LONDON — Losing your sense of smell and taste may be the best way to tell if you have Covid-19, according to a study of data collected via a symptom tracker app developed by British scientists to help monitor the pandemic caused by the new coronavirus.

Almost 60 per cent of patients who were subsequently confirmed as positive for Covid-19 had reported losing their sense of smell and taste, the data analysed by the researchers showed.

That compared with 18 per cent of those who tested negative.

These results, which were posted online but not peer-reviewed, were much stronger in predicting a positive Covid-19 diagnosis than self-reported fever, the researchers at King's College London said.

Of 1.5 million app users between March 24 and March 29, 26 per cent reported one or more symptoms through the app. Of these, 1,702 also reported having been tested for Covid-19, with 579 positive results and 1,123 negative results.

Using all the data collected, the research team developed a mathematical model to identify which combination of symptoms — ranging from loss of smell and taste, to fever, persistent cough, fatigue, diarrhoea, abdominal pain and loss of appetite — was most accurate in predicting Covid-19 infection.

"When combined with other symptoms, people with loss of smell and taste appear to be three times more likely to have contracted Covid-19 according to our data, and should therefore self-isolate for seven days to reduce the spread of the disease," said Dr Tim Spector, a King's professor who led the study.

Dr Spector's team applied their findings to the more than 400,000 people reporting symptoms via the app who had not yet had a Covid-19 test, and found that almost 13 per cent of them are likely to be infected.

This would suggest that some 50,000 people in Britain may have as yet unconfirmed Covid-19 infections, Dr Spector said.

Official figures showed confirmed cases rose 14 per cent in Britain between Monday (March 30) and Tuesday to 25,150 as of Tuesday at 0800 GMT (4pm Singapore time).

The government said 1,789 people have died in hospitals from coronavirus as of 1600 GMT on Monday. REUTERS