Risk Stratification With Chest CT to Rule-out Suspected SARS-CoV-2 Infections

To prevent spreading of the new coronavirus (SARS-CoV-2) from patients who are infected but
in whom infection was not detected by means of Reverse transcription polymerase chain
reaction (RT-PCR) and who are to be admitted to ordinary wards of hospitals, we aimed to
determine validity of exclusion of pneumonia immediately before admission by means of chest
computed tomography.

Patients admitted to the emergency department of the university hospital Jena with Covid-19
symptoms (temperature > 37.5°C; respiratory and/or gastrointestinal symptoms) whose RT-PCR
test resulted negative, undergo a chest CT scan. Those patients without pulmonary infiltrates
can be safely ruled out for Covid-19. Thus, CT has perfect selectivity evidence regarding
pulmonary infiltrates; it has limited selectivity concerning the pathogenesis of the
infiltration.

The study objective is to investigate the diagnostic value and consistency of chest CT as
compared with comparison to RT-PCR assay in COVID-19 in patients which were stratified for
hospital admission.

The hypothesis is that chest CT has the greatest clinical evidence (no detection of lung
infiltration) when the RT-PCT is tested negative. We assume that chest CT has a high
sensitivity for diagnosis of respiratory dominant COVID-19. A pulmonary COVID-19 in epidemic
areas can be best ruled out when chest CT is negative for the presence of infiltrations of
the lung parenchyma. This is described by the SNOUT principle which is an acronym for
'Sensitive test when Negative rules OUT the disease' under the condition of a low pretest
probability.