The Importance of Bone Mineral Density Exams (DXA scans)

A dual-energy absorptiometry (DXA) scan can provide a snapshot of your bonehealth. This test determines bone mineral density (BMD) and helps in establishingfracture risk, and, with serial testing, is a way to measure response to osteoporosistreatment. The most widely recognized test for determining BMD is the central DXAscan. It is painless – similar to having an x-ray but much less radiation. The scanmeasures bone density at your hip and spine. (Often, a scan of the forearm will alsobe performed during central DXA testing.) Peripheral bone density testing measuresdensity at the wrist, finger, or heel and are typically used for screening purposes only.

DXA scans measure your bone mineral density and compares it to that of an established norm or standard to give you a score. Although no bone density testis 100-percent accurate, the central DXA can be an important predictor of whether a person will have a fracture in the future. Most commonly, DXA resultsare compared to the ideal or peak bone mineral density of a healthy young adult,and given a T score. A score of 0 means your BMD is equal to the norm for ahealthy young adult. Differences between your BMD and that of a healthy youngadult norm are measured in units called standard deviations (SDs). The more standard deviations below 0, indicated as negative numbers, the lower your BMD and the higher your risk of fracture.

The National Osteoporosis Foundation (NOF) and the U.S. Preventative Services TaskForce (USPSTF) recommended osteoporosis screening with DXA for women 65 yearsand older, and for men over 70. Earlier screening is recommended for both groups if riskfactors are present. (Risk factors are such things as family history of osteoporosis, weight under 127 pounds, history of smoking or excessive alcohol consumption, poordiet, etc.)

A recent review published in the Journal of General Internal Medicine determined thattoo few women are getting bone density scans. Researchers examined the medical records of 51,000 women aged 40 to 85 living in California and determined that only57.8% of women aged 65 – 74 and 42.7% of women over age 75 received DXAscreenings. Even with women age 60 to 64 with at least one risk factor, only 58.8%had a DXA. The researchers concluded that DXA screening is being underutilized.