What Is a T-Score?

As a body ages, the bones become more thin and brittle. This is called osteoporosis. In the past, it was not possible to measure a person's risk of getting a bone fracture when becoming older. Professionals at such health care centers as the Mayo Clinic report that the bone test densitometry or DEXA scan, can show how susceptible someone of bone damage.

Bone Density Test

• The bone density test, or densitometry, relies on unique X-rays to measure the number of grams of bone minerals, such as calcium, in a single section of bone. This DEXA scan is not 100 percent perfect, but it does quite clearly demonstrate risk. You can know how your bone density is in comparison to others your age and sex.

DEXA Scan

• The DEXA scan is a mathematical and graphic measurement. The standard or norm that is used for measurement is the bone density of an average young adult at 30 years of age. The "T-score" is the number of standard deviations below this norm. There is a T-score for different groups of people, such as for all women, Hispanic women, or Caucasian men. The more negative the T-score, the more chance of bone fractures. One person can have a different T-score for individual parts of the body, for example, the hip or neck.

T-Score, Caucasian Women

• The World Health Organization defines these categories based on bone density for Caucasian women, for example: A normal bone density of a Caucasian woman is a T-score of better than -1 (negative 1). A risk of pre-osteoporosis, or osteopenia, is a T-score between -1 and -2.5. A risk of severe osteoporosis is a T-score less than -2.5. About 16 percent of "young" women have a risk of pre-osteoporosis. By the time most women become 80 years old, only a few have a normal bone density.

The Z-Score

• The T-score compares a person to the standard or norm, or someone else 30 years of age with a peak bone density. The Z-score compares one individual with another one the same age. Once again, there are a variety of Z-scores depending on the group tested.

Test Recommendations

• In general, this bone mineral density test is recommended for all women who are the age of 65 and older; postmenopausal women who are under the age of 65, but at greater risk because of their health status; postmenopausal women who presently have or previously had a bone fracture; women and men on steroid medicines for over three months; and men having a present or earlier fracture or who are at greater risk because of such factors as low testosterone or alcoholism.