Research reference only. BioConst updates and corrects content over time, but it cannot replace clinician-guided diagnosis, treatment, medication, or testing decisions.

Medical Wiki

Z-score

A comparison between measured BMD and an age-matched reference group.

What it is

A Z-score compares BMD with people closer to the same age, and is preferred over T-score in younger adults and children.^[1,2]

Why it matters

It helps flag whether bone density is lower than expected for age, but it is not a diagnosis by itself.^[2,3]

What it affects

ISCD defines Z-score -2.0 or lower as below the expected range for age, and above -2.0 as within the expected range for age.^[2]
In children and adolescents, osteoporosis should not be diagnosed from densitometry alone.^[3]

Interpretation traps

Z-score needs population and growth context, especially in children, chronic disease, delayed puberty, or small body size.^[3]

Related conditions

Low bone mass / osteopenia Osteogenesis imperfecta and heritable fragility Osteomalacia and rickets