What are the current guidelines for initiating and repeating DEXA scanning, interpreting T‑scores, and managing osteoporosis, including recommended treatment options and follow‑up intervals?

DEXA Screening Guidelines

All women ≥65 years and men >70 years should undergo DEXA screening, along with younger individuals (≥50 years) who have osteoporosis risk factors. 1

Who Should Get Initial DEXA Screening

Universal Screening (No Risk Factors Required)

• Women ≥65 years
• Men >70 years 1

Targeted Screening (Age ≥50 with Risk Factors)

Consider DEXA in women and men ≥50 years with any of the following risk factors 1:

• Prior fragility fracture
• Chronic glucocorticoid use (≥5 mg prednisone equivalent daily for ≥3 months)
• Height loss >4 cm
• Parental history of hip fracture
• Current smoking
• Excessive alcohol consumption
• Rheumatoid arthritis
• Secondary causes of osteoporosis (hyperparathyroidism, hyperthyroidism, hypogonadism)

Younger Adults (<50 Years)

Consider DEXA in premenopausal women and men <50 years only with 1:

• Specific diseases causing bone loss
• Medications affecting bone metabolism
• History of fragility fracture

Anatomic Sites to Measure

DEXA BMD measurement should be performed at the lumbar spine, total hip, and femoral neck. Add one-third radius measurement when 1:

• Lumbar spine/hip are not evaluable (severe arthritis, hardware, obesity)
• Primary hyperparathyroidism is present
• Very obese patients (>300 lbs)

T-Score Interpretation

Osteoporosis is diagnosed when T-score ≤-2.5 at any measured site (lumbar spine, femoral neck, total hip, or one-third radius). 1

Diagnostic Categories

• Normal BMD: T-score ≥-1.0
• Osteopenia/Low bone mass: T-score between -1.0 and -2.5
• Osteoporosis: T-score ≤-2.5 1

Critical Points

• Use the lowest T-score from any measured site for diagnosis 1
• Use NHANES III reference database (20-29 year-old White women) for T-score calculation in both men and women 1
• Some societies presume osteoporosis diagnosis with low-trauma major fracture (hip, spine, forearm, humerus, pelvis) even with normal BMD 1

Special Populations

For premenopausal women and men <50 years, use Z-scores rather than T-scores. A Z-score ≤-2.0 indicates "bone mineral density below expected range for age" 1

Vertebral Fracture Assessment (VFA)

Evaluate for vertebral fractures with VFA or standard radiography in patients ≥50 years with T-score <-1.0 plus any of the following 1:

• Women ≥70 years or men ≥80 years
• Historical height loss >4 cm
• Self-reported but undocumented vertebral fracture
• Glucocorticoid therapy (≥5 mg prednisone equivalent daily for ≥3 months)
• T-score ≤-2.5 at spine or hip
• Acute onset back pain with osteoporosis risk factors

Follow-Up DEXA Intervals

Repeat DEXA every 1-2 years until findings are stable, then continue at less frequent intervals depending on clinical circumstances. 2

Evidence-Based Intervals by Baseline BMD

Research suggests rescreening intervals can be extended based on initial T-score 3:

• Normal BMD (T-score ≥-1.0): ~15 years
• Mild osteopenia (T-score -1.0 to -1.5): ~15 years
• Moderate osteopenia (T-score -1.5 to -2.0): ~5 years
• Advanced osteopenia (T-score -2.0 to -2.5): ~1 year

On Treatment

For patients on osteoporosis therapy, repeat DEXA typically 1-5 years after starting or changing therapy 1. The specific interval depends on:

• Type of medication used
• Baseline fracture risk
• Clinical stability
• Reimbursement considerations

Treatment Thresholds

Pharmacologic therapy is strongly recommended for 2:

• T-score ≤-2.5 at any site
• T-score between -1.0 and -2.5 with FRAX 10-year major osteoporotic fracture risk ≥20% OR hip fracture risk ≥3%

Very High Risk Patients

Consider patients at very high fracture risk if they have 2:

• Recent fracture (within 12 months)
• Fractures while on osteoporosis therapy
• Multiple fractures
• T-score <-3.0
• High fall risk or history of injurious falls
• FRAX major osteoporotic fracture >30% or hip fracture >4.5%

For very high risk patients, initiate treatment with abaloparatide, denosumab, romosozumab, teriparatide, or zoledronate 2

High Risk Patients

For patients with osteoporosis but not meeting very high risk criteria, initiate therapy with alendronate, denosumab, risedronate, or zoledronate 2

Technical Considerations

Quality Control

• Each DXA facility must determine its precision error and calculate least significant change (LSC = 2.77 × precision error) 1
• Recalculate when new DXA system is installed
• Follow-up scans should ideally be performed at the same facility with the same DXA system 1, 2

Monitoring Changes

• Monitor serial changes using absolute BMD values (g/cm²), not T-scores or Z-scores 1
• A change exceeding the LSC represents a statistically significant change
• Ensure both initial and follow-up scans use identical positioning and analysis techniques

Common Pitfalls to Avoid

1. Don't use lumbar spine for monitoring if 1:

   • Severe degenerative changes present
   • Compression fractures exist
   • Surgical hardware overlaps measurement area

2. Don't use hip measurements if:

   • Hip dysplasia present
   • Bone metastases or Paget's disease
   • Incorrect femur rotation (lesser trochanter not visible)
   • Gluteal implants overlapping bone structures

3. Don't diagnose osteoporosis in children, premenopausal women, or men <50 years based solely on T-scores - use Z-scores and clinical context 1

4. Don't compare T-scores between scans - only compare absolute BMD values in g/cm² 1