Which test measures bone mineral density to diagnose osteoporosis?

• A. DEXA scan
• B. MRI
• C. X-ray
• D. CT scan

Answer: (A)

Bone mineral density testing is the primary way to diagnose osteoporosis, and the method of choice is a DEXA scan. This test uses two low-dose X-ray beams to quantify mineral content in critical bones, usually the hip and lumbar spine, giving a numeric T-score that compares your density to that of a healthy young adult. A T-score of -2.5 or lower is used to diagnose osteoporosis, reflecting significantly reduced bone density and higher fracture risk. Other imaging tests—MRI, standard X-rays, or CT scans—don’t measure bone density reliably for screening: X-rays show structure and fractures but not density, MRI focuses on soft tissues and marrow, and CT can measure density but involves more radiation and isn’t the routine first-line tool for BMD. DEXA is quick, involves minimal radiation, and is the standard method for tracking changes in bone density over time.