Skeletal Health Assessment Practice
What the exam expects
This domain covers the clinical workflow around the scan: appropriate referral, acquisition quality, reporting, and risk communication. Know who should be tested-women 65 and older, men 70 and older, younger adults with risk factors, and anyone with fragility fracture or conditions/drugs that threaten bone (glucocorticoids, aromatase inhibitors, androgen deprivation, hyperparathyroidism, malabsorption). Understand that DXA is a two-dimensional areal measure (g/cm²), so it is confounded by body size and cannot distinguish trabecular from cortical bone.
Quality control is heavily tested. Daily scanning of a phantom verifies scanner stability; technologist precision assessment (repeat scans on volunteers) establishes the LSC used for monitoring. Proper positioning matters: spine scans should be centered and straight, hips internally rotated, and the same side and same device/software should be used for follow-up. Recognize that forearm measurement is indicated when hip and spine cannot be used, when hyperparathyroidism is suspected, or in very obese patients exceeding table limits.
Traps
Questions blur screening with monitoring: a repeat DXA too soon after starting therapy cannot show change beyond the LSC. They may present a report that omits fracture risk or ignores prior fragility fracture, which alone can define osteoporosis regardless of T-score. Another common trap is comparing scans from different manufacturers or software versions as if interchangeable. Be careful with the term "osteopenia"-preferred language is "low bone mass."
Worked example
A 62-year-old woman on chronic prednisone has a spine T-score of −1.8 and total hip of −1.3. Her T-scores do not meet the osteoporosis threshold, but long-term glucocorticoid exposure is a major risk factor; the correct action is to assess fracture risk (FRAX), consider treatment per guidelines, and avoid concluding she is "normal."