What is the next step in diagnosis and treatment for a postmenopausal woman or older man with uncertain diagnosis between osteoporosis and osteopenia?

Bone Mineral Density Testing by DXA is the Definitive Next Step

If you are uncertain whether a patient has osteoporosis or osteopenia, order a dual-energy x-ray absorptiometry (DXA) scan of the lumbar spine and hip—this is the gold standard diagnostic test that will definitively distinguish between these conditions and guide all subsequent treatment decisions. 1

Why DXA is the Correct Test

• DXA is the internationally accepted standard for diagnosing osteoporosis and osteopenia, with established World Health Organization (WHO) criteria that provide clear diagnostic thresholds 1, 2
• The test measures bone mineral density at the lumbar spine (L1-L4) and proximal femur (femoral neck and total hip), the two most clinically relevant sites for fracture risk prediction 1
• DXA results are reported as T-scores, which compare the patient's bone density to a young healthy reference population, making interpretation straightforward 1, 3:
  • Normal bone density: T-score > -1.0
  • Osteopenia: T-score between -1.0 and -2.5
  • Osteoporosis: T-score ≤ -2.5
• The diagnosis is based on the lowest T-score at any measured site 4

Who Should Get DXA Screening

The International Society for Clinical Densitometry (ISCD) and American College of Radiology provide clear indications 1:

• All women ≥65 years old (routine screening) 1
• All men ≥70 years old (routine screening) 1
• Younger postmenopausal women (<65 years) or men (50-69 years) with risk factors including 1:
  • Estrogen deficiency or premature menopause
  • Maternal hip fracture after age 50
  • Low body weight (<127 lb or 57.6 kg)
  • Current smoking
  • Loss of height or thoracic kyphosis
  • History of amenorrhea >1 year before age 42
• Any individual with a fragility fracture (wrist, hip, spine, proximal humerus with minimal trauma) 1
• Anyone with osteopenia or fractures visible on other imaging (radiographs, CT, MRI) 1

Critical Interpretation Points

• If the patient has already sustained a low-trauma major osteoporotic fracture (hip, spine, forearm, humerus, pelvis), they meet diagnostic criteria for osteoporosis regardless of their DXA T-score, even if the scan shows normal bone density 5
• This is particularly important for vertebral compression fractures, which are often asymptomatic but automatically establish the diagnosis of osteoporosis and the need for pharmacologic treatment 5
• Degenerative changes in the lumbar spine (facet arthritis, osteophytes, spondylosis) can artificially elevate BMD measurements, potentially masking true bone loss 1, 4
  • If more than 2 vertebral levels must be excluded due to artifact, scan the contralateral hip or the distal one-third radius of the non-dominant forearm as alternative sites 1

What Happens After the DXA Scan

For Osteoporosis (T-score ≤ -2.5):

• Initiate pharmacologic therapy immediately with oral bisphosphonates (first-line), IV bisphosphonates, or denosumab 4
• Ensure calcium 1000-1200 mg daily (diet plus supplements) and vitamin D 800-1000 IU daily 4
• Repeat DXA in 1-2 years on the same machine to monitor treatment response 4

For Osteopenia (T-score -1.0 to -2.5):

• Calculate 10-year fracture risk using FRAX (Fracture Risk Assessment Tool) to determine if pharmacologic treatment is warranted 6, 7
• Treatment with bisphosphonates is indicated if 10-year major osteoporotic fracture risk ≥10-15% or hip fracture risk ≥3% 6
• Evidence shows that oral and IV bisphosphonates cost-effectively reduce fractures in older osteopenic women, as most fractures actually occur in the osteopenic population due to their larger numbers 7
• The diagnosis of osteopenia alone is not an indication for treatment or reassurance—it must be combined with comprehensive fracture risk assessment 7

For All Patients:

• Ensure adequate calcium and vitamin D intake before initiating any pharmacologic therapy 4
• Recommend weight-bearing exercise, fall prevention strategies, smoking cessation, and limiting alcohol to <3 units/day 6
• Consider vertebral fracture assessment (VFA) imaging during the DXA scan, as vertebral fractures are often asymptomatic and are the strongest predictor of future fractures 5

Common Pitfalls to Avoid

• Do not rely on peripheral bone density measurements (heel ultrasound, finger densitometry) for diagnosis—these cannot be used to apply WHO diagnostic criteria and should not guide treatment decisions 1
• Do not compare T-scores between different DXA machines—when monitoring treatment response, use the same machine and compare absolute BMD values (g/cm²) rather than T-scores 5
• Do not discontinue denosumab without transitioning to another antiresorptive agent, as this causes rapid rebound bone loss and dramatically increased fracture risk 4, 8
• Do not assume normal DXA means no osteoporosis if the patient has a history of fragility fracture—the fracture history alone establishes the diagnosis 5