Glossary · Tests

DEXA (Dual-energy X-ray Absorptiometry)

Also called: DXA, Bone density scan.

Definition: DEXA is the gold-standard imaging test for bone mineral density. A DEXA scan measures bone density at the hip and lumbar spine, generating T-scores (versus young-adult mean) and Z-scores (versus age-matched mean). T-score ≤ -2.5 defines osteoporosis; -1.0 to -2.5 defines osteopenia. Postmenopausal women should have a baseline DEXA at 65, or earlier if risk factors are present.

Detailed definition

Dual-energy X-ray absorptiometry (DEXA, also DXA) measures bone mineral density (BMD) using two X-ray beams at different energies. Scans typically image the lumbar spine and proximal femur (femoral neck and total hip) and report results as T-scores and Z-scores. The T-score compares the patient's BMD to the mean of healthy young adults of the same sex; the Z-score compares to age-matched peers. WHO criteria define normal as T-score ≥ -1.0, osteopenia as T-score between -1.0 and -2.5, and osteoporosis as T-score ≤ -2.5. USPSTF and Bone Health and Osteoporosis Foundation recommend DEXA screening for all women starting at age 65, or earlier for women with risk factors (early menopause, low BMI, prior fragility fracture, family history, glucocorticoid use, smoking, etc.). Repeat DEXA timing depends on baseline result and risk factors but is typically every 2–3 years for women with osteopenia or on bone-active treatment.

Why it matters in menopause

For women starting HRT primarily for symptoms, baseline DEXA isn't required for treatment but provides useful context for the bone-protective benefit and for tracking. For women with concerns about osteoporosis or with any risk factor, DEXA is an essential workup.

Sources

External references: Wikipedia.

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