Z-score
Bone density expressed in standard deviations relative to age-matched peers (versus T-score, which compares to young-adult peak). Z ≤ −2.0 in premenopausal women, men under 50, or children flags secondary osteoporosis workup.
Why it matters to buyers: Premenopausal women, pediatrics, and secondary-osteoporosis workups use Z-score as the primary clinical reference. Standard reporting on every DXA study.
Why it matters to engineers: Less standardized across vendors than T-score. Used clinically but not the headline number for postmenopausal-osteoporosis-screening reimbursement decisions.