Professor Philip Nolan, Chair of the NPHET Irish Epidemiological Modelling Advisory Group has warned that even though the first COVID test shows that there is no virus, it does not mean that you are ‘COVID-free’.
Prof. Philip Nolan made it clear that this is why the close contacts of the confirmed case would be tested twice and that their movements would need to be re-controlled even if the first test was negative.
He added that one in ten people is at risk of contracting the disease through close contact with an infected person.
Prof. Nolan explained through twitter that why COVID-19 tests sometimes fail to detect virus cases. He said there are two reasons for that:
● Initially, 30% of infected people are in the latent period, three to five days after infection, when the virus is spreading within their cells and is not yet detectable.
● Even as they began to transmit the virus, a sensitivity of between 70% and 90% means that the test cannot find the virus anywhere in 10% to 30% of cases.
Professor stated that if someone has symptoms of COVID-19 and the first test result is negative, the doctor can test you again on the suspicion that you may have the SARS-CoV-2 virus that causes COVID-19.
He said that if the probability of a result being negative where there is no virus is 99.7%, then three of every 1,000 tests is a false positive.
Speaking at RTÉ’s Brendan O’Connor, Dr. Martin Coyne said that if a person’s first COVID test result is negative, he / she will confirm that they don’t have the virus.
He pointed out there were instances that when a patient was first tested negative and later tested positive. So people should check again on the seventh day after the first test, Dr. Martin added.