In the United States, an estimated 10 million people already have osteoporosis, while another 34 million are at an increased risk for the disease due to low bone mass, according to the National Osteoporosis Foundation. This disease reduces bone mineral density, causing an alteration of the amount of protein in bones and decreasing bone strength. The weakening of bones increases the risk of fractures, which most commonly will occur in the wrists, hips, or spine. The results of these fractures can be both devastating and painful as they often may require major surgery, impair a person’s ability to walk, or even cause permanent disability.

Osteoporosis is difficult to detect and often it is not discovered until after a fracture occurs. The National Osteoporosis Foundation reports that one in two women and one and four men over the age of 50 will experience a fracture due to the disease in their remaining lifetime. There are several different ways that osteoporosis can be diagnosed, including bone scans, lab tests, and x rays. In the past, standard x rays were only able to detect bone loss after 30 percent of an individual’s skeleton had been depleted, meaning the disease already had taken effect and they were at risk of fractures. Today, an enhanced form of x ray technology called DXA, dual-energy x-ray absorptiometry, is the standard for measuring bone mineral density. Not only is the DXA the most accurate test for the diagnosis of osteoporosis, it also is an accurate way to estimate the risk of fracture.

This noninvasive medical test requires the patient to expose a part of the body to a small amount of ionizing radiation. Most often performed on the lower spine and hips, the DXA machine sends x rays that have two distinct energy peaks through the bones that are being examined. The majority of one peak is absorbed by soft tissue and the other is absorbed by the bone. To determine the patient’s bone mineral density, the soft tissue amount is subtracted from the total. Test results are given in two scores: the T score and the Z score. The T score compares the patient’s bone amount with a young adult with peak bone mass and is used to determine diagnosis and fracture risk. The Z score compares the patient’s bone amount with people in their age group, of the same gender, and similar size. If the Z score is either too high or too low, it may indicate that the patient needs to undergo further testing.