Bone Density
Test for Osteoporosis
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What is the
test?
This test, which is also called bone densitometry,
uses specialized x-rays to measure the thickness
and strength of your bones. Various scanners
use different techniques, such as dual-energy
x-ray absorptiometry (DXA) and radiographic absorptiometry.
Quantitative ultrasound, which does not involve
x-rays, may also be used.
When bones are somewhat thin, the condition
is called osteopenia; when bones become very
thin, the condition is called osteoporosis. Bone
density tests provide a precise measure of whether
you have osteopenia or osteoporosis.Men, and
particularly women, usually begin to lose bone
thickness around age 50. Exercise and various
treatments can help prevent and even restore
bone loss; that's why diagnosing thin bones is
important.Many authorities now recommend screening
for thin bones. Not only is this test used to
help detect osteoporosis, but it is also helpful
in monitoring your progress if you're taking
bone-building medications.
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How
do I prepare for the test?
Be sure to tell your doctor if you might be
pregnant. A screening test that uses x-rays can't
be performed during pregnancy because it may
increase the risk of birth defects.
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What
happens when the test is performed?
Bone density tests can be done in the radiology
department of a hospital, a radiology diagnostic
center, or a doctor's office.You lie on a table
that has an overhanging cover, resembling a tanning
bed, while a radiologist or x-ray technician
moves a scanner above your spine, hip, or wrist.
The test takes 10-20 minutes. The test itself
is painless, but you may experience some discomfort
because you have to lie still.
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What
risks are there from the test?
The test doesn't have any significant risks.
Bone density tests that use x-rays expose you
to about one-tenth the amount of radiation as
in a single chest x-ray; this is too small an
amount to be likely to cause any harm, except
to a fetus in a pregnant woman.
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Must
I do anything special after the test is over?
No.
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How
long is it before the result of the test is
known?
You'll get the results within a few days. The
results will include two scores, the T-score
and the Z-score. The T-score measures your bone
density compared with the average values in young
adults of the same race and sex. The Z-score
shows how your bone density compares with that
of people your own age, race, and sex. A positive
T-score means your bones are stronger than the
average in a young adult, and a negative score
means that your bones are weaker. If you have
a T-score that is between -1.0 and -2.5, you
have osteopenia. If it is below -2.5, you have
osteoporosis.
In general, the lower your bone density, the
higher your risk of breaking a bone. Fractures
of the hip are particularly disabling, and fractures
of the spine are common and painful. Bone density
measured at the hip and spine by DXA is regarded
by most experts as the best predictor of hip
and spine fracture. DXA also is excellent for
diagnosing thin arm bones; wrist fractures occur
more easily in people with osteopenia or osteoporosis.
Fortunately, treatment options exist. Talk with
your doctor.
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