What To Know When Testing For COVID-19 At Home

COVID-19 vaccination has now started and is gaining momentum both in the United States and around the world. However, nobody should be complacent because it does not mean that we are out of the pandemic woods. Regular virus testing remains an important factor in helping slow the spread of the disease, but has typically required a trip to your doctor or local clinic.

Luckily, that’s no longer the case. In recent months, the U.S. Food and Drugs Administration (FDA) has approved a number of COVID-19 tests which can be administered in the comfort of one's own home and return results in a matter of minutes rather than days.

If a person took an in-person COVID test in the last year, their nasal swab sample was likely diagnosed using a real time reverse transcription–polymerase chain reaction (real time RT–PCR), which is among the most accurate and widely used lab-based methods for detecting viral pathogens such as Zika, Ebola and coronavirus.

The coronavirus only contains single strand RNA for genetic material which, unlike DNA, cannot be independently reproduced without the assistance of a host. As such, the virus must infect and repurpose healthy cells in order to make more of itself. RT–PCR mimics this process by first converting any coronavirus RNA present in a given sample into DNA — hence "reverse transcription" — then creating billions of copies of the genetic material and marking them with a fluorescent dye for identification.

The process is an offshoot of the more general PCR method, which is used to detect pathogens whose genetic material comes in DNA form and therefore doesn’t need amplification. This process is sensitive and highly accurate, albeit time-consuming, but does enable pathologists to detect a coronavirus infection in its early stages since only a minute amount of initial RNA is required. While the RT–PCR technique poses a low chance of outside contamination, its capability is limited in that it can only spot the coronavirus when it's currently present in a sample. This method cannot tell if someone has been previously infected.

Some at-home tests rely on a similar process called isothermal amplification. Like PCR, isothermal amplification generates numerous copies of the coronavirus’ genetic material to aid in detection. Though IA is not as sensitive as the lab-based PCR method, it's more accurate than other at-home tests which look for antigens — bits of coronavirus proteins that provoke the body’s immune response.

The antigen method provides more of a general estimate as to how contagious you are, Dr. Gigi Gronvall of Johns Hopkins University told the NYT. "If you test positive on that, you really need to isolate," she said.

So, if you are asymptomatic, a PCR or similar molecular-based test should be sufficient. If you suddenly find that you can’t smell or taste anything, pick up either a PCR or the most sensitive antigen-based test you can find. If you test positive, regardless of the type of test you use, isolate yourself immediately and call a doctor.