OBJECTIVES: Value of chest CT was mainly studied in area of high COVID-19 incidence . The aim of this study was therefore to evaluate chest CT performances to diagnose COVID-19 pneumonia with regard to RT-PCR as reference standard in a low incidence area .
METHODS: A survey was sent to radiology department in 4 hospitals in an administrative French region of weak disease prevalence (3.4 %). Study design was approved by the local institutional review board and recorded on the clinicaltrial.gov website (NCT04339686). Written informed consent was waived due to retrospective anonymized data collection . Patients who underwent a RT-PCR and a chest CT scan within 48 h for COVID-19 pneumonia suspicion were consecutively included . Diagnostic accuracy including the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of chest CT regarding RT-PCR as reference standard were calculated .
RESULTS: One hundred twenty-nine patients had abnormal chest CT findings compatible with a COVID-19 pneumonia (26% , 129/487). Among the 358 negative chest CT findings , 3% (10/358) were RT-PCR positive . Chest CT sensitivity, specificity, positive, and negative predictive value were respectively 87% (IC95 : 85 , 89; 69/79), 85% (IC95 : 83 , 87; 348/408), 53% (IC95 : 50 , 56; 69/129), and 97% (IC95 : 95 , 99; 348/358).
CONCLUSIONS: In a low prevalence area, chest CT scan is a good diagnostic tool to rule out COVID-19 infection among symptomatic suspected patients .
KEY POINTS: â¢ In a low prevalence area (3.4% in the administrative area and 5.8% at mean in the study) chest CT sensitivity and specificity for diagnosing COVID-19 pneumonia were 87% and 85% respectively . â¢ In patients with negative chest CT for COVID-19 pneumonia, the negative predictive value of COVID-19 infection was 97% (348/358 subjects). â¢ Performance of CT was equivalent between the 4 centers participating to this study.