Dual-energy X-ray Absorptiometry Monitoring with Trabecular Bone Score: 2019 ISCD Official Position

doi:10.1016/j.jocd.2019.07.006

Journal of Clinical Densitometry

Volume 22, Issue 4, October–December 2019, Pages 501-505

https://doi.org/10.1016/j.jocd.2019.07.006 Get rights and content

Abstract

Trabecular bone score (TBS) is a textural index that evaluates pixel gray‐level variations in the lumbar spine image by dual-energy X-ray absorptiometry. It provides an indirect assessment of trabecular microarchitecture that is an independent predictor of fracture risk. TBS does not appear to be clinically useful to monitor the skeletal effects of bisphosphonates and denosumab, but is potentially useful as a component of monitoring the skeletal effects of teriparatide and abaloparatide. The least significant change (LSC) for TBS can be conservatively estimated to be about 5.8% (the largest LSC in published data) or calculated by a dual-energy X-ray absorptiometry facility using the same methodology that is used for bone mineral density (BMD) precision assessment to calculate BMD LSC. A review of the best available evidence at the 2019 ISCD Position Development Conference concluded that the role of TBS in monitoring antiresorptive therapy is unclear and that TBS is potentially useful for monitoring anabolic therapy. For patients treated with teriparatide or abaloparatide, a statistically significant increase in TBS may represent a clinically meaningful improvement in trabecular structure. A significant decrease of TBS may represent a worsening of trabecular structure, suggesting the need for further clinical assessment and possible change in treatment strategies. Since BMD measures bone quantity and TBS measures bone quality, these tests can be considered complementary in assessing fracture risk and response to therapy in appropriate patients.

Introduction

Bone strength is determined by bone mineral density (BMD) and non-BMD skeletal properties, such as bone geometry, mineralization, microdamage, remodeling, and microarchitecture. Trabecular bone score (TBS iNsight software, Medimaps Group, Geneva, Switzerland) is a textural index that evaluates pixel gray‐level variations in the lumbar spine (LS) image by dual-energy X-ray absorptiometry (DXA). It provides an indirect assessment of trabecular microarchitecture (1,2) that is an independent predictor of fracture risk (3). TBS is included as a risk factor with the fracture risk tool, FRAX, and may influence treatment decisions by altering the estimated 10-yr fracture probability. TBS has been cleared by the US Food and Drug Administration for use as a complement to DXA analysis and clinical examination for assessment of fracture risk and monitoring the effects of therapy (4).

Clinical applications of TBS were addressed at a previous Position Development Conference (PDC) of the ISCD and reported in this journal (5). It was determined that:

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TBS is associated with vertebral, hip and major osteoporotic fracture risk in postmenopausal women.
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TBS is associated with hip fracture risk in men over the age of 50 yr.
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TBS is associated with major osteoporotic fracture risk in men over the age of 50 yr.
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TBS should not be used alone to determine treatment recommendations in clinical practice.
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TBS can be used in association with FRAX and BMD to adjust FRAX-probability of fracture in postmenopausal women and older men.
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TBS is not useful for monitoring bisphosphonate treatment in postmenopausal women with osteoporosis.
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TBS is associated with major osteoporotic fracture risk in postmenopausal women with type II diabetes.

For the 2019 ISCD PDC, held in Kuala Lumpur, Malaysia, a task force was formed to review new medical evidence about the use of TBS for monitoring treatment with approved osteoporosis treatments. This is a report of relevant ISCD Official Positions developed from the PDC.

Section snippets

Methodology

A PubMed search limited to the English language was conducted for terms that included “trabecular bone score” or “TBS.” Within these matches a search was made for “precision,” “least significant change,” “least significant change (LSC),” “reproducibility,” “variation,” “variability,” “osteoporosis,” “treatment,” “pharmacologic treatment” and each of the US-approved osteoporosis medications at the time of the search in 2018 (prior to approval of romosozumab, a therapeutic agent with a “dual

ISCD Official Position

Question: Is TBS useful to monitor patients treated with antiresorptive agents?

ISCD Official Position: The role of TBS in monitoring antiresorptive therapy is unclear.

Grade: Good-A-W

Rationale for oral bisphosphonates: Approved bisphosphonates, whether administered orally or parenterally, reduce bone remodeling, increase BMD, and reduce fracture risk, but are not known to alter bone structure. Many of the reports evaluating TBS while on oral bisphosphonates include subjects receiving other

Acknowledgments

The authors wish to thank Didier Hans, PhD, for his helpful suggestions in reviewing the medical literature and analyzing the data. He had no role in the drafting of the Official Positions or the writing of this manuscript.

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Osteoporosis can currently be diagnosed by applying the WHO classification to bone mineral density (BMD) assessed by dual-energy x-ray absorptiometry (DXA). However, skeletal factors other than BMD contribute to bone strength and fracture risk. Lumbar spine TBS, a grey-level texture measure which is derived from DXA images has been extensively studied, enhances fracture prediction independent of BMD and can be used to adjust fracture probability from FRAX® to improve risk stratification. The purpose of this International Society for Clinical Densitometry task force was to review the existing evidence and develop recommendations to assist clinicians regarding when and how to perform, report and utilize TBS. Our review concluded that TBS is most likely to alter clinical management in patients aged ≥ 40 years who are close to the pharmacologic intervention threshold by FRAX. The TBS value from L1-L4 vertebral levels, without vertebral exclusions, should be used to calculate adjusted FRAX probabilities. L1-L4 vertebral levels can be used in the presence of degenerative changes and lumbar compression fractures. It is recommended not to report TBS if extreme structural or pathological artifacts are present. Monitoring and reporting TBS change is unlikely to be helpful with the current version of the TBS algorithm. The next version of TBS software will include an adjustment based upon directly measured tissue thickness. This is expected to improve performance and address some of the technical factors that affect the current algorithm which may require modifications to these Official Positions as experience is acquired with this new algorithm.
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: Conflicts of interest: KK has served on scientific advisory boards or consulted for Radius and Alexion. He serves on the speaker's bureau for Radius and Alexion. He receives a retirement pension from Lilly USA.

: Y-SC has received institutional grant from Maeil Daires; he has served on scientific advisory boards or consulted for Eli Lilly, Amgen, Samsung Bioepis, and Yuyu; he serves on the speakers’ bureau for Pfizer, Hanmi, Handok, and Hanall; he is a board member of the Korea Women's Health and Osteoporosis Foundation.

: ES has served on scientific advisory boards or consulted for Radius. He serves on the speaker's bureau for Radius.

: EML has received no direct income from potentially conflicting entities. His employer, New Mexico Clinical Research & Osteoporosis Center, has received research grants from Radius, Amgen, Mereo, Bindex; income for service on scientific advisory boards or consulting for Amgen, Radius, Alexion, Sandoz, Samsung Bioepis; service on speakers’ bureaus for Radius, Alexion; project development for University of New Mexico; and royalties from UpToDate for sections on DXA, fracture risk assessment, and prevention of osteoporosis. He is a board member of the National Osteoporosis Foundation, International Society for Clinical Densitometry, and Osteoporosis Foundation of New Mexico.

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2019 ISCD Official PositionDual-energy X-ray Absorptiometry Monitoring with Trabecular Bone Score: 2019 ISCD Official Position

Abstract

Introduction

Section snippets

Methodology

ISCD Official Position

Acknowledgments

Bone

Bone

J Clin Densitom

J Clin Densitom

Bone

J Clin Densitom Epub

J Clin Densitom

J Clin Densitom

Effects of anti-resorptive agents on trabecular bone score (TBS) in older women

Osteoporos Int

2019 ISCD Official Position
Dual-energy X-ray Absorptiometry Monitoring with Trabecular Bone Score: 2019 ISCD Official Position