How is a DEXA scan interpreted with T-scores and Z-scores?

• A. The T-score compares to a young healthy reference; ≤ −2.5 defines osteoporosis; The Z-score compares to age- and sex-matched norms and is not diagnostic for osteoporosis
• B. The T-score compares to age-matched norms
• C. The Z-score defines osteoporosis
• D. The T-score is not used clinically

Answer: (A)

Interpreting a DEXA scan centers on two scales that compare bone density to reference groups. The T-score measures how the patient’s bone mineral density stacks up against a young, healthy reference population. A T-score of -2.5 or lower at key sites like the spine or hip defines osteoporosis, while -1 to -2.5 indicates osteopenia and above -1 is normal. The Z-score, on the other hand, compares density to age- and sex-matched norms and is not used to diagnose osteoporosis. A low Z-score can signal that bone loss is unusually advanced for the patient’s age and may prompt evaluation for secondary causes. So the T-score provides the diagnostic threshold against peak bone mass, while the Z-score offers age- and sex-adjusted context.