From the earliest days of the COVID-19 pandemic, clinicians and researchers recognized the importance of rapid diagnosis in containing the spread of the virus. Due in part to the limited availability of laboratory testing, there was interest in the role of chest imaging, particularly CT, in quickly providing a diagnosis.

A systematic review published by the Cochrane Library in February of 2021 evaluated the accuracy of thoracic imaging by compiling data from 51 studies published to date. ^[1] Islam N, Ebrahimzadeh S, Salameh JP, et al. Thoracic imaging tests for the diagnosis of COVID‐19. Cochrane Database Syst Rev. 2021(3). The studies were largely cross sectional, and looked at the correlation between CT findings and results of laboratory testing in persons with suspected COVID-19 infection. The pooled sensitivity of chest CT in suspected COVID-19 participants was 87.9% (95% CI, 84.6 to 90.6), while the pooled specificity was 80.0% (95% CI, 74.9 to 84.3).

While CT was able to detect changes consistent with COVID-19 infection, it was less useful in distinguishing it from other types of viral pneumonia. This was important information for clinicians who were struggling to identify and isolate potential cases and waiting on confirmatory laboratory testing. Based on the evidence, our criteria for Thoracic CT were expanded to include persons under investigation (including persons who meet specific criteria for suspected COVID-19 infection) for COVID-19 pneumonia when reverse transcription polymerase chain reaction (RT-PCR) was negative or unavailable, thus providing guidance for our clients in a rapidly evolving situation.

With increasing availability of laboratory testing, the role of imaging has evolved. The World Health Organization (WHO) recently published a set of recommendations ^[2] Akl EA, Blažić I, Yaacoub S, et al. Use of chest imaging in the diagnosis and management of COVID-19: a WHO rapid advice guide. Radiology. 2021;298(2):E63-e9.  which provide further guidance to clinicians. They address specific scenarios along the care continuum, including factors to consider when choosing an imaging modality, and are consistent with several other society positions. ^[3]American College of Radiology, ACR recommendations for the use of chest radiography and computed tomography (CT) for suspected COVID-19 infection, (2020) Reston, VA, American College of Radiology, 2 … Continue reading ^[4] Society of Thoracic Radiology, The American Society of Emergency Radiology, STR / ASER COVID-19 position statement, (2020) East Dundee, IL, Society of Thoracic Radiology, 1 pg.

The guideline development team at Carelon will continue to evaluate the literature and update our criteria in accordance with the most recent recommendations.