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Osteoporosis - Diagnosis

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of osteoporosis.

Diagnosis:

Candidates for Bone Density Testing

Because osteoporosis can occur with few symptoms, testing is important. Bone density testing is recommended for:

All women over age 65
Postmenopausal women under age 65 with one or more risk factors for osteoporosis
All men over age 70
Men ages 50 - 70 with one or more risk factors for osteoporosis
Any man or woman over age 50 who has suffered a fracture

Risk factors that may indicate a need for bone mineral density testing include:

Long-term use of medications associated with low bone mass or bone loss such as corticosteroids, some anti-seizure medications, Depo-Provera, thyroid hormone, or aromatase inhibitors. Long-term use of glucocorticoids (more than 5 mg/day for more than 3 months) is a specific risk factor.
History of treatment for prostate cancer or breast cancer
History of medical conditions such as diabetes, thyroid imbalances, estrogen or testosterone deficiencies, early menopause, anorexia nervosa, rheumatoid arthritis
Significant loss of height
Significant recent weight loss or low body mass index

Tests Used for Measuring Bone Density

Central DXA. The standard technique for determining bone density is a form of bone densitometry called dual-energy x-ray absorptiometry (DXA). DXA is simple and painless and takes 2 - 4 minutes. The machine measures bone density by detecting the extent to which bones absorb photons that are generated by very low-level x-rays. (Photons are atomic particles with no charge.) Measurements of bone mineral density are generally given as the average concentrations of calcium in areas that are scanned.

A bone density scan measures the density of bone in a person. The lower the density of a bone the higher the risk of fractures. A bone scan, along with a patient's medical history, is a useful aid in evaluating the probability of a fracture and whether any preventative treatment is needed. A bone density scan has the advantage of being painless and exposing the patient to only a small amount of radiation.

Bone mineral density is usually measured at the hip and spine.

Click the icon to see an image of a hip fracture.

Other Tests. Other tests may be used, but they are not usually as accurate as DXA. They include ultrasound techniques and quantitative computed tomography (QCT) scan.

Screening tests using these technologies are sometimes given at health fairs or other non-medical settings. These screening tests typically measure peripheral bone density in the heels, fingers, or leg bones. The results of these tests may vary from DXA measurements of spine and hip. While these peripheral tests may help indicate who requires further BMD testing, a central DXA test is best for diagnosing osteoporosis and monitoring treatment response.

Diagnosing Osteoporosis and Predicting the Risk for Fracture

Osteoporosis is diagnosed when bone density has decreased to the point where fractures will happen with mild stress, the so-called fracture threshold. This is determined by measuring bone density and comparing the results with the norm, which is defined as the average bone mineral density in the hipbones of a healthy 30-year-old adult.

The doctor then uses this comparison to determine the standard deviation (SD) from this norm. Standard deviation results are given as Z and T scores:

A T score gives the standard deviation of the patient in relationship to the norm in young adults. Doctors often use the T-score and other risk factors to determine the risk for fracture.
A Z score gives the standard deviation of the patient in relationship to the norm in the patient� ' s own age group and body size. Z scores may be used to for diagnosing osteoporosis in younger men and women. They are not normally used for postmenopaual women or for men age 50 and older.

Results of T-scores indicate:

Between +1 and -1 indicates normal bone density.
Between -1 and -2.5 indicates low bone density (osteopenia).
A score of -2.5 or lower indicates a diagnosis of osteoporosis.

The lower the T-score, the lower the bone density, and the greater the risk for fracture. In general, doctors recommend beginning medication when T-scores are -2.5 or below. Patients who have other risk factors may need to begin medication when they have osteopenia (scores between -1 and -2.5).

Laboratory Tests

In certain cases, your doctor may recommend that you have a blood test to measure your vitamin D levels. A standard test measures 25-hydroxyvitamin D, also called 25(OH)D. Depending on the results, your doctor may recommend you take vitamin D2 supplements.

Resources

www.nof.org -- National Osteoporosis Foundation
www.niams.nih.gov/Health_Info/Bone -- National Institute of Arthritis and Musculoskeletal and Skin Diseases
www.iofbonehealth.org -- International Osteoporosis Foundation
www.healthywomen.org -- National Women's Health Resource Center
www.menopause.org -- North American Menopause Society

References

Ebeling PR. Clinical practice. Osteoporosis in men. N Engl J Med. 2008; 358(14): 1474-82.

Greenspan SL, Bone HG, Ettinger MP, Hanley DA, Lindsay R, Zanchetta JR, et al. Effect of recombinant human parathyroid hormone (1-84) on vertebral fracture and bone mineral density in postmenopausal women with osteoporosis: a randomized trial. Ann Intern Med. 2007;146(5): 326-39.

Greenspan SL, Nelson JB, Trump DL and Resnick NM. Effect of once-weekly oral alendronate on bone loss in men receiving androgen deprivation therapy for prostate cancer: a randomized trial. Ann Intern Med. 2007;146(6): 416-24.

Heckbert SR, Li G, Cummings SR, Smith NL, Psaty BM. Use of alendronate and risk of incident atrial fibrillation in women. Arch Intern Med. 2008;168(8):826-31.

Kothawala P, Badamgarav E, Ryu S, Miller RM and Halbert RJ. Systematic review and meta-analysis of real-world adherence to drug therapy for osteoporosis. Mayo Clin Proc. 2007;82(12): 1493-501.

MacLean C, Newberry S, Maglione M, McMahon M, Ranganath V, Suttorp M, et al. Systematic review: comparative effectiveness of treatments to prevent fractures in men and women with low bone density or osteoporosis. Ann Intern Med. 2008;148(3): 197-213.

National Osteoporosis Foundation. Clinician's Guide to Prevention and Treatment of Osteoporosis -- 2008. Washington, DC.

Qaseem A, Snow V, Shekelle P, Hopkins R Jr., Forciea MA and Owens DK. Pharmacologic treatment of low bone density or osteoporosis to prevent fractures: a clinical practice guideline from the American College of Physicians. Ann Intern Med. 2008;149(6): 404-15.

Tang BM, Eslick GD, Nowson C, Smith C, Bensoussan A. Use of calcium or calcium in combination with vitamin D supplementation to prevent fractures and bone loss in people aged 50 years and older: a meta-analysis. Lancet. 2007 Aug 25;370(9588):657-66.

Reviewed last on: 11/18/2008
Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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