Bone mineral density loss that is less advanced than osteoporosis is described as osteopenia. People with osteopenia have a lower risk of fracture compared to people with osteoporosis, but their condition may still require treatment.
Without treatment, many people with osteopenia will continue to lose bone mineral density, eventually developing osteoporosis along with complications such as fractures of the wrist, hip or spine.
To determine bone mineral density (BMD), patients can undergo a dual-energy X-ray absorptiometry (DXA) scan. The exam is noninvasive and takes about 20 minutes to complete.
- When performed on the spine and hips, the scan consists of lying on an open bed while a scanner bar passes over the body.
- When performed on the extremities, such as the wrist, the scan consists of resting the wrist or heel in a small scanning device.
DXA scan results can be expressed in two numbers, a T-score and a Z-score. The T-score is the comparison of a patient’s DXA scan results to the ideal BMD of a 30-year-old.1 A lower T-score indicates lower bone density:
- T-scores of -1 or higher indicates normal bone health.
- T-scores of -1 to -2.5 indicates osteopenia, or beginning bone loss.
- T-scores of -2.5 or lower indicates osteoporosis.
The Z-score is a comparison of a patient’s DXA results with a typical individual of similar age. However, because low bone mineral density is more common in older adults, Z-score results can be misleading. It is often used as a secondary piece of data with which to determine whether or not there is an underlying cause for the bone loss, such as disease.1
People with borderline scores may want to make changes to their diet and exercise levels, as it is easier to maintain bone density than to rebuild it.
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Frequency of DXA Exam
There is some controversy over how often patients should undergo DXA scan. An often-cited recommendation is to have a scan every two years; however, this recommendation may not be appropriate for everyone. Research has shown that patients who had no signs of osteopenia at their initial DXA scan did not develop osteoporosis until an average of 16.8 years later, whereas patients with advanced osteopenia developed osteoporosis only 1.1 years later.2
In general, experts suggest that:
- Patients whose initial T-scores indicate moderate to advanced osteopenia would benefit from a DXA exam every two years.
- People whose initial T-scores indicate mild or no osteopenia can likely wait five or more years between exams.2
These recommendations do not apply in cases of other serious conditions, such as kidney disease or leukemia, which can rapidly accelerate bone loss. A knowledgeable physician can help determine an appropriate testing schedule.
- Bone Mass Measurement: What the Numbers Mean. NIH Osteoporosis and Related Bone Diseases National Resource Center. January 2012. Available at http://www.niams.nih.gov/health_info/bone/bone_health/bone_mass_measure.asp. Accessed December 2014.
- Craig KW, Stevermer JJ. DEXA screening—are we doing too much?. J Fam Pract. 2012;61(9):555-6.