There are number of diagnostic tools available for checking bone health including physical examination and blood and urine tests for measuring calcium levels of the body. In general, the doctor may order a bone mineral density test for patients above 45 years of age or suffering from conditions such as broken bone, height loss, change in posture, and back pain.
Bone density tests are used for diagnosing bone loss and osteoporosis like conditions. There are a variety of blood tests available that may help in diagnosis of osteoporosis. The basic tests are CBC (complete blood count), chemistry panels, and thyroid test. In severe cases, other tests such as parathyroid hormone test, kidney function test, measurement of male or female hormones, measurement of calcium in the urine, or vitamin D test may also be recommended.
The most widely employed bone mineral density test is Dual energy X-ray absorptiometry, commonly known as a DEXA scan. DEXA scan measures the amount of calcium and minerals in bones. DEXA scan is used to diagnose osteoporosis, a disease in which bones become fragile and more likely to fracture. DEXA scan is a quick and painless way of measuring BMD.
People who are highly recommended to have a DEXA scan include:
- Women aged above 65 and men aged above 70
- A fracture following a minor fall or injury
- Other disorders such as rheumatoid arthritis, chronic kidney disease, and eating disorders
- Early menopause
- Use of corticosteroid therapy for more than three months
- Cigarette smoking
- History of hormone treatment for prostate cancer or breast cancer
- Loss of height due to fracture of a vertebra (back bone)
- A family history of osteoporosis
- Alcohol intake of more than two drinks per day
Normally, there are no restrictions on eating prior to a DEXA scan. Calcium supplements should be discontinued 24 hours before the test. Women who are pregnant should always inform their physician or X-ray technologist. The scan usually takes between 10 to 20 minutes. The bones commonly scanned are the hip and lower spine.
Test results are in the form of two scores:
- T score: It is the difference between your bone density and that of young healthy person. A T score of -1.0 or above is considered normal. A score between -1 and -2.5 indicates osteopenia (low bone mass). A score below -2.5 indicates osteoporosis.
- Z score: It is the difference between your bone density and other people of same age, sex, and race.
Certain medical conditions such as lumbar spinal deformity (scoliosis), atherosclerosis (accumulation of calcium in the blood vessels), or multiple fractures can change the results of your DEXA scan.
The Fracture Risk Assessment Tool (FRAX) has been developed by WHO, World Health Organization, to evaluate fracture risk in patients. It acts as a prediction tool for assessing fracture risks over a 10 year time frame and provides general clinical guidance for making treatment decisions. It is based on the individual patient model which incorporates the risks related with clinical risk as well as bone mineral density (BMD) at the femoral neck.