What are the recommendations for Dexa (Dual-Energy X-ray Absorptiometry) scan frequency and management for patients at risk of osteoporosis?

DEXA Scan Recommendations for Osteoporosis Screening and Management

Initial Screening Recommendations

DXA of the lumbar spine and hip(s) is the primary modality for osteoporosis screening and should be performed in all women ≥65 years, men ≥70 years, and younger individuals with specific risk factors. 1

Who Should Get Initial DEXA Screening:

• Women ≥65 years and men ≥70 years (routine screening) 1

• Postmenopausal women and men ≥50 years with any of the following risk factors: 1

  • Previous fragility fracture
  • Chronic glucocorticoid therapy (≥3 months at ≥5 mg prednisone equivalent daily) 1
  • Chronic inflammatory conditions (rheumatoid arthritis, inflammatory bowel disease) 1
  • Hypogonadism or premature menopause 1
  • Malabsorption syndromes or gastrointestinal disorders 1
  • Chronic renal failure 1
  • Organ transplantation 1
  • Cancer survivors on endocrine therapy (aromatase inhibitors, androgen deprivation therapy, GnRH agonists) 1
  • FRAX 10-year hip fracture risk ≥3% or major osteoporotic fracture risk ≥20% 1

• Premenopausal women and men <50 years only if they have medical conditions or medications that adversely affect bone density 1

Technical Specifications:

The preferred assessment uses DXA of the total spine, hip, and femoral neck as this provides the most comprehensive evaluation of fracture risk. 1 For patients with advanced degenerative spine changes or scoliosis that may spuriously elevate BMD, either DXA of the distal forearm or quantitative CT (QCT) of the lumbar spine and hip should be used instead. 1

Follow-Up DEXA Scan Frequency

The standard monitoring interval for repeat DEXA is every 2 years for both treated and untreated patients. 1

Specific Follow-Up Intervals:

• Standard interval: Every 2 years for patients with established osteoporosis or low bone density 1

• Accelerated interval: Every 1 year for patients at high risk of rapid bone loss: 1

  • Initiating osteoporosis therapy
  • Receiving glucocorticoid therapy
  • Cancer patients with chemotherapy-induced ovarian failure 1
  • Other conditions associated with substantial short-term BMD decreases 1

• Intervals <1 year are discouraged and bone mineral density assessment should not be conducted more frequently than annually 1

Critical Technical Requirement:

Patients must be scanned on the same DXA scanner for follow-up studies as vendor differences in technologies prohibit direct comparison unless cross-calibration has been performed. 1 Compare BMD values (not T-scores) between previous and current scans. 1

Vertebral Fracture Assessment (VFA)

VFA should be performed concomitantly with DXA in patients with T-scores <-1.0 and one or more of the following: 1

• Women ≥70 years or men ≥80 years 1
• Historical height loss >4 cm (>1.5 inches) 1
• Self-reported but undocumented prior vertebral fracture 1
• Glucocorticoid therapy ≥5 mg prednisone equivalent daily for ≥3 months 1

The utility of VFA is critical because 50% of fragility fractures occur in postmenopausal women with T-scores >-2.5, and identification of vertebral fractures can reclassify patients who would otherwise not qualify for treatment based solely on BMD measurements. 1 Studies demonstrate that 60% of patients with vertebral fractures detected on VFA were in the nonosteoporotic range by BMD criteria. 1

Special Populations

Cancer Survivors:

Repeat DXA every 2 years or as clinically indicated for patients on aromatase inhibitors, androgen deprivation therapy, or those with chemotherapy-induced ovarian failure. 1 If bone density does not demonstrate osteoporosis and FRAX is below treatment thresholds, repeat in 2 years or in 1 year if medically indicated. 1

Premenopausal Women and Men <50 Years:

Use Z-scores (not T-scores) for interpretation, as WHO criteria do not apply to this population. 1 Z-scores ≤-2.0 are considered below the expected age range and warrant evaluation for secondary causes of osteoporosis. 1

Patients on Glucocorticoids:

One-year follow-up intervals are recommended due to the risk of substantial short-term decreases in mineralization. 1 Consider baseline DEXA before initiating long-term glucocorticoid therapy (>3 months). 1

Common Pitfalls to Avoid

• Do not use peripheral DXA or QUS for diagnosis in standard populations—these are screening tools only and cannot be interpreted using WHO criteria 1
• Do not scan more frequently than annually—the precision of DXA measurements and the rate of bone turnover make more frequent scanning clinically unhelpful 1
• Do not compare scans from different DXA machines without cross-calibration 1
• Do not rely solely on spine DXA in patients with degenerative disease—spuriously elevated BMD from spondylosis occurs in >81% of falsely elevated measurements 1