Is a Coronavirus Test Always Accurate?

Testing negative on a coronavirus test doesn’t mean that a person doesn’t have the virus as it can take some time even days for the virus to appear on the test. Dr. Leana Wen, an emergency physician, said that it is common knowledge that the incubation period for the virus is 14 days and before the incubation period is over you may test negative and show no symptoms but in reality, you may actually be developing the disease inside your body and may be able to transfer it to other people.

A person can be contagious even if he has tested negative for the virus in the coronavirus test.

According to Dr. Rochelle Walensky, who is the chief of Massachusetts General Hospital’s division of infectious diseases, people after testing negative feel like they are out of the woods but in fact, they are not.

She further added that for people who are tested positive with the virus, symptoms may take 5 days or two weeks to appear after that and the general perception is that people are most infectious for the two days before and after the symptoms show up.

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According to estimates from the US Centers for Disease Control and Prevention (CDC), 40% of the people who are infected with the coronavirus show no symptoms and around 50% of the transmissions happen before the symptoms of the virus begin. Walensky called it one of the biggest Achilles heels and also one of the biggest challenges because other coronaviruses don’t transmit without symptoms.

She said that the reason the SARS outbreak was controlled quickly and it didn’t turn into a pandemic was because it did not spread by people who were asymptomatic.

If a person is infected with the virus, he probably may not be tested positive for the virus the next day in the coronavirus test, according to a study published in the medical journal Annals of Internal Medicine. The study projected that during the first four days of being exposed to the virus, when a person is asymptomatic, the probability is 100% of that person getting a wrong negative test result. On the day the person begins to show symptoms the false negativity rate drops to 38% and three days after the beginning of symptoms the false negativity rate dropped to 20%, according to the study.

A senior author of the study and an associate professor of epidemiology Justin Lessler said that that the coronavirus takes some time to replicate and reach detectable levels in the body. He further added that a person can get infected by very few particles but these particles cannot be detected until the particles replicate themselves to become detectable. Lessler believes that getting a coronavirus test before the third day of getting infected is not of much use.

So, what should a person do, if he wants to meet with his loved ones? According to Walensky, the best way to do this is after quarantining for 14 days at least, and if it’s a proper quarantine then there will be no need for testing as it’s the cleanest way for it.

She said that quarantine means staying at home and that ‘quarantine’ and ‘grocery store’ are two words that don’t belong together.