DEXA scan in London, for bone density and body composition

What a DEXA scan is

DEXA, also written DXA, stands for dual-energy X-ray absorptiometry. It measures the calcium and other minerals in your bones, and the denser the bone, the less likely it is to break [1]. It is usually done on the lower spine and the hip, the bones most likely to break when they are weak [1].

The same scanner can measure the whole body and separate fat from lean tissue, including fat stored around the organs [2]. That is the body composition scan.

Why it is done and who it is for

A bone density scan finds bone loss before a fracture, estimates your future risk of breaking a bone, and can confirm osteoporosis [1]. NICE recommends assessing fracture risk in everyone aged 50 and over, and in women after the menopause, who have had a fragility fracture or take steroid tablets regularly, such as 5 mg or more of prednisolone a day for over 3 months [3].

NICE also suggests considering an assessment in all men aged 75 and over, all women aged 65 and over, and in people aged 50 to 74 with other risk factors [3]. A doctor first estimates your 10-year fracture risk with a tool such as FRAX or QFracture, and NICE advises considering a DEXA scan when that risk is 10% or more [3].

• Two or more falls in the last year
• A parent or sibling who broke a hip before the age of 80
• A body mass index below 18.5
• Smoking, or more than 14 units of alcohol a week
• Height lost, about 4 cm or 1.5 inches or more
• An early menopause, or treatment that lowers sex hormones

What body composition can tell you

A body composition scan shows where you carry fat and how much lean tissue you have, which a weighing scale cannot. Repeated on the same scanner, it shows whether a change in training or diet is altering fat or muscle [4].

The International Society for Clinical Densitometry supports body composition DEXA in some settings, such as large weight loss, and states that its effect on health outcomes is uncertain [4]. It is most useful as a measure to act on with a doctor, alongside your blood pressure and bloods.

Who it is not for, and its limits

DEXA is avoided in pregnancy, and the International Society for Clinical Densitometry lists pregnancy as a reason not to have a body composition scan [1] [4]. If you have recently had a barium test or contrast for a CT or nuclear medicine scan, you may need to wait 10 to 14 days [5].

The scan cannot say who will break a bone, only how likely it is, and it cannot show what is causing low bone density [5] [1]. Arthritis or scoliosis of the spine, or earlier spinal surgery, can make the spine reading less accurate [1]. Checks on the heel, finger or wrist are less accurate than a scan of the hip and spine [1].

Risks

The radiation dose is very low, about 0.001 mSv, comparable to about 3 hours of natural background radiation [6]. That is much less than a chest X-ray, and the scan is painless [1].

How you prepare and what to expect on the day

You can eat and drink as normal and take your usual medicines, but do not take calcium supplements for 24 hours before the scan [7] [1]. Wear clothes without zips, buttons or underwiring, because metal affects the result [7].

You lie on a padded table while an arm moves slowly above you, first over the hip, then the spine, with your legs resting on a block [7]. You feel nothing, and a scan of the hip and spine takes 10 to 30 minutes [1]. A whole body scan for body composition is done on the same table.

Results and what happens next

Your report gives a T-score, which compares your bone density with a healthy young adult. A score of -1 and above is healthy, between -1 and -2.5 is low bone density, called osteopenia, and -2.5 and below suggests osteoporosis [1]. Before the menopause, and in men under 50, a Z-score comparing you with people of your own age is used instead, and osteoporosis cannot be diagnosed in men under 50 on bone density alone [4].

Low bone density does not always mean a high fracture risk, so the doctor reads the score together with your history and fracture risk tool [4]. A follow-up scan is useful when its result would change what you do [4].

• What is my 10-year fracture risk, and does the scan change it?
• What might be causing low bone density in me?
• What can I change in exercise, diet and vitamin D?
• When, if ever, should I repeat the scan?

How The Wellness can help

DEXA is on our imaging page for bone density, fracture risk and body composition, takes 15 to 20 minutes, and is reported in 24 to 48 hours [2]. It is included in the Longevity Foundation programme at £6,995, with a full body MRI, VO2max testing, a metabolic and hormone panel and a physician roadmap [8].

Our clinics are on Baker Street in Marylebone and Eccleston Street in Belgravia, open from 7am to 9pm every day, and a GMC registered doctor explains every result with you.