Bone Density Test

Bone Density Test

 

Definition

A bone density test, or scan, is designed to check for osteoporosis, a disease that occurs when the bones become thin and weak. Osteoporosis happens when the bones lose calcium and other minerals that keep them strong. Osteoporosis begins after menopause in many women, and worsens after age 65, often resulting in serious fractures. These fractures may not only bring disability, but may affect longevity. As many as one-fourth of women who fracture their hip after age 50 die within one year.
Most people today will get a bone density scan from a machine using a technology called Dual Energy X-ray Absorptiometry or DEXA for short. This machine takes a picture of the bones in the spine, hip, total body and wrist, and calculates their density. If a DEXA machine is not available, bone density scans can also be done with dual photon absorptiometry (measuring the spine, hip and total body) and quantitative computed tomography scans (measuring the spine). Bone density scanners that use DEXA technology to just measure bone density in the wrist (called pDEXA scans) provide scans at some drugstores. Yet these tests are not as accurate as those that measure density in the total body, spine or hip—where most fractures occur.

Purpose

A bone density scan measures the strength of an individual's bones and determines the risk of fracture. An observation of any osteoporosis present can be made.

Description

To take a DEXA bone density scan, the patient lies on a bed underneath the scanner, a curving plastic arm that emits x rays. These low-dose x rays form a fan beam that rotates around the patient. During the test, the scanner moves to capture images of the patient's spine, hip or entire body. A computer then compares the patient's bone strength and risk of fracture to that of other people in the United States at the same age and to young people at peak bone density. Bones reach peak density at age 30 and then start to lose mass. The test takes about 20 minutes to do and is painless. The DEXA bone scan costs about $250. Some insurance companies and Medicare cover the cost. pDEXA wrist bone scans in drugstores are available for about $30.

Preparation

The patient puts on a hospital gown and lies on the bed underneath the scanner. Not all doctors routinely schedule this test. If the following factors apply to a patient, they may need a bone density scan and can discuss this with their doctor. The patient:
  • is at risk for osteoporosis
  • is near menopause
  • has broken a bone after a modest trauma
  • has a family history of osteoporosis
  • uses steroid or antiseizure medications
  • has had a period of restricted mobility for more than six months

Risks

The DEXA bone scan exposes the patient to only a small amount of radiation-about one-fiftieth that of a chest x ray, or about the amount you get from taking a cross-country airplane flight.

Normal results

The patient, when compared with people at "young normal bone density" (called the T-score) has the same or denser bones than a healthy 30-year-old. T scores above 1 mean that a patient has a healthy bone mass. Scores from 0 to −1 mean that the patient has borderline bone mass and should repeat the test in two to five years.

Abnormal results

The patient has two to four times the risk of a broken bone as other people in the United States at the same age and those at peak bone density. If a patient's T score ranges from −1 to −2.5 they have low bone mass and are at risk for osteoporosis. A T score below −2.5 means osteoporosis is already evident. These patients should have a repeat bone density scan every year or two.

Resources

Organizations

National Osteoporosis Foundation. 1150 17th St., NW, Suite 500, Washington, DC 20036-4603. (800) 223-9994. http://www.nof.org.

Key terms

Calcium — A mineral that helps build bone. After menopause, when women start making less of the bone-protecting hormone estrogen, they may need to increase their intake of calcium.
DEXA bone density scan — A bone density scan that uses a rotating x-ray beam to measure the strength of an individual's bones and his or her fracture risk.
Osteoporosis — A disease that occurs when the bones lose the calcium and structure that keep them strong. It often occurs after menopause (around age 50) in women and in old age in men.
References in periodicals archive ?
Before undergoing bone density test, the participants were asked to answer four questions to gauge their satisfaction in life.
For a woman, it can be worthwhile to get an initial bone density test, but NOT before age 65.
In a population-based cohort of older men and women not yet treated for bone loss, the result of a second bone density test within four years of the first did not "meaningfully improve" fracture prediction, according to Sarah Berry, M.
Another barrier is the confusion among physicians about who should get a bone density test.
The list includes: women who are post-menopausal, those of Caucasian or Asian descent, anyone with a family history of osteoporosis or easily broken bones, those who do not consume enough calcium or vitamin D, people who do not exercise regularly, and anyone with a low bone mass per a bone density test.
Those universal recommendations are summarized in five steps to bone health: get the daily recommended amounts of calcium and vitamin D, engage in regular weight-bearing and muscle-strengthening exercise, avoid smoking and excessive alcohol consumption, talk to a health care provider about bone health and have a bone density test and take medication when appropriate.
gt;> When appropriate, have a bone density test and take medication.
79) times the adjusted odds of having a past bone density test, 2.
In all likelihood the therapy is working, but "noise" in the bone density test results in a lower density measurement.
They will have their blood pressure and cholesterol checks and may also have a bone density test for osteoporosis and checks looking at the risk of heart problems.
The National Osteoporosis Foundation recommends that women get a bone density test at age 65, or earlier if she has other risk factors at menopause.
Figure 3 Number of Years Since Most Recent Bone Density Test, by Percent of Aged Medicare Females Living in the Community: 2000 Years Percent Less than 1 43 1-2 32 2-3 14 3-5 7 More than 5 5 Note: Table made from bar graph.