Cardiac CT Scans Can Be Used for Osteoporosis Screening

Steve Cimino

July 14, 2020

A new study has determined a benefit of cardiac CT scans beyond assessing heart health: Evaluating fracture rate and potential osteoporosis through the bone mineral density (BMD) of thoracic vertebrae.

"Our results represent a step toward appraisal and recognition of the clinical utility of opportunistic BMD screening from cardiac CT," wrote Josephine Therkildsen, MD, of Hospital Unit West in Herning, Denmark, and coauthors. The study was published July 14 in Radiology.

To determine if further analysis of cardiac CT could help determine BMD and its association with fracture rate, the investigators launched a prospective observational study of 1,487 Danish patients with potential coronary artery disease who underwent cardiac CT scans between September 2014 and March 2016. Their mean age was 57 years (standard deviation, 9; range, 40-80). Nearly all of the patients were white, and 52.5% (n = 781) were women.

All participants underwent a noncontrast-enhanced cardiac CT, from which volumetric BMD of three thoracic vertebrae was measured via commercially available semiautomatic software. Their mean BMD was 119 mg/cm3 (SD, 34) with no significant difference noted between male and female patients. Of the 1,487 participants, 695 were defined as having normal BMD (> 120 mg/cm3), 613 as having low BMD (80-120 mg/cm3), and 179 as having very low BMD (< 80 mg/cm3). Median follow-up was 3.1 years (interquartile range, 2.7-3.4).

Incident fracture occurred in 80 patients (5.4%), of whom 48 were women and 32 were men. Patients who suffered fractures were significantly older than patients with no fractures (mean 59 years vs. 57 years; P = .03). Of the 80 patients with fractures, 31 were osteoporosis related.

In an unadjusted analysis, participants with very low BMD had a greater rate of any fracture (hazard ratio [HR], 2.6; 95% confidence interval, 1.4-4.7; P = .002) and of osteoporosis-related fracture (HR, 8.1; 95% CI, 2.4-27.0; P = .001). After adjustment for age and sex, their rates remained significantly greater for any fracture (HR, 2.1; 95% CI, 1.1-4.2; P = .03) and for osteoporosis-related fracture (HR, 4.0; 95% CI, 1.1-15.0; P = .04).

"Opportunistic" Use of Scans Benefits Both Physicians and Patients

"The concept of using a CT scan that was done for a different purpose allows you to be opportunistic," Ethel S. Siris, MD, the Madeline C. Stabile Professor of Clinical Medicine in the department of medicine at Columbia University and director of the Toni Stabile Osteoporosis Center of the Columbia University Medical Center, New York–Presbyterian Hospital, New York, said in an interview. "If you're dealing with older patients, and if you have the software for your radiologist to use to reanalyze the CT scan and say something about the bone, it's certainly a way of estimating who may be at risk of future fractures.

Dr Ethel Siris

"From a practical point of view, it's hard to imagine that it would ever replace conventional bone mineral density testing via DXA [dual-energy x-ray absorptiometry]," she added. "That said, osteoporosis is woefully underdiagnosed because people don't get DXA tested. This study showed that, if you have access to the scan of the thoracic or even the lumbar spine and if you have the necessary software, you can make legitimate statements about the numbers being low or very low. What that would lead to, I would hope, is some internists to say, 'This could be a predictor of fracture risk. We should put you on treatment.' And then follow up with a conventional DXA test.

"Is that going to happen? I don't know. But the bottom line of the study is: Anything that may enhance the physician's drive to evaluate a patient for fracture risk is good."

Whatever the Reason for the Scan, CT Can Help Diagnose Osteoporosis

This study reinforces that CT exams — of the chest, in particular — can serve a valuable dual purpose as osteoporosis screenings, Miriam A. Bredella, MD, professor of radiology at Harvard Medical School and vice chair of the department of radiology at Massachusetts General Hospital, Boston, wrote in an accompanying editorial.

Dr Miriam Bredella

"In the United States, more than 80 million CT examinations are performed each year, many of which could be used to screen for osteoporosis without additional costs or radiation exposure," she wrote. And thanks to the findings of the study by Therkildsen et al., which relied on both established and new BMD thresholds, the link between thoracic spine BMD and fracture risk is clearer than ever.

"I hope this study will ignite interest in using chest CT examinations performed for other purposes, such as lung cancer screening, for opportunistic osteoporosis screening and prediction of fractures in vulnerable populations," she added.

The authors acknowledged their study's limitations, including a small number of fracture events overall and the inability to evaluate associations between BMD and fracture rate at specific locations. In addition, their cohort was largely made up of white participants with a certain coronary artery disease risk profile; because of ethnical differences in BMD measurements, their results "cannot be extrapolated to other ethnical groups."

Several of the study's authors reported potential conflicts of interest, including receiving grants and money for consultancies and board memberships from various councils, associations, and pharmaceutical companies. Dr. Bredella reported no conflicts of interest. Dr. Siris has no relevant disclosures.

SOURCE: Therkildsen J et al. Radiology. 2020 Jul 14. doi: 10.1148/radiol.2020192706.

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