According to WHO criteria, osteoporosis is defined by a T-score ≤ -2.5 at which sites?

• A. A T-score ≤ -2.5 at the lumbar spine, femoral neck, or total hip defines osteoporosis.
• B. A T-score ≤ -3.5 at any site defines osteoporosis.
• C. A T-score ≤ -2.0 at the femoral neck defines osteoporosis.
• D. A Z-score ≤ -2.0 at the lumbar spine defines osteoporosis.

Answer: (A)

Osteoporosis is diagnosed by a bone mineral density measure reported as a T-score, which compares a person’s BMD to that of a young healthy reference population. The World Health Organization defines osteoporosis when the T-score is -2.5 or lower at fracture-prone sites, specifically the lumbar spine, femoral neck, or total hip. Using these sites reflects areas most predictive of fracture risk and are the standard locations assessed by DXA in practice. The threshold is a fixed cut-off: reaching -2.5 or lower at any of these sites indicates osteoporosis.

Other options don’t fit because a T-score of -3.5 is not the standard diagnostic threshold, a T-score of -2.0 at the femoral neck corresponds to osteopenia rather than osteoporosis, and the Z-score of -2.0 at the lumbar spine describes an age-related target for investigation of secondary causes rather than a diagnostic criterion for osteoporosis.