Detection of anemia based on blood attenuation cutoff value of combined cardiovascular structures using non-contrast chest CT

Luis G. Garcia-Armas, Department of Imaging, Hospital General Regional No.1, Instituto Mexicano del Seguro Social, Tijuana, Baja California, Mexico;
Omar Rebollar-Garay, Department of Imaging, Hospital General Regional No.1, Instituto Mexicano del Seguro Social, Tijuana, Baja California, Mexico;

Introduction: Low blood attenuation, measured in Hounsfield units (HU) on non-contrast chest computed tomography (CT), has been proposed as an imaging marker of anemia. This study evaluated the correlation between blood attenuation (HU) on non-contrast chest CT and serum hemoglobin levels, and determined the optimal HU cutoff value, based on a combined assessment of multiple cardiovascular structures, for detecting anemia in adult patients. Material and methods: This casecontrol study included adult patients who underwent non-contrast chest CT and a complete blood count within 24 hours. A region of interest (ROI) was defined in five cardiovascular structures – the ascending aorta, aortic arch, descending aorta, and the left and right ventricles – to measure blood attenuation. Correlation analyses and ROC curves were calculated to assess performance metrics for each structure and for the combined cardiovascular structures. Results: Eighty-eight patients were included: 44 with anemia and 44 controls with normal serum hemoglobin. Mean hemoglobin levels were 9.5 ± 1.7 and 13.7 ± 1.3 g/dL, respectively (p < 0.001). A significant positive correlation was observed between blood attenuation and serum hemoglobin across all cardiovascular structures (Spearman’s ρ = 0.697-0.817; p < 0.001). In the ROC curve analysis, a blood attenuation cutoff ≤ 38.0 HU in at least three of five cardiovascular structures showed high diagnostic performance for detecting anemia, with sensitivities of 77.3% to 86.4%, specificities of 93.2% to 100%, and accuracies of 71.6% to 85.2%. Moreover, diagnostic performance increased progressively with anemia severity. Conclusions: A cutoff value ≤ 38 HU based on combined blood attenuation measurements in at least three of five cardiovascular structures on non-contrast chest CT is a simple and reliable method for detecting anemia; the diagnostic performance of this cutoff value increases in direct proportion to anemia severity.

Keywords: Anemia. Chest tomography. Cardiovascular structures. Hemoglobin. Diagnostic imaging.