What are the indications for bone densitometry in patients with risk factors for osteoporosis, such as postmenopausal women, older adults, and those with a history of fractures or certain medical conditions like rheumatoid arthritis or thyroid disorders?

Indications for Bone Densitometry

All postmenopausal women aged ≥65 years and men aged ≥70 years should undergo DXA screening regardless of risk factors, while younger individuals require screening only if they have specific risk factors such as prior fractures, chronic glucocorticoid use, or conditions associated with accelerated bone loss. 1, 2

Universal Screening by Age

• Women aged ≥65 years should receive routine DXA screening without requiring additional risk factor assessment 1, 2
• Men aged ≥70 years should undergo DXA screening as part of standard care 1
• Postmenopausal women aged 60-64 years with risk factors warrant screening 2
• Younger postmenopausal women (<60 years) without risk factors do not need routine screening 2

Risk Factor-Based Screening in Younger Adults

Prior Fracture History:

• Any adult aged ≥50 years with a previous fragility fracture (low-trauma fracture) should undergo DXA testing 1
• Self-reported but undocumented prior vertebral fracture warrants assessment 1
• Historical height loss >4 cm (>1.5 inches) suggests possible vertebral fractures and indicates DXA 1
• Prospective height loss ≥0.8 inch from last documented measurement requires evaluation 1

Glucocorticoid Therapy:

• Adults ≥40 years on chronic steroids should obtain baseline BMD within 6 months of starting glucocorticoid treatment 2
• Oral glucocorticoid therapy equivalent to ≥5 mg prednisone daily for ≥3 months is an indication 1
• Men and women initiating or continuing systemic glucocorticoids ≥7.5 mg prednisone equivalent daily with expected duration ≥6 months require screening 3, 4

Medical Conditions Associated with Bone Loss

Endocrine Disorders:

• Hyperparathyroidism warrants DXA assessment 1
• Thyroid disorders associated with bone loss require evaluation 1
• Hypogonadism in both men and women indicates screening 1

Rheumatologic Conditions:

• Rheumatoid arthritis patients should undergo bone density assessment 1

Cancer-Related Bone Loss:

• Men with prostate cancer receiving androgen deprivation therapy (ADT) require screening and 1- to 2-year interval follow-up for risk stratification 1, 3
• Women receiving adjuvant aromatase inhibitor therapy for breast cancer need DXA assessment 1, 3

Spinal Cord Injury:

• All adults with spinal cord injuries resulting in permanent motor or sensory dysfunction should have DXA of total hip, proximal tibia, and distal femur as soon as medically stable 1
• This requires specialized DXA equipment and referral to specialized centers should be considered 1

Vertebral Fracture Assessment Indications

When T-score is <-1.0, vertebral fracture assessment (VFA) or standard radiography is indicated if any of the following apply:

• Women aged ≥70 years or men aged ≥80 years 1
• Historical height loss >4 cm 1
• Self-reported undocumented prior vertebral fracture 1
• Chronic glucocorticoid use as described above 1
• Acute onset back pain with osteoporosis risk factors 1
• BMD T-score ≤-2.5 at spine or hip 1
• Kyphosis on physical examination 1

Special Populations

Transgender Persons:

• Screening should be based on hormone therapy compliance, gonadal removal status, and additional osteoporosis risk factors 1
• Post-pubertal trans children and adolescents on gonadotropin-releasing hormone without sex steroid hormone therapy may be at risk for decreasing bone density 1

Common Pitfalls to Avoid

• Do not use T-scores or apply WHO diagnostic criteria to premenopausal women or men <50 years; use Z-scores instead 5
• Recognize that degenerative spondylosis and facet osteoarthritis can spuriously elevate lumbar spine BMD, potentially leading to underdiagnosis 5
• Individual vertebral levels with spuriously elevated BMD due to degenerative changes, fractures, or facet arthropathy should be excluded from analysis 5
• The majority of postmenopausal fractures occur in women without osteoporosis by densitometry criteria, so clinical risk factors must also guide management 6

Integration with Treatment Decisions

• DXA results combined with clinical risk factors (using tools like FRAX) determine treatment thresholds 5, 7
• Patients with T-score ≤-2.5 have confirmed osteoporosis and warrant treatment consideration 5
• For those with osteopenia (T-score -1.0 to -2.5), treatment decisions should incorporate 10-year fracture probability calculations 5
• BMD measurement is essential before exposing patients to potential adverse effects of bisphosphonates and other osteoporosis medications 6