Diagnostic Accuracy of North America Expert Consensus Statement on Reporting CT Findings in Patients Suspected of Having COVID-19 Infection: An Italian Single-Center Experience

Abstract

Purpose In suspected COVID-19, Real-Time Polymerase Chain Reaction (RT-PCR) is the reference standard but affected by long reporting time (6-48 hours); the aim of the study was to evaluate the diagnostic accuracy of the four standardized categories for CT reporting proposed by Radiological Society of North America (RSNA) to support a faster triage. Materials and Methods Retrospective analysis of 569 HRCT performed for suspected COVID-19 from February 27 to March 27, 2020 (peak of infection in Italy). Imaging pattern was classified according to RSNA statement in “typical”, “indeterminate”, “atypical” and “negative” and compared to RT-PCR, available in 460 patients. Inter-observer variability in reporting between a senior and a junior radiologist was evaluated. Utility of vascular enlargement sign in indeterminate cases, was also assessed. Results Diagnosis of COVID-19 was made in 211/460 patients (45.9%). “Typical” pattern (n=172) showed a sensitivity of 71.6%, a specificity of 91.6% and a Positive Predictive Value (PPV) of 87.8% for COVID-19. “Atypical” (n=67) and “negative” (n=123) pattern demonstrated PPV of 89.6% and 86.2% for non COVID-19. “Indeterminate” (n=98) was non-specific, but vascular enlargement was most frequently found in patients with COVID-19 (86.1%- p<0.001). Inter-observer agreement was good for “typical” and “negative” pattern, fair for “indeterminate” and “atypical” (k=0.5, p=0.002). Conclusion In an epidemic setting, application of the four categories proposed by RSNA provides a standardized diagnostic hypothesis, strongly linked to the RT-PCR results for “typical”, “atypical” and “negative” pattern. In “indeterminate” pattern, the analysis of vascular enlargement sign could facilitate the interpretation of imaging features.