Bone Densitometry Exam DEXA

Some people learn they have osteoporosis after they break a bone, but you can proactively address bone loss before you experience a painful fracture by taking a bone densitometry exam, also known as a bone density test, bone mineral density test, or dual energy x-ray absorptiometry (DEXA or DXA).

This test provides a snapshot of your bone health, and it can both diagnose osteoporosis or determine if you’re at risk for developing it. Bone densitometry measures the bone density (the amount of bone) in your hip and spine. The results of this test can help your doctor craft the right treatment plan to protect your bones and prevent spinal fractures.

Should you talk to your doctor about getting a DEXA exam? Do the risks outweigh the benefits? How often do you need to get a bone density test? This article will answer the most common questions about DEXA exams to help you make an informed health care decision.
bone densitrometry examinationBone densitometry measures the bone density (the amount of bone) in your hip and spine.What Can I Learn from a Bone Density Test?
A DEXA exam will determine whether you fall into 1 of these 3 categories:

  1. Normal, healthy bone density
  2. Lower than average bone density, called osteopenia: This test can help predict your likelihood for developing osteoporosis and fracture risk.
  3. Osteoporosis: This means you have low bone density that puts you at a heightened risk for breaking a bone. Sometimes, it’s a fracture that prompts people to get a DEXA exam—and that’s how they learn they have osteoporosis.

Follow-up DEXA exams can help your doctor understand if your bone health is improving or worsening by comparing current images to past scans. If your bone density is worsening, your doctor will adjust your treatment plan (such as changing your osteoporosis medication regimen).

Should I Ask My Doctor for a Bone Density Test?
The National Osteoporosis Foundation recommends that the following people get a bone density test1:

  • Women age 65 or older
  • Men age 70 or older
  • People older than age 50 who have experienced fracture
  • Women of menopausal age with risk factors (you can read about these risk factors in our Osteoporosis Overview)
  • Postmenopausal women under age 65 with risk factors
  • Men between age 50 and 69 with risk factors
  • People who have lost a half inch or more of height in a year
  • People who have lost 1.5 inches of total height in their lifetime

You should also consider a DEXA exam if you’re taking medications that can harm bone health (such as corticosteroids) or if you have any of the following conditions:

  • Type 1 diabetes
  • A thyroid or parathyroid condition
  • Kidney disease
  • Liver disease

Why Does the DEXA Test Focus Only on My Hip and Spinal Bones?
The DEXA test measures the bone density in your hip and spine. These 2 locations are measured because:

  • The hip and spine are common fracture sites in people with osteoporosis.
  • Hip and spinal bone density helps predict fracture in other bones in your body.
  • Fracturing a hip or spinal bone can be extremely painful and problematic, and understanding density levels at those sites first helps your doctor address any issues early.

How Do I Prepare for a Bone Density Test?
Tell your doctor and/or the technician administering the exam if you are or suspect you may be pregnant. Also, do not take calcium supplements for at least 24 hours before your scan.

Dress in loose clothing, and don’t wear jewelry. Avoid wearing anything with buttons, snaps, or zippers from the waist down. Wearing pants with an elastic waistband or a saree or a salwar kameez will allow you to remain fully clothed during the exam. Clean fresh cotton gowns are available in case you need to change.

Tell your doctor or technician if you have had any x-rays using contrast material, such as barium, or any nuclear medicine studies recently, as you may have wait a week before having a DEXA scan.

What Should I Expect During the Bone Density Test?
DEXA exams are typically performed in an outpatient facility. You will not experience any pain during your test, and it’s usually completed in less than 15 minutes. During the scan, you will be asked to lie still on a table. You may be asked to bend your knees. The examiner positions a triangular-shaped cushion under your knees for your comfort. Sometimes an additional support is added to hold one or both of your ankles in proper position.

The type of equipment used during the scan is called a central DEXA device, which uses an arm that is positioned over a table to take the images. The technician will ask you to adjust your breathing and may position you in certain ways to ensure the images are clear and conclusive.

Should I Be Concerned About My Radiation Exposure During This Test?
DEXA emits radiation, but the exposure is extremely minimal. The radiation emitted by a bone density exam is less than one-tenth of that from a chest x-ray. Put another way: The dose is considerably less than what you would receive on a roundtrip flight between New York and San Francisco.

All medical procedures carry risks, and bone density exams are no different. While there is a very rare chance of radiation exposure leading to cancer, the benefit of achieving an osteoporosis diagnosis far outweighs this risk.

I Got My Results, and My Doctor Mentioned a T-score and Z-score. What Are Those?
The results of your DEXA scan will be ready quickly, the same day in many cases. Your treating physician will let you know the results of the scan along with details on next steps (if any).

Your test will give you a T-score, which compares your DEXA results to an average score for a healthy adult of your gender and race who has reached their peak bone mass (usually around age 25 or 30). A lower T-score correlates to lower bone density. Here’s how it breaks down:

  • A T-score of -1.0 or above means you have normal bone density.
  • A T-score between -1.0 and -2.5 means you have below average bone density, or osteopenia.
  • A T-score lower than -2.5 means you have osteoporosis.

Your test will also give you a Z-score, which compares your bone density to others of similar age and gender. Some people, such as children and adolescents, younger men, and premenopausal women, may only receive a Z-score. Your doctor may use your Z-score to determine if you need additional testing to understand your bone health and fracture risk.

How Often Do I Need to Get My Bones Tested?
If you’re taking an osteoporosis medication, your doctor may request that you have a DEXA scan every 1 to 2 years—this length of time between scans will show whether your medication is boosting your bone density.

If you need repeated bone density tests, it’s helpful to get your scans at the same facility. Different clinics use different equipment, so consistently going to the same facility ensures that the comparisons between scans are most accurate.

I Have My Results—Now What?
A bone density test will help you and your doctor understand your bone health. You can learn what osteoporosis preventive measures you can take to reduce your risk of fracture, or you can start a treatment regimen to protect weakening bones if the scan confirms an osteoporosis diagnosis.

If your DEXA scan shows that you have normal bone density, your doctor will likely not recommend treatment outside of monitoring and practicing good lifestyle habits (like eating for bone health). However, if your results show that you have osteopenia or osteoporosis, your doctor may prescribe medications to slow bone loss and/or build up your bone density.

While the results of your bone density scan are integral to confirming an osteoporosis diagnosis, they aren’t the only thing your doctor will rely on when crafting your treatment plan. Your doctor may also examine your personal risk factors, medical history, and results from the FRAX® fracture risk assessment. Adhering to your doctor’s treatment plan (which includes having follow-up DEXA exams) is the best way to proactively protect your spinal—and overall—bone health.

Updated on: 06/06/18
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Bone Mineral Density (BMD) Measurement

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