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dual energy X-ray absorptiometry (DEXA)

Indications: - most common study to assess bone mineral density - osteopenia, osteoporosis* * see screening for osteoporosis Procedure: Absolute measurement routinely made: 1) at the lumbar spine (predominantly trabecular bone)* 2) hip (both trabecular bone & cortical bone) 3) evaluation for unexplained, significant loss of height* should include central DEXA to determine risk of osteoporotic fracture based on T-score & simultaneous vertebral fracture assessment [3] 4) peripheral DEXA can be used to assess global fragility fracture risk, - ability to predict vertebral fracture risk is weaker than central DEXA - data insufficient to predict fracture risk in men [3] 5) computed tomography of the spine can also assess bone mineral density & predict vertebral fracture risk but cost & radiation exposure limit use [3] * significant loss of height is >4 cm (>1.5 inches) [3] * postmenopausal women with diabetes mellitus have higher bone mineral density but lower trabecular bone scores than women without diabetes mellitus [3] Interpretation: Results are compared to both: 1) young, normal controls 'T score' 2) age & sex-matched controls 'Z score' By World Health Organization Standards a 'T score' 1) <= -2.5 standard deviations indicates osteoporosis 2) -1.0 to -2.4 standard deviations indicates osteopenia 3) > -1.0 is normal Each standard deviation below peak bone mass indicates a 2-3 fold increase risk of fracture. * diagnoses of osteoporosis in premenopausal women & men < 50 years can be made with 'Z score' < -2.0 [1] * reviewing DEXA scans for accuracy is a key part of BMD interpretation - artifacts that may affect bone mineral density reporting should be excluded by radiology review before additional tests are ordered or treatment is changed [3]

Related

bone

Specific

Dual energy X-ray absorptiometry for vertebral fracture vertebral fracture assessment

General

bone mineral density (BMD)

References

  1. Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 19 American College of Physicians, Philadelphia 1998, 2006, 2022 - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  2. Greendale GA, UCLA Intensive Course in Geriatric Medicine & Board Review, Marina Del Ray, CA, Sept 12-15, 2001
  3. Geriatric Review Syllabus, 10th edition (GRS10) Harper GM, Lyons WL, Potter JF (eds) American Geriatrics Society, 2019 - Geriatric Review Syllabus, 10th edition (GRS11) Harper GM, Lyons WL, Potter JF (eds) American Geriatrics Society, 2022
  4. Krueger D, Shives E, Siglinsky E, et al. DXA errors are common and reduced by use of a reporting template. J Clin Densitom. 2019;22(1):115-124 PMID: 30327243 https://www.sciencedirect.com/science/article/abs/pii/S1094695018301586
  5. Martineau P, Morgan SL, Leslie WD. Bone mineral densitometry reporting: pearls and pitfalls. Can Assoc Radiol J. 2021 Aug;72(3):490-504 PMID: 32309998 https://journals.sagepub.com/doi/10.1177/0846537120919627
  6. Morgan SL, Prater GL. Quality in dual-energy X-ray absorptiometry scans. Bone. 2017;104:13-38 PMID: 28159711 https://www.sciencedirect.com/science/article/abs/pii/S8756328217300339
  7. Roux C, Briot K. Current role for bone absorptiometry. Joint Bone Spine. 2017;84(1):35-37 PMID: 27282091 https://www.sciencedirect.com/science/article/abs/pii/S1297319X16300677
  8. Ginther JP, Ginther AW, Brodersen LD. Adding VFA to DXA identifies fracture risk in a way not duplicated by other measures. Endocr Pract. 2017;23(12):1375-1378 PMID: 29019717 https://www.endocrinepractice.org/article/S1530-891X(20)35163-6/abstract