Opportunistic Screening for Osteoporosis Using Abdominal Computed Tomography Scans Obtained for Other Indications

TLDR: Abdominal CT images obtained for other reasons that include the lumbar spine can be used to identify patients with osteoporosis or normal BMD without additional radiation exposure or cost.

Abstract: Osteoporosis is prevalent and treatable and conveys a considerable lifetime fracture risk, yet it remains substantially underdiagnosed and undertreated (1-4). Currently, nearly half of all female Medicare beneficiaries have never undergone bone mineral density (BMD) testing (5), and more than 80% of all persons with a major osteoporosis-related fracture do not have BMD testing or receive pharmacologic agents to reduce fracture risk (6). Furthermore, because normal BMD and mild osteopenia confer a very low risk for osteoporosis (7), efficient and cost-effective stratification of the unscreened population into groups at low and high risk for osteoporosis and fractures is desirable. Central dual-energy x-ray absorptiometry (DXA) of the hips and lumbar spine is widely recognized as the reference standard for diagnosing osteoporosis (8, 9), but it is underutilized. Safe and cost-effective alternatives to increase detection of this condition are needed. More than 80 million computed tomography (CT) scans were performed in the United States in 2011 (10), most of which carry potentially useful information about BMD. Retrieval of BMD data available on body CT examinations ordered for other indications requires no additional cost, patient time, equipment, software, or radiation exposure, and these data can be retrospectively acquired. It could therefore expand population screening efforts for osteoporosis. In a recent feasibility study of adults who underwent osteoporosis screening with DXA and colorectal cancer screening with CT colonography, we showed that a single CT measurement of vertebral attenuation was equivalent to the more complex dedicated quantitative CT (QCT) assessment but was considerably easier to obtain (10). The purpose of this study was to evaluate CT-derived BMD assessment compared with DXA screening by using CT scans that were performed for other clinical indications in a larger patient population, focusing on the L1 level because it is easily identified as the first non-rib-bearing vertebra and is included on all abdominal and thoracic CT scans in routine practice.