COVID-19 Evidence Alerts
from McMaster PLUSTM

Current best evidence for clinical care (more info)

Diagnosis Skalidis I, Nguyen VK, Bothorel H, et al. Unenhanced computed tomography (CT) utility for triage at the emergency department during COVID-19 pandemic. Am J Emerg Med. 2020 Jul 28. pii: S0735-6757(20)30654-9. doi: 10.1016/j.ajem.2020.07.058.
Abstract

BACKGROUND: Unenhanced chest computed tomography (CT) can assist in the diagnosis and classification of coronavirus disease 2019 (COVID-19), complementing to the reverse-transcription polymerase chain reaction (RT-PCR) tests; the performance of which has yet to be validated in emergency department (ED) setting. The study sought to evaluate the diagnostic performance of chest CT in the diagnosis and management of COVID-19 in ED.

METHODS: This retrospective single-center study included 155 patients in ED who underwent both RT-PCR and chest CT for suspected COVID-19 from March 1st to April 1st, 2020. The clinical information, CT images and laboratory reports were reviewed and the performance of CT was assessed, using the RT-PCR as standard reference. Moreover, an adjudication committee retrospectively rated the probability of COVID-19 before and after the CT calculating the net reclassification improvement (NRI). Their final diagnosis was considered as reference. The proportion of patients with negative RT-PCR test that was directed to the referent hospital based on positive CT findings was also assessed.

RESULTS: Among 155 patients, 42% had positive RT-PCR results, and 46% had positive CT findings. Chest CT showed a sensitivity of 84.6%, a specificity of 80.0% and a diagnostic accuracy of 81.9% in suggesting COVID-19 with RT-PCR as reference. Concurrently, corresponding values of 89.4%, 84.3% and 86.5% were retrieved with the adjudication committee diagnosis as reference. For the subgroup of patients with age > 65, specificity and sensitivity were 50% and 80.8%, respectively. In patients with negative RT-PCR results, 20% (18/90) had positive chest CT finding and 22% (4/18) of those were eventually considered as COVID-19 positive according to the adjudication committee. After CT, the estimated probability of COVID-19 changed in 10/104 (11%) patients with available data: 4 (4%) were downgraded, 6 (6%) upgraded. The NRI was 1.92% (NRI event -2.08% + NRI non-event 5.36%). No patient with negative RT-PCR but positive CT was eventually directed to hospital.

CONCLUSION: Chest CT showed promising sensitivity for diagnosing COVID-19 across all patients' subgroups. However, CT did not modify the estimated probability of COVID-19 infection in a substantial proportion of patients and its utility as an emergency department triage tool warrants further analyses.

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Comments from MORE raters

Emergency Medicine rater

This is important information. Most doctors involved in Covid-19 management already know that no single test will predict outcome. The combination of tests to improve positive and negative prediction percentages is urgently needed.

Hospital Doctor/Hospitalists rater

Interesting concept, but not all patients require CT Scans of the Chest if they are diagnosed with COVID-19.

Internal Medicine rater

I am worried the reference standard used was not the optimal (PCR has false negatives!).

Internal Medicine rater

A good paper shows the operating characteristics of CT-scan for C-19 diagnosis and the limit of its use in the ED.

Respirology/Pulmonology rater

This retrospective study, with a relatively small sample, provides limited evidence on an already well-studied aspect of COVID-19.

Respirology/Pulmonology rater

This is useful information despite the retrospective single center design which weaken results.