Dual-Energy X-Ray Absorptiometry

Abstract

Assessment of bone mineral density (BMD) by dual-energy x-ray absorptiometry (DXA) plays a vital role in the diagnosis of osteoporosis and in monitoring a patient's response to drug therapy. This commentary will discuss controversies surrounding the use of DXA for screening and monitoring of BMD in women. The National Osteoporosis Foundation (NOF) has estimated that more than 43.6 million Americans have osteoporosis or osteopenia (low bone mass) [1]. In 2005, 2 million fractures were attributed to osteoporosis, with a direct cost of $17 billion; 71% of these fractures occurred in women [2]. By 2025, costs associated with fractures are projected to increase to $25.3 billion [2].Bone mineral density (BMD) testing by dual-energy x-ray absorptiometry (DXA) is the recognized standard for the clinical assessment of skeletal health. DXA allows for the diagnosis of osteoporosis or low bone mass, strongly correlates with mechanical strength [3], is a good predictor of fracture risk [4], and affords excellent accuracy and precision [5] while minimizing patients' exposure to ionizing radiation [6]. Moreover, drug therapy has been shown to be cost effective in postmenopausal women with osteoporosis [7]. Given that approximately 40% of white women older than 50 years will have an osteoporotic fracture in their lifetime [8], having clear recommendations for screening and monitoring using DXA are essential. Because of the absence of pertinent studies in men, this commentary will only address the evaluation of BMD in women.DXA screening for low bone mass or osteoporosis is well accepted in women aged 65 years or older, regardless of risk factors, and in younger women with risk factors such as rheumatoid arthritis, glucocorticoid use, malabsorption syndromes, hyperthyroidism, hyperparathyroidism, or gastric bypass surgery. Screening of these individuals is recommended by NOF [1], the US Preventive Services Task Force (USPSTF) [9], the International Society for Clinical Densitometry (ISCD) [10], the American Association of Clinical Endocrinologists (AACE) [11], the American College of Radiology [12], and the North American Menopause Society (NAMS) [13]. Despite the fact that DXA testing has been added to the "Welcome to Medicare Exam," only 14% of eligible women had a DXA study in 2010 [14]. Over the 7-year period from 2002 through 2008, 48% of older women did not have a DXA study [14]. Is DXA Testing Overused in Younger Women?Potential misuse of DXA testing is a concern that has been raised by the Centers for Medicare & Medicaid Services (CMS) and the National Committee for Quality Assurance, which have together submitted for public comment a quality measure regarding "appropriate use of DXA scans in women under 65 years who do not meet the risk factor profile" [15]. The quality measure cites a small, retrospective study of 615 women [16], in which 41.3% of women younger than 65 years who had been sent for DXA screening were found to have been screened inappropriately, based on their lack of any of the recognized risk factors li...

Dielectric properties of bones for the monitoring of osteoporosis

“…The report further states that in the EU, a hip fracture is reported every 30 seconds approximately, with about 1700 fractures reported per day; moreover, this number is expected to double by 2050. In the US, osteoporosis is considered the most commonly-encountered bone disease [14]. Almost 50% of American women and 25% of men over 50 years of age, have an osteoporosis-related bone fracture and around 43.6 million suffer from osteopenia, a precursor to osteoporosis [22].…”