Scans and tests and osteoporosis

Transcription

1 Scans and tests and osteoporosis

2 What is osteoporosis? Osteoporosis occurs when the struts which make up the mesh-like structure within bones become thin causing them to become fragile and break easily, often following a minor bump or fall. These broken bones are often referred to as 'fragility fractures'. The terms fracture and broken bone mean the same thing. Although fractures can occur in different parts of the body, the wrists, hips and spine are most commonly affected. It is these broken bones or fractures which can lead to the pain associated with osteoporosis. Spinal fractures can also cause loss of height and curvature of the spine. Strong dense bone Fragile osteoporotic bone This leaflet covers specific information on scans and tests. If you would like more general information on osteoporosis, please ask us for a copy of our publication All About Osteoporosis.

3 Bone density (DXA) scanning Bone density scanning is the most commonly used diagnostic technique for osteoporosis but other scans and tests may be used to help understand what is happening to your bones. Most of these tests or scans help to predict how likely it is you will break bones and some are specifically used to diagnose osteoporosis as it is currently defined. Why measure bone density? As osteoporosis causes no symptoms until a bone is broken, it has traditionally been difficult to pinpoint which individuals have fragile bones prior to a fracture occurring. With advances in technology and the development of bone densitometry (the measurement of bone density), it has become possible to measure bone and assess its density. This is particularly useful because low bone density has been linked to an increased risk of fracture. Osteoporosis can now be diagnosed prior to bones

4 breaking, giving individuals, who have other risk factors and are at high risk of fractures, the opportunity to take treatments and adopt lifestyle changes which will reduce their risk of breaking their bones. How is bone density measured? The most common means of measuring bone density involves a simple test called dual energy x-ray absorptiometry (DXA). DXA machines usually scan bones in the lower spine and hip, two of the main areas at risk from osteoporotic fractures. This is called an axial or central scan. Other areas can also be assessed including the forearm and the heel using a peripheral scanner. These techniques use a low radiation dose, which is similar to natural background radiation less than one tenth of the dosage of a chest x-ray. A DXA scan will take between ten and twenty minutes and is not in any way unpleasant. An axial DXA scan involves lying on a firm couch whilst a scanning arm passes over the body taking an image of the spine and hips. It does not involve being enclosed in a mechanical tunnel or having an injection. Generally, clothing does not have to be removed but clothes with metal should be avoided.

5 What will the results tell me? A DXA scan produces a printout in which your bone density is compared to a reference range of young healthy adults with average bone density. The difference between this average and your bone density is then calculated and expressed in terms of standard deviations (SD) and you are given a T score. If the T score is: Between +1 and -1 SD Between -1 and -2.5 SD Below -2.5 SD this is normal this is termed osteopenia this is defined as osteoporosis Osteopenia is the name for the category between normal and osteoporosis, when bone is less dense than the average but not low enough to be classed as osteoporosis. Lifestyle changes such as the adoption of a well-balanced, calcium-rich diet and regular weight-bearing exercise are often recommended for people in this category. When a DXA scan is performed, a Z score is also calculated. This is a comparison between your bone density and that of a reference range of people of your own age. Although this is not used to diagnose

6 osteoporosis, it is useful sometimes for the doctor in the assessment of treatments in older people or children, when a comparison with a young adult reference range may not be so relevant. DXA scanning of the hip and spine is a very useful tool to help assess an individual s risk of fracture. However, there is more to fracture risk than just bone density. Low bone density, as diagnosed on a DXA scan, should be considered as a risk factor for fracture and not a perfect measure of bone strength, i.e. there will be people who have low bone density who never break a bone and vice versa. Sometimes, if bones are breaking very easily with an osteopenic result, bone fragility is likely and drug treatments may be appropriate. A referral to a specialist can be helpful in this situation.

7 Who should be offered a scan? Since 1999 The Royal College of Physicians clinical guidelines for prevention and treatment of osteoporosis (1999) have been used to decide who needs a scan to help with decisions about drug treatments. This guidance recommends that bone density measurements should be available to postmenopausal women over 45 years at high risk of osteoporosis if results may influence the doctor s decision regarding treatment. Recently, research has shown that although measuring bone density and identifying osteoporosis is useful, other risk factors for fracture can also be used to identify who is at greatest risk and who needs a treatment. A fracture risk assessment tool called FRAX has been developed by the World Health Organisation (WHO). It has been incorporated by a group of UK experts called the National Osteoporosis Guideline Group (NOGG) into a guideline to help health professionals identify people at highest risk of fracture who would benefit from treatment. These guidelines help to identify those who need to have a bone density scan. Further information is available at and

8 Is a bone density scan useful for everyone? As DXA scans are not a perfect measure of bone strength or fragility, screening everyone, even over the age of 50, would be very expensive and would not always pick up those at highest risk of breaking bones. A DXA scan can tell if a bone is likely to be fragile but other things about you will help to predict your risk of fracture even more accurately. Doctors have to take into account all of their patient s risk factors such as family history or corticosteroid use, as a way of identifying which people are at greatest risk of breaking bones. For some people, a bone density measurement will be necessary to ensure they are at high enough risk to need a drug treatment. Sometimes your risk of fracture is so high because of other risk factors, that a scan is not necessary before treatment is prescribed. This is particularly likely if you are over 75 years of age. Interpretation of the results of bone density measurements, especially of the spine, may be more difficult after the age of 65 years. As we age, the spine can be affected by other degenerative processes such as

9 osteoarthritis. Such changes can make bone appear denser than it actually is when it is scanned, therefore, affecting the accuracy of the results. The presence of previous fractures in the spine can also affect the results of a bone density scan. It is generally thought that scanning is most appropriate if it is going to make a difference to the management of a person s osteoporosis or affect a decision with regards to treatment. The evidence supporting the use of DXA scanning as a means of diagnosing osteoporosis is strongest in women after the menopause. Although it can be useful in younger women and men, it will require specialist interpretation.

10 Should I have further scans in the future to monitor my progress? Bone density scanning is generally used to help decide if a drug treatment is needed. If bone density is not sufficiently low to require treatment, a repeat scan might be performed after two to five years to determine whether a treatment is needed at a later date. As more is understood about what influences a person s risk of fracture and how the drug treatments for osteoporosis work, repeat scanning is now not so commonly used to see if a treatment is working. If a person is on a drug treatment that they tolerate well and they have not had fractures whilst on that treatment, then it is likely that the drug is working (as shown in the drug trials) and another scan is not necessary. However, if a person does have problems taking a treatment, or has fractures despite being on a treatment, then the doctor may decide that another scan to check bone density would be useful to make an informed decision about what to do next. If scans are repeated it is important they are performed on the same machine so that comparisons can be made.

11 The National Osteoporosis Society Helpline nurses are happy to discuss your bone density scan results but there is no facility for general scan interpretation. This should take place at scanning centres, with explanations and recommendations for treatment sent to GPs. How useful are DXA scans of the forearm or other sites? Peripheral DXA (pdxa) machines scan parts of the body other than the hip and spine. They might scan your forearm, heel or even finger. These scans can be used to help decide if you need a treatment. If a pdxa scan shows that you have very low bone density your doctor might decide to prescribe a treatment. However, usually when a pdxa scan shows that you have low bone density, your doctor would refer you for a scan of the hip or spine. Scanning these sites will allow them to diagnose osteoporosis and make the best treatment decision.

12 Ultrasound scanning DXA of the hip and spine is a relatively expensive procedure using a large, static piece of equipment which is usually located in a hospital. Research into less expensive, more portable techniques that can predict fracture risk has been carried out. Ultrasound is one of these portable techniques. What is ultrasound? Ultrasound can be used to examine structures inside the body. Sound waves of extremely high frequency, inaudible to the human ear, are beamed into the body. The echoes of reflected sound, or the rate and path of transmission of the sound, are used to build up an electronic image or measurement of the structure being examined. Ultrasound does not use radiation. What is ultrasound used for? Ultrasound scanning has proved useful in visualising many different parts of the body. It can be used for scanning in pregnancy, or imaging the liver, kidney, gallbladder, spleen, ovaries, bladder, breasts and eyes. Ultrasound waves may also be used to treat soft tissue injuries, e.g. muscles, ligaments and tendons. The treatment is thought to improve blood flow, reduce inflammation and speed up healing.

13 Portable and relatively inexpensive ultrasound machines have been developed, which are designed to look at bone structure and strength, usually of the heel bone (calcaneus), wrist or finger. They give a picture of the bone and provide measurements of the speed of the ultrasound wave through the bone or the absorption of the beam. The measurement is referred to as quantitative ultrasound to distinguish it from ultrasound used for imaging body structures.

14 Can quantitative ultrasound scanning (QUS) measurements be used to diagnose and monitor osteoporosis? Osteoporosis is defined according to World Health Organisation (WHO) criteria in terms of bone density measured by DXA scanning, when bone density is compared to data collected from young, healthy adult measurements. DXA scans of the hip and spine are, therefore, the current preferred method for diagnosing osteoporosis. There is currently no established, accepted definition of osteoporosis based on QUS measurements, so QUS cannot currently be used to confirm the diagnosis of osteoporosis. Ultrasound cannot be used to monitor rates of bone loss or bone gain with treatment. Who may benefit from heel ultrasound? Large studies suggested that heel ultrasound in older women (70+) may predict hip fracture risk as well as DXA. Heel ultrasound is also useful in predicting osteoporotic fracture risk in women around the time of the menopause and of Colles (wrist) fracture in women in their early post-menopausal years. There is no conclusive evidence that heel ultrasound can accurately predict fracture at other sites in women prior to the menopause, or in men.

15 There may also be problems using drug treatments based on ultrasound readings because research studies to determine the benefits of osteoporosis drug treatments were all based on DXA readings. Further research is needed. Some people are more at risk of osteoporosis because of factors such as early menopause (before age 45) or long-term tablet corticosteroid use. Identification of these high-risk groups may be useful in pinpointing those who may benefit from a DXA scan. QUS may sometimes be used as an improved method of targeting women for hip and spine DXA scanning to diagnose osteoporosis. What does a heel ultrasound involve? A heel ultrasound is a simple and painless procedure, taking a few minutes. In some machines, the heel is placed into a small water bath machine. In others, gel is applied to the heel, finger or wrist area and a dry machine is used. The test may be done at a unit that also does DXA scanning as part of the research into the usefulness of heel ultrasound, or within a doctor s surgery.

16 What about the advertised heel scans which test anyone for a fee? Due to the difficulties with using heel ultrasound to diagnose and monitor osteoporosis, and the lack of wellestablished, normal reference ranges, heel scans are not generally used in the same way as DXA scans. If someone is concerned about their bone health and osteoporosis risk and has a QUS heel scan, it may still be appropriate to consider bone density measurement by DXA scan especially when decisions need to be made about using drug treatments. If I decide to have a heel ultrasound scan I have seen advertised locally, what questions would be helpful? Does the company have a medical practitioner with responsibility for the service? Will the company scan anyone or just women after the menopause? Is the operator a healthcare professional with knowledge of osteoporosis? Is the service linked to the sale of dietary supplements or other products?

17 Computerised tomography (CT) scanning Computerised tomography (CT) scanning This type of scanning uses x-rays and a computer to take pictures of bone and put images together. CT scanners can be used to measure bone density and may be useful following compression fractures in the spine, when getting an accurate result can be more difficult. However, CT scans use higher levels of radiation than a DXA scan, which is usually considered preferable.

18 Magnetic resonance imaging (MRI) scanning This uses a strong magnetic field and radio waves to produce detailed pictures of soft tissue such as ligaments and muscles. It does not provide information about bone tissue so cannot diagnose osteoporosis or measure bone density. However, sometimes fractures might be identified using MRI, especially hip or vertebral fractures not seen on a normal x-ray. Often, MRI is used to indicate if another disease is present.

19 X-rays Normal x-rays are used to see if a hip, wrist or other bone has broken. Your doctor will also refer you for an x-ray if it is necessary to confirm that a fracture has occurred in the spine. Sometimes, identifying spinal fractures on an x-ray is complex and it may be difficult to determine how recent the fracture is. You will need to tell your doctor of any previous accident that might have resulted in damage to the spine. Sometimes, other tests will be carried out to ensure fractures have not been caused by another disease. A DXA scan might be useful after the x-ray to see if bone density is low and confirm that fractures are caused by osteoporosis. A DXA scan may be able to identify a fracture if it has occurred in the area being scanned. Scanners are being further developed and in the future may be used more widely to diagnose compression or wedge fractures in the spine. Height loss and spinal curvature are not always caused by osteoporotic fractures, but may result from arthritis in the spine or disc disease. Spine x-rays may, therefore, be appropriate to investigate the cause of height loss and curvature.

20 Bone (radioisotope) scanning Bone (radioisotope) scanning These scans might be used to pick up fractures that have been difficult to identify on x-ray. You are given an injection of radio active material which will show up as hot spots on the image that is produced. Other tests might then be necessary to ensure that any fractures identified are not caused by other conditions.

21 Urine and blood tests Bone marker tests: what are bone markers? Throughout life, the skeleton is continually renewing itself through a process known as remodelling or bone turnover. In healthy bone, the rate of bone breakdown is linked to the rate of bone formation so that bone strength is maintained. As we get older, the rate at which bone is broken down increases and exceeds the rate at which bone is formed. This results in loss of bone and may lead to osteoporosis and an increased risk of fracture. During the bone remodelling process chemicals are produced which can be detected in the blood and urine. These products are known as biochemical markers of bone turnover. An assessment of levels of these markers can be used to measure the rate of bone turnover, thus providing useful information about factors that might affect bone strength.

22 How useful is the test? The bone marker test is simple and requires a sample of urine or blood, which is then sent off to the laboratory for testing. Although the test can assess the rate at which bone is being broken down or formed, it cannot be used to diagnose osteoporosis or determine bone strength. Bone density scanning is more useful to help work out how likely fractures or broken bones are. Bone markers may be able to assess the effectiveness of treatment. Most treatments for osteoporosis work by reducing the rate of bone turnover, so monitoring bone loss using this technique may allow adjustment of the dosage of a treatment or change to another therapy if bone turnover is not reduced or back to normal within six months.

23 Where can I obtain the test? The test is only currently available in specialist centres when it is felt that the additional information provided could affect the type of treatment offered. They are also often used in the research field. Bone marker tests are not generally available from GPs as a tool to monitor treatment. This is because outside of the specialist setting it is difficult to avoid inaccuracies. A referral to a specialist centre to see a consultant is by GP referral only. The GP will be able to advise whether a consultant referral is required, as routine treatment of osteoporosis is usually managed by the GP.

24 Other blood and urine tests Sometimes, especially at a hospital appointment, levels of calcium in the blood might be checked. Low blood calcium levels do not indicate that you have osteoporosis, but may be due to vitamin D deficiency which can be treated with supplements. High calcium levels in the blood can mean you have other medical conditions that might be causing osteoporosis or fractures. Other blood tests may also help to check for other diseases that cause pain or bone fragility. Vitamin D levels may be checked by a blood test. Low levels can indicate you have a related condition called osteomalacia (soft bones) that can be treated with supplements of vitamin D.

25 A blood test (and occasionally a urine test) might be used to check that your kidneys are working well. This is not a routine procedure, but if there is concern about your kidney function your doctor might ask for this test before prescribing some of the osteoporosis drug treatments. If you are unsure about whether you are at risk of osteoporosis and the benefits of available tests, you may want to discuss this with your doctor or telephone the National Osteoporosis Society Helpline to speak to one of the nurses.

26 Factors which can help to maintain healthy bones are a well-balanced diet with adequate calcium-rich foods; regular weightbearing exercise; avoiding smoking and keeping alcohol consumption within the recommended limits.

27 Join the National Osteoporosis Society today Become a member and support the only UK-wide charity dedicated to improving the diagnosis, prevention and treatment of osteoporosis. You can join today, either call us or visit our website: Our publications are free of charge but we would welcome a donation You can support the work of the National Osteoporosis Society by making a single or regular donation: For osteoporosis information and support contact our Helpline: nurses@nos.org.uk

28 Other leaflets and factsheets in this range: Anorexia nervosa and osteoporosis Anti-epileptic drugs and osteoporosis Breast cancer treatments and osteoporosis Clothing, body image and osteoporosis Coeliac disease and osteoporosis Complementary and alternative therapies and osteoporosis Complex regional pain syndrome and osteoporosis Drug treatments and osteoporosis Exercise and osteoporosis Glucocorticoids and osteoporosis Further Food Facts and bone - beyond calcium and vitamin D Healthy living for strong bones Hip protectors and osteoporosis Hormone therapy in men and women and osteoporosis Hyperparathyroid disease and osteoporosis Osteoarthritis and osteoporosis Osteogenesis imperfecta and osteoporosis Osteoporosis in children Percutaneous vertebroplasty and balloon kyphoplasty and osteoporosis Pregnancy and osteoporosis The contraceptive injection (Depo Provera) and osteoporosis Thyroid disease and osteoporosis Transsexual people and osteoporosis Vibration therapy and osteoporosis (General Enquiries) (Helpline) Camerton, Bath BA2 0PJ President: HRH The Duchess of Cornwall National Osteoporosis Society is a registered charity no in England and Wales and no. SC in Scotland. Registered as a company limited by guarantee in England and Wales no Last reviewed October 2014 NOS/00147