Has trabecular scoring for Dual-Energy X-ray Absorptiometry (DEXA) studies been clinically validated and useful for management?

Trabecular Bone Score (TBS) for DEXA: Clinical Validation and Management Utility

TBS is clinically validated as an independent predictor of fracture risk, but should be used only as an adjunct to BMD and FRAX—never alone for screening or treatment decisions. 1

Clinical Validation Status

TBS has been extensively validated across multiple populations and consistently demonstrates:

• Independent fracture prediction: TBS predicts major osteoporotic fractures independently of BMD, clinical risk factors, and FRAX probability, with a gradient of risk of 1.44 per 1 SD decrease when adjusted for age 2
• Complementary information: TBS captures bone microarchitecture quality that BMD cannot detect, allowing differentiation between two patients with identical BMD but different fracture risks 1, 3
• Retrospective application: TBS can be calculated from previously obtained DXA scans without additional radiation exposure or patient visits 1
• Resistance to artifacts: Unlike BMD, TBS is not significantly impacted by overlying calcifications or degenerative spine changes 1

Appropriate Clinical Applications

When TBS Adds Value

Use TBS in patients near treatment thresholds where additional risk stratification could change management decisions 1:

• Patients with T-scores between -1.0 and -2.5 (osteopenia range) where FRAX probability is borderline for treatment 1
• Patients with normal BMD but clinical suspicion for increased fracture risk 4
• Secondary osteoporosis conditions where BMD underestimates fracture risk 1, 5:
  • Type 2 diabetes mellitus
  • Glucocorticoid therapy
  • Primary hyperparathyroidism
  • Chronic kidney disease
  • Rheumatoid arthritis

Specific Populations with Enhanced Utility

TBS demonstrates substantially higher association with fracture risk than BMD in secondary osteoporosis, particularly in patients on glucocorticoid therapy, those with diabetes, and hyperparathyroidism 1, 5. In these populations, TBS can identify increased fracture risk even when BMD appears normal 1.

Integration with FRAX

TBS-adjusted FRAX probabilities provide more accurate fracture risk prediction than standard FRAX alone 2:

• TBS can be incorporated into the FRAXplus® platform to modify fracture probability 1
• When adjusted for TBS, FRAX gradient of risk increases from 1.70 to 1.76 for major osteoporotic fractures 2
• This adjustment is most clinically meaningful for patients with borderline FRAX probabilities 1, 4

Limitations and Contraindications

Technical Limitations

TBS should only be performed in patients with BMI 15-37 kg/m² 1:

• Excess abdominal fat induces image noise that artificially reduces TBS values 1
• New software algorithms accounting for soft tissue thickness (rather than BMI) are emerging to address this limitation 1

Clinical Limitations

TBS has limited utility for monitoring most osteoporosis treatments 1:

• Minimal value for bisphosphonate or short-term denosumab therapy 1
• May add information for anabolic therapy or long-term denosumab treatment 1
• Least significant change (LSC) for TBS is 5.8%, larger than BMD changes with most therapies 1

Appropriateness Ratings from ACR Guidelines

The American College of Radiology assigns TBS the following appropriateness ratings 1:

• Initial screening: Rating 4/9 ("may be appropriate") 1
• Follow-up of established low BMD: Rating 2/9 ("usually not appropriate") 1

These ratings reflect that TBS should never replace standard DXA BMD measurements but serves as supplementary information in select cases 1.

Practical Implementation Algorithm

Step 1: Obtain standard DXA with BMD of lumbar spine and hip 1

Step 2: Calculate TBS if patient meets criteria:

• BMI 15-37 kg/m² 1
• AND one of the following:
  • T-score -1.0 to -2.5 with borderline FRAX probability 1
  • Secondary osteoporosis (diabetes, glucocorticoids, hyperparathyroidism, CKD, rheumatoid arthritis) 1, 5
  • Normal BMD but clinical suspicion for increased fracture risk 4

Step 3: Integrate TBS with BMD and FRAX:

• Use TBS-adjusted FRAX probability via FRAXplus® platform 1
• Lower TBS values (indicating degraded microarchitecture) increase fracture risk independent of BMD 3, 4

Step 4: Make treatment decision based on combined assessment, not TBS alone 1

Critical Pitfalls to Avoid

• Never use TBS as a standalone screening tool or for treatment decisions without BMD and clinical risk factors 1
• Do not calculate TBS in patients with BMI <15 or >37 kg/m² due to unreliable results 1
• Avoid using TBS for routine monitoring of bisphosphonate therapy where it provides minimal additional information 1
• Do not apply TBS in follow-up scans if significant weight change occurred between measurements 1
• Remember that TBS appropriateness rating for follow-up is only 2/9 ("usually not appropriate"), emphasizing its limited role in serial monitoring 1