Tomorrow, I'm going for a bone density test.
Loss of bone or osteoporosis is a common long-term side effect of gastric bypass surgery. Because the body doesn't absorb calcium properly after surgery, there is a greater risk of developing osteoporosis. Also caused by bypassing the duodenum, some patients experience bone pain, loss of height, humped back and fractures of the ribs and hip bones, called metabolic bone disease.
From Mayo Clinic:
A bone density test uses special X-rays to measure how many grams of
calcium and other bone minerals (collectively known as bone mineral
content) are packed into a segment of bone. The higher your mineral
content, the denser your bones are. And the denser your bones, the
stronger they are and the less likely they are to break. Doctors use a
bone density test to determine if you have, or are at risk of,
osteoporosis.
Bone density tests are not the same as bone scans. Bone scans
require an injection beforehand and are usually used to detect
fractures, cancer, infections and other abnormalities in the bone.
Who should have a bone density test?
The U.S. Preventive Services Task Force recommends a bone density test if:
- You're a woman age 65 or older
- You're 60 and at increased risk of osteoporosis
The older you get, the higher your risk of osteoporosis because your
bones become weaker as you age. Your race also makes a difference.
You're at greatest risk of osteoporosis if you're white or of Southeast
Asian descent. Black and Hispanic men and women have a lower but still
significant risk. Other risk factors for osteoporosis include low body
weight, a personal history of fractures, a family history of
osteoporosis and using certain medications that can cause bone loss.
How do you prepare for a bone density test?
Bone density tests are easy, fast and painless. Virtually no
preparation is needed. In fact, some simple versions of the bone
density tests can be done at your local pharmacy or drugstore.
If you're having the test done at a medical center or hospital, be
sure to tell your doctor beforehand if you've had recent oral contrast
or nuclear medicine tests. These tests require an injection of
radioactive tracers that might interfere with your bone density test
How is a bone density test done?
Bone density tests are usually done on bones that are most likely to
break because of osteoporosis. These sites include the lumbar
vertebrae, which are in the lower region of your spine, the narrow neck
of your femur bone adjoining the hip, and the bones of your wrist and
forearm.
The equipment for bone density tests includes large machines on
which you can lie down (central devices) as well as smaller, portable
machines that measure bone density on the periphery of your skeleton,
such as in your finger, wrist or heel (peripheral devices).
Central devices
- DXA scan. Dual energy X-ray absorptiometry (DXA)
scans measure the bone density at your hip or spine. This test offers
very precise results and is the preferred test for diagnosing
osteoporosis. During this test, you lie on a padded platform for a few
minutes while an imager — a mechanical arm-like device — passes over
your body. It won't touch you. The test does, however, emit radiation,
though your exposure during a bone density test is commonly about
one-tenth of the amount emitted during a chest X-ray. This test usually
takes five to 10 minutes to complete.
- Quantitative CT scan. This
test uses a computerized tomography (CT) scanner combined with computer
software to determine your bone density, usually at your spine.
Quantitative CT (QCT) scans provide detailed, three-dimensional images
and can take into account the effects of aging and diseases other than
osteoporosis on your bones. QCT scans emit more radiation than DXA
scans do. For a QCT test, you lie on a movable table that's guided into
a large tube-like area where images are taken. It typically takes less
than 10 minutes.
Peripheral devices
Peripheral devices are found in pharmacies and are considerably less
expensive than are central devices. But these smaller machines do have
limitations.
Measurements taken at your hip and spine generally are considered
more accurate assessments of your osteoporosis risk because these are
the locations where major fractures tend to occur — fractures that can
severely limit the quality and even the length of your life.
A test done on a peripheral location, such as your heel, may predict
risk of fracture in your spine and hip as well. But because bone
density tends to vary from one location to the other, a measurement
taken at the heel usually isn't as accurate as a measurement taken at
the spine or hip.
Measurements of bone density in your heel or finger still can be
used to screen for osteoporosis, though. If your test is positive, your
doctor might recommend a DXA scan at your spine or hip to confirm your
diagnosis.
The results of your bone density test are reported in two numbers: T-scores and Z-scores.
T-score
Your T-score is your bone density compared with what is normally
expected in a healthy young adult of your sex. Your T-score is the
number of units — standard deviations (SD) — that your bone density is
above or below the standard.
| T-score | What your score means |
|---|
| Above -1 | Your bone density is considered normal. |
| Between -1 and -2.5 | Your score is a sign of osteopenia, a condition in which bone density is below normal and may lead to osteoporosis. |
| Below -2.5 | Your bone density indicates you have osteoporosis. |
Keep in mind that these scores apply mostly to white postmenopausal
women, who tend to have lower bone density as compared with other
racial groups and men. Interpretations may vary if you're a woman of
color or a man.
Z-score
Your Z-score is the number of standard deviations above or below what's
normally expected for someone of your age, sex, weight, and ethnic or
racial origin. This is helpful because it may suggest you have a
secondary form of osteoporosis through which something other than aging
is causing abnormal bone loss. A Z-score less than -1.5 might indicate
these other factors are to blame. Your doctor would then try to
determine if there's any underlying cause for the low bone mass. If he
or she can identify a cause, that condition can often be treated and
the bone loss slowed or stopped.
What are the pros and cons of the bone density test?
Bone density testing is a valuable tool in the diagnosis of
osteoporosis and is a fairly accurate predictor of your risk of
fractures. Significant differences in the various testing methods do
exist, however. Central devices are more accurate, but cost
significantly more than peripheral devices do.
Not all health insurance plans cover bone density tests, so ask your
insurance provider whether it provides coverage that applies to your
situation. Medicare pays for bone density tests only in the following
instances:
- If you're postmenopausal and at risk of osteoporosis
- If you have primary hyperparathyroidism
- If you have certain spinal abnormalities that might indicate a fracture
- If you're on long-term corticosteroid therapy, such as prednisone
- If your doctor wants to assess your response to osteoporosis medications
A bone density test can confirm that you have low bone density, but
it can't tell you why. To answer that question, you need a complete
medical evaluation, including a history and physical. This information
can help your doctor better interpret the results of the bone density
test.
Tomorrow, I'm going for a bone density test.
Loss of bone or osteoporosis is a common long-term side effect of gastric bypass surgery. Because the body doesn't absorb calcium properly after surgery, there is a greater risk of developing osteoporosis. Also caused by bypassing the duodenum, some patients experience bone pain, loss of height, humped back and fractures of the ribs and hip bones, called metabolic bone disease.
From Mayo Clinic:
A bone density test uses special X-rays to measure how many grams of calcium and other bone minerals (collectively known as bone mineral content) are packed into a segment of bone. The higher your mineral content, the denser your bones are. And the denser your bones, the stronger they are and the less likely they are to break. Doctors use a bone density test to determine if you have, or are at risk of, osteoporosis.
Bone density tests are not the same as bone scans. Bone scans require an injection beforehand and are usually used to detect fractures, cancer, infections and other abnormalities in the bone.
Who should have a bone density test?
The U.S. Preventive Services Task Force recommends a bone density test if:
The older you get, the higher your risk of osteoporosis because your bones become weaker as you age. Your race also makes a difference. You're at greatest risk of osteoporosis if you're white or of Southeast Asian descent. Black and Hispanic men and women have a lower but still significant risk. Other risk factors for osteoporosis include low body weight, a personal history of fractures, a family history of osteoporosis and using certain medications that can cause bone loss.
How do you prepare for a bone density test?
Bone density tests are easy, fast and painless. Virtually no preparation is needed. In fact, some simple versions of the bone density tests can be done at your local pharmacy or drugstore.
If you're having the test done at a medical center or hospital, be sure to tell your doctor beforehand if you've had recent oral contrast or nuclear medicine tests. These tests require an injection of radioactive tracers that might interfere with your bone density test
How is a bone density test done?
Bone density tests are usually done on bones that are most likely to break because of osteoporosis. These sites include the lumbar vertebrae, which are in the lower region of your spine, the narrow neck of your femur bone adjoining the hip, and the bones of your wrist and forearm.
The equipment for bone density tests includes large machines on which you can lie down (central devices) as well as smaller, portable machines that measure bone density on the periphery of your skeleton, such as in your finger, wrist or heel (peripheral devices).
Central devices
Peripheral devices
Peripheral devices are found in pharmacies and are considerably less expensive than are central devices. But these smaller machines do have limitations.
Measurements taken at your hip and spine generally are considered more accurate assessments of your osteoporosis risk because these are the locations where major fractures tend to occur — fractures that can severely limit the quality and even the length of your life.
A test done on a peripheral location, such as your heel, may predict risk of fracture in your spine and hip as well. But because bone density tends to vary from one location to the other, a measurement taken at the heel usually isn't as accurate as a measurement taken at the spine or hip.
Measurements of bone density in your heel or finger still can be used to screen for osteoporosis, though. If your test is positive, your doctor might recommend a DXA scan at your spine or hip to confirm your diagnosis.
The results of your bone density test are reported in two numbers: T-scores and Z-scores.
T-score
Your T-score is your bone density compared with what is normally expected in a healthy young adult of your sex. Your T-score is the number of units — standard deviations (SD) — that your bone density is above or below the standard.
Keep in mind that these scores apply mostly to white postmenopausal women, who tend to have lower bone density as compared with other racial groups and men. Interpretations may vary if you're a woman of color or a man.
Z-score
Your Z-score is the number of standard deviations above or below what's normally expected for someone of your age, sex, weight, and ethnic or racial origin. This is helpful because it may suggest you have a secondary form of osteoporosis through which something other than aging is causing abnormal bone loss. A Z-score less than -1.5 might indicate these other factors are to blame. Your doctor would then try to determine if there's any underlying cause for the low bone mass. If he or she can identify a cause, that condition can often be treated and the bone loss slowed or stopped.
What are the pros and cons of the bone density test?
Bone density testing is a valuable tool in the diagnosis of osteoporosis and is a fairly accurate predictor of your risk of fractures. Significant differences in the various testing methods do exist, however. Central devices are more accurate, but cost significantly more than peripheral devices do.
Not all health insurance plans cover bone density tests, so ask your insurance provider whether it provides coverage that applies to your situation. Medicare pays for bone density tests only in the following instances:
A bone density test can confirm that you have low bone density, but it can't tell you why. To answer that question, you need a complete medical evaluation, including a history and physical. This information can help your doctor better interpret the results of the bone density test.