key messages

– The results indicate that a single symptom included in this review cannot accurately diagnose COVID-19.

– Loss of the sense of taste or smell could be a warning sign of the presence of COVID-19. Cough or fever can be helpful in identifying people who may have COVID-19. These symptoms can be useful in prompting further testing if they are present.

– We need more research to look at combinations of symptoms and signs with other information such as recent contact or travel history or vaccination status in children and adults aged 65 and over.

What are symptoms or signs of COVID-19?

The symptoms are experienced by the patients. COVID-19 symptoms include cough, sore throat, high temperature, diarrhea, headache, muscle or joint pain, fatigue, and loss of smell and taste.

The signs are measured by medical staff during the clinical examination. These include lung sounds, blood pressure, blood oxygen levels, and heart rate.

Symptoms and signs of COVID-19 can be important for people to know if they and those they come into contact with are self-isolating, undergoing a rapid lateral flow test or a (laboratory-based) PCR test, or should be hospitalized.

What were we trying to find out?

The symptoms and signs of COVID-19 are varied and can indicate other diseases, not just COVID-19. We wanted to know how accurate the diagnosis of COVID-19 is based on symptoms and signs of a medical examination. We are interested in people with suspected COVID-19 who go to their doctor, outpatient test centers or the hospital.

What did we do?

We searched for studies that assessed the accuracy of symptoms and signs to diagnose COVID-19. Studies could only be carried out in general practitioners’ practices, outpatient test centers or hospital outpatient clinics. We only included studies of people in the hospital if signs and symptoms were recorded on admission to the hospital, for example through the emergency room.

what did we find

In this review, we focused on 42 studies with 52,608 participants. The studies assessed 96 separate or combined symptoms and signs. 35 studies were conducted in emergency departments or outpatient COVID-19 testing centers (46,878 participants), 3 studies in general practice (1230 participants), 2 studies in children’s hospitals (493 inpatients and outpatients), and 2 studies in nursing homes (4007 participants). The studies were conducted in 18 different countries around the world. 23 studies were conducted in Europe, 8 in North America, 5 in Asia and 3 in South America and 3 in Australia. We did not find any studies conducted in Africa. Three focused specifically on children, and only 1 focused on adults aged 65 and over.

Most studies have not clearly differentiated between mild and severe COVID-19, so we present results for mild, moderate, and severe disease together.

Few studies reported single signs as diagnostic tests, so we mainly focus on the diagnostic value of symptoms. The most frequently reported symptoms were cough, fever, shortness of breath and sore throat.

According to the studies in our review, in a group of 1000 people suspected of having COVID-19, of whom 270 (27%) would actually have COVID-19, about 567 people would have a cough. Of those 567, 168 would actually have COVID-19. Of the 433 who don’t have a cough, 102 would have COVID-19. Out of the same 1000 people, about 283 people would have a fever. Of those 283, 102 would actually have COVID-19. Of the 717 people without a fever, 168 would have COVID-19.

Someone who has lost their sense of smell or taste is five times more likely to have COVID-19 than someone who doesn’t.

Other symptoms, such as a sore throat or runny nose, are more indicative of the presence of an infectious disease other than COVID-19. Out of the same 1000 people as described above, about 362 people would have a sore throat. Of those, only 84 actually had COVID-19. Of the 638 patients without a sore throat, 186 would have COVID-19. We found similar numbers for a runny nose.

What are the limits of the evidence?

The results of this updated review are more reliable than those in previous versions because we included more high-quality studies. However, the accuracy of individual symptoms varied between studies, and the diagnostic value of symptoms such as fever, cough, or other respiratory symptoms might still be overestimated, since most studies included participants knowingly because they had these symptoms.

The results do not clearly distinguish between people with mild, moderate, or severe COVID-19. Few studies have examined symptom-based diagnosis of COVID-19 in children or older adults.

How up to date is this review?

This review updates our previous review. The evidence is current to June 2021.

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