Bone Density Test
Overview
A bone density test checks how strong bones are by measuring the amount of minerals, such as calcium, in a certain area of bone. Common testing areas include the spine, hip, and sometimes the forearm. This test helps detect conditions like osteoporosis by showing if bone loss has occurred.
Key Points:
- Measures bone mineral density (BMD).
- Shows levels of bone mineral content.
- Helps identify low bone mass.
- Detects risk of bone loss and fractures.
- Assesses if peak bone density is being maintained.
Reasons for Testing
A bone density test helps healthcare providers check how strong and healthy a person’s bones are. This type of test can spot low bone mass early, even before someone gets a bone fracture. Finding low bone density early gives people a better chance to take steps to avoid broken bones in the future. The test can:
- Detect osteoporosis or osteopenia in patients who have a higher risk.
- Estimate the chance of future bone fractures by checking bone strength.
- Confirm reasons for decreasing height or fragility fractures, which can happen when the bones become weaker.
- Track how well treatments for osteoporosis are working over time.
People who may benefit from a bone density test include those who:
| Reason | Description |
|---|---|
| Lost significant height | Losing about 1.5 inches or more may signal spine fractures or weak bones. |
| Had a fracture from a minor injury | Fragility fractures suggest bones could break easily in the future. |
| Take steroid medicines regularly | Long-term steroid use can lower bone mass and raise fracture risk. |
| Had hormone changes (e.g., menopause) | Lower estrogen or testosterone can make bones less dense and more fragile. |
Bone density testing differs from a bone scan. The main use is to measure the mineral content in bones, especially in areas like the hip, spine, and wrist, where fractures from weak bones are most common.
Doctors use bone strength information to offer advice about ways to maintain or improve bone health and lower the chances of osteoporosis or future fractures. This is useful for both men and women, especially as they age or have certain health conditions.
Possible Concerns
Bone density tests use a small amount of X-ray radiation, but the exposure is very low. Pregnant people should avoid these tests. Different testing devices measure various bones, and tests for the spine and hip usually give more precise results. Devices for the forearm, finger, or heel may not provide as accurate results.
Spinal conditions, such as severe arthritis, previous back surgeries, or scoliosis, can affect the accuracy of test results. The test shows if bones are weaker than normal but does not explain the reason for bone loss. Doctors must perform further medical evaluation to find the root cause.
Insurance may not always cover this test, so people should check their coverage first. Risk factors for low bone density include:
- Advancing age
- Post-menopausal women
- Low body weight or BMI
- Family history of osteoporosis or hip fracture
- Rheumatoid arthritis
- Hyperthyroidism or hyperparathyroidism
- Type 1 diabetes, liver or kidney disease
- Anorexia nervosa
- Inactivity
Steps You Should Take Before the Test
Eating Habits and Medicine Use
- Do not take calcium pills, including vitamins and antacids, for at least 24 hours before the test.
- Tell your doctor if you have had any recent testing with barium or contrast dye, as this could affect the results.
- Smoking and alcohol can impact bone health over time, but they do not affect the test results if used just before the exam.
- No need to fast; you can eat as usual unless your doctor says otherwise.
What to Wear and Bring
- Choose comfortable clothes that do not have metal items like buttons, zippers, or belts.
- Avoid wearing jewelry, watches, or any metal objects. Leave them at home if possible.
- You may need to change into a gown at the testing center, depending on their rules.
What You Might Experience
Bone densitometry testing usually focuses on bones that are at higher risk for osteoporosis, such as the lower spine, hip, or forearm. For most standard DEXA scans (dual-energy x-ray absorptiometry), you lie still on a cushioned table while a scanner arm moves slowly above.
The entire process is quick, taking around 10 to 30 minutes, and uses a very low dose of x-ray radiation—much less than what a regular chest x-ray gives. Most people find the exam painless and comfortable.
Portable bone densitometry devices can measure bone strength in smaller bones, like those in your finger, wrist, or heel. These peripheral bone density scans are often available at health fairs or community events. The table below highlights some key differences:
| Feature | Standard DEXA Scan | Peripheral Device Scan |
|---|---|---|
| Bone location tested | Spine, hip, forearm | Finger, wrist, heel |
| Setting | Hospital/clinic | Community/health fair |
| Accuracy | Higher | Lower (especially for fracture risk) |
| Follow-up needed | Rarely | Sometimes recommended |
If a peripheral scan suggests bone loss, a healthcare provider may order a standard DEXA scan at the spine or hip for a more precise diagnosis.
Test Outcomes
Comparison to Young Adult Standard
The T-score measures bone density by comparing a person’s results to what is typical for a healthy young adult. The score shows how many standard deviations a person’s bone density is above or below the average for this group.
| T-score Range | Meaning |
|---|---|
| -1 and above | Normal bone strength |
| Between -1 and -2.5 | Lower than normal (osteopenia) |
| -2.5 and below | Indicates osteoporosis |
A T-score of -1 or higher suggests strong bones, while scores below -1 can show signs of bone weakening.
Comparison to Peers
The Z-score compares a person’s bone density to others with the same age, sex, weight, and background. This number helps find out if bone loss might be happening for a specific reason. Scores much higher or lower than the typical value might suggest that health professionals should check further to understand the possible causes.
