Evaluating anemia on non-contrast thoracic computed tomography

Anemia is a major global disease burden factor linked to an adverse impact on overall prognosis and negatively affects the quality of life. There are some suggested findings for anemia on non-contrast chest CT, like relatively dense interventricular septum (septal sign) or fairly dense aortic wall (aortic ring sign). The measured attenuation value is a reproducible physical density measurement, readily obtainable from a standard CT examination. There is no reliable cut-off for blood attenuation to suggest anemia on the non-contrast chest CT. In the current study, we evaluated subjective and objective criteria' diagnostic accuracy for diagnosing anemia on unenhanced thoracic CT. This study is approved by Mashhad University of Medical Sciences. The patients admitted in the internal medicine ward of our hospital from June 2019 to March 2020 for whom a non-contrast chest CT was acquired for any non-traumatic medical indication, were enrolled in this retrospective study. For the subjective assessment, the radiologists were asked to record the presence or absence of the "aortic ring sign" and "interventricular septum sign". For the objective evaluations, blood density was measured at various anatomic locations. A total of 325 patients were included in this study. There was a significant correlation between blood attenuation in all measured segments and Hb level (0.78 (R²: 0.61), p = 0.000). Findings revealed that considering the aortic arch threshold value as 20 HU is the best diagnostic performance for detecting severe anemia. Subjective analysis revealed that the aortic ring sign was more sensitive (82.5%) than the interventricular septum sign (32%) in detecting anemia, whereas the latter character was more specific (87% and 99.2%, respectively). The results suggest that it is possible to detect anemia from an unenhanced chest CT scan. Both objective and subjective criteria show promising sensitivity and specificity.