Low-Dose Chest CT for the Diagnosis of COVID-19—A Systematic, Prospective Comparison With PCR

Abstract

Background: Only limited evidence has been available to date on the accuracy of systematic low-dose chest computed tomography (LDCT) use in the diagnosis of COVID-19 in patients with non-specific clinical symptoms.

Methods: The COVID-19 Imaging Registry Study Aachen (COVID-19-Bildgebungs-Register Aachen, COBRA) collects data on imaging in patients with COVID-19. Two of the COBRA partner hospitals (RWTH Aachen University Hospital and Dueren Hospital) systematically perform reverse transcriptase polymerase chain reaction (RT-PCR) from nasopharyngeal swabs as well as LDCT in all patients presenting with manifestations that are compatible with COVID-19. In accordance with the COV-RADS protocol, the LDCT scans were prospectively evaluated before the RT-PCR findings were available in order to categorize the likelihood of COVID-19.

Results: From 18 March to 5 May 2020, 191 patients with COVID-19 manifestations (117 male, age 65 ± 16 years) underwent RT-PCR testing and LDCT. The mean time from the submission of the sample to the availability of the RT-PCR findings was 491 minutes (interquartile range [IQR: 276-1066]), while that from the performance of the CT to the availability of its findings was 9 minutes (IQR: 6-11). A diagnosis of COVID-19 was made in 75/191 patients (39%). The LDCT was positive in 71 of these 75 patients and negative in 106 of the 116 patients without COVID-19, corresponding to 94.7% sensitivity (95% confidence interval [86.9; 98.5]), 91.4% specificity [84.7; 95.8], positive and negative predictive values of 87.7% [78.5; 93.9] and 96.4% [91.1; 98.6], respectively, and an AUC (area under the curve) of 0.959 [0.930; 0.988]. The initial RT-PCR test results were falsely negative in six patients, yielding a sensitivity of 92.0% [83.4; 97.0]; these six patients had positive LDCT findings. 47.4% of the LDCTs that were negative for COVID-19 (55/116) exhibited pathological pulmonary changes, including infiltrates, that were correctly distinguished from SARS-CoV-2 related changes.

Conclusion: In patients with symptoms compatible with COVID-19, LDCT can esablish the diagnosis of COVID-19 with comparable sensitivity to RT-PCR testing. In addition, it offers a high specificity for distinguishing COVID-19 from other diseases associated with the same or similar clinical symptoms. We propose the systematic use of LDCT in addition to RT-PCR testing because it helps correct false-negative RT-PCR results, because its results are available much faster than those of RT-PCRtesting, and because it provides additional diagnostic information useful for treatment planning regardless of the type of the infectious agent.

Figure 1:

LDCT findings of two patients who each presented with fever and cough and with a) COV-RADS 5 (COVID-19 typical finding) b) COV-RADS 2 (pathological finding but without changes suspicious of COVID-19) The PCR examination confirmed a SARS-COV-2 infection of patient (a) and did not result in virus detection in patient (b).

Figure 2

Likelihood of COVID-19 by COV-RADS category COV-RADS, COVID-19 Reporting and Data System

eFigure 1

Time to availability of RT-PCR results (a) and time to availability of LDCT results (b) for the first 124 patients at Aachen University Hospital (UKA) a) time from sample arrival at central laboratory of the UKA until availability of RT-PCR results b) time from LDCT acquisition until availability of LDCT findings IQR, interquartile range

eFigure 2

Time interval between availability of CT findings and availability of RT-PCR results for the first 124 patients at Aachen University Hospital

eFigure 3

ROC curve of LDCT Distinctions between four categories of increasing probability of COVID-19: COV-RADS 1 and 2 (equally no evidience of COVID-19), COV-RADS 3 (possible), COV-RADS-4 (probable), COV-RADS-5 (typical). 95% CI, 95% confidence interval; AUC, area under the curve; COV-RADS, COVID-19 Reporting and Data System; ROC, receiver operating characteristic