A third of coronavirus cases could have been missed because people aren't able to get a test on the NHS unless they have one of the classic symptoms.

People have to present either a cough, a fever or loss of smell or taste to qualify for a test.

But researchers at King’s College London (KCL) said that extending the list of symptoms to include fatigue, sore throat, headache and diarrhoea would allow “millions of cases” that have gone unconfirmed to be detected.

The findings, published in the Journal of Infection, are based on data from 122,000 UK adult users of the Zoe Covid Symptom Study app who underwent PCR swab testing.

Professor Tim Spector, lead scientist on the Zoe app and professor of genetic epidemiology at 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.

The Argus: Researchers said extending the list of symptoms would allow “millions of cases” that have gone unconfirmed to be detectedResearchers said extending the list of symptoms would allow “millions of cases” that have gone unconfirmed to be detected

“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.”

Scientists at KCL teamed up with the Coalition for Epidemic Preparedness Innovations (Cepi) to analyse data from 122,000 users, 1,202 of whom reported a positive PCR test within a week of first feeling ill.

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They found that testing people with any of the three classic symptoms would have spotted 69 per cent of symptomatic cases, with 46 people testing negative for every person testing positive.

But the researchers said that extending the list of symptoms to fatigue, headache, sore throat and diarrhoea in the first three days of illness would have detected 96% of symptomatic cases – with 95 testing negative for every positive test.

In addition, the researchers found that 31 per cent of people who are ill with Covid-19 do not have any of the classic symptoms in the early stages of the disease when most infectious.

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

Dr Jakob Cramer, head of clinical development at Cepi, said: “Accurate diagnosis of Covid-19 cases is crucial when assessing the efficacy of Covid-19 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.”

What should I do if I have symptoms?

Anyone with COVID-19 symptoms or a positive test result should stay at home and self-isolate immediately.

This is because you could pass the infection on to others, even if you don’t have symptoms.

You could be fined if you do not self-isolate following a notification by NHS Test and Trace[footnote 1].

You may be entitled to a one-off payment of £500 through the NHS Test and Trace Support Payment scheme if you are required to stay at home and self-isolate.

It may be difficult for some people to separate themselves from others in their household.

Not all these measures will be possible if you are living with children or have caring responsibilities but follow this guidance to the best of your ability in these circumstances.

When to seek emergency medical attention

Look for emergency warning signs. If someone is showing any of these signs, seek emergency medical care immediately:

  • Trouble breathing
  • Persistent pain or pressure in the chest
  • New confusion
  • Inability to wake or stay awake
  • Bluish lips or face