Bone density or DEXA scan

A bone density scan, also called a DEXA scan, uses low-level X-rays to check the density (strength) of the bones. This is usually for diagnosing or assessing the risk for osteoporosis, a health condition that weakens the bone and elevates the risk of bone breakage.

A bone density scan is painless and quick. It is also a more effective scan than the normal X-rays to identify low bone density.

What is a bone density test?

A bone density test measures the strength and mineral content of the bone. It may involve using a special CT scan that uses computer software to analyse the density of the spine or hip, dual-energy X-ray absorptiometry (DXA or DEXA), or X-rays. The DEXA scan is known as the gold standard or the most accurate test for several reasons.

The bone density test informs the healthcare provider if there is decreased bone mass, a condition where the bones are more brittle and likely to fracture or break easily.

A bone density test is usually used to diagnose osteoporosis and osteopenia and helps determine the risk of future fractures. The test measures the density of the bone in the hip, spine, and lower arm. Portable testing may use the fingers, heel, wrist, or radius (one of the two bones of the lower arm), but it isn’t as precise as the non-portable methods because portable testing checks only one bone site.

The standard X-ray testing may show weakened bones, but at the point the standard X-ray detects bone weakness, the damage would be too advanced to treat. Bone densitometry testing can detect decreasing bone strength and density earlier when treatment is still beneficial.

Who needs a DEXA bone density test?

Anyone in any of these categories should get the DEXA bone density test.

• Men aged 70 or older
• Women aged 65 or older
• Adults with fragility fracture (a fracture with little or no trauma, such as falling from a standing height)
• Women who have lost over 1.5 inches and men who have lost over 2 inches from their tallest height
• Adults with a condition or disease associated with bone loss or bone mass
• Adults taking medications associated with bone loss or low bone mass
• Women during menopause and men below age 70 with risk factors for low bone mass, including prior fracture and low body weight
• Adults with lifestyle factors that can cause bone loss, such as excess alcohol intake and smoking

What happens during a bone density scan?

The healthcare provider will ask that you stop taking calcium supplements 24 – 48 hours before your scheduled bone density scan. Different facilities have varying guidelines. They will also ask you to remove any metal jewellery (such as belly button piercings) and clothing with metal fasteners (hooks, zippers, and buckles).

With your clothes on, you will lay back a padded table. Your legs can be rested or straight on the padded table. The scanner will pass over your hip and lower spine while another scanning device will pass beneath you. The machine will also scan your wrist while you are seated next to it. In some facilities, a separate scanner will evaluate your wrist.

The healthcare professional may ask you to hold your breath during the scanning. Ensure you lie still to prevent motion artefacts from interfering with the images the radiologist or technologist will evaluate on the computer screen.

Bone density test results

The bone density test determines your bone mineral density (BMD). The healthcare professional will compare your BMD to two norms – age-matched adults (your Z score) and healthy young adults (your T-score).

First, the healthcare professional will compare your BMD results to healthy 25 – 35-year-old adults of your ethnicity and sex. The standard deviation (SD)is the difference between your BMD and the BMD of the two healthy young adults. This gives your T-score. If your T-score is positive, your bone is stronger than normal, while a negative T-score indicates your bone is weaker than normal.

The World Health Organisation defined osteoporosis based on the following bone density levels.

• A T-score of 2.5 SD or lower than the young adult mean (greater than -2.5 SD) indicates osteoporosis.
• A T-score of 1 – 2.5 SD, which is lesser than the young adult mean (-1 to -2.5 SD), shows low bone mass.
• A T-score within 1 SD (-1 or +1) of the young adult mean shows normal bone density.

Generally, the risk of bone fracture increases with every SD value below the normal. This means if a person has a bone mass density of 1 SD below the moral T-score (-1), the person is twice as likely to have a bone fracture than a person with a normal BMD.

With this information, people with a high risk for bone fracture can get treatment to prevent future fractures. Severe or established osteoporosis means having a bone density over 2.5 SD below the young adult’s mean with one or several past fractures resulting from osteoporosis.

The second phase involves comparing your BMD to an age-matched norm called your Z-score. The calculation for a Z-score is the same as the T-score, but the comparison is with someone of your height, weight, race, and age.

Your healthcare professional may also recommend other tests with bone densitometry, such as blood tests to help detect kidney disease, evaluate the parathyroid function, the effect of cortisone therapy, or assess the mineral levels in the body related to bone strength, such as calcium.

If you are at risk of osteoporosis, visit Medical Express Clinic. for your bone density test. At our clinic, we offer same-day doctor appointments with fast turnaround times. Our services include tests for diagnosis, prevention, and monitoring.