Diagnostic accuracy and interobserver variability of CO-RADS in patients with suspected coronavirus disease-2019: a multireader validation study

Abstract

Objective: To conduct a multireader validation study to evaluate the interobserver variability and the diagnostic accuracy for the lung involvement by COVID-19 of COVID-19 Reporting and Data System (CO-RADS) score.

Methods: This retrospective study included consecutive symptomatic patients who underwent chest CT and reverse transcriptase-polymerase chain reaction (RT-PCR) from March 2020 to May 2020 for suspected COVID-19. Twelve readers with different levels of expertise independently scored each CT using the CO-RADS scheme for detecting pulmonary involvement by COVID-19. Receiver operating characteristic (ROC) curves were computed to investigate diagnostic yield. Fleiss' kappa statistics was used to evaluate interreader agreement.

Results: A total of 572 patients (mean age, 63 ± 20 [standard deviation]; 329 men; 142 patients with COVID-19 and 430 patients without COVID-19) were evaluated. There was a moderate agreement for CO-RADS rating among all readers (Fleiss' K = 0.43 [95% CI 0.42-0.44]) with a substantial agreement for CO-RADS 1 category (Fleiss' K = 0.61 [95% CI 0.60-0.62]) and moderate agreement for CO-RADS 5 category (Fleiss' K = 0.60 [95% CI 0.58-0.61]). ROC analysis showed the CO-RADS score ≥ 4 as the optimal threshold, with a cumulative area under the curve of 0.72 (95% CI 66-78%), sensitivity 61% (95% CI 52-69%), and specificity 81% (95% CI 77-84%).

Conclusion: CO-RADS showed high diagnostic accuracy and moderate interrater agreement across readers with different levels of expertise. Specificity is higher than previously thought and that could lead to reconsider the role of CT in this clinical setting.

Key points: • COVID-19 Reporting and Data System (CO-RADS) demonstrated a good diagnostic accuracy for lung involvement by COVID-19 with an average AUC of 0.72 (95% CI 67-75%). • When a threshold of ≥ 4 was used, sensitivity and specificity were 61% (95% CI 52-69%) and 81% (95% CI 76-84%), respectively. • There was an overall moderate agreement for CO-RADS rating across readers with different levels of expertise (Fleiss' K = 0.43 [95% CI 0.42-0.44]).

Keywords: COVID-19; ROC curve; Sensitivity and specificity; Severe acute respiratory syndrome coronavirus 2; Tomography, X-ray computed.

Fig. 1

Study flowchart for the inclusion and exclusion criteria of the patient sample and CO-RADS ratings. Note: CO-RADS, COVID-19 Reporting and Data System; COVID-19, coronavirus disease-2019; RT-PCR, reverse transcriptase-polymerase chain reaction; PCR+, single or multiple RT-PCR testing positive for SARS-CoV-2 infection; mPCR−, multiple negative RT-PCR testing; sPCR-/FU-, single negative RT-PCR testing and negative follow-up during the 14 days following the CT scan

Fig. 2

Receiver operating characteristic curve of high-experience group (a), intermediate-experience group (b), low-experience group (c), and group of radiographers (d) for predicting lung involvement by coronavirus disease-2019 using the COVID-19 Reporting and Data System (CO-RADS). Note: AUC, area under the curve

Fig. 3

Distribution of final diagnosis among each cumulative CO-RADS score category. Red columns show the percentage of patients with positive RT-PCR (PCR+), dark green columns show the percentage of patients with multiple negative RT-PCR (mPCR−), and light green columns show the percentage of patients with initial negative RT-PCR and negative clinical follow-up the 14 days after CT scan (sPCR-/FU-). Note: CO-RADS, COVID-19 Reporting and Data System

Fig. 4

Pictorial overview portraying axial chest CT images from our study population illustrating imaging findings characteristics of the CO-RADS 1 (a, b), CO-RADS 2 (c, d), CO-RADS 3 (e, f), CO-RADS 4 (g, h), and CO-RADS 5 (i, j, k, l) scores and their corresponding descriptions. Note: CO-RADS, COVID-19 Reporting and Data System