The Z-score compares an individual's BMD to what reference group?

• A. Age- and sex-matched reference population.
• B. Young healthy reference population of the same sex.
• C. Height-adjusted reference.
• D. Bone turnover index.

Answer: (A)

The Z-score measures where a person’s bone mineral density stands compared with peers of the same age and sex. It represents how many standard deviations the individual's BMD is from the mean of an age- and sex-matched reference population. This makes it ideal for assessing whether bone density is appropriate for age, rather than comparing to a young adult reference (which is what a T-score does). Height-adjusted references or bone turnover indices aren’t the standard reference groups used for Z-scores.