Opportunistic screening for osteoporosis on routine computed tomography? An external validation study

OBJECTIVES: Opportunistic screening for osteoporosis using computed tomography (CT) examinations that happen to visualise the spine can be used to identify patients with osteoporosis. We sought to verify the diagnostic performance of vertebral Hounsfield unit (HU) measurements on routine CT examinations for diagnosing osteoporosis in a separate, external population.

METHODS: Consecutive patients who underwent a CT examination of the chest or abdomen and had also received a dual-energy X-ray absorptiometry (DXA) test were retrospectively included. CTs were evaluated for vertebral fractures and vertebral attenuation (density) values were measured. Diagnostic performance measures and the area under the receiver operator characteristics curve (AUC) for diagnosing osteoporosis were calculated.

RESULTS: Three hundred and two patients with a mean age of 57.9 years were included, of which 82 (27%) had osteoporosis according to DXA and 65 (22%) had vertebral fractures. The diagnostic performance for vertebral HU measurements was modest, with a maximal AUC of 0.74 (0.68 - 0.80). At that optimal threshold the sensitivity was 62% (51 - 72%) and the specificity was 79% (74 - 84%).

CONCLUSIONS: We confirmed that simple trabecular vertebral density measurements on routine CT contain diagnostic information related to bone mineral density as measured by DXA, albeit with substantially lower diagnostic accuracy than previously reported.

KEY POINTS: • We externally validated the value of vertebral trabecular bone attenuation for osteoporosis • These diagnostic performance measures were, however, substantially lower than previously reported • This information might be useful when considering the implementation of opportunistic osteoporosis screening.