A DEXA scan is used to measure bone density and assess the risk of bone fractures. It is often used to help diagnose osteoporosis and other similar bone conditions, including osteopenia and osteomalacia.
DEXA scans can also be used to measure body composition (the amount of bone, fat and muscle in the body).
Identifying bone conditions
Unlike ordinary X-rays, DEXA scans can measure very small changes in bone mineral density, making it possible to diagnose osteoporosis (weak and brittle bones) in its early stages before fractures occur.
A DEXA scan also uses a low dose of radiation, which means that the risks to health are lower than with X-rays.
DEXA scans can also help identify other conditions that affect bone density, such as osteopenia, where bone density is lower than average but not low enough to be classed as osteoporosis, and osteomalacia, where the bones are softened due to a vitamin D deficiency.
The results of a DEXA scan are used by doctors to help them decide whether treatment for low bone density is needed. For example, if you are diagnosed with osteopenia, lifestyle changes may be recommended to improve your bone health. These might include:
- eating a healthy, balanced diet that is high in calcium
- spending more time in the sun to help increase your levels of vitamin D
- regularly doing weight-bearing exercise, such as walking or running
When a DEXA scan is recommended
A DEXA scan may be recommended if you have an increased risk of developing a bone condition such as osteoporosis. Your risk is increased if you:
- have had a fracture after a minor fall or injury
- are a woman who has experienced an early menopause, or you have had your ovaries removed at a young age (below 45) and have not had hormone replacement therapy (HRT)
- are a post-menopausal woman and you smoke or drink heavily, have a family history of hip fractures, or you have a body mass index (BMI) of less than 21
- are a man or a woman with a condition that leads to low bone density, such as rheumatoid arthritis (pain and swelling in the joints)
- are a woman who has large gaps between periods (more than a year)
- are a man or a woman who is taking oral glucocorticoids for three months or more (glucocorticoids help treat inflammation but can also cause weakened bones)
Limitations
A DEXA scan is not the only way of measuring bone strength or fragility.
Other risk factors need to be taken into account, such as family history and medication use, to determine who is at risk of developing bone fractures. All of the risk factors will need to be considered before a DEXA scan is recommended and before any treatment is started.
Some people will need to have a DEXA scan to confirm that their risk of developing bone fractures is high enough to need treatment. For other people, particularly the elderly, the risk of fracture may be so high that there is no need for them to have a DEXA scan before treatment is prescribed.
It can be difficult to interpret the results of a DEXA scan, particularly of the spine, when someone has a degenerative condition, such as osteoarthritis. In such cases, spinal abnormalities or a previous spinal fracture can give a false result.
