Osteoporosis

DXA scans, FRAX and other tests for osteoporosis

The standard way of measuring bone density is a simple test called dual x-ray absorptiometry (DXA). The DXA scan is an accurate and reliable technique of assessing the strength of bones. A DXA scan usually measures bone mass (the amount of bone) in the spine and hip and wrist – parts of the body which are more at risk of osteoporotic fractures. Ultrasound can also be used to assess bone strength but cannot be used to monitor treatment.
 
A DXA scan measurement provides an assessment of a person’s bone density and his/her likelihood of having a fracture; it is also used to help decide if medication is needed. There is no national screening programme for osteoporosis but at present a doctor would request a DXA scan for a patient with strong risk factors such as maternal history of the condition, early menopause and use of oral corticosteroids. Using risk factors, together with height and weight, your GP can use the WHO FRAX tool to decide whether you need a DXA scan or whether the risk is high enough to warrant treatment (see also Who develops osteoporosis?).
 
A DXA scan involves lying on a couch whilst a thin metal arm moves up and down taking an image of the spine and hips. Clothes do not need to be removed, except for garments with metal at the hips or along the spine (trouser zips are fine). No injection or mechanical tunnel (like for an MRI scan) is involved in the procedure.
 
The level of radiation of a DXA scan is lower than that of an ordinary x-ray and more similar to natural daily radiation levels. The whole procedure takes between ten to twenty minutes and no one we talked to found it unpleasant.
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Many people requested their DXA scan through their GP, in many cases because their mother or father had osteoporosis, and/or after they had been using hormone replacement therapy (HRT). In other cases the GP initiated the scan after a wrist fracture or a complaint of back pain for some time - as in the cases of Carol and Alice respectively. In some cases x-ray results prompted hospital doctors to send patients like Jane for further investigations including a DXA scan. And others, like Iris, happened to attend fracture clinics in hospitals that routinely screen postmenopausal women with a fracture for osteoporosis. Doctors in fracture clinics made the postmenopausal women we talked to aware of the need to have a DXA scan. Gloria was told to ask her GP for one. Jenny however, had worried about osteoporosis long before her diagnosis and asked for a bone density scan to find out the impact of a dairy-free diet on her bones. For almost twenty years Jenny managed her ME and other allergies by not consuming dairy products. Joan made an appointment and paid for her first DXA scan at a private hospital because she realised her back was becoming bent and her mother had osteoporosis.

Not all hospitals have DXA scans. Some GPs can offer a DXA scan on the NHS but in areas where resources are scarce, people may have to pay for the scan themselves. People who were diagnosed many years ago often had to travel to have a DXA scan since fewer scanners were available then. But the situation has improved. People diagnosed in the last five years tend to have a scan done on average every three years. A few have been told by their GP’s that subsequent scans will be done every five years. Apart from DXA scans other tests, like blood and urine tests are also used to measure bone loss, predict fracture risks and to check the person's response to the medication (see below).
 
In a few cases and thanks to the fund raising activities of local support groups, hospitals have been able to get a DXA scanner and a printer to print the results that are sent to the GP. Pat, however, continues to pay for hers privately because in the city where she lives no NHS hospital has the facility.

Waiting times for a bone scan vary. After their GP requested a DXA scan some people received an appointment within a couple of weeks while others waited for 3-4 months. Moreover, people’s perception of ‘a long wait’ also differed. For Gloria a 3 months wait ‘wasn’t very long’ while Susan experienced 3 months as ‘waiting for ages’.
 
But Gloria waited a year for her second DXA scan after diagnosis and was anxious to know if the medication was working. After almost a year she learnt from the hospital that the request for another scan was pending and hadn’t even got on to the appointment list. She wrote to the Health Minister about it.

A DXA scan is generally used to decide if a person needs medication. A few people hadn’t needed medication at first because their bone density was not sufficiently low, but a later scan showed the need for it.
 
Many people felt that regular scanning gave them an accurate assessment of the strength of their bones and reliably monitored their treatment. Many were eager to know whether the medication had produced the expected improvement, had made no difference or, worse, if their bones had got thinner. Knowing that the bone density had improved made people confident about their treatment.

The frequency of scans varied. Some people were told they could have a scan on the NHS every two or three years to see if their medication was working. But most had to ask their doctor as it wasn’t automatically offered to them. Joan was taking strontium ranelate and had an annual bone density scan. People who paid for a scan privately could have one more frequently.
 
Some people had scans less often. Neville and Sarah had a scan at the time of their diagnosis several years ago but haven’t had one since. A few people said it had been five years or more since their last scan but they hadn’t felt the need to have another so hadn’t asked for one.

Several women who at the time of their fracture were not offered a DXA scan felt upset about the lack of preventive medicine because their diagnosis and treatment was delayed, sometimes for years (see Being diagnosed with osteoporosis).
Several close relatives of the people we talked to requested a DXA scan themselves to find out if they had osteoporosis. For most of these people, their GP arranged this. Diana’s and Sheila’s daughters, have also been diagnosed with the condition. But Laurence feels frustrated that his daughter and also his wife with a maternal history of the condition were denied a scan.

The results of the DXA scan are usually sent to the GP with whom people can discuss the results. Accurate interpretation of results depends on repeat scans being performed on the same machine, especially if they are being used to monitor a treatment or bone loss. For a few people comparisons couldn't be made because their tests had been done on different scanners. To get around this problem Jenny paid for her subsequent scans to be done on the original machine after her GP clinic started arranging DXA scans at another hospital. Having her scans done there would have made it impossible to compare previous scan results with newer ones.
 
In some parts of the UK support groups have raised funds to buy or contribute to the cost of a DXA scanner to ensure that one is available locally ensuring that patients’ scan results can be compared accurately.

Evidence suggests that a bone scan may not be the best way to assess fracture risk in the elderly because degenerative conditions of the spine such as osteoarthritis may occur as part of the ageing process. In turn, this can affect the reading of a DXA scan hence giving a misleading estimate of a person’s bone mass. This happened in Joan’s case.
Blood and urine tests: biochemical markers
 
During bone remodelling substances are produced which can be detected in the blood and urine. These are known as biochemical bone markers. The levels of these markers can be used to measure the rate of bone turnover, giving useful indicators of bone strength and future fracture risks. Blood and urine tests alone cannot diagnose osteoporosis, people also need a DXA scan, but can be used to assess the effectiveness of treatment. Most treatments for osteoporosis work by reducing the rate of bone turnover, so monitoring bone loss with this technique may help with dosage adjustments of medication or help indicate the need to change to another medication if bone turnover is not reduced or back to normal within six months.
 
Some units use biochemical markers instead of DXA for monitoring treatment, the tests are a bit awkward; the patient has to fast and the sample must be taken at the same time of day each time. A few people told us that the biochemical markers of bone turnover are being used to assess their response to the prescribed medication.
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Last reviewed June 2017
​Last updated June 2017.

Last updated June 2017

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