Osteoporosis Testing: DEXA, QUS, pQCT, MRI—Methods and Indications

Bone mineral density (BMD) testing identifies osteoporosis, assesses fracture risk, and monitors treatment. Several modalities exist:

1. DEXA (Dual-Energy X-ray Absorptiometry) — Gold Standard

• Sites: Lumbar spine (L1–L4), proximal femur (total hip, femoral neck), distal ⅓ radius.
• Output: T-score (vs. young adult peak), Z-score (age-matched).
• Diagnosis (WHO): T-score ≤ –2.5 = osteoporosis; –1 to –2.5 = osteopenia.
• Radiation: Very low (<0.01 mSv).
• Indications: Women ≥65, men ≥70, postmenopausal women <65 with risk factors, fractures, glucocorticoid therapy, monitoring.

2. Quantitative Ultrasound (QUS) — Heel (Calcaneus)

• Measures speed of sound (SOS) and broadband ultrasound attenuation (BUA).
• No radiation; portable; low cost.
• Limitation: Not diagnostic; cannot monitor treatment; used for screening/referral to DEXA.

3. Peripheral QCT (pQCT) — Forearm or Tibia

• 3D volumetric BMD; separates cortical vs. trabecular bone.
• Assesses bone geometry, strength indices.
• Research tool; limited clinical availability.

4. MRI / HR-pQCT

• High-resolution microarchitecture (trabecular number, thickness, separation).
• Research applications; not routine clinical screening.

Choosing the Right Test

DEXA remains the clinical standard for diagnosis and monitoring. QUS may be used for community screening. pQCT/MRI reserved for research or complex cases. Discuss with your provider based on age, risk factors, and availability.