CT colonography—aka ‘virtual colonoscopy’—can also screen for osteoporosis

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 - elderly woman

Close to 70 percent of aging women at risk of osteoporosis don’t bother to have their bone density checked with the current clinical standard, dual-energy x-ray absorptiometry (DXA).

Why would they? Symptoms generally don’t present until the condition is serious, hip fracture being the most devastating consequence. Plus, screening programs have likely decreased as reimbursements have fallen.

Good news comes from a study in  Radiology acknowledging those realities and showing that CT colonography (CTC) scans—also known as “virtual colonoscopy”—are quite good at revealing not only polyps in the colon but also weakening of strength and mineral density in the bones.

In fact, the study authors, led by Jeff Fidler, MD, a Mayo Clinic radiologist, conclude that biomechanical analysis of CTC for colorectal screening “provides a comprehensive osteoporosis assessment without requiring changes in imaging protocols.”

Fidler and colleagues arrived at that by retrospectively comparing CTC and DXA in 136 women aged 43 and older who underwent both of those exams within a 6-month period.

Blinded to the DXA data, clinicians applied biomechanical analysis of the CTC images to measure bone mineral density and bone strength in the neck, spine and hip.

The researchers found that, for bone mineral density T scores at the femoral neck, the CTC readings highly correlated with those from the DXA (R 2 = 0.84), revealing osteoporosis with 100 percent sensitivity in eight of eight patients and 98.4 percent specificity in 126 of 128 patients.

The results with hip and spine interpretations weren’t quite as precise, but they were still impressive.

Here patients deemed to be at high risk of fracture in biomechanical CT analysis—the women previously diagnosed through DXA with osteoporosis or “fragile bone strength”—correlated with those who received DXA diagnoses to the tune of 82.8 percent sensitivity in 24 of 29 patients and 85.7 percent specificity in 66 of 77 patients (T score ≤−2.5 at the hip or spine).

The authors noted as limitations the study’s retrospective nature, its inclusion of only women and its small sample size.

They write that the current study builds on previous work showing that biomechanical CT analysis can be used to identify patients who don’t have osteoporosis but are nevertheless at elevated risk for fractures. The  study they cite compared DXA with CT enterography for patients with inflammatory bowel disease.

Such procedures use intravenous contrast material, the authors point out, “which prevents application of the test to the spine. Overcoming that limitation, the purpose of this [CTC] study was to retrospectively evaluate the ability of additional analysis of CT colonography to provide a comprehensive osteoporosis assessment.”

The scientific details of the promising results can be explored ahead of print here.