Fig 1.
Flow diagram for patients’ inclusion.
A total of 80 patients with COVID-19 were retrospectively included from four institutions, while 92 patients without COVID-19 were included from single institution. Among patients with COVID-19, 67 exhibited findings of pneumonia on chest CT obtained within 24 hours from CXR, while the other 13 patients did not exhibited any findings of pneumonia on chest CT.
Fig 2.
Representative case with COVID-19 pneumonia.
A CXR (A) of a patient with confirmed COVID-19 shows patchy infiltrates in both lower lung fields (arrows). The corresponding chest CT image (B) obtained in the same day with the CXR shows multifocal patchy ground-glass opacities in both lower lobes of the lung. The CT severity score of the patient was 13. The CAD system correctly detected pulmonary infiltrates with a probability score of 56% (C). In the reader-alone interpretation, four thoracic radiologists correctly identified the abnormality while none of the non-radiologist physicians identified the abnormality. In the CAD-assisted interpretation, all five thoracic radiologists and four non-radiologist physicians identified the abnormality.
Fig 3.
Representative case without COVID-19 pneumonia.
A CXR (A) and corresponding chest CT (B) of a patient with fever and dyspnea but negative RT-PCR result for COVID-19 show no pulmonary abnormality suggestive of pneumonia. The CAD system did not detect any abnormalities in the CXR and the probability score was 13% (C). In the reader-alone interpretation, four thoracic radiologists and four non-radiologist physicians misclassified the CXR as having findings of pneumonia. In the CAD-assisted interpretation, only one thoracic radiologist and two non-radiologist physicians made false-positive classification of the CXR. Mediastinal window CT image (D) show pulmonary embolism in the right descending pulmonary artery (arrow), presumed cause of patients’ symptom.
Table 1.
Clinical and radiological information of patients.
Fig 4.
Performance of the CAD versus reader-alone interpretations.
For identification of RT-PCR-positive COVID-19 patients (A), the CAD exhibited AUC of 0.714 (black line), which did not significantly differ from that of thoracic radiologists (0.701, blue line) but significantly higher than that of non-radiologist physicians (0.584, red line). For identification of pneumonia defined on chest CT (B), the CAD exhibited AUC of 0.790 (black line), which was not significantly different from that of thoracic radiologists (0.784, blue line), but significantly higher than that of non-radiologist physicians (0.650, red line).
Table 2.
The CAD and physician’s performances with reference standard of diagnosis of COVID-19 by RT-PCR.
Table 3.
The CAD and physician’s performances with reference standard of pneumonia on chest CT.
Fig 5.
Performance of physician alone versus CAD-assisted interpretations.
For identification of RT-PCR positive COVID-19 patients, the AUCs of thoracic radiologists did not significantly differ between reader-alone (red line) and CAD-assisted interpretations (blue line) (0.701 vs. 0.699; P = .815) (A), while the AUC non-radiologist physicians was significantly improved in the CAD-assisted interpretation (blue line) compared to the reader-alone interpretation (red line) (0.584 vs. 0.664; P = .006) (B). For identification of pneumonia defined on chest CT, the AUCs of thoracic radiologists also did not significantly differ between reader-alone (red line) and CAD-assisted interpretations (blue line) (0.784 vs. 0.789; P = .524) (C), while the AUC non-radiologist physicians was significantly improved in the CAD-assisted interpretation (blue line) compared to the reader-alone interpretation (red line) (0.650 vs. 0.738; P = .003) (D).
Table 4.
Sensitivities varied by clinical and radiological findings.
Table 5.
Comparison of performance of CAD for identifying COVID-19 with results from different studies.