Extending the list of symptoms used to trigger a COVID-19 test could help detect about a third more cases, a study has shown.

Scientists at King’s College London found the current method of only giving PCR tests through the NHS to those displaying a cough, fever or loss of smell missed cases of the virus.

Extending the list to include fatigue, headache, sore throat and diarrhoea would have detected 96% of symptomatic cases, researchers found, compared to 69% under the current approach.

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Scientists at the university and the Coalition for Epidemic Preparedness Innovations (CEPI) analysed data from more than 122,000 adult users of the ZOE COVID Symptom Study app – which tracks symptoms and the spread of virus across the UK – who underwent PCR swab testing.

These users reported experiencing an array of possible COVID-19 symptoms, and 1,202 reported a positive PCR test within a week of first feeling ill.

Analysis of the data found giving PCR swab tests to people with the three classic symptoms of cough, fever or loss of smell would have missed around of third of cases – picking up 69% of symptomatic cases.

But testing people with any of the seven symptoms of cough, fever, loss of small, fatigue, headache, sore throat and diarrhoea in the first three days of illness would have detected 96% of symptomatic cases.

Additionally, according to the data, 31% of people who are ill with coronavirus do not have any of the three classic symptoms in the early stages of the disease when they are most infectious.

Researchers also found users of the app were more likely to select headache and diarrhoea within the first three days of symptoms, and fever during the first seven days, reflecting how different symptoms can hit at different times during the course of the virus.

Cough or dyspnoea (shortness of breath) were reported by 46% of individuals positive for COVID-19 within the first three days of the virus.

Professor Tim Spector from King’s College London said: “We’ve known since the beginning that just focusing testing on the classic triad of cough, fever and anosmia misses a significant proportion of positive cases.

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“We identified anosmia as a symptom back in May and our work led to the government adding it to the list, it is now clear that we need to add more.

“By inviting any users who log any new symptoms to get a test, we confirmed that there are many more symptoms of COVID-19.

“This is especially important with new variants that may cause different symptoms. For us, the message for the public is clear: if you’re feeling newly unwell, it could be COVID and you should get a test.”

The team said their findings could also be used in vaccine efficacy trials.

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Dr Jakob Cramer, head of clinical development at CEPI, said: “Accurate diagnosis of COVID-19 cases is crucial when assessing the efficacy of coronavirus vaccine candidates in large-scale studies, especially since the signs and symptoms associated with the disease are extensive and overlap with other common viral infections.

“The findings of this study provide important insights that will help optimise the choice of triggering symptoms for diagnostic work-up in COVID-19 vaccine-efficacy trials.

“We hope the findings of this study will not only aid CEPI’s COVID-19 vaccine development partners but also the wider R&D community.”

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