ABSTRACT
Bone density scans using the technique of dual energy X-ray absorptiometry (DXA) are
widely seen as having an essential role in the evaluation of patients at risk of osteoporosis.
DXA scans of the spine and hip are the most useful because fractures at these sites
result in the greatest impairment of quality of life. A hip DXA scan is the most reliable
way of evaluating hip fracture risk, and the spine is the most sensitive site for
monitoring response to treatment. Fundamental to the clinical role of DXA scanning
are the findings of epidemiological studies that relate fracture risk to bone mineral
density. The results of spine and hip DXA scans are interpreted using the World Health
Organisation (WHO) definition of osteoporosis as a T-score less than -2.5. DXA scans
are also used in longitudinal studies, both for research studies and for follow-up
scans of individual patients. Although the former have an important role in the development
of new treatments for osteoporosis, the latter are more controversial and are likely
to be less important in the future. There is also interest in the use of smaller,
less expensive DXA systems for scanning sites in the peripheral skeleton. However,
in general, the results from these devices cannot be interpreted using the WHO definition
of osteoporosis, and until there is a consensus over establishing an equivalent threshold,
their use is premature.
KEYWORD
Bone mineral density - dual energy X-ray absorptiometry - osteoporosis
