Currently only those with one of three symptoms - cough, fever and anosmia – are eligible to book a PCR test. However, a study led by researchers at King's College London who developed the ZOE COVID Symptom Study app, suggests that adding fatigue, sore throat, headache and diarrhoea to the list would have helped to detect 96% of cases.
The study published in the Journal of Infection looked at data from more than 122,305 UK adults using the ZOE app who reported experiencing any potential COVID-19 symptoms between 24 March and 15 September 2020 and received a PCR test result within seven days of symptom onset. App users who had previously recorded having COVID-19 were excluded. Of these 1,202 tested positive for COVID-19.
Symptoms that were recorded between three and seven days of onset were covered by the analyses.
Overall the research found that those with cough or dyspnoea, fever and anosmia/ageusia (which are considered one symptom in the reporting app) accounted for 69% of positive cases.
The study said: 'Cough or dyspnoea were reported by 46% of individuals positive for COVID-19 within the first three days of symptom onset. The addition of fever increased sensitivity to 60%, while the further addition of anosmia/ageusia increased sensitivity to 69%.'
The study found that testing people with cough, fever, anosmia, fatigue, headache, sore throat or diarrhoea in the first three days of illness would have detected 96% of symptomatic cases.
The researchers said that people using the app were more likely to select headache and diarrhoea within the first three days of symptoms, and fever during the first seven days. They added that 31% of people who subsequently tested positive for COVID-19 did not have any of the three symptoms required for a test in the early stages of the disease when they were most infectious.
However, the study also acknowledged that expanding the list of symptoms that made people eligible for a swab test would double the number of tests needed.
For every person who tested positive for COVID-19 with the current three eligible symptoms 46 people tested negative. However on expanding to seven symptoms for every person who tested positive, 95 would test negative.
Professor Tim Spector from Kings College London's School of Life Course Sciences 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.
'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.'