Most people don’t consider bone health until an issue arises, such as following a fracture or osteoporosis diagnosis. However, your bones can (and should) be examined as part of a preventative measure, just like your heart or metabolism.
Bone density tests can help with that. These examinations gauge bone strength, spot early indications of bone loss, and assist in directing treatment or lifestyle choices.
The DEXA scan, which stands for dual-energy X-ray absorptiometry, is generally regarded as the gold standard among the available options. However, there are alternative techniques, such as CT-based scans and ultrasound.
What is the comparison between these tests, then? And when is the right time to pick one over the other?
This guide breaks it down.
Table of Contents
What Is a Bone Density Test?
The amount of minerals (primarily calcium and phosphorus) in your bones is determined by a bone density test. Your bones are stronger and less likely to break if they are denser.
Tests for bone density are frequently used to:
- Diagnose osteoporosis or osteopenia
- Calculate your chance of getting fractures in the future.
- Track changes in bone over time, particularly while undergoing treatment
- Identify bone loss due to ageing, menopause, or certain medical conditions
1. DEXA Scan (Dual-Energy X-ray Absorptiometry)
How it works
A DEXA scan measures bone mineral density (BMD) using two low-dose X-ray beams. The scan usually focuses on important fracture-prone regions, such as the hips, spine, and occasionally the forearms.
Benefits
- High accuracy and reproducibility
- Minimal radiation exposure—much less than that of a typical chest X-ray
- Recognised as the clinical gold standard for diagnosing osteoporosis
- Beneficial for monitoring changes over time and assessing the efficacy of treatment
- Able to evaluate body composition (muscle mass and fat)
Limitations
- Typically requires a hospital or specialised clinic
- May be less accurate in people with spinal abnormalities or implants
- Medicare may only pay for it every two years unless there is a valid medical reason.
2. QUS (Quantitative Ultrasound)
How it works
This technique evaluates bone characteristics, typically at the heel bone (calcaneus), using sound waves rather than X-rays. It calculates bone strength based on the speed and quality of sound transmission rather than directly measuring bone mineral density.
Benefits
- No radiation
- Portable and inexpensive
- Quick and non-invasive
- Useful in remote or community settings
Limitations
- Not as accurate or predictive as DEXA
- Restricted to the limbs (not the hip or spine)
- Can’t monitor treatment effectiveness or diagnose osteoporosis on its own
- It works best as a screening tool rather than a diagnostic one.
3. pQCT (Peripheral Quantitative Computed Tomography)
How it works
pQCT scans measure both trabecular and cortical bone to produce a three-dimensional image of the bone structure at the wrist or leg. It provides more thorough information about the strength and geometry of bones.
Benefits
- More thorough than DEXA
- Evaluates both bone density and quality.
- Can evaluate bone shape, thickness, and structure
Limitations
- Not widely available
- More expensive and radiation-intensive than DEXA
- Not currently used for routine diagnosis of osteoporosis
- Mostly used in research settings or advanced clinical cases
4. QCT (Quantitative Computed Tomography)
How it works
QCT is a CT-based technique that uses cross-sectional imaging to measure bone mineral density (BMD) at the hip and spine. It is frequently used when more precise imaging is needed and can distinguish between trabecular and cortical bone types.
Benefits
- High precision
- Helpful in situations where DEXA is inappropriate (such as obesity and spinal deformities).
- Helps predict the risk of fractures
Limitations
- More radiation than DEXA
- Less accessible and more costly
- Usually not utilised for regular screening
- Requires skilled radiologists and specialised software.
5. FRAX (Fracture Risk Assessment Tool)
How it works
FRAX is a mathematical model created by the World Health Organisation, but it is not a scan. It calculates the 10-year risk of fracture using clinical information (age, sex, BMI, prior fractures, smoking, etc.) with or without a DEXA score.
Benefits
- Beneficial in primary care settings
- Helps guide decisions about further testing or treatment
- Can be used without DEXA if not available
Limitations
- It is not a measurement; rather, it is an estimator.
- May underestimate risk in individuals with peculiar medical histories.
- Best used as a complement to imaging, not a replacement
Summary: DEXA vs. Other Bone Tests
| Test | Accuracy | Radiation | Key Use | Limitation |
| DEXA | High | Low | Diagnosis + Monitoring | Clinic required |
| QUS | Low-Med | None | Screening only | Not diagnostic |
| pQCT | High | Moderate | Bone structure | Limited access |
| QCT | High | High | Advanced diagnosis | Cost + exposure |
| FRAX | NA | None | Risk estimation | Indirect only |
When Should You Get a Bone Density Test?
Bone density testing is generally recommended if you:
- Are a woman over 65 or man over 70
- Possess risk factors; low testosterone or are postmenopausal.
- Have a family history of osteoporosis
- Have diseases or medications that deplete bone (e.g., thyroid disease, steroids)
- Have had a minimal trauma fracture (atraumatic or break from a minor fall)
The most popular and reliable test to begin with is a DEXA scan. DEXA offers the most accurate and transparent image if you’re worried about the condition of your bones or wish to monitor changes over time.
Final Thoughts
Bone health is often overlooked until a fracture or other issue reveals underlying problems. However, bone loss can be detected early and accurately through screening. Early detection allows for preventive measures to reduce the risk of fractures or permanent disability.
The DEXA scan is still the most reliable, secure, and generally used method of diagnosing osteoporosis and determining bone strength, even though other tests have their uses.
If you’re thinking about getting a bone density test, don’t just pick the simplest option; pick the one that provides you with the most valuable information. That usually entails beginning with a DEXA scan.