Obesity Increases Precision Errors in Dual-Energy X-Ray Absorptiometry Measurements

Knapp, Karen; Welsman, Joanne R.; Hopkins, Sue; Fogelman, Ignac; Blake, Glen M.

doi:10.1016/j.jocd.2012.01.002

Cited by 74 publications

(69 citation statements)

References 27 publications

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“…Higher body mass index (BMI) has been demonstrated to contribute to increased DXA precision error that may be attributable to greater tissue inhomogeneity at the site of the lumbar spine and a reduction in signal to noise ratio in larger participants [17] . Whilst short-term precision has been reported for DXA BMD measurement [18,22] information is very limited regarding in vivo short-term precision error (STPE) for TBS [19] . This study investigated the STPE of TBS and BMD and the effect of obesity on precision error.…”

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confidence: 99%

Short-term Precision Error in Dual Energy X-Ray Absorptiometry, Bone Mineral Density and Trabecular Bone Score Measurements; and Effects of Obesity on Precision Error

Hopkins

Welsman

Knapp

2014

JBGC

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Introduction: Bone mineral density (BMD) measured by dual energy x-ray absorptiometry (DXA) is the primary screening tool for diagnosis of osteopenia and osteoporosis. BMD alone does not provide information regarding the structural characteristics of bone and this limitation has been a driver for the development of techniques, including trabecular bone score (TBS) software, to assess bone microarchitecture. Precision error in DXA is important for accurately monitoring changes in BMD and it has been demonstrated that BMD precision error increases with increasing body mass index (BMI). Information on in vivo precision error for TBS is very limited. This study evaluated short-term precision error (STPE) of lumbar spine BMD & TBS measurement, and investigated the effect of obesity on DXA precision error.Method: DXA lumbar spine scans (L1-L4) were performed using GE Lunar Prodigy. STPE was measured in ninety-one women at a single visit by duplicating scans with repositioning in-between. Precision error was calculated as the percentage coefficient of variation. Participants were sub-divided into four groups based on BMI to assess the effect of obesity on STPE.Results: STPE is poorer for TBS than for BMD. STPE is adversely affected for both BMD and TBS measurements by increasing BMI but this effect is mitigated for TBS in the highest BMI category where use of the thick scanning mode improves signal to noise ratio. Conclusion:Results from serial BMD and TBS measurements should take account of differences in precision error in the two techniques and in different BMI categories.

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confidence: 99%

Short-term Precision Error in Dual Energy X-Ray Absorptiometry, Bone Mineral Density and Trabecular Bone Score Measurements; and Effects of Obesity on Precision Error

Hopkins

Welsman

Knapp

2014

JBGC

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“…The intraclass correlations demonstrate a good correlation between the scanners with r=0.99 for both sites. While the paired t-test yielded p-values demonstrating a statistically significant difference between the scanners, the percentage agreement of 0.9% and 0.7% for the lumbar spine and total hip respectively suggests that these differences are unlikely to be clinically significant and fall within the reported precision errors of DXA scanners [7].…”

Section: Discussionmentioning

confidence: 82%

“…The volunteer group showed greater differences between the two measurements for the femur with increased BMI, but not between the spinal measurements. This may be as a result of greater difficulty replicating hip positioning in larger patients [7]. The presence, in obese subjects of an overlying fat panniculus at the femur site when the subjects were supine may affect precision at this site by altering soft tissue densities in a non-uniform manner [16].…”

Section: Discussionmentioning

confidence: 99%

“…This information was intended to assist in the formation of local pathway policy about which patients are scanned on which scanner and to determine whether in practice it made any difference. Since precision errors vary between subjects due to differences in body habitus, bone mass, soft tissue ratio and adipose tissue distribution it is important to measure a set of subjects representative of a centre's workload [7] [8].…”

Section: Introductionmentioning

confidence: 99%

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Static and mobile DXA scanner in-vivo cross-calibration study

2013

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Cross calibration of DXA scanning equipment with phantom subjects has been recommended for assessing agreement between devices co-located within DXA scanning services.This study evaluated in-vivo and in-vitro cross calibration of a static and a mobile DXA scanner within the same service in their individual clinical settings. 50 individuals from a volunteer group were recruited to take part in this study and had DXA measurements made on two GE Lunar Prodigy Advance (GE Lunar, Bedford, UK) scanners.Results in this study showed that the scanners agreed, with no statistically significant differences in BMD measurements made at the same site on the individual devices used in this study. The in-vivo cross calibration of the instruments was a useful experience, which demonstrated closely calibrated systems and raised the profile of the bone densitometry service within the hospital.3 Introduction Central dual energy x-ray absorptiometry (DXA) of the spine and hip is the current preferred method for the diagnosis of osteoporosis [1]. DXA scanners have good long term precision due to stable calibration and effective instrument quality control procedures to detect long term drift [1]. However, the results from DXA scanners produced by different manufacturers and even the same make of scanner made by the same manufacturer cannot be directly compared due to potential differences in calibration [2]. When introducing additional or replacing DXA scanners it is therefore recommended to perform cross calibration whether the new machine is from the same manufacturer or not [3]. While cross calibration between two machines of the same manufacturer and using the same manufacture's phantom has been reported to have good agreement of 0.2%, in vivo measurements may differ by more than 2%[4] The increased errors in-vivo can be partly attributed to the increased precision errors introduced by virtue of scanning an individual who has in-homogeneity within their tissue, meaning that the x-ray photons may not pass though the same structures on both scans. Precision errors within DXA are also important for the characterisation of it's ability to assess bone mineral density and detect longitudinal change. Monitoring measurement errors within a service is also dependant on QA systems to detect scanner changes [5]. When introducing a new scanner, it is recommended to undertake a cross-calibration of the scanners within a service. The optimum technique for undertaking a cross-calibration study of DXA scanners is to use in-vivo measurements since this is how DXA scanners are used in clinical practice [4,6].In 2009, a GE Lunar Prodigy DXA scanner (GE Healthcare, Bedford, UK) was purchased and commissioned to operate in a mobile vehicle, alongside the existing static GE Lunar Prodigy within the Healthy Bones Service at Derriford Hospital (Plymouth UK). While it is not good practice to make longitudinal measurements of

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“…BMD by dual-energy X-ray absorptiometry (DXA) is higher in obese people, but higher BMI and soft tissue thickness cause error in DXA measurement [8] through assumptions about abdominal thickness and beam hardening effects. However, other quantitative imaging methods (CT and ultrasound) also support higher BMD by DXA (although other methods are also subject to some influence from surrounding soft tissue).…”

Section: Obesity Fracture and Bmdmentioning

confidence: 99%

Comparison of Metabolic Risk Factors and Physical Fitness according to Femur Osteoporotic Status in Elderly Women

cho¹,

Lee²,

Kang³

2017

Exerc Sci

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clinicians. However, the limited available evidence suggests that osteoporosis treatment does reduce fracture risk in obesity and T2DM with generally similar efficacy to other patients.Keywords Bone · Obesity · Diabetes · Fat · Fracture Obesity, Type 2 Diabetes and BoneObesity is a major and growing public health problem; for example, in the UK, 40% of adults will be obese by 2025 [1]. Obesity is the most important risk factor for type 2 diabetes (T2DM), and the global prevalence of T2DM is likely to be 592 million by 2035 [2]. As the population ages, the burden of osteoporosis and fragility fracture also increases. Obesity and T2DM have effects on fracture risk, and fractures in T2DM are associated with greater morbidity than in the general population. Understanding how to assess and treat fracture risk in these groups is important for health care planning and individual patients. Additionally, the study of the mechanisms of action of obesity and T2DM on bone has already offered insights that may be applicable in the broader study of osteoporosis, such as the effects of adipokines on bone cells and the effects of collagen glycation on material properties of bone. There are some similarities in the effect of obesity and T2DM on bone, but some important differences such as cortical porosity and collagen glycation.In this review, we describe the effects of obesity and T2DM on fracture risk and discuss possible mechanisms of their effects. We also consider the validity of existing fracture risk prediction tools and efficacy of osteoporosis treatment in these patient groups. AbstractIn an increasingly obese and ageing population, type 2 diabetes (T2DM) and osteoporotic fracture are major public health concerns. Understanding how obesity and type 2 diabetes modulate fracture risk is important to identify and treat people at risk of fracture. Additionally, the study of the mechanisms of action of obesity and T2DM on bone has already offered insights that may be applicable to osteoporosis in the general population. Most available evidence indicates lower risk of proximal femur and vertebral fracture in obese adults. However the risk of some fractures (proximal humerus, femur and ankle) is higher, and a significant number fractures occur in obese people. BMI is positively associated with BMD and the mechanisms of this association in vivo may include increased loading, adipokines such as leptin, and higher aromatase activity. However, some fat depots could have negative effects on bone; cytokines from visceral fat are pro-resorptive and high intramuscular fat content is associated with poorer muscle function, attenuating loading effects and increasing falls risk. T2DM is also associated with higher bone mineral density (BMD), but increased overall and hip fracture risk. There are some similarities between bone in obesity and T2DM, but T2DM seems to have additional harmful effects and emerging evidence suggests that glycation of collagen may be an important factor. Higher BMD but higher fracture risk presents challenges i...

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Obesity Increases Precision Errors in Dual-Energy X-Ray Absorptiometry Measurements

Cited by 74 publications

References 27 publications

Short-term Precision Error in Dual Energy X-Ray Absorptiometry, Bone Mineral Density and Trabecular Bone Score Measurements; and Effects of Obesity on Precision Error

Short-term Precision Error in Dual Energy X-Ray Absorptiometry, Bone Mineral Density and Trabecular Bone Score Measurements; and Effects of Obesity on Precision Error

Static and mobile DXA scanner in-vivo cross-calibration study

Comparison of Metabolic Risk Factors and Physical Fitness according to Femur Osteoporotic Status in Elderly Women

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