When should someone get a repeat bone density scan if their first one was normal?

Repeat Bone Density Scanning After Normal Initial Results

For patients with normal bone mineral density (BMD) on initial screening, repeat DXA scanning should be performed no earlier than 15 years after the baseline scan, as evidence indicates that less than 10% of older postmenopausal women with normal BMD will develop osteoporosis within this timeframe. 1

Recommended Intervals Based on Initial BMD Results

The appropriate interval for repeat bone density testing depends on the results of the initial scan:

• Normal BMD (T-score ≥ -1.0):

  • Repeat testing in approximately 15 years 1
  • Evidence shows that osteoporosis would develop in less than 10% of older postmenopausal women during this interval

• Mild Osteopenia (T-score -1.01 to -1.49):

  • Repeat testing in approximately 15 years 1

• Moderate Osteopenia (T-score -1.5 to -1.99):

  • Repeat testing in approximately 5 years 1

• Advanced Osteopenia (T-score -2.0 to -2.49):

  • Repeat testing in approximately 1-2 years 1

Technical Considerations for Repeat BMD Testing

When performing repeat BMD measurements:

• Use the same DXA machine, software, scan mode, and patient positioning 2
• Ensure the same hip and forearm are scanned for accurate comparisons 2
• Compare absolute BMD values in g/cm², not T-scores or Z-scores 2, 3
• A minimum of 2 years between scans is generally needed to reliably measure a change in BMD due to limitations in testing precision 2

Special Considerations

Risk Factors That May Warrant Earlier Rescreening

Consider more frequent monitoring in patients with:

• Glucocorticoid therapy 3
• Conditions associated with rapid bone loss
• Initiation of osteoporosis therapy
• Multiple risk factors for fracture

Common Pitfalls to Avoid

• Comparing T-scores rather than absolute BMD values between scans 3
• Performing repeat scans too frequently (less than 2 years apart) 2, 4
• Using different DXA machines or protocols for follow-up scans 2
• Failing to account for artifacts or degenerative changes that may falsely elevate BMD readings 3

Current Practice Patterns

Despite recommendations for longer intervals after normal results, studies show that repeat DXA scanning often occurs earlier than necessary:

• Among women not on treatment with normal initial BMD, approximately 8% receive repeat scans within 2 years 4
• By 5 years, approximately 43% of women with low-risk initial results receive repeat scans 4

This pattern of early rescreening represents low-value care, as highlighted by the Choosing Wisely campaign, which specifically recommends against repeating DXA scans within 2 years of initial screening 4.

Rationale for Extended Intervals

The recommendation for extended intervals between scans for those with normal BMD is based on:

1. The slow rate of bone loss in individuals with normal baseline BMD
2. The long transition time from normal BMD to osteoporosis (estimated at 16.8 years for women with normal BMD) 1
3. The limited benefit of early rescreening in terms of fracture prevention
4. Cost-effectiveness considerations in osteoporosis screening programs

By following these evidence-based intervals for repeat bone density testing, clinicians can optimize the use of DXA scanning resources while ensuring appropriate monitoring for patients at risk of osteoporotic fractures.