Dual energy X-ray absorptiometry: Pitfalls in measurement and interpretation of bone mineral density

Abstract

Osteoporosis is common disorder of elderly population all over the world as well as in India. The presence of osteoporosis predicts fracture risk. Fragility fracture has marked morbidity as well as mortality. Thus, osteoporosis has marked therapeutic and economic implications. Osteoporosis is defined by low bone mineral density (BMD). The gold-standard method to assess BMD is dual X-ray absorptiometry (DXA). In India, hologic and lunar machines are most commonly used to measure BMD; these machines have their own normative data from which patients BMD is compared and results are generated. As per recommendations, all postmenopausal women and men above 70 years need BMD estimation other than quite a few other specific indications as well. With increasing life expectancy, increased awareness of osteoporosis, and availability of DXA machines, there is flooding of requests for BMD estimation. In view of all this, it becomes imperative on part of physicians, orthopedicians, rheumatologists, and endocrinologists alike to be fully aware about pitfalls in BMD assessment by DXA and interpretation of BMD reports.

Effect of high-dose vitamin D supplementation on bone density in youth with osteogenesis imperfecta: A randomized controlled trial

“…This x-ray machine allows for quick and reproducible measurements all while causing minimal radiation to the subject and minimal scatter to the practitioner [116]. DXA is recognized as the gold-standard technique for measuring BMD and also allows for whole body composition assessment [116].…”

“…For example, slight rotation of the spine will result in larger vertebral area assessed by the x-rays [116]. This variation will not affect bone mineral content but will decrease BMD values since DXA evaluates density based on a two dimensional equation (g/cm 2 ) [116].…”

“…This variation will not affect bone mineral content but will decrease BMD values since DXA evaluates density based on a two dimensional equation (g/cm 2 ) [116]. Lumbar spine areal BMD for patients with scoliosis is thus affected since straight positioning cannot be achieved [116]. This must be considered in patient with OI since scoliosis is frequent due to vertebral compression…”

Osteoporosis: a discussion on the past 5 years

“…While the normal baseline in the T-score value is for women, there are studies that show it can be applied to men with equal efficacy [99•, 100]. Several limitations to DXA scans have been documented, including previous fracture, osteoarthritis, osteomalacia, metal implants, and collection and interpretation of results [101,98]. Even with its limitations, it has become the gold standard for diagnosing osteoporosis.…”

Evaluating Bone Loss with Bone Turnover Markers Following Acute Spinal Cord Injury

“…However, conventional DEXA scanning, measuring BMD at the lumbar spine and proximal femur, may not be an ideal tool in the SCI population as BMD loss differs at distal and proximal epiphysis of trabecular bones in patients with SCI [8]. DEXA scanning has its own limitations, being an expensive investigation with limited availability in many parts of India [11]. An alternative is peripheral quantitative computed tomography scanning, which determines both regional BMD and cortical thinning of the diaphysis, but it is also costly and not readily available.…”