What is the role of a Z-score?

• A. To measure systemic changes
• B. To assess fracture risk in older adults
• C. To compare a patient's bone density to that of a healthy age- and sex-matched population
• D. To evaluate machine performance

Answer: (C)

The role of a Z-score is specifically to compare a patient's bone mineral density (BMD) to that of a healthy population that is age- and sex-matched. This metric helps clinicians determine how an individual’s BMD relates to the expected values for their demographic. When a Z-score is calculated, it reflects how many standard deviations a patient's bone density deviates from the mean BMD of a reference population. This comparison is crucial for assessing whether the patient's bone density is within the normal range for their age and sex, allowing for appropriate clinical decisions regarding diagnosis and treatment options.

The Z-score is particularly valuable because it provides context beyond a simple comparison to a standard average, taking into account factors such as age and sex that can significantly impact bone density levels. This is especially relevant in populations where biological variations may affect bone density, making it a more precise tool for identifying individuals who may require further investigation or intervention regarding their bone health.