RT-PCR test and clinical synthesis
RT-PCR and chest CT were performed for these patients. Coronavirus nucleic acid was collected with nasopharyngeal swab or/and bronchial aspiration. RT-PCR was performed using gene amplification RdRpE, and/or N (CNR Pasteur technic, AllPlex Seegene, Bosphore Anatolia; depending on availabilities). For patients who presented a high clinical probability of infection, two or three RT-PCR were performed if the previous results were negative, with a minimum of 48-72 hours between samples.
If one RT-PCR was positive, COVID-19 diagnosis was confirmed. In case of multiple chest CTs, we used the one that was closest, timewise, to the first RT-PCR. All patients were included whatever the time between RT-PCR and chest CT.
We also included the notion of highly probable COVID-19 infection, i.e. some cases had multiple RT-PCR negative results but the clinical (dyspnoea, fever, fatigue, cough), biological history (lymphopenia, high reactive C-protein, high D-Dimers and LDH), chest CT and epidemiology (contagion with a positive RT-PCR) arguments were consistent with a COVID-19 infection.10 There was a follow-up and additional chest CTs to conclude if the patient was infected or not, based on clinical assessment and medical records.