization on VFA, addition of reverse positioning improves visualization and may enhance vertebral fracture detection.

Interobserver reproducibility of criteria for vertebral body exclusion.

UNLABELLED: We studied reproducibility of the ISCD vertebral exclusion criteria among four interpreters. Surprisingly, agreement among interpreters was only moderate, because of differences in threshold for diagnosing focal structural defects and choice of which vertebra among a pair discordant for T-score, area, or BMC to exclude. Our results suggest that reproducibility may be improved by specifically addressing the sources of interobserver disagreement. INTRODUCTION: Although DXA is widely used to measure vertebral BMD, its interpretation is subject to multiple confounders including osteoarthritis, aortic calcification, and scoliosis. In an attempt to standardize interpretation and minimize the impact of artifacts, the International Society for Clinical Densitometry (ISCD) established criteria for vertebral exclusion, including the presence of a focal structural defect (FSD), discrepancy of >1 SD in T-score between adjacent vertebrae, and a lack of increase in BMC or area from L1 to L4. Whereas the efforts of the ISCD represent an important advance in BMD interpretation, the interobserver reproducibility with application of these criteria is unknown. We hypothesized that there would be substantial agreement among four interpreters regarding application of the exclusion criteria and the final lumbar spine T-score. MATERIALS AND METHODS: Each interpreter read a set of 200 lumbar DXA scans obtained on male veterans, applying the ISCD vertebral body exclusion criteria. RESULTS: Surprisingly, agreement among interpreters was only moderate. Differences in interpretation resulted from differing thresholds for recognition of FSD and the choice of excluding the upper or lower vertebral body for the criteria requiring comparison between adjacent vertebrae. CONCLUSIONS: Despite their apparent simplicity, the ISCD vertebral exclusion criteria are difficult to apply consistently. In principle, appropriate refinement of the exclusion criteria may significantly improve interobserver agreement.

Use of the lowest vertebral body T-score to diagnose lumbar osteoporosis in men: is "cherry picking" appropriate?

In this study, we hypothesized that use of the lowest T-score among four lumbar vertebral bodies would lessen the impact of degenerative arthritis and other artifacts on diagnostic categorization at this site and increase study sensitivity, classifying more men with prior fracture as osteoporotic than the other two methods of lumbar spine analysis. Bone density studies of 533 male veterans measured between January and October 2002 were reviewed to determine diagnostic classification using the L1-L4 average, International Society for Clinical Densitometry (ISCD)-determined, and lowest lumbar vertebral body T-score. We calculated sensitivity and specificity of the three methods of spine analysis, using spine osteoporosis to indicate a positive test and prior fracture as the true indicator of osteoporosis. The lowest lumbar T-score performed with similar sensitivity and specificity to that of the lowest hip or wrist T-score in the ability to classify men with prior fracture as osteoporotic, whereas the average L1-L4 and ISCD-determined T-scores performed with lower sensitivity, but better specificity. In conclusion, this retrospective study suggests that use of the lowest vertebral body T-score among men increases diagnostic sensitivity of lumbar spine bone mass measurement. Prospective studies are needed to determine which of these three methods of lumbar spine analysis best predicts future fragility fracture in men and women.

An overlying fat panniculus affects femur bone mass measurement.

Dual-energy X-ray absorptiometry (DXA) is currently the gold standard technique for osteoporosis diagnosis. However, DXA has limitations, including artifacts, such as degenerative disease or metallic foreign bodies, that may confound bone mineral density (BMD) results. Because fat folds overlying the proximal femur may alter soft-tissue density in a nonuniform manner, this may be a currently unappreciated confounder of proximal femur BMD measurement. This possibility was evaluated in 127 patients (52 women/75 men) referred for routine BMD measurement who were identified as having a fat panniculus overlying their proximal femur scan area. Presence of a fat panniculus within the scan field was confirmed by visual assessment of images obtained utilizing a GE Lunar Expert-XL. Subsequently, these individuals were rescanned while retracting their fat panniculus away from the femur scan area without other repositioning between scans. In 49% of the men, and 56% of the women, either the femoral neck, trochanter, or total femur BMD differed by more than the least significant change at our facility. No pattern was observed to predict whether BMD would increase or decrease upon fat retraction. Subsequently, 30 patients were scanned using the standard and retracted technique twice, with repositioning between scans to establish precision. Retracted and standard precision was similar. In conclusion, an overlying fat panniculus may alter proximal femur BMD measurement, which would be expected to impair the ability to accurately diagnose low bone mass and monitor osteoporosis therapy. When a fat panniculus overlays the proximal femur scan area, its retraction should be part of routine densitometric practice.

Densitometric diagnosis of osteoporosis in men: effect of measurement site and normative database.

Controversy exists regarding which sites to measure, and the appropriate reference database to use, for densitometric diagnosis of osteoporosis in men. While hip and spine bone mineral density (BMD) measurement is routine, spinal osteoarthritis often elevates measured BMD in older men. Additionally, the use of male reference data is standard practice; however, recent reports suggest that a female database may be more appropriate. This study evaluated the effect of sites measured, and normative database utilized, on the densitometric diagnosis of osteoporosis in men. Spine, femur, and ultradistal radial BMD T-scores were determined in 595 male veterans using the GE Lunar male normative database. Subsequently, World Health Organization diagnostic criteria were applied, identifying 282 men with osteoporosis (T-score