Bone Mineral Densitometry (DXA)
What is bone mineral density testing?
Bone mineral density testing is a simple imaging test that measures the amount of minerals, such as calcium, in a person's bones. It is commonly used to detect osteoporosis and assess the risk of fractures. The test is performed using a dual-energy X-ray absorptiometry (DXA) machine.
During a bone scan, the patient lies down on a table while the X-ray machine scans specific areas of the body, such as the spine, hip, or forearm. The machine sends a low-dose X-ray beam through the bones, and a detector measures how much of the X-ray passes through the bones. The results are then analyzed to determine the bone mineral density.
Bone density tests are an important tool in the diagnosis of osteoporosis because it can identify low bone density and assess the risk for fracture. Osteoporosis is a condition characterized by weak bones that are more prone to fractures. The lower the bone mineral density, the higher the risk of fractures. By measuring bone density, healthcare providers can determine the severity of osteoporosis and develop an appropriate treatment plan.
The test is typically performed on the spine, hip, and forearm, as these areas are most susceptible to fractures. The BMD results are presented as T-scores, which compare the patient's bone density to the average bone density of a young, healthy adult.
What is a BMD test for?
A bone density scan is a diagnostic tool used to assess the bone strength and density. The purpose of this test is to evaluate the risk of fracturing a bone, diagnose osteoporosis, and measure the effectiveness of osteoporosis treatment.
BMD testing calculates bone density. The test allows healthcare providers to measure the bone mineral content, including the amount of calcium present in the bones. Based on the results, they can determine whether the bones are weakened and at a higher risk for fractures.
A BMD test is particularly crucial for individuals who have a family history of osteoporosis or have certain medical conditions and medications that affect bone health. By identifying low bone density early on, preventative measures can be taken, such as lifestyle modifications, calcium supplements, and appropriate medications, to reduce the risk of fractures and manage osteoporosis effectively. Furthermore, BMD tests are regularly conducted to monitor the response to treatment and adjust interventions accordingly.
Who needs a BMD test (DXA)?
Several factors determine who should consider getting a BMD test. Firstly, post-menopausal women over the age of 65 are recommended to undergo this test as they are at a higher risk of developing osteoporosis. Additionally, men above the age of 70 should also consider BMD testing.
Other risk factors for osteoporosis that may indicate the need for a BMD test include a family history of osteoporosis, a broken bone due to a minor fall or injury, or medical conditions such as rheumatoid arthritis or hyperthyroidism. Furthermore, individuals who have taken medications known to cause bone loss, such as corticosteroids or certain anti-seizure drugs, should consult their healthcare provider for a BMD test.
It is important to consult with a healthcare provider to determine whether bone density testing is necessary. They can evaluate your risk factors, review your medical history, and provide personalized recommendations. Regular DXA testing can help identify low bone mass or osteoporosis early on, enabling timely intervention and reducing the risk of fractures.
You should consider DXA:
When starting hormone therapy during menopause (Estrogen is a key factor in maintaining bone density.
You are taking glucocorticoid medication.
You have recently had a fracture in which osteoporosis is suspected;
You already have osteoporosis, and you and your physician are monitoring the effectiveness of the treatment.
You have been undergoing chemotherapy (especially for haematologic or breast cancer), where bone loss could be anticipated and needs to be confirmed.
You are a man with hypogonadism (low testosterone levels).
You and your health care provider have done a risk factor assessment and, for various reasons, have determined that you are a high risk individual.
How can I prepare for a BMD?
Preparing for a bone density scan is important to ensure accurate results. Here are the steps to prepare for a BMD test:
1. Avoid calcium supplements: It is recommended to refrain from taking calcium supplements for at least 24 hours prior to the test. Calcium can interfere with the accuracy of the results.
2. Wear comfortable clothing: On the day of the test, wear loose and comfortable clothing without metal zippers, buttons, or belts. These metal objects can interfere with the test results.
3. Remove metal objects: Before the test, remember to remove any metal objects, such as jewelry, eyeglasses, and removable dental work. These items can also affect the accuracy of the BMD test.
4. Joint implants are generally not a problem: If you have joint implants, you do not need to worry, as they usually do not interfere with the BMD test. However, it is always best to inform the healthcare provider about any joint or dental implants you may have.
By following these steps, you can ensure a smooth and accurate BMD test. Remember to discuss any concerns or questions with your healthcare provider before the test to ensure a proper preparation and testing process.
Bone Mineral Density (BMD)
BMD is short for bone mineral density. Bone density testing, also known as DXA, is an important diagnostic tool used to assess bone health, fracture risk, and diagnose conditions like osteoporosis. It measures the amount of minerals, primarily calcium, in a segment of bones.
What should I expect during a BMD test?
During a BMD test, also known as DXA, the patient is typically positioned on an exam table. The test is non-invasive.
The technologist will use an X-ray machine and a detector to obtain images of your spine and hips, which are the common areas assessed for bone density. The X-ray machine emits a low dose of radiation, capturing images that measure bone mineral content in the bones.
The technologist will move the detector over your spine and hips, ensuring proper positioning and alignment to obtain accurate measurements. There may be variations in leg and foot positions to optimize the images and assess different segments of the bones.
In some cases, a VFA (vertebral fracture assessment) may be included as part of the BMD test. This involves additional X-ray images of the spine, focusing on the vertebrae to determine if any fractures or abnormalities are present.
The BMD test typically takes around 10-30 minutes, depending on the specific protocol and equipment used. Patients can expect to receive their results from their primary physician, who will receive a report from the radiologist who interprets the scan results within 24-48 hours.
What Your DXA Results Mean
The BMD test results in bone density measurements, which are usually given as T-scores and Z-scores.
What is a T-score?
The T-score compares an individual's BMD to that of a healthy young adult of the same gender. A T-score below -2.5 indicates osteoporosis, a condition characterized by weak bones that are more prone to fractures.
What is a Z-score?
A Z-score compares an individual's BMD to that of individuals of the same age and sex. A Z-score below -2.0 suggests low bone mass, which may be due to factors other than aging.
It is important to note that a low T-score or Z-score does not necessarily mean an individual will experience a fracture but rather indicates an increased risk. Other factors, such as family history, medical conditions, and lifestyle choices, also contribute to an individual's risk of bone loss and fractures.
If the DXA results indicate low bone density or osteoporosis, healthcare providers may recommend treatment options such as calcium and vitamin D supplements, lifestyle modifications, and medication to manage and improve bone health. Regular follow-up bone density tests may be recommended to monitor progress and evaluate the effectiveness of treatment.
What is Osteoporosis?
Osteoporosis is a disease characterized by low bone mass and deterioration of bone tissue. This leads to increased bone fragility and risk of fracture, particularly of the hip, spine and wrist. Many patients are diagnosed with osteoporosis once they have suffered broken bones or a fracture. More than 1.4 million Canadians suffer from osteoporosis - one in every four women over the age of 50 suffers from osteoporosis. In contrast, one man in eight over the age of 50 has the disease.
Who is not a candidate for DXA?
Not everyone is a candidate for a bone mineral density (BMD) test. Certain criteria may disqualify someone from undergoing this test.
One of the main factors that would disqualify someone from a BMD test is pregnancy. During pregnancy, hormonal changes can affect bone density measurements, making the results inaccurate. It is recommended to wait until after pregnancy to undergo a BMD test.
Additionally, recent medical procedures involving the use of barium, contrast injections, or CT scans may also prevent someone from undergoing a DXA. Barium enemas, contrast injections, and some imaging tests can interfere with the accuracy of the DXA results and, therefore, need to be avoided before taking the test.
Other conditions or situations that may disqualify someone from a BMD test include recent fractures, recent major surgery, or the presence of metal implants in the area being tested. These factors can affect the accuracy of the test results and may require the test to be postponed.
It is important to consult with your healthcare provider to determine if you are a suitable candidate for a BMD test and to discuss any potential disqualifying factors or concerns that may exist.
How Often Should I Get BMD Tested?
Individuals who are taking medication for osteoporosis should have a BMD test annually to monitor the effectiveness of their treatment and ensure that their bone density is improving or at least not declining. On the other hand, those who do not have osteoporosis may need a BMD test every 2 years to track any changes in their bone density.
Health care providers consider several criteria when recommending a BMD test. Age is an important factor, as bone density naturally decreases as we age. Women who have gone through menopause are also at a higher risk of osteoporosis, so they may need more frequent testing. Other risk factors, such as family history, medical conditions, and previous bone fractures, also play a role in determining the frequency of BMD testing. Additionally, healthcare providers may recommend a BMD test if a person experiences height loss, back pain, or hormonal changes.
What does OHIP cover?
If your doctor has determined that you are at high risk for osteoporosis and future fractures, OHIP will cover annual BMD tests.
For those at Low Risk for Osteoporosis, OHIP covers a baseline BMD test and a second BMD test 36 months after the baseline. Third and subsequent BMD tests for low-risk individuals are insured by OHIP once every 60 months.
Current recommendations do not support the need for low-risk individuals to be tested more than every three to five years after a baseline test and at later intervals of seven to ten years when previous testing has shown a rate of bone loss of less than 1%.