DEXA Data Interpretation & Reporting 4 — Questions and Answers
Question 1: A DEXA report for a 68-year-old woman shows a lumbar spine BMD of 1.050 g/cm². However, the scan shows significant aortic calcification overlying L2 and L3. What is the appropriate action?
- Report L1–L4 average as normal
- Exclude L2 and L3 from the analysis and report L1 and L4 only (Correct answer)
- Apply a correction factor of -10% to the reported BMD
- Discard the lumbar scan entirely and rely solely on hip data
Correct answer: Exclude L2 and L3 from the analysis and report L1 and L4 only
Aortic calcification overlying vertebral levels artificially elevates BMD; affected vertebrae should be excluded and remaining levels used if at least two are valid.
Question 2: ISCD guidelines recommend that a minimum of how many lumbar vertebrae must be analyzable for a valid spine BMD result?
- One
- Two (Correct answer)
- Three
- Four
Correct answer: Two
ISCD states that at least two evaluable lumbar vertebrae are required to report a valid spine BMD result.
Question 3: On a pediatric DEXA report, which skeletal sites are recommended by ISCD for BMD assessment in children?
- Femoral neck and Ward's triangle
- Lumbar spine (PA) and total body less head (TBLH) (Correct answer)
- Calcaneus and distal radius
- Total hip and lateral spine
Correct answer: Lumbar spine (PA) and total body less head (TBLH)
ISCD recommends PA lumbar spine and total body less head (TBLH) as the primary sites for pediatric DXA, since hip norms for children are less robust.
Question 4: A serial DEXA comparison report references the patient's baseline scan performed on a different manufacturer's scanner. What is the recommended approach?
- Directly compare the raw BMD numbers since g/cm² is a universal unit
- Cross-calibrate or use caution interpreting the comparison, as BMD values differ between manufacturers (Correct answer)
- Average the two scanner values to obtain a more accurate baseline
- Report the newer scanner's BMD as the only valid measurement
Correct answer: Cross-calibrate or use caution interpreting the comparison, as BMD values differ between manufacturers
BMD values are not interchangeable between manufacturers due to differences in bone edge detection algorithms and calibration; cross-calibration is required for valid comparisons.
Question 5: Which of the following findings on a DEXA scan report would most indicate the need for a Vertebral Fracture Assessment (VFA)?
- T-score of -1.2 at the femoral neck
- Height loss of 1.5 inches or more since peak height (Correct answer)
- BMI greater than 30
- Age under 50 with normal Z-scores
Correct answer: Height loss of 1.5 inches or more since peak height
ISCD indications for VFA include historical height loss ≥1.5 inches, which suggests possible vertebral compression fractures.
Question 6: In body composition DEXA reporting, lean mass, fat mass, and bone mineral content should sum to approximately what value?
- Total bone mass only
- Total body weight as measured on a scale (Correct answer)
- Total soft tissue mass excluding bone
- Total body water content
Correct answer: Total body weight as measured on a scale
In DEXA body composition, lean mass + fat mass + bone mineral content equals total body weight, which should closely match scale weight.
Question 7: A DEXA report for a patient on long-term glucocorticoid therapy shows a T-score of -1.8. According to ACR guidelines for glucocorticoid-induced osteoporosis (GIOP), how should fracture risk be categorized?
- Low risk — T-score is above -2.5
- Moderate risk — apply GIOP-adjusted FRAX or ACR risk calculator (Correct answer)
- High risk — T-score below -1.0 always qualifies as high risk in GIOP
- Not assessable — FRAX cannot be used in glucocorticoid users
Correct answer: Moderate risk — apply GIOP-adjusted FRAX or ACR risk calculator
ACR GIOP guidelines recommend using FRAX with a glucocorticoid dose correction or the ACR calculator to appropriately stratify fracture risk, which may elevate category above what BMD alone suggests.
DEXA Data Interpretation & Reporting 4
A DEXA report for a 68-year-old woman shows a lumbar spine BMD of 1.050 g/cm².
However, the scan shows significant aortic calcification overlying L2 and L3.
What is the appropriate action?