A new study published on 8 October in the journal Clinical Epidemiology used data from the Office for National Statistics Coronavirus (COVID-19) Infection Survey on a representative population sample of 36,061 people living in England, Wales and Northern Ireland who were tested between 26 April and the 27 June 2020.
According to the data, out of the 115 (0.32%) of those who tested positive, only 16 (13.9%) reported symptoms, while the remaining 99 (86.1%) did not report any common symptoms of infection.
When adjusted for a wider range of symptoms, such as fatigue and shortness of breath, 27 (23.5%) of those who tested positive were symptomatic and 88 (76.5%) had no symptoms to report on the day of the test.
“The fact that so many people who tested positive were asymptomatic on the day of a positive test result calls for a change to future testing strategies. More widespread testing will help to capture “silent” transmission and potentially prevent future outbreaks,” said Professor Irene Petersen (UCL Epidemiology & Health Care).
Petersen claims that future testing programmes should include a wider range of individuals, both symptomatic and asymptomatic, and conduct more frequent tests in high-risk settings like factories and universities.
To save time and resources, testing could be performed by pooling a number of tests in a single analysis to determine the overall level of prevalence, rather than focusing primarily on individual tests.
Even though some previous studies have shown varying levels of asymptomatic spreaders, the new study used a large sample size and representative sampling which make the data more reliable and easier to extrapolate.
“When considering SARS Cov 2 testing it is important to consider the purpose of the test. A test done to indicate whether a person currently has virus levels that are likely to mean they are infectious, and not to rule in or rule out any presence of virus, does not require such a high sensitivity and cheaper rapid tests are more feasible,“ explained co-author Professor Andrew Phillips (UCL Institute of Global Health).