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Results
By Mayo Clinic staff
The results from a bone density test can let you know how your fracture risk compares with that of other people of your age, sex and other similar characteristics.
Your bone density test results are reported in two numbers: T-score and Z-score.
T-score
Your T-score is your bone density compared with what is normally expected in a healthy young adult of your sex. Your T-score is the number of units — standard deviations (SD) — that your bone density is above or below the average.
| T-score | What your score means |
|---|---|
| Above -1 | Your bone density is considered normal. |
| Between -1 and -2.5 | Your score is a sign of osteopenia, a condition in which bone density is below normal and may lead to osteoporosis. |
| Below -2.5 | Your bone density indicates you have osteoporosis. |
Keep in mind that these scores apply mostly to white postmenopausal women, who tend to have lower bone density as compared with other racial groups and men. Interpretations may vary if you're a woman of color or a man.
Z-score
Your Z-score is the number of standard deviations above or below what's normally expected for someone of your age, sex, weight, and ethnic or racial origin. This is helpful because it may suggest you have a secondary form of osteoporosis through which something other than aging is causing abnormal bone loss.
A Z-score less than -1.5 might indicate these other factors are to blame. Your doctor would then try to determine if there's any underlying cause for the low bone mass other than aging or menopause, which are expected causes of bone loss. If your doctor can identify a cause, that condition can often be treated and the bone loss slowed or stopped.
- Bone mass measurement: What the numbers mean. National Institute of Arthritis and Musculoskeletal and Skin Diseases. http://www.niams.nih.gov/Health_Info/Bone/Bone_Health/bone_mass_measure.asp. Accessed Aug. 19, 2009.
- Screening for osteoporosis in postmenopausal women: Recommendations and rationale. U.S. Preventive Services Task Force. http://www.ahrq.gov/clinic/3rduspstf/osteoporosis/osteorr.htm. Accessed Aug. 19, 2009.
- Raisz LG. Screening for osteoporosis. http://www.uptodate.com/home/index.html. Accessed Aug. 19, 2009.
- Hansen KE, et al. Osteoporosis. In: Duthie EH, et al. Practice of Geriatrics. 4th ed. Philadelphia, Pa.: Saunders Elsevier; 2007. http://www.mdconsult.com/das/book/body/155482233-3/0/1532/150.html?tocnode=53845866&fromURL=150.html. Accessed Aug. 19, 2009.
- Bone density scan. Radiological Society of North America. http://www.radiologyinfo.org/en/info.cfm?pg=dexa&bhcp=1. Accessed Aug. 19, 2009.
- Fast facts on osteoporosis. National Osteoporosis Foundation. http://www.nof.org/osteoporosis/diseasefacts.htm. Accessed Aug. 19, 2009.
- Lane NE. Metabolic bone disease. In: Firestein GS, et al. Kelley's Textbook of Rheumatology. 8th ed. Philadelphia, Pa.: Saunders Elsevier; 2008. http://www.mdconsult.com/das/book/body/155482233-4/0/1807/695.html?tocnode=55733918&fromURL=695.html#4-u1.0-B978-1-4160-3285-4..10092-0_3381. Accessed Aug. 19, 2009.
- Bone mineral density (BMD) testing: What the numbers mean. National Osteoporosis Foundation. http://www.nof.org/osteoporosis/bmdtest.htm. Accessed Aug. 25, 2009.
