Screening performance of sternal CT attenuation for opportunistic osteoporosis

Osteoporosis represents a major global public health problem, yet it remains substantially underdiagnosed. Although dual-energy X-ray absorptiometry (DXA) is considered the clinical gold standard for bone mineral density (BMD) assessment, its routine use for population-based screening is limited. As an alternative, the use of routine computed tomography (CT) for opportunistic screening has emerged as a promising approach. This study aims to evaluate the feasibility of utilizing sternal CT values (Hounsfield units, HU) from chest CT scans to assess osteoporosis.

This retrospective study included 145 patients aged ≥ 50 years who underwent chest CT and DXA within a one-month interval. CT HU values were measured at the upper, middle, and lower levels of the sternum by three independent observers. Inter-observer reliability was assessed using intraclass correlation coefficients (ICC). Correlations between sternal CT values, T-score, age, and body mass index (BMI) were analyzed using Pearson correlation. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic performance of sternal CT HU values for identifying osteoporosis.

Significant positive correlations were observed between sternal CT HU values and DXA T-score at all measured levels (r > 0.506, P < 0.01), with the mean sternal CT value exhibiting the strongest association (r = 0.632). Inter-observer agreement was excellent across all sternal levels (ICC range: 0.926-0.980). Moreover, ROC analysis revealed that the lower sternal level provided the best diagnostic performance for osteoporosis, with an area under the curve (AUC) of 0.8712 (95% CI: 0.8128-0.9296). An optimal cutoff value of 64.90 HU was identified, with a sensitivity of 80.9% and a specificity of 85.7%.

Sternal CT HU values measured on chest CT scans are significantly correlated with DXA-measured BMD. In particular, measurements at the lower sternal level showed the best diagnostic performance and may serve as a potential supplementary tool for opportunistic osteoporosis screening in elderly patients.