Can symptoms and medical examination accurately diagnose COVID-19 disease?

A new systematic review from Cochrane Infectious Diseases Group published today; 'Signs and symptoms to determine if a patient presenting in primary care or hospital outpatient settings has COVID-19 disease'.

COVID-19 is an infectious disease caused by the SARS-CoV-2 virus. Most people with COVID-19 have a mild to moderate respiratory illness; others experience severe illness, such as COVID-19 pneumonia. Formal diagnosis requires laboratory analysis of nose and throat samples, or imaging tests like CT scans. However, the first and most accessible diagnostic information is from symptoms and signs from clinical examination. If initial diagnosis by symptoms and signs were accurate, the need for time-consuming, specialist diagnostic tests would be reduced.

Symptoms are experienced by patients. People with mild COVID-19 might experience cough, sore throat, high temperature, diarrhoea, headache, muscle or joint pain, fatigue, and loss of sense of smell and taste. Symptoms of COVID-19 pneumonia include breathlessness, loss of appetite, confusion, pain or pressure in the chest, and high temperature (above 38 °C).

Signs are evaluated by clinical examination, and include lung sounds, blood pressure and heart rate.

Often, people with mild symptoms visit their doctor (primary care physician) for an initial diagnosis. People with more severe symptoms might visit a hospital outpatient or emergency department. Depending on their symptoms and signs, patients may be sent home to isolate, may receive further tests or be hospitalised.

Why is accurate diagnosis important?
Accurate diagnosis ensures that people receive the correct treatment quickly; are not tested, treated or isolated unnecessarily; and do not risk spreading COVID-19. This is important for individuals and saves time and resources.

We wanted to know how accurate diagnosis of COVID-19 and COVID-19 pneumonia is in a primary care or hospital setting, based on symptoms and signs from medical examination.

What did we do?
We searched for studies that assessed the accuracy of symptoms and signs to diagnose mild COVID-19 and COVID-19 pneumonia. Studies could include people with possible COVID-19, or people known to have – and not to have – COVID-19. Studies had to be in primary care or hospital outpatient settings only and include at least 10 participants with any symptom or sign that might be COVID-19.

The included studies
We found 16 relevant studies with 7706 participants. The studies assessed 27 separate signs and symptoms, but none assessed combinations of signs and symptoms. Seven were set in hospital outpatient clinics (2172 participants), four in emergency departments (1401 participants), but none in primary care settings. No studies included children, and only one focused on older adults. All the studies confirmed COVID-19 diagnosis by the most accurate tests available.

The review authors searched for studies published from January to April 2020.

Main results
The studies did not clearly distinguish mild to moderate COVID-19 from COVID-19 pneumonia, so we present the results for both conditions together.

The results indicate that at least half of participants with COVID-19 disease had a cough, sore throat, high temperature, muscle or joint pain, fatigue, or headache. However, cough and sore throat were also common in people without COVID-19, so these symptoms alone are less helpful for diagnosing COVID-19. High temperature, muscle or joint pain, fatigue, and headache substantially increase the likelihood of COVID-19 disease when they are present.

How reliable are the results?
The accuracy of individual symptoms and signs varied widely across studies. Moreover, the studies selected participants in a way that meant the accuracy of tests based on symptoms and signs may be uncertain.

Conclusions
All studies were conducted in hospital outpatient settings, so the results are not representative of primary care settings. The results do not apply to children or older adults specifically, and do not clearly differentiate between milder COVID-19 disease and COVID-19 pneumonia.

The results suggest that a single symptom or sign included in this review cannot accurately diagnose COVID-19. Doctors base diagnosis on multiple symptoms and signs, but the studies did not reflect this aspect of clinical practice.

Further research is needed to investigate combinations of symptoms and signs; symptoms that are likely to be more specific, such as loss of sense of smell; and testing unselected populations, in primary care settings and in children and older adults.

This news item was originally posted on the Cochrane website