A person who has just been infected may test negative as the antibodies may not have been created at the time of the scrutiny, say the experts examining the effectiveness of tests. Christmas is approaching, and the authorities of the different countries fear a new coronavirus outbreak break with expected gatherings of people for celebrations. Many have recently warned that it is advisable to get tested for Covid-19 before attending family dinners while giving the caveat that a negative result is not always reliable.
False negatives have been extensively discussed throughout the health crisis as certain people having the virus appear negative as the test fails to detect the infection due to the low viral load or because of the so-called 'window time,' that is, the time elapsing between catching the disease and the likelihood of tests to detect it.
PCR vs serological test
In a diagnostic PCR test, the period between transmission and detection of infection is usually short since the genetic material is detected. However, the problem comes in serological tests, whose sensitivity is lower than those of PCR. Because each individual's immune system is different, this test may or may not detect the infection depending on the day of the infection.
According to several studies, the production of antibodies can be detected from 7 to 10 days after infection, but the correct virus detection will always depend on the sensitivity of the diagnostic tests that are performed. And this is where the false negatives arise, whose diagnosis will vary depending on the date on which the test was performed.
Get tested soon after observing the onset of symptoms
If a test is conducted on the first days of infection, the result may be negative. However, it does not rule out infection, but rather it might be about the lack of the antibodies produced by the immune system to be detected in the test. That is, a person can have the infection and test negative on Thursday but be positive after a couple of days. And this is when the fear arises on the authorities' part since individuals can trust the negative result and thus continue to infect their loved ones. For this reason, it is advisable to undergo the test once more when symptoms of the disease become more apparent or avoid mingling during Christmas altogether.