This is the key to the prevention of osteoporosis. Yet the disease frequently goes undiagnosed. Only one-third of people with spinal fractures caused by osteoporosis come to medical attention.

A bone scan is the only accurate way to determine bone mineral density and so diagnose osteoporosis.

Bone mineral density scans only tend to be available for people who are at high risk, but they are gradually becoming more widely available.

Bone scan - measurement of bone mineral density

The main bone scan is the Dual-energy X-ray absorptiometry (DXA), which can diagnose low bone mass, define the risk of future fractures, and assess response to treatment. 

It is the most accurate and reliable way of assessing bone strength and provides an estimate of the total amount of calcium in the skeleton.

The procedure itself is simple and painless, and uses very low doses of radiation. Whilst lying down, for just 10-15 minutes, an X-ray arm passes over you to take an image of your spine and hip.

The results shows how your bone density compares to the mean bone density of someone of your own age and sex, and compared to the mean bone density of a young adult of the same sex.

Osteoporosis is diagnosed if the bone density is significantly below (2.5 standard deviations) this latter mean value.  If your result falls in between the normal range and the range defined as osteoporosis, then you will be diagnosed with osteopenia (low bone density).

Unfortunately access to the bone scan equipment is still limited and reserved for high risk people and for monitoring the disease.

Those who should seek advice on having a bone scan:

• Women who have gone through an early menopause
• Those who have a curvature / deformity of the spine
• Those deciding whether to use hormone replacement therapy
• Those who have had X-rays that have indicated a potential problem
• Those who have been treated for osteoporosis, as a follow-up

This is not intended as a complete list - your doctor will advise on each individual case and refer you for a scan if it is appropriate.  He/she may start treatment without the use of a bone scan if there is enough medical evidence.

X-rays

X-rays can highlight the occurrence of a fracture, but are not as effective as the bone mineral density scan for diagnosing osteoporosis.  X-rays will only indicate that the disease is probably present if at least 30% of the bone density has already been lost.

Risk assessment tests

There are an increasing number of over the counter and home risk assessment kits available. They can only provide an indication of risk, however, not a diagnosis.

Home test kits may involve you sending a urine sample back to the supplier laboratory for analysis of deoxypyridinoline (Dpd).  Dpd is a product of bone resorption.  The higher the levels of Dpd in the urine, the greater the risk of developing osteoporosis. Although the method measures Dpd accurately, the National Osteoporosis Society has pointed out that there is a weak relationship between the high levels of Dpd and fracture risk.

Other tests

Blood tests and a bone biopsy may be carried out to exclude other bone disorders. Anyone with a family history of kidney stones, or who has suffered with them in the past, will be advised to have a blood test.  This will detect whether there is an abnormally high level of calcium in the blood, before any increase in dietary calcium is considered.

Recent developments and future possibilities

In the last decade, Broadband Ultrasound Attenuation (BUA) has been under development, a new and exciting means of predicting whether elderly patients are at risk of hip fractures.  It is a relatively inexpensive method and does not use radiation. It does not, however, measure bone mineral density and so cannot define osteoporosis.

There are other potential simple tests that are being investigated as a means to assessing risk.  These include looking at skin thickness (a possible relationship between thickness and bone mass); and looking at the gene that controls vitamin D uptake. Visit the Latest Research section for updates in all these areas.

If you are diagnosed with osteoporosis, there are many treatments available to minimise the risk of further bone loss.  There are also a number of preventive measures that can be taken to reduce further bone loss and guard against the potential severity of the disease.

20/05/2009