What does a T-score represent in bone mineral density assessment?

• A. The number of standard deviations a person's BMD is from the BMD of a young healthy reference population of the same sex and background.
• B. The number of standard deviations from the age- and sex-matched mean.
• C. The absolute mass of calcium in the bone.
• D. The ratio of BMD between the spine and hip.

Answer: (A)

The main idea is that the T-score quantifies how far your bone density is from peak bone density in a young, healthy reference group. It is expressed as the number of standard deviations away from that young reference mean, using the same sex and background. So a T-score tells you how many SDs your BMD sits above or below the young adult reference value. This makes it useful for classifying bone health and fracture risk, with thresholds that define normal, osteopenia, and osteoporosis. It’s different from a Z-score, which compares your BMD to an age- and sex-matched mean, and it isn’t about absolute calcium mass or the ratio between spine and hip.