Mike: Hello, I'm Mike Clarke, podcast editor for the Cochrane Library. Cochrane is preparing a series of reviews to help decision makers deal with the COVID-19 pandemic and its impact. We are keeping these up to date as new evidence becomes available and the review of using signs and symptoms to diagnose whether someone has the disease has been updated for the second time. The review was first published in June 2020 and the most recent update was published in May 2022. Here's the lead author, Thomas Struyf from the Katholieke Universiteit Leuven in Belgium, to tell us about the latest findings.

Thomas: The accurate diagnosis of COVID-19 is important to identify individuals who need treatment or to isolate to prevent spread of the infection. It's also important not to label someone as having COVID-19 when they don't, because this might lead to unnecessary further testing, treatment, isolation (of them and their close contacts), and false reassurance about having immunity in the future.
Our review examines some of the evidence on this. We wanted to find out how accurate symptoms (such as cough, fever, or loss of smell or taste) and signs from medical examination (such as an increased heart rate) are for diagnosing COVID-19. We had hoped to separate out the diagnosis of mild disease and COVID-19 pneumonia, but the studies did not clearly distinguish between the two, so we present the findings for both of these combined.
Our most recent searches bring the evidence up to June 2021 and we now include 42 studies, with just under 53,000 patients in total. These had investigated 96 different individual symptoms and signs or combinations of these and I'll focus on the two commonest in this podcast: cough and fever, as well as sore throat.
The accuracy of individual symptoms and signs varied widely across studies. In all but two studies, the diagnosis of COVID-19 was confirmed by the most accurate laboratory test available. Most studies were done in ambulatory settings, which is where most assessments for COVID-19 continue to take place. The diagnostic value of symptoms such as the presence of fever, cough or other respiratory symptoms might still be overestimated, because most studies deliberately included participants because they had these symptoms.
The overall results showed that for every 1000 adults suspected of having COVID-19, 270 would actually have the disease. More specifically, an average of 567 of the 1000 would have a cough and 168 of these would actually have COVID-19. Conversely, of 433 patients without a cough, 102 would have COVID-19. In the same group of 1000 adults, 283 patients would have fever and 102 of these would have COVID-19, which means that 168 of the 717 patients without fever, would actually have COVID-19.
Other symptoms, such as a sore throat or runny nose, are more likely to indicate the presence of an infectious disease other than COVID-19. For example, in 1000 people with suspected COVID-19, 362 people would have a sore throat but only 84 would actually have COVID-19, while 186 of the 638 patients without sore throat, would have the disease.
In summary, our review of the research up to June 2021 suggests that no single symptom or sign is good at detecting whether someone has COVID-19. However, the presence of a cough or high temperature may be useful to identify people who might have COVID-19. There is an ongoing need for research to investigate combinations of symptoms and signs along with other information such as recent contact or travel history, or vaccination status.

Mike: If you would like to read more about the value of using signs and symptoms for the diagnosis of COVID-19, this latest version of the review is available free online at Cochrane Library dot com. Just go to the website and search "Signs and symptoms of COVID-19".