Osteoporosis on DXA Scan

Understanding Your Bone Density Test

A bone density test is the standard way to diagnose osteoporosis. Before understanding your results, let's look at why this test is important.

Here's how accurate DXA is at detecting bone problems:

Think of your bones like a savings account—you build up bone density during childhood and young adulthood, then gradually withdraw as you age. A DXA scan measures your current "bone balance" and predicts your fracture risk.

What Is Osteoporosis?

Osteoporosis means "porous bone"—bones become less dense, more brittle, and prone to fracture. You can't feel bone loss happening, which is why screening is important.

How DXA works:

• Uses two X-ray beams at different energy levels
• Measures how much X-ray passes through bone (calculates density)
• Takes about 10-15 minutes, completely painless
• Usually scans hip and lower spine (lumbar vertebrae)

What the numbers mean:

| T-score | Bone Density | Fracture Risk | Treatment | |---------|--------------|---------------|------------| | ≥ -1.0 | Normal | Low | None needed | | -1.0 to -2.5 | Osteopenia | Moderate | Consider prevention | | ≤ -2.5 | Osteoporosis | High | Treatment usually recommended |

T-score vs Z-score:

• T-score: Comparison to healthy young adult (age 30) peak bone mass
• Z-score: Comparison to age-matched peers (used for premenopausal women, men ＜ 50)

How Bone Density Appears on DXA

Let's visualize what healthy bone looks like compared to osteoporotic bone on a DXA scan:

Key Findings Pattern

When interpreting your DXA scan, radiologists look for specific patterns that indicate bone health problems:

When Your Doctor Orders This Test

Here's a typical scenario where a DXA scan is recommended:

Screening DXA is recommended for:

• All women ≥ 65 years
• Men ≥ 70 years
• Postmenopausal women ＜ 65 with risk factors
• Anyone who has fractured a bone after age 50
• Adults on long-term corticosteroids (≥ 3 months)
• Anyone with medical conditions associated with bone loss (RA, hyperthyroidism, etc.)

How often: Every 2 years for monitoring, or sooner if risk factors change.

Understanding Your Results

Your T-score falls into one of several categories, each with different implications for your bone health:

FRAX: Your Fracture Risk Score

Your doctor may use the FRAX tool to estimate your 10-year fracture risk:

| Risk Factor | Why It Matters | |-------------|----------------| | Age | Risk increases each year after menopause | | Low bone mass (T-score) | Lower T-score = higher fracture risk | | Previous fracture | Having had one fracture doubles risk of another | | Parent had hip fracture | Family history increases risk | | Smoking | Current smokers have higher fracture risk | | Glucocorticoids | Long-term steroid use increases risk | | Rheumatoid arthritis | Chronic inflammation accelerates bone loss | | Secondary causes | Diabetes, osteogenesis imperfecta, etc. | | Alcohol ＞ 2 drinks/day | Excessive alcohol increases fracture risk |

Treatment threshold: Medication may be recommended if your 10-year major osteoporotic fracture risk is ≥ 20% or hip fracture risk ≥ 3%.

How Accurate Is DXA?

The evidence supporting DXA as the gold standard for bone density measurement is strong:

What Happens Next?

If your DXA shows abnormal bone density, here's the typical care pathway:

Frequently Asked Questions

Do I need to undress for a DXA scan?

You'll need to remove clothing with metal (zippers, buttons, underwire bras). Wear loose, comfortable clothes without metal. You may be asked to change into a gown. Remove all jewelry.

Should I stop calcium supplements before the scan?

No, unlike some other tests, DXA is not affected by recent calcium intake. Continue your usual diet and supplements. However, tell the technologist about any recent imaging studies with contrast (barium studies, CT with contrast)—wait 7-14 days after these.

Can I have DXA if I'm pregnant?

DXA uses X-rays, so it's generally avoided during pregnancy unless medically necessary. Tell your doctor if you're pregnant or might be pregnant. For most women, DXA can wait until after pregnancy.

What if I have metal implants?

Hip replacements, spinal hardware, or surgical clips can interfere with DXA measurements. The technologist will avoid scanning those areas and use alternative sites (forearm, other hip) if needed.

How often should I repeat DXA?

• Every 2 years for monitoring osteopenia or osteoporosis
• Every 1-2 years after starting treatment to monitor response
• Every 5-10 years if normal and low risk
• More frequently if on long-term steroids or high-risk medications

References

Medical Disclaimer: This information is for educational purposes. Always discuss your imaging results with your healthcare provider for personalized medical advice.