Mike: Hello, I'm Mike Clarke, podcast editor for the Cochrane Library. The Cochrane programme of reviews for COVID-19 covers both the diagnosis and treatment of the disease and reviews are being updated as new evidence becomes available. Among these is a review of chest imaging for diagnosing the condition, and its fourth version was published in May 2022. We asked the lead author, Sanam Ebrahimzadeh, from The Ottawa Hospital Research Institute in Canada, to describe the latest findings in this podcast.

Sanam: The current gold standard for diagnosing COVID-19 is a PCR test but this can have a high false negative rate of up to 41 percent, which means that it could miss many cases. This is related to the time since symptom onset and the type of swab used. Chest imaging might provide an alternative or additional test and we're doing this living systematic review to see how useful it might be for detecting COVID-19.
We're evaluating the diagnostic accuracy of imaging such as chest CT, X-ray and ultrasound in people with suspected COVID-19 and we did the search for the latest version of the review in February 2021. This identified 98 studies, with chest CT evaluated in 96 studies, chest X-ray in 17 and ultrasound of the lung in 15.
Of these nearly 100 studies, we were able to include 94 in our assessment of the diagnostic accuracy of chest imaging for people with suspected COVID-19. This showed that CT and ultrasound are similar in their ability to correctly identify individuals with the disease and that both are better than X-ray. All three techniques are similar for correctly identifying that someone does not have COVID-19.
Our conclusions have strengthened with each version of this living review. In the original version, the uncertainty resulting from the poor study quality and the heterogeneity of included studies limited our ability to confidently draw any conclusions. However, in the third and this, the fourth, version, the evidence in favour of chest CT has become clearer, while the evidence for X-ray and ultrasound is continuing to improve.
In summary, the evidence in this latest version means that we are confident that chest CT has the best utility for ruling out COVID-19 and that ultrasound of the lung probably has greater utility than chest X-ray.

Mike: If you would like to read more about the current evidence, and watch for future updates of this review as the evidence moves forward, it's available at Cochrane Library dot com with a simple search for 'thoracic imaging and COVID-19'.