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High Subcutaneous Fat Measured by DXA is Associated with Low Grip Strength and Poor Physical Capacity in Older Men - The STRAMBO Study
Abstracts 5 Vertebral Fracture Assessment in a Paediatric Population Using Dual-Energy X-ray Absorptiometry Sheila Shepherd; Developmental Endocrinology Research Group Andreas Kyriakou Background: Vertebral Fractures (VF) are recognized as an important aspect of bone health in children and adolescents. The clinical utility of Vertebral Fracture Assessment (VFA) using Dual-energy X-ray Absorptiometry (DXA) has not been evaluated in the paediatric population. Method: VFA was performed independently by two non-radiologist observers, in 165 patients (77M/88F) as part of their investigation for low bone mineral density. Lateral thoracolumbar x-ray images (LXR) were obtained in 20/165 patients. The median age of the patients was 13.4yrs (3.6,18). Lateral DXA images of the spine from T6 to L4 were obtained using Lunar Prodigy DXA device. The diagnosis of VF was performed according to Genant’s Semi-quantitative classification. Results: Interobserver agreement in vertebral readability using VFA was 94% (kappa, 0.73 [95%CI, 0.68, 0.73]). The vertebrae not readable by both observers were 287/1815 (16%) and 266/287 (93%) were located between T6 and T9. Conversely, 1134/1155 (98%) of vertebrae from T10 through L4 were adequately visualised (p!0.0001). Among the 1528 vertebrae visualised by both observers, 72 (4.7%) in 45 (27%) patients and 84 (5.5%) in 48 (29%) patients were classified as VF by observer 1 and by observer 2, respectively. Interobserver per-vertebra agreement for the presence of VF was 99% (kappa, 0.85 [95%CI, 0.79, 0.91]). Interobserver per-patient agreement was 91% (kappa, 0.78 [95%CI, 0.66, 0.87]). The two observers had in common 67 (4.5%) VF in 39 (24%) patients and 18 (27%) of them were classified as moderate or severe. The anatomical distribution of VF was biphasic, with peaks located on T9 (odds ratio, 2.1 [1.1,4.2]) and L4 (odds ratio, 1.7 [1.0,3.4]). Among those who underwent both LXR and VFA, 24 (11%) VF in 6 (30%) patients and 20 (9%) VF in 5 (25%) patients were identified by LXR and VFA, respectively. Per-vertebra agreement was 95% (kappa, 0.79 [95%CI, 0.62, 0.92]) and per-patient agreement was 95% (kappa, 0.88 [95%CI, 0.58, 1.0]). Specificity of VFA was 98.4% per-vertebra and 100% per-patient. Conclusion: VFA reaches an excellent level of agreement between observers and a high level of specificity in identifying VF in paediatric population. The readability of vertebrae from T6 to T9 is suboptimal and interpretation at this level should be exercised with caution.
6 High Subcutaneous Fat Measured by DXA is Associated with Low Grip Strength and Poor Physical Capacity in Older Men The STRAMBO Study Pawel Szulc; INSERM UMR 1033, University of Lyon, Hospital Edouard Herriot Francois Duboeuf, Roland Chapurlat Background: The association of sarcopenia (low muscle mass) with obesity is characterized by dynapenia (low muscle strength) and poor physical capacity. The association of visceral or subcutaneous fat with dynapenia and physical capacity is not clear. Our aim was to assess the association of subcutaneous and visceral fat mass with grip strength and physical capacity in older men. Methods: In 897 men aged 50 we assessed regional body composition (Hologic Discovery A), i.e. gynoid fat (subcutaneous fat) and android fat (abdominal subcutaneous and visceral fat). Upper limb relative appendicular skeletal muscle mass (RASM-u.l.) is calculated as the sum of arm lean mass divided by (height)2. Lower limb RASM (RASM-l.l.) is calculated similarly. Men had measures of grip strength and clinical tests of muscle strength and balance. We calculated a score accounting for the ability and time to perform each test (0-16). Results: After adjustment for age, height, alcohol intake, physical activity, diabetes mellitus, hypertension, Parkinson disease, and RASM-u.l., higher body mass index was associated with lower grip strength. Grip strength determinants were analyzed by stepwise linear regression including the above variables. Gynoid fat was retained in the model as a significant (p!0.001) determinant of grip strength. Android fat was not significant and not retained. In a similar stepwise linear regression model, subcutaneous abdominal fat was retained in the model as a significant (p!0.001) determinant of grip strength. Again, visceral fat was not retained. Both higher gynoid fat and higher subcutaneous abdominal fat were associated with lower grip strength (p!0.02 and p50.005, respectively). Men in the upper quartile of subcutaneous abdominal fat had 6% lower grip strength (p50.02) vs.
423 the lowest quartile. By contrast, higher android fat and higher visceral fat were not associated with grip strength. Low physical capacity score (!9) was found in 219 men (24%). After adjustment for RASM-l.l. and other variables, higher gynoid fat was associated with poor physical capacity (upper vs. first quartile, OR56.34, p!0.001), whereas higher android fat was not associated. High subcutaneous fat was associated with poor physical capacity (OR52.46, p!0.005), whereas higher visceral fat was not. Conclusion: In older men, higher subcutaneous fat is associated with lower grip strength and poor physical capacity of the lower limbs, whereas higher visceral fat is not.
Posters P01
An Evaluation of Lumbar Spine BMD and TBS Precision
Jessie Libber; University of Wisconsin Diane Krueger, Neil Binkley ISCD currently recommends that lumbar spine DXA reports include at least two vertebral bodies. This recommendation is based on the poorer precision observed when smaller bone regions are reported. However, spine DXA is often confounded by degenerative changes, fracture and surgical hardware, thus necessitating exclusion of three or all four vertebrae. Thus, it is plausible that future recommendations might allow diagnosis and monitoring using a single vertebra. Similarly, while trabecular bone score (TBS) is less confounded by degenerative changes, other confounders could affect it, (e.g., metallic hardware) making monitoring using fewer than 4 vertebral bodies appropriate. As such, knowledge regarding individual vertebral precision is needed; this project reports BMD and TBS precision of individual vertebral bodies compared to routine L1-L4 analysis. Scans previously obtained as part of a research precision assessment acquired by one ISCD certified technologist were used and re-analyzed to obtain TBS data. All scans were acquired using a GE Lunar iDXA and analyzed with enCORE version 14.0 and Medimaps TBS software version 2.1.0. Two AP spine scans were acquired in routine manner i.e., with repositioning between, in 30 men and 30 women (mean age 75.1 6.5/72.5 6 years and BMI 25.9 2.94/27.1 4.6). BMD and TBS least significant change (LSC) were calculated using the ISCD precision calculator (Table). Precision was compared between sites using the F-Test (Excel). Overall, BMD and TBS precision is similar between males and females across individual vertebral bodies and at the L1-4 spine. As might be expected, BMD and TBS precision is reduced when less than four vertebral bodies are considered. This reduced precision for both BMD and TBS must be considered when fewer than four vertebral bodies are used to monitor change over time
Table. BMD and TBS LSC Values Male
Female
Site
BMD
%CV
TBS
%CV
BMD
%CV
TBS
%CV
L1 L2 L3 L4 L1-2 L1-3 L1-4
0.066* 0.083* 0.055 0.073* 0.053 0.041 0.040
1.9 2.5 1.7 2.0 1.5 1.2 1.2
0.130* 0.104* 0.093* 0.078 0.082* 0.067 0.056
3.9 2.9 2.5 2.1 2.4 1.9 1.6
0.062* 0.089* 0.053 0.063* 0.060* 0.045 0.040
2.3 3.0 1.8 2.0 2.0 1.5 1.3
0.200* 0.098* 0.097* 0.085* 0.081* 0.066 0.054
6.0 2.8 2.6 2.3 2.4 1.9 1.5
*5 Different from L1-L4 p ! 0.05
P02 Spine Trabecular Bone Score (TBS) Cross-Calibration for GE Prodigy and iDXA Scanners William Leslie; University of Manitoba Didier Hans (Lausanne University Hospital) Aims: Spine Trabecular Bone Score (TBS), a gray-level measurement derived from lumbar spine DXA image texture, is related to fracture risk independently
Journal of Clinical Densitometry: Assessment & Management of Musculoskeletal Health
Volume 18, 2015
6 High Subcutaneous Fat Measured by DXA is Associated with Low Grip Strength and Poor Physical Capacity in Older Men The STRAMBO Study Pawel Szulc; INSERM UMR 1033, University of Lyon, Hospital Edouard Herriot Francois Duboeuf, Roland Chapurlat Background: The association of sarcopenia (low muscle mass) with obesity is characterized by dynapenia (low muscle strength) and poor physical capacity. The association of visceral or subcutaneous fat with dynapenia and physical capacity is not clear. Our aim was to assess the association of subcutaneous and visceral fat mass with grip strength and physical capacity in older men. Methods: In 897 men aged 50 we assessed regional body composition (Hologic Discovery A), i.e. gynoid fat (subcutaneous fat) and android fat (abdominal subcutaneous and visceral fat). Upper limb relative appendicular skeletal muscle mass (RASM-u.l.) is calculated as the sum of arm lean mass divided by (height)2. Lower limb RASM (RASM-l.l.) is calculated similarly. Men had measures of grip strength and clinical tests of muscle strength and balance. We calculated a score accounting for the ability and time to perform each test (0-16). Results: After adjustment for age, height, alcohol intake, physical activity, diabetes mellitus, hypertension, Parkinson disease, and RASM-u.l., higher body mass index was associated with lower grip strength. Grip strength determinants were analyzed by stepwise linear regression including the above variables. Gynoid fat was retained in the model as a significant (p!0.001) determinant of grip strength. Android fat was not significant and not retained. In a similar stepwise linear regression model, subcutaneous abdominal fat was retained in the model as a significant (p!0.001) determinant of grip strength. Again, visceral fat was not retained. Both higher gynoid fat and higher subcutaneous abdominal fat were associated with lower grip strength (p!0.02 and p50.005, respectively). Men in the upper quartile of subcutaneous abdominal fat had 6% lower grip strength (p50.02) vs.
423 the lowest quartile. By contrast, higher android fat and higher visceral fat were not associated with grip strength. Low physical capacity score (!9) was found in 219 men (24%). After adjustment for RASM-l.l. and other variables, higher gynoid fat was associated with poor physical capacity (upper vs. first quartile, OR56.34, p!0.001), whereas higher android fat was not associated. High subcutaneous fat was associated with poor physical capacity (OR52.46, p!0.005), whereas higher visceral fat was not. Conclusion: In older men, higher subcutaneous fat is associated with lower grip strength and poor physical capacity of the lower limbs, whereas higher visceral fat is not.
Posters P01
An Evaluation of Lumbar Spine BMD and TBS Precision
Jessie Libber; University of Wisconsin Diane Krueger, Neil Binkley ISCD currently recommends that lumbar spine DXA reports include at least two vertebral bodies. This recommendation is based on the poorer precision observed when smaller bone regions are reported. However, spine DXA is often confounded by degenerative changes, fracture and surgical hardware, thus necessitating exclusion of three or all four vertebrae. Thus, it is plausible that future recommendations might allow diagnosis and monitoring using a single vertebra. Similarly, while trabecular bone score (TBS) is less confounded by degenerative changes, other confounders could affect it, (e.g., metallic hardware) making monitoring using fewer than 4 vertebral bodies appropriate. As such, knowledge regarding individual vertebral precision is needed; this project reports BMD and TBS precision of individual vertebral bodies compared to routine L1-L4 analysis. Scans previously obtained as part of a research precision assessment acquired by one ISCD certified technologist were used and re-analyzed to obtain TBS data. All scans were acquired using a GE Lunar iDXA and analyzed with enCORE version 14.0 and Medimaps TBS software version 2.1.0. Two AP spine scans were acquired in routine manner i.e., with repositioning between, in 30 men and 30 women (mean age 75.1 6.5/72.5 6 years and BMI 25.9 2.94/27.1 4.6). BMD and TBS least significant change (LSC) were calculated using the ISCD precision calculator (Table). Precision was compared between sites using the F-Test (Excel). Overall, BMD and TBS precision is similar between males and females across individual vertebral bodies and at the L1-4 spine. As might be expected, BMD and TBS precision is reduced when less than four vertebral bodies are considered. This reduced precision for both BMD and TBS must be considered when fewer than four vertebral bodies are used to monitor change over time
Table. BMD and TBS LSC Values Male
Female
Site
BMD
%CV
TBS
%CV
BMD
%CV
TBS
%CV
L1 L2 L3 L4 L1-2 L1-3 L1-4
0.066* 0.083* 0.055 0.073* 0.053 0.041 0.040
1.9 2.5 1.7 2.0 1.5 1.2 1.2
0.130* 0.104* 0.093* 0.078 0.082* 0.067 0.056
3.9 2.9 2.5 2.1 2.4 1.9 1.6
0.062* 0.089* 0.053 0.063* 0.060* 0.045 0.040
2.3 3.0 1.8 2.0 2.0 1.5 1.3
0.200* 0.098* 0.097* 0.085* 0.081* 0.066 0.054
6.0 2.8 2.6 2.3 2.4 1.9 1.5
*5 Different from L1-L4 p ! 0.05
P02 Spine Trabecular Bone Score (TBS) Cross-Calibration for GE Prodigy and iDXA Scanners William Leslie; University of Manitoba Didier Hans (Lausanne University Hospital) Aims: Spine Trabecular Bone Score (TBS), a gray-level measurement derived from lumbar spine DXA image texture, is related to fracture risk independently
Journal of Clinical Densitometry: Assessment & Management of Musculoskeletal Health
Volume 18, 2015