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What is bone density testing?
Bone density testing, also known as DEXA (an acronym for dual-energy X-ray absorptiometry) scanning, is a way of assessing bone mineral density using advanced, low-dose X-ray technology. It’s commonly used to diagnose osteoporosis, a condition involving gradual loss of calcium that causes bones to thin and become more vulnerable to breaks, and osteopenia (decreased bone mass).[1]
Why is a DEXA scan recommended?
Your doctor may recommend a bone density scan to diagnose suspected osteoporosis or osteopenia, assess bone loss, and determine the likelihood that you’ll experience a bone fracture in the future. If the scan shows bone loss, then steps may be taken to reduce your chances of bone breakage. Treatments can include dietary changes, weight-bearing and muscle-strengthening exercises, and/or a variety of medications.[2]
DEXA scans are recommended for people who are at higher risk for osteoporosis. Factors that can increase risk include
- Decreased estrogen production resulting from menopause
- Long-term use of steroids or certain other medications
- High alcohol consumption
- Low body mass
- Tobacco smoking
- Age of at least 65 (women) or 70 (men)
- Family history of hip fractures
- A personal history of certain diseases, including type 1 diabetes, rheumatoid arthritis, or kidney, liver, or thyroid disease
If one or more of these risk factors apply to you, discuss your osteoporosis risk and the potential benefits of a bone density scan with your doctor.
Are there risks involved with bone density scanning?
Because a DEXA scan uses X-rays, it is not entirely risk free. The ionizing radiation in X-rays has been shown to increase a patient’s risk of cancer. However, the amount of radiation used in a DEXA scan is very small, amounting to only one tenth the radiation used in a standard chest X-ray and less than what a person normally absorbs through the natural environment in one day (from sources such as sunlight and naturally occurring radon).[3]
The scan itself is quick and painless and takes only about 10 minutes. A scanner arm will simply pass slowly over your hip or spine as you lie on a padded table. No contrast material is needed. Afterward, you can resume your normal activities.
What do the results mean?
After your exam, the radiologist will report the results to your referring physician. These results will include a T score and a Z score. The T score indicates the amount of bone mass you have compared to a typical young adult of the same sex with peak bone mass, and the Z score compares your bone mass to adults of the same age, sex, and size. A T score above -1 (one standard deviation below the bone mass of a young, healthy adult) is considered normal. T scores between -2.5 and -1 indicate osteopenia, and those above 2.5 indicate osteoporosis.[4]
The risk of bone fracture tends to double with each standard deviation below a T score of 0. So, a person with a score of -1 would face twice the risk of a young, healthy adult with peak bone mass, and someone with a T score of -2 would be at four times the risk.[5] Because it’s not realistic to expect to maintain the bone strength of a 20-year old as we age, it’s important to keep your T score in perspective by comparing it with your Z score.
Iowa Radiology offers bone density testing at our Clive Ankeny, and downtown Des Moines clinics. Click the link below to contact us with any questions.
[1] "Bone Densitometry (DEXA)." Radiologyinfo.org. Radiological Society of North America, 30 Sept 2006. Accessed 11 April 2018.
[2] "Osteoporosis: Diagnosis and Treatment." WebMD, 27 Sept 2017. Accessed 11 April 2018.
[3] "Bone Densitometry (DEXA)." Radiologyinfo.org. Radiological Society of North America, 30 Sept 2006. Accessed 11 April 2018.
[4] Ibid.
[5] "Bone Densitometry." HopskinsMedicine.org. The Johns Hopkins University, The Johns Hopkins Hospital, and Johns Hopkins Health System, 29 April 2016. Accessed 11 April 2018.
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