More high-quality research is necessary to establish diagnostic chest computed tomography (CT) criteria for coronavirus disease 2019 (COVID-19), according to the results of a systematic review and meta-analysis published in Chest.
Currently, real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay of nasal and pharyngeal swab specimens is considered the gold standard for the diagnosis of COVID-19. Real-time RT-PCR testing, however, is time-consuming and suboptimal for the rapid triaging of patients. In consideration of the potential benefit of chest CT for the diagnosis of COVID-19, in concert with clinical examination and RT-PCR, a team of researchers performed a systematic review to assess the methodologic quality of studies on the use of chest CT imaging in patients with COVID-19 and to determine the frequency of different chest CT findings.
Studies that reported the prevalence of chest CT findings in patients with a diagnosis of COVID-19 confirmed by RT-PCR or gene sequencing were eligible for inclusion. In addition, only studies that provided a detailed description of chest CT findings according to the glossary of terms for thoracic imaging of the Fleischner Society were included.
The analysis included 28 studies with a total of 3466 patients published between February 20, 2020, and May 15, 2020. The median number of patients with COVID-19 per study was 124 (range, 50-476); the median prevalence of symptomatic patients was 99% (range, >76.3-100).
Almost all studies (27/28) were of retrospective design, and concerns regarding methodologic quality were ubiquitous. These concerns included failure to report whether patient recruitment was consecutive or random (13 studies), exclusion of patients without any CT abnormalities (8 studies), failure to report the time interval between CT and RT-PCR/gene sequencing (24 studies), lack of information on observer agreement variability in the interpretation of chest CT (27 studies), and failure to report whether chest CT was interpreted without knowledge of CT and RT-PCR/gene sequencing results (14 studies).
A critical finding of this meta-analysis was that 10.6% of symptomatic patients with confirmed COVID-19 had normal chest CT findings. “Therefore, it is questionable if chest CT can be used for accurate stratification of patients in a screening setting that aims to strictly isolate individuals with COVID-19 from those without,” noted the authors.
The following 6 imaging findings observed in more than 70% of patients with confirmed COVID-19 are presented in order of decreasing frequency: posterior predilection, ground-glass opacity, bilateral abnormalities, left lower lobe involvement, vascular thickening, and right lower lobe involvement. On the other hand, the following 6 imaging findings were observed in ≤5% of patients with confirmed COVID-19, also presented in order of decreasing frequency: pleural effusion, lymphadenopathy, airway secretions/tree-in-bud sign, central lesion distribution, pericardial effusion, and cavitation/cystic changes. Pooled prevalence of other CT findings ranged between 10.5% and 63.2%.
“Future studies are required to test which chest CT criteria achieve optimal sensitivity and specificity in differentiating COVID-19 from other entities in different clinical settings and with different disease prevalence rates,” stated the authors. In addition, the findings of this study “may be helpful to further develop existing confidence scales for COVID-19, such as the [chest CT classification scale] that was recently issued under auspices of the Radiological Society of North America,” they added.
Adams HJA, Kwee TC, Yakar D, Hope MD, Kwee RM. Chest CT imaging signature of COVID-19 infection: in pursuit of the scientific evidence [published online June 25, 2020]. Chest. doi:10.1016/j.chest.2020.06.025