What T-score requires treatment for osteoporosis?

T-Score Threshold for Osteoporosis Treatment

A T-score of -2.5 or lower requires treatment for osteoporosis, according to the World Health Organization (WHO) criteria. 1

Diagnostic Criteria for Osteoporosis

The diagnosis of osteoporosis is based on bone mineral density (BMD) measurements using dual-energy x-ray absorptiometry (DXA), with the following classifications:

• Normal BMD: T-score ≥ -1.0
• Osteopenia/Low bone mass: T-score between -1.0 and -2.5
• Osteoporosis: T-score ≤ -2.5 1, 2

The T-score represents the number of standard deviations that a patient's BMD is above or below the mean of a young, healthy reference population. This classification system was established by the World Health Organization and is endorsed by the National Osteoporosis Foundation and the American Association of Clinical Endocrinologists 1.

Sites for Measurement

BMD should be measured at the following sites:

• Lumbar spine (L1-L4)
• Hip (total hip and femoral neck)
• Distal one-third radius (when spine or hip measurements are not available) 1

The diagnostic classification is based on the lowest T-score at any of these recommended DXA regions 1.

Treatment Thresholds

Treatment is recommended for:

1. All patients with T-score ≤ -2.5 at the lumbar spine, femoral neck, or total hip 2

2. Patients with fragility fractures regardless of BMD (these patients should be diagnosed with osteoporosis even if their T-scores are above -2.5) 3

3. Patients with osteopenia (T-score between -1.0 and -2.5) who have:

   • High fracture risk based on FRAX assessment (10-year probability of hip fracture ≥ 3% or major osteoporotic fracture ≥ 20%) 1, 2
   • History of fragility fractures, particularly vertebral, proximal humerus, pelvic, or in some cases, distal forearm fractures 3

4. Special populations:

   • For glucocorticoid-induced osteoporosis: Treatment should be considered at a T-score < -1.5 4
   • For patients with PSC (Primary Sclerosing Cholangitis): Assessment of bone mineral density is recommended at diagnosis 1

Treatment Approach

First-line treatment for osteoporosis includes:

• Oral bisphosphonates (alendronate 70mg once weekly or risedronate) 2
• Calcium (1200 mg daily) and vitamin D (800-1000 IU daily) supplementation 2
• Weight-bearing exercise and resistance training as tolerated 2
• Fall prevention strategies 2

For patients who cannot tolerate bisphosphonates or have contraindications:

• Denosumab is recommended as a second-line treatment 2
• For very high fracture risk: Consider anabolic agents (teriparatide or romosozumab) followed by antiresorptive therapy 2

Important Considerations

• A "drug holiday" may be considered after 3-5 years of bisphosphonate treatment, except in patients with severe osteoporosis 2
• Monitoring during treatment is not routinely recommended during the first 5 years of pharmacologic treatment 2
• Denosumab requires continuous treatment or transition to bisphosphonate when discontinued to prevent rebound bone loss 2

Common Pitfalls to Avoid

1. Relying solely on BMD for diagnosis: While a T-score ≤ -2.5 confirms osteoporosis, patients with fragility fractures should be diagnosed with osteoporosis regardless of their T-score 3.

2. Ignoring secondary causes: Z-scores (comparison to age-matched controls) should be used to detect secondary causes of osteoporosis, especially in premenopausal women and men under 50 years 1.

3. Inappropriate site selection: When the lumbar spine measurement is compromised by arthritis or fractures, the hip or distal one-third radius should be used 1.

4. Overlooking high-risk patients with osteopenia: Patients with T-scores between -1.0 and -2.5 may still require treatment if they have additional risk factors or high FRAX scores 1, 2.

By following these evidence-based guidelines, clinicians can appropriately identify and treat patients with osteoporosis, ultimately reducing fracture risk and improving quality of life.