What is the gold standard for identifying osteoporosis?

• A. CT scan
• B. MRI
• C. Dual-energy x-ray absorptiometry (DEXA) scan
• D. Ultrasound

Answer: (C)

Measuring bone mineral density with a DEXA scan is the gold standard for identifying osteoporosis. This test directly quantifies how dense the bones are, especially at the hip and spine, which are the most predictive sites for fracture risk. The results are expressed as a T-score, with a value at or below -2.5 defining osteoporosis according to established criteria, providing a standardized threshold to diagnose and guide treatment. DEXA is preferred because it is accurate, reproducible, widely available, and involves only a small amount of radiation, making it suitable for screening and monitoring over time. Other imaging methods have limitations: CT can estimate bone density but involves higher radiation and is not routinely used for diagnosis; MRI doesn’t provide a reliable measure of bone density; ultrasound can assess peripheral bone properties but cannot diagnose osteoporosis or predict fracture risk as reliably as DEXA.