Assessment of a Diagnostic Strategy Based on Chest Computed Tomography in Patients Hospitalized for COVID-19 Pneumonia: an observational study

Objectives To assess the relevance of a diagnostic strategy for COVID-19 based on chest computed tomography (CT) in patients with hospitalization criteria. Setting Observational study with retrospective analysis in a French emergency department (ED). Participants and intervention From March 3 to April 2, 2020, 385 adult patients presenting to the ED for suspected COVID-19 underwent an evaluation that included history, physical examination, blood tests, real-time reverse transcription-polymerase chain reaction (RT-PCR) and chest CT. When the time-interval between chest CT and RT-PCR assays was longer than 7 days, patients were excluded from the study. Only patients with hospitalization criteria were included. Diagnosis accuracy was assessed using the sensitivity and specificity of RT-PCR. Outcomes Sensitivity and specificity of RT-PCR, chest CT (also accompanied by lymphopenia) were measured and were also analyzed by subgroups of age and sex. Results Among 377 included subjects, RT-PCR was positive in 36%, while chest CT was compatible with a COVID-19 diagnosis in 59%. In the population with positive RT-PCR, there were more men (55% vs 37%, p=0.015), a higher frequency of reticular and, or, interlobular septal thickening (53% vs 31%, p=0.02) as well as a higher frequency of bilateral lesion distribution (98% vs 86%, p=0.01) compared to the population with negative RT-PCR. The proportion of lymphopenia was higher in men vs women (47% vs 39%, p=0.03) and varies between patients >80 versus 50-80 and p<0.001). Using CT as reference, RT-PCR obtained a sensitivity of 61%, specificity of 93%. There was a significant difference between CT and RT-PCR diagnosis performance (p < 0.001). When CT was accompanied by lymphopenia, sensitivity and specificity of RT-PCR were respectively 71% and 94%. CT abnormalities and lymphopenia provided diagnosis in 29% of patients with negative PCR. Conclusions Chest CT had a superior yield than RT-PCR in COVID-19 hospitalized patients, especially when accompanied by lymphopenia.