What Is A Bone Mineral Density Test? | Orthopaedics

Bone mineral density test

Bone Density Testing uses X-rays to measure the number of minerals in your bones, namely calcium. This test is especially important for people at risk for osteoporosis, especially women and the elderly.

The test is also known as dual-energy x-ray absorptiometry (DXA). This is an important test for osteoporosis, the most common type of bone disease. Osteoporosis is a disease in which bone tissue becomes thinner and weaker over time and leads to the cessation of fractures.

What is the purpose of the bone density test?

Your doctor may order a bone mineral density test to show that your bones are weak, that you are showing signs of osteoporosis, or that you are old enough to need preventive tests.

The National Institutes of Health (NIH) recommend that the following people undergo preventive bone mineral density tests:

  • All women over 65
  • Women under 65 are at increased risk of fractures.

Women are at risk of developing osteoporosis if they smoke or consume three or more alcoholic drinks a day:

  • Chronic kidney disease
  • Early menopause
  • Eating disorder as a result of low body weight
  • Family history of osteoporosis
  • “Brittle fracture” (bone broken by normal activity)
  • Arthritis
  • Significant loss of height (an indication of compression fractures in the spine)
  • A sedentary lifestyle with low weight activities

How to prepare for the bone mineral density test

Bone density tests are easy, fast and painless. Virtually no preparation is needed. In fact, some simple versions of bone density tests can be done at your local pharmacy or drugstore.

If you’re having the test done at a medical centre or hospital, be sure to tell your doctor beforehand if you’ve recently had a barium exam or had contrast material injected for a CT scan or nuclear medicine test. Contrast materials might interfere with your bone density test.

How’s it performed?

The bone mineral density test is painless and does not require medication. You lie on a bench or table while the test is performed. The test can be done if you have the right equipment in your doctor’s office. If not, you may be sent to a specialized testing centre.

There are two types of bone density scans:

Central DXA

This test looks at your spine and hip bones. It tends to be more accurate. It also costs more. Central DXA stands for Dual Energy X-ray Absorptiometry.

Peripheral DXA

This scan examines the bones of your forearm, wrist, fingers, or heel. This scan is generally used as a screening tool to find out if you need Central DXA. The test only takes a few minutes.

Risks of bone mineral density test

Bone Density Testing uses X-rays, there is a small risk associated with radiation exposure. However, the radiation levels from the test are very low. Experts agree that the risk of radiation exposure is much lower than the risk of not recognizing osteoporosis before suffering a fracture. Tell your doctor if you are pregnant. X-ray radiation can harm your fetus.

After the bone mineral density test

Your doctor will review the results of your test. The results, known as the T-score, based on a 30-year healthy bone mineral concentration compared to your own value. A score of 0 is considered ideal.

The NIH provides the following guidelines for bone density scores:

  • Common: between 1 and -1
  • Low bone mass: -1 to -2.5
  • Osteoporosis: -2.5 or less
  • Acute osteoporosis: -2.5 or less with fractures

Your doctor will discuss your results with you. Depending on your results and the reason for the test, your doctor may want to run an additional test. They will work with you to create a treatment plan to address any problems.


Dual-Energy X-ray Absorptiometry (DEXA, DXA) | Orthopaedics

What is a bone density scan (DEXA, DXA)?

Bone density test, also called dual-energy X-ray absorptiometry (DXA) or bone density measurement, is an improved form of X-ray technology used to measure bone loss. Dual-energy X-ray absorptiometry (DXA) is the standard in force today for measuring bone mineral density (BMD).

X-ray (radiography) is a non-invasive medical test that helps doctors diagnose and treat medical conditions. X-ray imaging involves exposing a part of the body to a small dose of ionizing radiation to produce images inside the body. X-rays are the oldest and most widely used form of medical imaging.

Dual-energy X-ray absorptiometry (DXA) is nearly often performed on the lower spine and hips. In children and some adults, the whole body is sometimes examined. Peripheral devices that use X-rays or ultrasound are sometimes used to detect a low bone mass, mostly in the forearm. In some societies, CT may also be used with special software to diagnose or monitor low bone mass (QCT). This is accurate but is less frequently used than the DXA scan.

How the dual-energy x-ray absorptiometry is performed?

A bone density test can be done in several ways. The most common and accurate method uses dual-energy X-ray absorptiometry (DEXA) scanning. DEXA uses a low-dose X-ray. (She receives more radiation from a chest X-ray.)

There are two types of Dual-energy X-ray absorptiometry (DEXA) assays:

  • Central DEXA: You lie on a soft table. The scanner passes over the lower part of the spine and the hip. In most cases, you do not need to take off your clothes. This scan is the best test for predicting the risk of developing a fracture, especially of the hip.
  • Peripheral DEXA (p-DEXA): These smaller devices measure the density of the bone in your wrist, fingers, leg, or heel. These machines are found in health care offices, pharmacies, malls, and health fairs.

How to prepare for the dual-energy x-ray absorptiometry?

  • If you are or could be pregnant, tell your provider before having this test. Do not take calcium supplements for 24 hours before the test.
  • You will be required to remove all metal items from your body, such as jewellery and buckles.

Who interprets the results and how will I get them?

A radiologist, a physician specially trained to supervise and interpret radiology examinations, analyzes the images and sends a signed report to your primary care or referring physician, who will discuss the results with you.

Dual-energy X-ray absorptiometry (DXA) scans are also interpreted by other doctors such as rheumatologists and endocrinologists. A physician should review your DXA scan while evaluating the presence of clinical risk factors such as:

  • Rheumatoid arthritis
  • Chronic renal and liver disease
  • Respiratory disease
  • Inflammatory bowel disease

Your test results will be in two degrees:

  • T score: This number shows the amount of bone that I compared a young adult of the same sex with a peak bone mass. A grade of -1 and above is considered normal. A score between -1.1 and -2.4 is classified as osteopenia (low bone mass). A score of -2.5 and below is known as osteoporosis. The T score is used to estimate your risk of a fracture and also to determine whether treatment is required.
  • Z score: This number reflects the amount of bone that you compared with other people of your age group and the same size and sex. If this score is unusually high or low, it may indicate the need for further medical tests.

Small changes are usually noticed between scans due to differences in positioning and are usually insignificant.

Risks of dual-energy X-ray absorptiometry

Bone mineral density uses a small amount of radiation. Most experts feel the risk is very low compared to the benefits of detecting osteoporosis before a bone is broken.