The results of your bone density test can do more than confirm a diagnosis of osteoporosis -- they can also determine your risk for fractures and gauge your response to treatment. Test results are compared to those of a healthy 30-year-old and also to what is expected in someone of your age and body size. These scores indicate your overall bone density.

Bone Density Test: An Overview

A bone mineral density test (BMD), a non-invasive and painless test, is the best way to determine your bone health. Bone density tests can:  

• Identify osteoporosis
• Determine your risk for fractures
• Monitor your response to an osteoporosis treatment.  

Different bone density tests may measure your:  

• Hip
• Spine
• Wrist
• Finger
• Shin bone
• Heel.  

Results of the Bone Density Test

Your bone density test results are compared to two norms: "young normal" and "age-matched." Young normal, known as your T-score, compares your BMD to optimal or peak density of a 30-year old healthy adult and determines your fracture risk, which increases as BMD falls below young-normal levels.   Age-matched, known as your Z-score, compares your BMD to what is expected in someone your age and body size. Among older adults, however, low BMD is common, so comparison with age-matched norms can be misleading.   The difference between your BMD and that of a healthy, young adult is referred to as a "standard deviation" (SD). As outlined in the World Health Organization's diagnostic categories, individuals whose T-score is within one standard deviation of the "norm" are considered to have normal bone density.   Scores below the norm are indicated in negative numbers. For example, a score from -1.0 to -2.5 SD below the norm indicates low bone mass, or osteopenia, and a score of more than -2.5 SD below the norm is considered a diagnosis of osteoporosis. For most BMD tests, -1 SD equals a 10 percent to 12 percent decrease in bone density.