Understanding your DEXA scan results

A DEXA scan records how dense your bones are, most often at the hip and in the lower spine, and density is one guide to strength. On the report that reading becomes a score, set against an expected value so that every result can be read on the same terms. Two scores appear most often: a T-score and a Z-score.

Neither is a mark out of ten or a test you pass or fail. Each shows a specialist where your density stands beside a reference group, and that is the opening of a conversation about your bones, not its last word.

The T-score is usually the first score doctors look at when checking for osteoporosis; it measures your density against the usual range for a healthy young adult. The Royal Osteoporosis Society, among other UK sources, gives three bands:

• Normal: anything from +1 down to -1.
• Low bone density (osteopenia): from -1 down to -2.5, slightly under the young adult's range and common as people get older.
• Osteoporosis: -2.5 and below, which means the density sits well under the young adult's range.

Measuring against a young adult means that some drop over the years is only natural, one reason the T-score is read in the light of your age and the rest of your risk.

Your Z-score instead measures you against people of the same age, sex and ethnic background. Since density naturally falls as we age, this can make for a fairer comparison, and it counts for more in younger adults, where a low figure may lead to tests for a cause.

The two scores work alike in one respect: a lower figure points to a greater chance of a break, and the Z-score can count when treatment is being decided. Yet a Z-score in the normal range for your age does not rule out bones weak enough to need treatment, since bones generally weaken in later life; what matters is what the figure means in your case.

A DEXA score measures density; what happens to your bones is not settled by it, or by the label it carries. Density is only one of several things that decide how likely a break is, and that likelihood is what really matters. A fracture risk assessment puts the score beside your age, bones broken in the past, a parent, brother, sister or child who broke a hip, osteoporosis in the family, steroid tablets taken for long spells or in repeated courses, smoking, drinking and your health more widely.

Calculators such as FRAX or QFracture turn these factors into a ten-year chance of a break, beside a full assessment of your health; FRAX can include a DEXA result where there is one, and works without one where there is not. This is why the same T-score can lead to quite different advice for two people: the number is read as part of the whole.

With the result placed in context, attention moves to what, if anything, needs doing. Very often, and with osteopenia most of all, the answer lies in lowering the risk without a medicine: regular exercise, a balanced diet, enough calcium and vitamin D, and tackling habits such as smoking. A finding of osteopenia asks you to care for your bones; it does not of itself call for treatment.

When density is lower, or the overall chance of a break is higher, a medicine that protects the bones, a bisphosphonate for example, may be recommended to strengthen them and reduce the risk. The medicines, how each is taken and how its effect is checked are covered fully in our guide to osteoporosis and bone health. In every case, any plan is made with you and fitted to your circumstances.

A specialist can go through a DEXA result you are unsure about, make sense of it and propose a plan. It is especially worth asking for one when:

• The scan points to osteoporosis, or to osteopenia when other risk factors are present too
• A minor fall or knock has broken one of your bones in the past
• Steroid tablets have been part of your life for long or repeated spells
• Osteoporosis or a broken hip runs in your family
• Your bone density is low for your age, which can mean an underlying cause needs looking for

At an appointment, the scores are set beside the rest of your health, and any plan is one you have agreed. Sudden, severe back pain, back pain that is getting worse quickly, or back pain with a fever or feeling hot, cold, shivery or generally unwell, should be seen by your GP or NHS 111 the same day; every other sign that needs help sooner is set out, with where to go for it, under When to seek help in our osteoporosis guide. If you cannot tell how urgent something is, asking is never a mistake.

How should I read my T-score?

It sets your bone density against the normal range of a healthy young adult, and doctors use it more than any other score to look for osteoporosis. Broadly, anything from +1 down to -1 counts as normal, a figure between -1 and -2.5 is called low bone density, or osteopenia, and a figure of -2.5 or lower falls in the osteoporosis range. Some loss of density is expected with age, so the figure says most when your age and your other risks are weighed with it. Your own figure is best talked through with a specialist.

Does a low score, or being told I have osteopenia, mean I must have treatment?

Not necessarily. Osteopenia especially tends to be a signal to care for your bones rather than a reason to begin a medicine, and many people with it are advised to stay active, eat a balanced diet and keep their calcium and vitamin D up. Whether a medicine for the bones is advised depends on your overall chance of a break, not on the score alone, and it is something to talk over and agree within a full assessment.

Does the DEXA number alone decide how likely I am to break a bone?

No, and of everything here this matters most. Bone density is just one factor in your chance of breaking a bone, and that chance is the real question. A proper assessment also counts your age, any bones broken before, osteoporosis in the family, the use of steroids, smoking and drinking, often with the help of a calculator such as FRAX. Two people with an identical T-score may therefore be advised quite differently.

Is it worth seeing a specialist about my result?

Yes, if you are unsure what the result means, and particularly if it shows osteoporosis, or osteopenia alongside other risk factors. A review makes sense too after a bone broken earlier in a minor fall, after long or repeated steroid courses, when osteoporosis or a broken hip runs in the family, or when your density is low for your age. Dr Borukhson looks at DEXA results as one part of a complete bone-health assessment, going through your scores with you and settling together what happens next. Back pain that started suddenly and is severe, back pain that is getting worse quickly, or back pain with a fever or feeling hot, cold, shivery or generally unwell, is for your GP or NHS 111 the same day; the rest of the signs needing help sooner, with the route for each, are under When to seek help in our osteoporosis guide.

My DEXA result was not what I expected. What does that mean?

Many people find their result hard to make sense of, and a surprise is not in itself a reason to worry. A score in the osteoporosis range does not always mean you need a medicine, and one in the osteopenia range sometimes does, because the decision rests on your whole chance of a break, worked out with a fracture risk assessment. A Z-score lower than expected for your age can point to another condition affecting the bones, and further tests may be offered to look for it. If you have had scans before, a small fall in density between them is expected with age, and a result that has held steady or dropped only slightly can be good news; scans compare best when they are done on the same machine. A specialist review can place an unexpected result in the context of your health and explain what, if anything, should change.