How Is Bone Density Test Done?

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A bone density test is used to determine if you have osteoporosis, a condition which leads to bones becoming more fragile and more likely to break.

Osteoporosis

Osteoporosis is a disease that arises when the body loses too much bone (a customary condition as we age,) produces too little bone or, perhaps, does both. As a result of this condition, bones become weak and fragile and may break from a fall or, in some extreme cases, even from sneezing or from minor bumps.

The meaning of the word osteoporosis is “porous bone.” When observed under a microscope, healthy bone appears like a honeycomb. When osteoporosis is present, the holes and spaces in the honeycomb are much larger and porous-looking than those in healthy bone. Bones suffering from osteoporosis have lost their density and hold an abnormal tissue structure.

As bones become less dense, they weaken and break more easily. If you are 50 years old or older and have broken a bone, then you should ask your doctor or health care provider about getting a bone density test.

In the past, before these tests were widely available, the suspicion of osteoporosis arose only after a bone fracture had happened. However, by that point, the bones might have already become quite weak. These days, a bone density analysis is more readily available, used by health care providers and more accurately predicts your risk of bone fractures. The most commonly analyzed bones are those of the spine, hip and, sometimes, the forearm.

What Is a Bone Density Test?

A bone density test is used to determine the amount of bone loss in your bones. Doctors use bone density analysis for the following reasons:

  • To identify the percentage of reduction of bone density before a fracture occurs
  • To determine the risk of fractures or broken bones
  • To confirm a diagnosis of osteoporosis
  • To monitor the treatment of osteoporosis

The higher the bone mineral content, the greater the density of the bones. And the denser the bones, the stronger and less prone to fracture they are.

Bone density analysis differs from bone scintigraphy. Bone scintigraphy requires a previous injection and is used most frequently to detect fractures, cancer, infections and other bone abnormalities.

Why You Should Have One

Although osteoporosis is more common in older women, men also can suffer from this disease. Regardless of your age or gender, your doctor may recommend a bone density test in the following cases:

You Have Lost Height

People who lose at least 1.6 inches (4 centimeters) of height may have compression fractures in their spine, which can be caused primarily by osteoporosis.

You Fractured A Bone

Fractures tend to occur when a bone is so fragile that it breaks much more easily than expected. Sometimes, a strong cough or sneeze can cause a fragility fracture.

You Take Certain Medications

Prolonged consumption of steroid medications, such as prednisone, interferes with the process of bone reconstruction, which can lead to osteoporosis. Use of medications such as these are common indicators for keeping an eye on your bone health through bone density tests.

You Have Received A Transplant Recently 

People who have received an organ or bone marrow transplant run a higher risk of osteoporosis, in part because anti-rejection medications also interfere with the process of bone reconstruction.

You Have Suffered a Decrease In Your Hormonal Levels

In addition to the natural hormonal decline that occurs after menopause, there may also be a decrease in estrogen in women during certain cancer treatments. Also, some treatments for prostate cancer reduce testosterone levels in men. Reduced levels of sex hormones in both men and women can weaken the bone.

What Are the Limitations of This Test?

The limitations of a bone density analysis include:

Differences in the Methods of Analysis

Devices that measure the density of hip and spine bones are more accurate, but cost much more than devices that measure the density of the peripheral bones of the forearms, heels and fingers.

Limited Insurance Coverage

Not all health insurance plans cover bone density studies, so be sure you ask your health insurance provider first if you have coverage before you schedule your test.

Insufficient Information

A bone density study can confirm that you have low bone density, but cannot tell you why. To answer that question, you must complete a more complete medical study.

How Do You Prepare for a Bone Density Test?

Bone density tests are easy to do — quick and painless. Virtually no preparation is needed for this test. In fact, some simple versions of bone density tests can be performed at the local pharmacy. If you do the test in a medical center or a hospital, be sure to let your doctor know in advance if you recently had a barium test or if you injected contrast material for a computerized tomography or a nuclear medicine test. Contrast materials may interfere with bone density analysis.

Medications

Avoid taking calcium supplements for at least 24 hours before performing the bone density test.

Clothing and Personal Items

Wear loose and comfortable clothes, and avoid wearing garments with zippers, belts or buttons. Remove all metal objects from your pockets, such as keys, bill holders, coins, your cell phone, etc.

On What Areas of the Body Is a Bone Density Test Performed?

Bone density tests are usually performed on the bones most likely to rupture due to osteoporosis. Those areas include the following:

  • Bones of the lower part of the spine (lumbar vertebrae)
  • The narrow neck of the thigh bone (femur) next to the hip joint
  • The bones of the forearm

How Is a Bone Density Test Done?

If you have a bone density analysis performed in a hospital, then it is likely to be done with a central device where you lie on a padded platform while a mechanical arm passes over your body. The amount of radiation you will be exposed to is very low — much lower than the amount emitted during a chest x-ray. The test usually takes between 10 and 30 minutes.

A small, portable machine can measure bone density in the bones of the ends of the human skeleton, such as those in the finger, wrist or heel. These instruments are called “peripheral devices” and are found frequently in pharmacies. Peripheral bone density tests are less expensive than tests performed using central devices.

Because bone density can vary according to the area of the body, a measurement taken at the heel is not as accurate as a predictive factor as the measurement taken on the spine or hip. Therefore, if your test on a peripheral device yields a positive result, the doctor may recommend a follow-up scan of the spine or hip to confirm this diagnosis.

How Are Results Presented?

The results of a bone density study are reported in two figures: T and Z.

T Rating

Your T rating is your bone density compared to what is normally expected in a healthy young adult of your same gender. It is the number of units, called “standard deviations,” of your bone density above or below the average.

The meaning of your T rating can be interpreted as follows:

  • If you have a rating of -1 or above: Your bone density is considered normal.
  • If you receive a T rating between -1 and -2.5: This reflects osteopenia, because your bone density is below normal and can progress to osteoporosis.
  • If you receive a T rating of -2.5 or less: This indicates you more than likely have osteoporosis.

Z Rating

The Z score is the number of standard deviations above and below what is normally expected for a person of your age, sex, weight and ethnic or racial origin. A Z score that is significantly higher or lower than the average could suggest that another factor other than age is causing an abnormal decrease in bone mass. If your doctor can identify the underlying problem, that disease can often be treated, and the decrease in bone mass can be slowed or stopped.

Conclusion

Osteoporosis is common, serious and costly. It can sneak up on you when you least expect it.

Do you meet any of the following conditions?

  • You are a woman 65 years or older
  • You are a man aged 70 or older
  • You have broken a bone after the age of 50
  • You are a woman of menopausal age with risk factors
  • You are a post-menopausal woman under age 65 with risk factors
  • You are a man aged 50-69 with risk factors

If so, then you should talk with your doctor about getting a bone density test to get a better handle on the risks you face of suffering osteoporosis. Only then can you take steps to minimize or prevent this risk.

A bone densitometry is performed with a special device that measures the loss of bone mass of the patient. To accomplish this, it uses an improved x-ray technique with which images of the interior of the body are captured, usually from the hip area or the lower vertebrae of the spine.

It is an easy, accessible, painless, fast test that can be performed at any time. Don’t let time go by without discussing the possible risks of bone loss and osteoporosis with your primary care physician. Together, you can take preventative actions to result in a much stronger future for you.

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