What do the results of a bone density test mean?

Bone density test results are an objective way to measure bone density, which then can be used to assess whether you have osteopenia (sub-normal bone density) or osteoporosis (a condition characterized by decrease in bone mass). A bone density test can give you a baseline reading as to whether you need treatment or not. If treatment is needed, a bone density test should be done every two years to make sure that the treatment is actually working.

Two different scores are used to report the results of bone density tests. First, a T-score compares your particular bone density with the average bone density for a "reference population." In theory, this group consists of "normal young adult women" (as determined by certain criteria set up by researchers). Second, a Z-score compares your particular bone density with that for all women your age.

Having bone density that's lower than average is not a disease. It only means you're more likely to have fractures. Having a low bone density measurement is a reason to continue with diagnostic testing for osteoporosis or other bone diseases. It does not, in itself, establish a particular diagnosis or suggest which treatment (if any) you should get.

Bone density testing results have three parts:

• Your overall bone mineral density score reflects the amount of calcium in your bones.
• The T-score is created by comparing your bone density measurement to that of a healthy young adult at the peak of bone mass, which is achieved in the late 20s or early 30s.
• The Z-score compares your bone mineral density to the average value for someone who is the same age and gender as you.

Bone density testing helps determine if a person has osteopenia or osteoporosis. Both osteopenia and osteoporosis put people at greater risk for bone fractures. A normal bone density scan indicates good bone health and a decreased risk for bone fractures as a person ages.