An overview of Bone Density Test
A bone density test is a non-invasive medical procedure that uses X-rays to measure the amount of calcium and other minerals in a specific segment of bone. The test helps determine if a person has osteoporosis, a disorder characterized by fragile and brittle bones that are more prone to fractures. Bone density tests are painless, easy, and fast, requiring minimal preparation. They are typically done on the lower spine, hip, and forearm, and the results can help doctors identify decreases in bone density, assess the risk of fractures, and monitor the effectiveness of osteoporosis treatment. The test exposes the patient to very low levels of radiation, much less than a standard chest X-ray.
What is Bone Density Test used for?
A bone density test is used to determine if a person has osteoporosis, a disorder characterized by fragile and more likely to break bones. The test measures bone mineral content and density using X-rays, usually in the spine, hips, or forearm. Doctors use the results to identify decreases in bone density before a fracture occurs, assess the risk of fractures, confirm a diagnosis of osteoporosis, and monitor osteoporosis treatment. Bone density tests are easy, fast, and painless, with no special preparation needed. They differ from bone scans, which are used to detect fractures, cancer, infections, and other abnormalities in the bone.
How is Bone Density Test conducted?
A bone density test is conducted using X-rays to measure the amount of calcium and other bone minerals in a segment of bone. The test is performed on the bones that are most commonly tested, such as the spine, hip, and sometimes the forearm. During the test, you lie on a padded platform while a mechanical arm passes over your body. The test usually takes around 10 to 30 minutes. For peripheral devices, bone density can be measured in the bones at the far ends of your skeleton, such as those in your fingers, wrist, or heel. Preparation for the test is simple, requiring no fasting or special clothing, and virtually no pain is involved.
How are Bone Density Test results reported?
Bone density test results are reported using two numbers: T-score and Z-score. The T-score represents your bone density compared to the average bone density of a healthy young adult of your sex. A T-score of -1 or above indicates normal bone density, between -1 and -2.5 indicates a condition called osteopenia that may lead to osteoporosis, and a score below -2.5 indicates osteoporosis. The Z-score compares your bone density to people of your age, sex, and ethnicity. It helps determine if your bone density is above or below the average for your age group.
Understanding the report
Bone density test results are interpreted by comparing the bone density of the tested area to the bone density of a healthy young adult of the same sex. The results are reported in two numbers: the T-score and the Z-score.
The T-score represents the number of standard deviations that the individual's bone density is above or below the average bone density of a healthy young adult. If the T-score is:
- 1 and above: The bone density is considered normal.
- Between -1 and -2.5: The score is a sign of osteopenia, a condition where bone density is below normal and may lead to osteoporosis.
- -2.5 and below: The bone density indicates that the individual likely has osteoporosis.
The Z-score is used to adjust the T-score for age and sex. It helps to determine whether an individual's bone density is above or below what would be expected for their age and sex, regardless of whether they have osteoporosis or not.
Interpreting the results of a bone density test is important for doctors to assess the risk of fractures, diagnose osteoporosis, or monitor the effectiveness of osteoporosis treatment.
Limitations and Considerations
Limitations of bone density testing include differences in testing methods, as devices that measure density of the bones in the spine and hip are more accurate but cost more than devices that measure density of the peripheral bones of the forearm, finger, or heel. Additionally, test results may not be accurate in people who have structural abnormalities in their spines, such as severe arthritis, previous spinal surgeries, or scoliosis.