Comparison of Chest CT Findings of COVID-19, Influenza, and Organizing Pneumonia: A Multireader Study
AJR Am J Roentgenol . 2021 Apr 14. doi: 10.2214/AJR.21.25640. Online ahead of print.
Sherief H Garrana, Avik Som, Gabrielle S Ndakwah, Tristan Yeung, Jennifer Febbo, Allen P Heeger, Min Lang, Shaunagh McDermott, Dexter P Mendoza, Eric W Zhang, Amita Sharma, Anand K Narayan, Brent P Little
Background: Previous studies have compared CT findings of COVID-19 pneumonia with those of other infections; however, to our knowledge, no studies have included non-infectious organizing pneumonia (OP) as a comparison group.
Objective: To compare chest CT features of COVID-19, influenza, and OP using a multireader design, and to assess radiologists' performance in distinguishing between these conditions.
Methods: This retrospective study included 150 chest CT examinations in 150 patients (mean age 58±16 years) with diagnosis of COVID-19, influenza, or non-infectious OP (50 randomly selected abnormal CT examinations per diagnosis). Six thoracic radiologists independently assessed CT examinations for 14 individual CT findings and Radiologic Society of North America (RSNA) COVID-19 category and recorded a favored diagnosis. CT characteristics of the three diagnoses were compared using random effects models; readers' diagnostic performance was assessed.
Results: COVID-19 pneumonia was significantly different (p<.05) from influenza pneumonia for seven of 14 chest CT findings, though different (p<.05) from OP for 4 of 14 findings [central or diffuse distribution in 10% and 7% of COVID-19 vs 20% and 21% of OP; unilateral distribution in 1% of COVID-19 vs 7% of OP; non-tree-in-bud nodules in 32% of COVID-19 vs 53% of OP; tree-in-bud nodules in 6% of COVID-19 vs 14% of OP]. A total of 70% of cases of COVID-19, 33% of influenza, and 47% of OP had an RSNA COVID-19 category of typical (p<.001). Mean percentage of correct favored diagnoses compared to actual diagnoses was 44% for COVID-19, 29% for influenza, and 39% for OP. Mean diagnostic accuracy of favored diagnoses was 70% for COVID-19 pneumonia and 68% for both influenza and OP.
Conclusion: CT findings of COVID-19 substantially overlap with influenza and, to a greater extent, with OP. Radiologists' diagnostic accuracy was low in a study sample containing equal proportions of these three types of pneumonia.
Clinical Impact: Recognized challenges in diagnosing COVID-19 by CT are furthered by our observed strong overlap between CT appearances of COVID-19 and OP. This challenge may be particularly evident in clinical settings with substantial proportions of patients with potential causes of OP such as ongoing cancer therapy or autoimmune conditions.
Read Full Article Here: https://doi.org/10.2214/ajr.21.25640