February 27, 2019
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Biomechanical CT cost-effective alternative to DXA for osteoporosis screening

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Among older adults who undergo an abdominal CT scan, an osteoporosis screening that uses biomechanical CT data may serve as a cost-effective alternative to usual care, particularly as DXA screening rates remain low, according to findings from a modeling analysis published in the Journal of Bone and Mineral Research.

According to U.S. Medicare data, only 9.5% of women and 1.7% of men aged at least 65 years undergo a recommended bone mineral density test via DXA scan, and the sensitivity of traditional DXA for predicting fracture is modest, Maria Pisu, PhD, associate professor of medicine at the University of Alabama at Birmingham, and colleagues wrote in the study background. As an alternative, finite element analysis of clinical-resolution CT scans could provide noninvasive estimates of the breaking strength of the hip and spine, the researchers wrote. Combining that measurement with a CT-based measurement of a DXA-equivalent BMD T-score could provide a more comprehensive assessment of osteoporosis vs. using bone strength or BMD alone, they noted.

“Thus, in any managed care system, it is highly feasible for ancillary [biomechanical] CT to be offered in a standing-order fashion to all screen-eligible patients undergoing abdominal or hip-containing CT when an osteoporosis screen is medically indicated,” Pisu and colleagues wrote. “With many millions of abdominal CT scans taken annually, such standing-order [biomechanical] CT-based screening in managed care systems could be clinically impactful if exploited for patients already undergoing CT — while continuing to rely on usual-care screening for all other patients.”

Pisu and colleagues analyzed data from a hypothetical cohort of 1,000 women and men aged at least 65 years who received an abdominal CT (in year 1) for any medical reason who did not undergo a recent DXA scan and were not taking an osteoporosis medication.

In analyses stratified by sex, the researchers compared two screening strategies: participation in the biomechanical CT program or usual care. Under the biomechanical CT strategy, all patients undergo a biomechanical CT test at year 1, with patients testing positive classified as high risk and eligible for 2 years of alendronate therapy. Researchers assumed for analyses that 50% of patients prescribed treatment filled prescriptions and were 100% adherent to therapy over 2 years.

Under the usual care strategy, the 1,000 patients were assumed to be screened by DXA each year at typical annual screening rates observed for Medicare patients aged at least 65 years — 9.5% for women and 1.7% for men. Other parameters were similar to the biomechanical CT strategy. For simplicity of modeling, researchers focused only on hip fractures. Researchers also assessed no screening and no treatment to calculate the absolute number of prevented hip fractures.

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The researchers found that biomechanical CT provided a greater clinical benefit at a lower cost vs. usual care. In the base model, biomechanical CT prevented 3.1 hip fractures per 1,000 women over 5 years and 1.9 hip fractures per 1,000 men over 5 years, and increased quality-adjusted life-years (2.95 per 1,000 women; 1.48 per 1,000 men), whereas usual care prevented 2.4 hip fractures per 1,000 women and 0.2 per 1,000 men over 5 years.

“Efficacy and savings increased further for higher-risk patient pools, greater treatment adherence and longer treatment duration,” the researchers wrote.

In analysis adjusting the sensitivity and specificity of biomechanical CT to parallel DXA measurements, the number of prevented hip fractures fell to 2.7 per 1,000 women and 1.5 per 1,000 men over 5 years.

The researchers noted that the findings are theoretical, although the results for clinical efficacy are consistent with available real-world clinical data.

“One large driver of overall cost-effectiveness is the cost of treating hip and other fractures that would otherwise occur without the screening and treatment program,” the researchers wrote. “Our effective total care cost of $50,000 during the first year after hip fracture is supported by numerous studies and may even be conservative.”

The researchers concluded that biomechanical CT screening results should go to the health care professional who ordered the test and who is charged with interpreting the results, and followed up with patient care.

“Since millions of patients age 65 and older already undergo abdominal CT each year in the U.S., the current results suggest that use of ancillary [biomechanical] CT may have a positive impact on the management of osteoporosis,” the researchers wrote. – by Regina Schaffer

Disclosures: Pisu reports she has received salary support paid to her institution via an NIH grant awarded to O.N. Diagnostics. Please see the study for all other authors’ relevant financial disclosures.