Currently bone density testing is considered the way to determine if a person has "osteoporosis" or "osteopenia" or normal bone density for their sex and age. Low bone density is an important risk factor, but alone does not predict future fracture.

This testing attempts to assess the density of your bones. Results are generally given in an absolute number, and as a "T score" and "Z score." The absolute number is most often grams per cubic centimeter. The "T score" compares your density to that of an ideal young standard of the same sex. The "Z score" compares your bone density to that of people your same sex and age.

The tests for measuring bone density include dual-energy x-ray absorptiometry (DEXA); single-photon absorptiometry (SPA); broadband ultrasound attenuation (Ultrasound), and quantitative computed tomography (QCT).

• The DEXA commonly measures the bone density of the spine and the hip. It is among the most precise tests. The DEXA scan is the most widely used of all existing tests and is considered by many as the "gold standard" for bone density testing.

• SPA is a simple radiation scanning technique used to measure "appendicular" bones, such as the wrist or heel. As with Ultrasound, measurements of the wrist, finger, or heel are good screening tests, but they do not necessarily tell us about the density of the bones that are most likely to fracture, the hip and spine.

• Ultrasound is a simple technique using sound waves to estimate strength of certain bones such as those of the heel, wrist, shinbone, or finger. Ultrasound measurements are best seen as "screening tests" which reveal the possibility of low bone density and bone weakness. However, there is often, but not always, a fairly good correlation between ultrasound measurements of the heel and density of the hip or spine.

• QCT is another radiation-based technology, which directly measures the "central" bones such as the spinal vertebral bodies.