Do DXA (DEXA) Scans Actually Predict Fractures?

Accuracy in the ability to predict fracture has recently been called to question, as DXA scans may not show the entire picture.

 

When testing for bone mass density, the most common of tests is a DXA scan. This scan entails a 20 min. process where two x-ray emissions are aimed into specific areas of the body to analyze the density or porosity of the bone mass. These DXA scans have been considered the gold standard for evaluation of density and bone for many years, however their value has come into question. These scans do not address or compare groups that have significant differences with their bone mass, specifically ethnic groups, geographical region groups, and cultural dietary habits.

English: Bone Density Scan of Individual with ...

English: Bone Density Scan (Photo credit: Wikipedia)

 

Asian females for example, have smaller bones (girth of bone, as well as links in long bones) on average in comparison with European, Middle Eastern, or African descent females. As a result of this, Asian women test poorly in their DXA scans, however have lower fracture rates. Regional and cultural differences in bone are apparent when looking at individuals with similar bone size, but burying fracture rates, this can be seen when comparing fracture rates in Africa versus North America. A thinner bone can have greater density, and a wider larger bone can have lower density, yet current bone mass density testing does not clearly distinguish between strong or weak bones, as girth of an individual bone is not a variable that is accounted for.

 

As each x-ray emission in a DXA scan passes through bone to determine its density, how much bone but it must pass through becomes an element that skews comparing one individual to the next with varying girth of bone. To complicate the situation further, bisphosphonate drugs stunt the natural shedding process of old bone, which occurs on the surface of the bone. In a DXA scan, an individual who takes bisphosphonate drugs can show high, or healthy levels of bone mass density, but the success of the scan may only be “surface deep.” The FDA announced in 2010 that bisphosphonate use “carry a small but meaningful risk of femoral fractures,” and has ordered that product labels be updated accordingly.

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