How is a Z-score defined in bone densitometry?

• A. A comparison to a person's age-matched population
• B. A measure of bone density solely
• C. A calculation of total bone volume
• D. A comparison to an average population

Answer: (A)

A Z-score in bone densitometry is defined as a statistical measurement that compares an individual's bone density to the mean bone density of a healthy age-matched population. This means that the Z-score indicates how many standard deviations a person's bone density measurement is from the average bone density of individuals in the same age group. This comparison is particularly useful as it helps to assess whether an individual has lower or higher bone density relative to their peers, which can indicate potential risk for osteoporosis or bone fractures.

Using an age-matched population allows for a more precise assessment of bone health, as bone density changes with age, and it controls for the effects of aging on bone strength. By focusing on this demographic factor, healthcare providers can make more informed decisions regarding diagnosis and treatment.

The other choices do not accurately describe the Z-score. While measuring bone density is a component of bone health evaluation, a Z-score is not solely a measure of bone density, nor does it calculate total bone volume. It also does not compare an individual's bone density to an average population without considering age. Therefore, the age-matched aspect is crucial in understanding the context and relevance of the Z-score in bone densitometry assessments.