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| |  Tool Identifies Which DXA Tables May Fail to Fit Obese Patients: Presented at ASBMR By John Otrompke DENVER -- September 18, 2009 -- Because tables for dual energy x-ray absorptiometry (DXA) were originally designed to scan small, frail, elderly women with osteoporosis, they do not always fit obese patients. As knowledge grows that DXA scanners can identify fat and lean mass, and the use of the devices grows outside the bone context, their early design can sometimes pose a problem for physicians and researchers. “Now, as obesity becomes a growing problem, especially in the United States, there is an increasing demand for the table to assess fat,” said Sally Warner, PhD, Musculoskeletal Imaging, Perceptive Informatics, Inc., Billerica, Massachusetts, on September 14 at the 31st Annual Meeting of the American Society for Bone and Mineral Research (ASBMR). “Clinics already have the scanners, and they’re not going to buy another one just to test obese people. Manufacturers are not going to design them larger, because they know they’re not going to sell them just for that purpose. The newer generation of scanners have gotten wider, but they are still not wide enough to fit most of the obese population, if their body mass index [BMI] is over 30,” said Dr. Warner, noting that new scanners are very expensive. Researchers realised the nature of the problem when accruing patients for a large study of a drug to reduce body fat. In the multicentre trial, 975 obese men and women were recruited from 47 sites. Patients were eligible if their whole body fit within the maximum field of view (FOV), with the option to exclude the left arm if necessary. But the trial encountered difficulty, because of a high scan failure rate, with a monthly peak of 53%. Therefore, researchers created a new tool, the DXA Exact Fit, used in the exam room prior to scheduling the DXA scan. If the patient did not fit within the margins of the tool, then there was a greater likelihood that the patient may not fit within the FOV for a whole body scan, resulting in a scan failure, unnecessary radiation exposure, time, and cost. Patients in the study were a mean of 164.59 cm (64.8 in) tall, plus or minus 16.76 cm (6.6 in), and mean weight was 102 kg (225 lbs), plus or minus 17.7 kg (39 lbs). Without the left arm in view, 441 scans were completed. Prior to the use of DXA Exact Fit, 35.4% of scans were not acceptable, and 44% of patients with a BMI >35 did not fit within the table FOV. Of the patients weighing more than 90.7 kg (200 lbs), 50% had DXA scan failures. Following prescreening with DXA Exact Fit, however, only 9.8% of 767 scans failed. Thus, scan failure rates were reduced by approximately 26%. Funding for this study was provided by Perceptive Informatics. [Presentation title: Whole Body DXA Pre-screening Tool Reduces Screen-Failure Rates in a Large Multicenter Trial. Abstract MO0276]
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