What are the reasons to perform a DEXA (Dual-Energy X-ray Absorptiometry) scan at age 51?

Reasons to Perform DEXA Scan at Age 51

A DEXA scan is recommended at age 51 for individuals with risk factors for osteoporosis, as this is a critical age for bone health assessment, particularly for women entering perimenopause or menopause when accelerated bone loss typically begins.

Primary Indications for DEXA Scan at Age 51

For Women

• Perimenopause or menopause status (typically occurring around age 51)
• History of premature menopause or early estrogen deficiency 1
• Low body weight (BMI <20-25 kg/m²) or weight loss >10% compared to usual adult weight 2
• Family history of osteoporosis or fragility fractures 2

For Both Men and Women

• Previous fragility fracture (regardless of BMD) 2

• Long-term glucocorticoid therapy (≥5 mg prednisone daily for ≥3 months) 1, 2

• Secondary causes of osteoporosis:

  • Endocrine disorders (hyperparathyroidism, hyperthyroidism, Cushing syndrome) 1
  • Gastrointestinal disorders (malabsorption, chronic inflammatory bowel disease) 1
  • Rheumatologic conditions (rheumatoid arthritis and other inflammatory arthritides) 1
  • History of gastric bypass surgery 1
  • Chronic alcoholism or established cirrhosis 1
  • Eating disorders including anorexia nervosa and bulimia 1

• Medications known to affect bone density:

  • Anticonvulsants 1
  • Aromatase inhibitors 1
  • Androgen deprivation therapy 1
  • Chronic heparin use 1

Diagnostic Criteria and Interpretation

Measurement Parameters

• For women at age 51 (perimenopausal/menopausal):

  • T-scores are used for diagnosis 1
  • T-score > -1.0: Normal bone density
  • T-score between -1.0 and -2.4: Osteopenia/Low bone mass
  • T-score ≤ -2.5: Osteoporosis 2

• For premenopausal women and men under 50:

  • Z-scores are recommended 1
  • Z-score ≤ -2.0 indicates "bone mineral density below the expected range for age" 1

Follow-up Recommendations

• Initial baseline scan at age 51 for those with risk factors 3
• Standard follow-up interval is typically 2 years 2
• Shorter intervals (1 year) for:
  • Patients initiating osteoporosis therapy
  • Those at high risk for accelerated bone loss
  • After cessation of pharmacologic therapy 2

Technical Considerations

• DXA of the lumbar spine and hip(s) is the gold standard for diagnosis 2
• Forearm DXA should be considered when hip/spine cannot be measured or interpreted 2
• QCT is recommended when advanced degenerative changes of the spine or scoliosis are present 2
• Follow-up scans should be performed on the same machine with the same software and positioning 1
• Comparison between scans should be based on absolute BMD values (g/cm²), not T-scores or Z-scores 1

Clinical Pearls and Pitfalls

• Degenerative changes in the spine can falsely elevate BMD measurements, particularly in older individuals 1
• If more than two vertebral levels show degenerative changes, the entire spine should be excluded from evaluation 1
• Vertebral fractures are diagnostic of osteoporosis even if BMD values are not in the osteoporotic range 4
• Simple screening tools like grip strength testing may help identify individuals who would benefit from BMD measurement 5
• The Osteoporosis Risk Assessment Instrument (ORAI) can help identify women at increased risk who should undergo testing 6

Treatment Thresholds

• Treatment is generally recommended for:
  • T-score ≤ -2.5 (osteoporosis)
  • Fragility fracture regardless of T-score
  • Osteopenia with elevated 10-year fracture risk based on FRAX 2
  • For glucocorticoid-induced osteoporosis, consider treatment at T-scores < -1.5 4

By identifying individuals at risk and performing appropriate DEXA scanning at age 51, clinicians can implement early interventions to prevent fractures and their associated morbidity and mortality.