CO-RADS: A Categorical CT Assessment Scheme for Patients Suspected of Having COVID-19—Definition and Evaluation

Abstract

statement Reporting and Data System, is a categorical assessment scheme for chest CT in patients suspected of COVID-19, representing the level of suspicion for pulmonary involvement. The substantial agreement among observers and its discriminatory value make it well-suited for use in clinical practice. Key results• CO-RADS, for COVID-19 Reporting and Data System, provides a standardized assessment scheme that simplifies reporting with a five-point scale of suspicion for pulmonary involvement of COVID-19 on chest CT • CO-RADS has a moderate to substantial agreement among observers with an overall Fleiss' kappa of 0.47 (95% CI 0.45-0.49).• The discriminatory power of CO-RADS for diagnosing COVID-19 was high, with a mean area under the ROC curve of 0.91 (95% CI 0.85-0.97) for positive RT-PCR results. AbbreviationsRT-PCR: reverse transcriptase-polymerase chain reaction. ROC: receiver operating characteristics. AUC: area under the ROC curve. CI: confidence interval. CT: computed tomography. IQR: interquartile range. Abstract PurposeTo introduce the COVID-19 Reporting and Data System (CO-RADS) for standardized assessment of pulmonary involvement of COVID-19 on non-enhanced chest CT and report its initial interobserver agreement and performance. MethodsThe Dutch Radiological Society (NVvR) developed CO-RADS based on other efforts for standardization, such as Lung-RADS or BI-RADS. CO-RADS assesses the suspicion for pulmonary involvement of COVID-19 on a scale from 1 (very low) to 5 (very high). The system is meant to be used in patients presenting with moderate to severe symptoms of COVID-19. The system was evaluated using 105 chest CTs of patients admitted to the hospital with clinical suspicion of COVID-19 in whom RT-PCR was performed (62 +/-16 years, 61 men, 53 with positive RT-PCR). Eight observers assessed the scans using CO-RADS. Fleiss' kappa was calculated, and scores of individual observers were compared to the median of the remaining seven observers. The resulting area under the receiver operating characteristics curve (AUC) was compared to results from RT-PCR and clinical diagnosis of COVID-19. ResultsThere was absolute agreement among observers in 573 (68.2%) of 840 observations. Fleiss' kappa was 0.47 (95% confidence interval (CI) 0.45-0.47), with the highest kappa for CO-RADS categories 1 (0.58, 95% CI 0.54-0.62) and 5 (0.68, 95% CI 0.65-0.72). The average AUC was 0.91 (95% CI 0.85-0.97) for predicting RT-PCR outcome and 0.95 (95% CI 0.91-0.99) for clinical diagnosis. The false negative rate for CO-RADS 1 was 9/161 (5.6%, 95% CI 1.0-10%), and the false positive rate for CO-RADS 5 was 1/286 (0.3%, 95% CI 0-1.0%). ConclusionsCO-RADS is a categorical assessment scheme for pulmonary involvement of COVID-19 on non-enhanced chest CT providing very good performance for predicting COVID-19 in patients with moderate to severe symptoms and has a substantial interobserver agreement, especially for categories 1 and 5.

Chest CT features of the novel coronavirus disease (COVID-19)

“…However, the groups in this classification are based on the results obtained from a systematic review, and clinical success and applicability of this classification are unknown. Recently, the Dutch Radiological Society defined a new classification (CO-RADS) for pulmonary involvement in cases presenting with moderate to severe symptoms of COVID-19 [51]. In this standardized assessment (CO-RADS), a substantial agreement was found among 8 observers (Fleiss' kappa of 0.47, 95% CI 0.45-0.49) and the discriminatory power of the CO-RADS for diagnosing COVID-19 was high (with an area under the curve value of 0.91, 95% CI 0.85-0.97).…”

“…In this standardized assessment (CO-RADS), a substantial agreement was found among 8 observers (Fleiss' kappa of 0.47, 95% CI 0.45-0.49) and the discriminatory power of the CO-RADS for diagnosing COVID-19 was high (with an area under the curve value of 0.91, 95% CI 0.85-0.97). Therefore, the authors stated that CO-RADS is very suitable for use in clinical practice [51] (Table 4).…”

“…The proposed CO-RADS categories and the corresponding level of suspicion for pulmonary involvement in COVID-19[51].…”

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“…Further assuming a sensitivity of RT-PCR of 70% in throat swabs in COVID-19 patients and a prevalence of [11]. Based on the experience of our interim analysis we developed a clinically based COVID-19 rating and diagnosis system (clinCO-RADS).…”

“…COVID-19 was diagnosed clinically based on history, examination, and ndings in particular laboratory values and chest CT. Previuos ndings such as SARS-CoV-2 PCR results were recorded and used for clinical COVID-19 diagnosis only. According to CO-RADS, which provides a standardized assessment scheme with a ve-point scale of suspicion for pulmonary involvement of COVID-19 on chest CT [11], we developed the clinical COVID-19 Rating And Diagnosis System (clinCO-RADS) with a ve-point scale for level of suspicion from "very low" and "low" to "high" and "very high". In between we de ned "intermediate" for cases otherwise classi ed "very low" or "low", if any PCR result for COVID-19 was positive.…”