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15-04-2013 | Radiology | Article

Incidental CT could boost osteoporosis detection

Abstract

Free abstract

medwireNews: Patients undergoing abdominal computed tomography (CT) could be assessed for incidental osteoporosis of the lumbar spine, US researchers say.

The team from the University of Wisconsin in Madison believes that opportunistic CT imaging could allow osteoporosis to be detected in patients undergoing CT for other reasons without extra cost, imaging, radiation exposure, or patient time.

Their study of 1867 adults who underwent bone mineral density (BMD) assessment using both CT and dual-energy X-ray absorptiometry (DXA) within 6 months shows that CT attenuation values were significantly lower at the T12 through L5 vertebrae for patients with osteoporosis on DXA than patients with a healthy BMD.

Indeed, a CT-attenuation threshold of160 HU or less at the L1 vertebrae was 99% sensitive for osteopenia, while a threshold of 110 HU achieved 90% specificity for differentiating between patients with osteopenia and those with a healthy BMD.

For osteoporosis, a CT-attenuation threshold below 100 HU gave a positive predictive value of at least 68%, while a 200 HU or above threshold gave a negative predictive value of 99%.

Of note, 119 patients had one or more moderate-to-severe vertebral fractures, but 52.1% of these patients had a false-negative DXA score for osteoporosis and 97% had a L1 or T12 to L5 vertebral attenuation of 145 HU or below.

"Our observations are consistent with prior studies documenting that many patients without osteoporosis diagnosed by DXA will sustain fragility fractures and suggest that CT attenuation may be a more accurate risk indicator," comment Perry Pickhardt and co-authors in the Annals of Internal Medicine.

Writing in an accompanying editorial, Sumit Majumdar (University of Alberta, Edmonton, Canada) and William Leslie (University of Manitoba, Winnipeg, Canada) note that although clinically significant incidental findings are frequently reported on CT scans, the majority of reports are not acted on.

The commentators therefore suggest that any referral strategy for osteoporosis should have a low tolerance for false-positive results, so to minimize testing cascades, additional radiation, and patient "hassle."

"Pickhardt and associates have laid all the groundwork needed to justify using conventional CT imaging to detect incidental osteoporosis-it is now up to the rest of us to safely and cost-effectively translate this new knowledge into everyday clinical practice," they conclude.

medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013

By Lynda Willams, Senior medwireNews Reporter

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