Diagnostic accuracy of X-ray versus CT in COVID-19: a propensity-matched database study. Issue 11 (6th November 2020)

• Record Type: Journal Article
• Authors: Borakati, Aditya; Perera, Adrian; Johnson, James; Sood, Tara
• Is Part Of: BMJ open. Volume 10:Issue 11(2020)
• Publication Date: 2020-11-06
• Subjects: COVID-19 -- Chest imaging -- accident & emergency medicine -- general medicine (see Internal Medicine) -- diagnostic radiology; Medicine -- Research -- Periodicals; 610.72
• DOI: 10.1136/bmjopen-2020-042946
• Languages: English
• ISSNs: 2044-6055

Abstract

Abstract : Objectives: To identify the diagnostic accuracy of common imaging modalities, chest X-ray (CXR) and CT, for diagnosis of COVID-19 in the general emergency population in the UK and to find the association between imaging features and outcomes in these patients. Design: Retrospective analysis of electronic patient records. Setting: Tertiary academic health science centre and designated centre for high consequence infectious diseases in London, UK. Participants: 1198 patients who attended the emergency department with paired reverse transcriptase PCR (RT-PCR) swabs for SARS-CoV-2 and CXR between 16 March and 16 April 2020. Main outcome measures: Sensitivity and specificity of CXR and CT for diagnosis of COVID-19 using the British Society of Thoracic Imaging reporting templates. Reference standard was any RT-PCR positive naso-oropharyngeal swab within 30 days of attendance. ORs of CXR in association with vital signs, laboratory values and 30-day outcomes were calculated. Results: Sensitivity and specificity of CXR for COVID-19 diagnosis were 0.56 (95% CI 0.51 to 0.60) and 0.60 (95% CI 0.54 to 0.65), respectively. For CT scans, these were 0.85 (95% CI 0.79 to 0.90) and 0.50 (95% CI 0.41 to 0.60), respectively. This gave a statistically significant mean increase in sensitivity with CT of 29% (95% CI 19% to 38%, p<0.0001) compared with CXR. Specificity was not significantly different between the two modalities. CXR findings were not statistically significantly or clinically meaningfully associated with vital signs, laboratory parameters or 30-day outcomes. Conclusions: CT has substantially improved diagnostic performance over CXR in COVID-19. CT should be strongly considered in the initial assessment for suspected COVID-19. This gives potential for increased sensitivity and considerably faster turnaround time, where capacity allows and balanced against excess radiation exposure risk.