A bone mineral density test is a diagnostic tool used for detecting osteopenia and osteoporosis. These disorders are characterized by bone weakness. Weak bones are fragile and prone to fractures.
A bone mineral density test is recommended for women to predict their risk of osteoporosis-induced fractures. In this article, you’ll learn more about the bone mineral density test, its indications, and the interpretation of the results.
What is a bone mineral density test?
A bone density test involves the use of X-rays or scanning machines. The test helps to determine how many grams of bone minerals, like calcium, are packed into a specific segment of the bone. The bones most commonly tested are the spine and the bones of the hip and forearm.  . The higher the mineral content is, the denser and stronger your bones are. Stronger bones are less likely to break. 
Why do you need a bone mineral density test?
Regular bone mineral density tests should be considered essential for women over 45 years old to:
- Detect the decline in bone density
- Determine the risk of fractures
- Confirm a diagnosis of osteopenia or osteoporosis
- Monitor the progress of osteoporosis treatment
Women should have regular bone mineral density tests because the reduced production of estrogen after menopause puts women at a risk of bone loss. However, men, as well as young women, can also develop osteoporosis and should also take this test.
A bone density test may be required in the following cases regardless of the gender or age of the patient:
- A decrease in height: Adult men and women who have lost more than 4 centimeters or 1.6 inches in height should get this test. The decrease in height could be due to compression fractures in the vertebral column as a result of reduced bone strength and osteoporosis.
- Fracture: Patients who have had a fracture after minimal trauma, a missed step, or fall should undergo bone mineral density tests. Bones that break in the absence of considerable pressure or force suggests the possibility of osteoporosis. 
- Fragile bones due to the loss of bone mineral density can even result in fractures when a person coughs or sneezes. A bone mineral density test can help to detect osteoporosis and allow patients to receive appropriate treatment.
- Use of certain drugs: Patients who are using medications, such as steroids, need regular bone mineral density tests. Some drugs may interfere with the bone-rebuilding processes and can lead to osteoporosis.
- Organ transplant: A bone marrow or organ transplantation can increase the risk of osteoporosis as the anti-rejection drugs given during treatment can affect the bone-remodeling processes. 
- Hormonal imbalances: The natural drop in the production of hormones, like estrogen, during and after menopause can trigger bone loss and lead to osteoporosis. A person’s estrogen levels may also drop during treatment for some types of cancer.
- Women who are likely to develop hormonal imbalances are advised to perform regular bone mineral density tests to assess the strength of their bones.
- Other factors: Women who suffer from chronic kidney diseases, early menopause, malnutrition, and eating disorders should ideally undergo bone mineral density tests. Women who have a family history of osteoporosis, rheumatoid arthritis, and fractures also need this test.
What to expect during a bone mineral density test
A bone mineral density test is usually painless and does not require you to take any medications. You simply need to lie on a table during the test.
The test can be performed in the doctor’s office or a specialized diagnostic center. Some health clinics and pharmacies also have portable machines to scan the bones for this test. It takes just a few minutes and has no downtime. People can go home or resume their routine activities immediately after the bone mineral density test.
There are two types of bone density test scans::
This test involves the exposure of the bone to X-rays. The X-ray machine scans the bones of the hip, spine, or torso to determine the amount of calcium and mineral content in them.
This test examines the bones of the forearm, fingers, wrist, or heels. It is usually used as a screening method to determine if the patient needs a central DXA. 
Interpretation of the results of a bone mineral density test
The results of the bone density test are expressed in two measures: T-score and Z-score.
The T-score refers to the bone density of the patient compared to the bone density of healthy young women. The T-score is the measure of the number of units, known as standard deviations, that indicate by how much your bone density is below or above the average.  
- A T-score of -2.5 or less can help to confirm the diagnosis of osteoporosis.
- A T-score from -1.0 to -2.5 indicates low bone density and suggests a diagnosis of osteopenia.
- A T-score of -1.0 or above indicates normal bone density.
The Z-score refers to the extent of standard deviations below or above what is normally expected from someone of the same age, gender, weight, and some other parameters. According to the International Society for Clinical Densitometry(ICSD), A Z-score above -2.0 is normal. 
How often should women repeat a bone mineral density test?
Women above the age of 45 years should ideally have this test once a year. Women at a high risk of osteoporosis should also perform this test once or twice a year.
Women who are already diagnosed with osteopenia, or osteoporosis, or have had a fracture should perform this test more frequently to assess their response to treatment.
Regular bone mineral density tests can play a significant role in the early detection of osteoporosis. The test can help women receive appropriate treatment to prevent the progress of the disease as well as complications like fractures.