COVID-19 Evidence Alerts
from McMaster PLUSTM

Current best evidence for clinical care (more info)

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Diagnosis Karam M, Althuwaikh S, Alazemi M, et al. Chest CT versus RT-PCR for the detection of COVID-19: systematic review and meta-analysis of comparative studies. JRSM Open. 2021 May 15;12(5):20542704211011837. doi: 10.1177/20542704211011837. eCollection 2021 May.

Objectives: To compare the performance of chest computed tomography (CT) scan versus reverse transcription polymerase chain reaction (RT-PCR) as the reference standard in the initial diagnostic assessment of coronavirus disease 2019 (COVID-19) patients.

Design: A systematic review and meta-analysis were performed as per the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. A search of electronic information was conducted using the following databases: MEDLINE, EMBASE, EMCARE, CINAHL and the Cochrane Central Register of Controlled Trials.

Setting: Studies that compared the diagnostic performance within the same patient cohort of chest CT scan versus RT-PCR in COVID-19 suspected patients.

Participants: Thirteen non-randomised studies enrolling 4092 patients were identified.

Main outcome measures: Sensitivity, specificity and accuracy were primary outcome measures. Secondary outcomes included other test performance characteristics and discrepant findings between both investigations.

Results: Chest CT had a median sensitivity, specificity and accuracy of 0.91 (range 0.82-0.98), 0.775 (0.25-1.00) and 0.87 (0.68-0.99), respectively, with RT-PCR as the reference. Importantly, early small, China-based studies tended to favour chest CT versus later larger, non-China studies.

Conclusions: A relatively high false positive rate can be expected with chest CT. It is possible it may still be useful to provide circumstantial evidence, however, in some patients with a suspicious clinical presentation of COVID-19 and negative initial Severe Acute Respiratory Syndrome Coronavirus 2 RT-PCR tests, but more evidence is required in this context. In acute cardiorespiratory presentations, negative CT scan and RT-PCR tests is likely to be reassuring.

Discipline / Specialty Area Score
Infectious Disease
Emergency Medicine
Pediatric Emergency Medicine
Hospital Doctor/Hospitalists
Internal Medicine
Public Health
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Comments from MORE raters

Emergency Medicine rater

Although CT can be used as an adjunct in ruling out COVID-19, it still has many limitations. It would be interesting to see CT's performance characteristics for outpatients (ie non-sick) as well as during non-pandemic times. The concern for false positives increasing as the findings can be non-specific, especially if there is not a clinical suspicion for COVID-19.

Infectious Disease rater

Useful information given the lack clarity in this area.