What does a DEXA (Dual-Energy X-ray Absorptiometry) scan T-score result between −1 and −2.5 indicate?

DEXA Scan T-score Between -1 and -2.5 Indicates Osteopenia

A DEXA scan T-score between -1 and -2.5 indicates osteopenia, which represents low bone mass that is not yet severe enough to be classified as osteoporosis but indicates increased fracture risk compared to normal bone density. 1

Understanding T-scores in DEXA Scans

• T-scores compare your bone mineral density (BMD) to that of a healthy young adult of the same sex at peak bone mass, expressed as standard deviations from this reference population 1
• The World Health Organization (WHO) classification system defines:
  • Normal bone density: T-score ≥ -1.0
  • Osteopenia (low bone mass): T-score between -1.0 and -2.5
  • Osteoporosis: T-score ≤ -2.5 2, 1
• An osteoporotic fracture (such as the distal radius fragility fracture in this patient) supersedes any DEXA measurement, meaning patients with osteopenia who have fragility fractures should be diagnosed with osteoporosis regardless of T-score 2

Clinical Significance of Osteopenia

• Osteopenia represents an intermediate state of bone loss that increases fracture risk compared to normal bone density but less than osteoporosis 3
• The presence of a fragility fracture (like this patient's distal radius fracture) in someone with osteopenia indicates significant bone fragility and warrants treatment 2, 4
• Patients with osteopenia may benefit from fracture risk assessment using tools like FRAX to determine if pharmacologic treatment is needed 1

Treatment Implications

• For patients with osteopenia (T-score between -1 and -2.5) who have already experienced a fragility fracture, bisphosphonate therapy is appropriate, as has been started for this patient 4
• The National Osteoporosis Foundation recommends pharmacologic treatment for:
  • All patients with osteoporosis (T-score ≤ -2.5)
  • Patients with osteopenia who have a 10-year probability of hip fracture ≥3% or major osteoporotic fracture ≥20% based on FRAX 2, 1
• The presence of a fragility fracture in this patient with osteopenia indicates the need for treatment regardless of T-score 2

Monitoring Considerations

• Follow-up DEXA scans are typically recommended at 1-2 year intervals after initiation of therapy 5
• Shorter intervals (approximately 1 year) are appropriate immediately after therapy has been initiated or changed 5
• Follow-up scans should ideally be performed on the same DEXA machine to ensure accurate comparison 5

Common Pitfalls in DEXA Interpretation

• Degenerative changes in the spine can falsely elevate BMD measurements, potentially masking the true degree of bone loss 1
• Relying solely on hip or spine measurements without considering other sites may lead to missed diagnoses; some studies show that forearm DEXA scans may detect low BMD in cases where hip scans appear normal 6, 7
• Failure to recognize that a fragility fracture automatically upgrades the diagnosis to osteoporosis regardless of T-score 2

Special Considerations for This Patient

• This 48-year-old woman with a distal radius fragility fracture and T-score between -1 and -2.5 has been appropriately started on bisphosphonates 4
• Despite having osteopenia by T-score definition, the presence of a fragility fracture indicates clinically significant bone fragility that warrants treatment 2
• Calcium and vitamin D supplementation should accompany bisphosphonate therapy, with a target of 1,200mg daily calcium (diet plus supplements) and 800-1,000 IU daily vitamin D 4