CT in relation to RT-PCR in diagnosing COVID-19 in the Netherlands: a prospective study

ABSTRACT

IntroductionEarly differentiation between emergency department (ED) patients with and without corona virus disease (COVID-19) is very important. Chest CT scan may be helpful in early diagnosing of COVID-19. We investigated the diagnostic accuracy of CT using RT-PCR for SARS-CoV-2 as reference standard and investigated reasons for discordant results between the two tests. MethodsIn this prospective single centre study in the Netherlands, all adult symptomatic ED patients had both a CT scan and a PCR upon arrival at the ED. CT results were compared with PCR test(s). Diagnostic accuracy was calculated. Discordant results were investigated using discharge diagnoses. ResultsBetween March 13th and March 24th 2020, 193 symptomatic ED patients were included. In total, 43.0% of patients had a positive PCR and 56.5% a positive CT, resulting in a sensitivity of 89.2%, specificity 68.2%, likelihoodratio (LR) + 2.81 and LR-0.16. Sensitivity was higher in patients with high risk pneumonia (CURB-65 score [≥]3; n=17, 100%) and with sepsis (SOFA score [≥]2; n=137, 95.5%). Of the 35 patients (31.8%) with a suspicious CT and a negative PCR, 9 had another respiratory viral pathogen, and in 7 patients, COVID-19 was considered likely. One of nine patients with a non-suspicious CT and a positive PCR had developed symptoms within 48 hours before scanning. DiscussionThe accuracy of chest CT in symptomatic ED patients is high, but used as a single diagnostic test, CT can not safely diagnose or exclude COVID-19. However, CT can be used as a quick first screening tool. O_TEXTBOXKey messages What is the key question? O_LIWe investigated the diagnostic accuracy of the chest CT scan using the PCR test for diagnosing COVID-19 as reference. C_LI What is the bottom line? O_LISensitivity of chest CT is high, especially in severely ill patients, but with moderate specificity, which could in part be explained by other respiratory viruses and false negative PCR tests. C_LI Why read on? Early differentation between patients with and without COVID-19 is extremely important, and CT scan should be considered a quick screening test, and may help to overcome suboptimal sensitivity of PCR tests. C_TEXTBOX