Evaluation of the RSNA and CORADS classifications for COVID-19 on chest computed tomography in the Brazilian population

Abstract

Objective: To determine the correlation between the two tomographic classifications for coronavirus disease (COVID-19), COVID-19 Reporting and Data System (CORADS) and Radiological Society of North America Expert Consensus Statement on Reporting Chest Computed Tomography (CT) Findings Related to COVID-19 (RSNA), in the Brazilian population and to assess the agreement between reviewers with different experience levels.

Methods: Chest CT images of patients with reverse transcriptase-polymerase chain reaction (RT-PCR)-positive COVID-19 were categorized according to the CORADS and RSNA classifications by radiologists with different levels of experience and who were initially unaware of the RT-PCR results. The inter- and intra-observer concordances for each of the classifications were calculated, as were the concordances between classifications.

Results: A total of 100 patients were included in this study. The RSNA classification showed an almost perfect inter-observer agreement between reviewers with similar experience levels, with a kappa coefficient of 0.892 (95% confidence interval [CI], 0.788-0.995). CORADS showed substantial agreement among reviewers with similar experience levels, with a kappa coefficient of 0.642 (95% CI, 0.491-0.793). There was inter-observer variation when comparing less experienced reviewers with more experienced reviewers, with the highest kappa coefficient of 0.396 (95% CI, 0.255-0.588). There was a significant correlation between both classifications, with a Kendall coefficient of 0.899 (p<0.001) and substantial intra-observer agreement for both classifications.

Conclusion: The RSNA and CORADS classifications showed excellent inter-observer agreement for reviewers with the same level of experience, although the agreement between less experience reviewers and the reviewer with the most experience was only reasonable. Combined analysis of both classifications with the first RT-PCR results did not reveal any false-negative results for detecting COVID-19 in patients.

Figure 1. Schematic representation of the RSNA classification. The upper left image shows “typical” CT findings of COVID-19 with multifocal rounded ground-glass opacities. The lower left image shows an “indeterminate” CT findings of COVID-19 with perihilar bilateral opacities and a lack of “typical” tomographic findings. The lower right image shows “atypical” CT findings of COVID-19 with lower lobe consolidation and bilateral “tree-in-bud” images. The upper right image shows “negative” CT findings without signs of infection. COVID-19, Coronavirus disease; CT, computed tomography; RSNA, Radiological Society of North America.

Figure 2. Schematic representation of the CORADS classification. The upper left image shows CORADS-1 CT findings without signs of infection but shows interlobular septa thickening, suggesting lung congestion. The upper right image shows CORADS-2 CT findings, with extensive consolidation of the right upper lobe with areas of cavitation. There is also widespread lung emphysema. The central image shows CORADS-3 CT findings, with diffuse ground-glass opacities. The lower right image shows CORADS-4 CT findings, with peripheral bilateral ground-glass opacities in a patient with emphysema. The lower left image shows CORADS-5 CT findings, with peripheral bilateral ground-glass opacities. CORADS, COVID-19 reporting and data system; CT, computed tomography.