Bone Densitometry (DEXA Scan) What can I expect during my BD test?
Like other organs in the body, bones are constantly changing. Throughout childhood and young adulthood, bones grow in strength and in size. Around the age of 30, bones reach their peak strength and then naturally become weaker with age. Osteoporosis is a condition where bones become weak to the point of breaking. This weakening may be due to aging, or caused by other factors that combine with age. Symptoms of osteoporosis do not occur until a lot of bone strength is lost. The most visible symptoms may include loss of height, along with curvature of the upper back. Osteoporosis also can result in a crippling and painful fracture, occurring most often in the hip, back, or wrist.
What can I expect during my BD test?
The bone densitometer is like a large examination table. It is padded and comfortable. Your name, age, height, weight and ethnicity will be entered into the computer before your test. This information is used to compare your results to a normal reference group. You will be asked to lie on your back, remaining in your normal clothing in most cases. Belt buckles, metal or thick plastic buttons and metal jewelry will need to be removed from the region being examined. The operator will position your arms and legs for the test, which is painless and typically takes 10 minutes. You just need to lie still and breathe normally.
How does the densitometer work?
A bone densitometer measures bone mineral density (BMD). The amount of bone mineral relates directly to bone density. The bone densitometer uses small amounts of x-ray to measure BMD and to produce images of the spine, hip, or even the whole body. The technical term for the method is “dual-energy x-ray absorptiometry”, or DXA.
What information will the test give?
A bone densitometry test is an aid to doctors in the diagnosis of osteoporosis. The test compares your bone to that of a “young adult” at peak bone strength (T-score).
The World Health Organization (WHO) has developed categories that define the amount of bone loss:
CATEGORY T-SCORE
Normal . . . . . . . . . . . . . . . . . . . . .above –1
Osteopenic (low bone mass) . . . . . . –1 to –2.5
Osteoporoticbelow . . . . . . . . . . . . . . . . –2.5
Your T-score combined with other risk factors, will enable your doctor to estimate what your risk of a hip fracture or other major osteoporosis-related fracture will be in the next 10 years. This information will help your doctor determine what course of action should be taken. The bone densitometry test is also useful in following bone changes. Your doctor may suggest follow-up tests to detect change over time.
Who Should have a DEXA Scan?
• Women aged 65 and older
• For post-menopausal women younger than age 65 a bone density test is indicated if they have a risk factor for low bone mass such as:
• Low body weight
• Prior fracture
• High risk medication use
• Disease or condition associated with bone loss
• Women during the menopausal transition with clinical risk factors for fracture, such as low body weight, prior fracture, or high-risk medication use.
• Men aged 70 and older.
• For men < 70 years of age a bone density test is indicated if they have a risk factor for low bone mass such as:
• Low body weight
• Prior fracture
• High risk medication use
• Disease or condition associated with bone loss.
• Adults with a fragility fracture.
• Adults with a disease or condition associated with low bone mass or bone loss.
• Adults taking medications associated with low bone mass or bone loss.
• Anyone being considered for pharmacologic therapy.
• Anyone being treated, to monitor treatment effect.
• Anyone not receiving therapy in whom evidence of bone loss would lead to treatment.
Women discontinuing estrogen should be considered for bone density testing according to the indications listed above.
Is the test safe?
Even though x-rays are used, the amount absorbed by the patient is only about 1/10th of that received from a chest x-ray. The x-ray dose from the bone
densitometry test is comparable to the naturally occurring radiation you are exposed to in one week.*
*DPX or Prodigy series only, ref. U.S. EPA Students Radiation Protection Program, May, 2006.
Caution: Even though the x-ray dose from the bone densitometry test is very low, please inform the operator if you are pregnant or might be pregnant before your test!
Where can I get more information about bone measurements and osteoporosis?
The National Osteoporosis Foundation (NOF) is one of the leading sources of information about osteoporosis and bone measurements.
website: www.nof.org