Everything you need to know about at-home COVID testing

See if you're infected from the comfort of your couch.

Hannah Mckay / reuters

COVID vaccination efforts continue to gain momentum both in the US and around the world but that doesn’t mean we’re out of the pandemic woods just yet. Regular 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 FDA has approved a number of COVID tests which can be administered in the comfort of your own home and return results in a matter of minutes rather than days.

If you’ve taken an in-person COVID test in the last year, your 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.

For example, an antigen-based BinaxNOW test correctly detects the virus only about 64 percent of the time in symptomatic people. That figure drops to just 35 percent in asymptomatics. Because antigen tests don’t include a reverse transcription phase, they are faster and less expensive to perform than PCR- and IA-based methods but are less accurate and return higher rates of false negatives — especially among people who have only recently been exposed.

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.

So far, only a handful of at-home tests have earned Emergency Use Authorization (EUA) from the FDA. EUAs are otherwise-unapproved treatments, tests or medical countermeasures that have been allowed to sidestep the formal (and lengthy) FDA approval process in response to life-threatening health crises like the one we are currently facing.

The Ellume COVID-19 Home Test is the first at-home test available without a prescription. It is antigen-based and takes 15 minutes to return a result. You’ll have to swab your nose then drop the sample in a desktop analyzer along with some processing liquid. Once the device does its thing, the results are transmitted via Bluetooth to your smartphone. That data is also shared through a secure, HIPAA compliant cloud connection to health authorities to aid in outbreak mapping. The test is expected to cost around $30 though the company has yet to announce where and when it might become available. The Ellume test displayed 96 percent accuracy in people ages 2 and up during its US clinical trial.

The Biden administration recently announced a $231.8 million deal with the Australian company to purchase 8.5 million units of the test. Ellume “will be delivering 100,000 tests per month from the Australian manufacturing facility until the U.S. facility is built,” a company representative told NPR. “At full capacity, the U.S facility will be able to produce up to 19 million tests per month. The 8.5 million tests for the US government is a portion of the overall manufacturing." However, not all health professionals are excited about this public-private partnership, with one going so far as to characterize the effort as “a spit in the ocean.”

The Cue OTC Test will also soon be available over the counter but unlike the Ellume, it uses a nucleic acid amplification test (similar to PCR) for improved accuracy and generates results in 20 minutes. Per a recent press release, “in prospective studies to evaluate the use of the Cue OTC Test, the results were 97.4% agreement for positive cases and 99.1% agreement for negative cases compared to the results from a highly sensitive EUA PCR laboratory-based test.” The company has not yet announced pricing or availability.

Abbott's BinaxNOW COVID-19 Ag Card Home Test isn’t just a mouthful to say, it’s a whole process. After answering a series of screening questions via the eMed digital health website, Abbot will deliver a test to your home. You’ll then be connected with a “telehealth professional” who will guide you through the sample collection process. Once you drop your sample into the analyzer, you should get your results in about 15 minutes through the Navica smartphone app. The Abbot test costs $25 and is only available with a prescription.

The Lucira COVID-19 All-In-One Test Kit costs $50 and, like the Cue, uses molecular tech. As with BinaxNOW, it requires a prescription so your doctor will have to order it on your behalf. The Lucira test is intended for use by people ages 14 and up, it returns results in 11 to 30 minutes.

If you don’t mind waiting a bit for your results, Amazon is selling Dxterity mail-in tests. Each one costs $110 and requires you post it to the company’s LA-area lab for diagnosis. On the plus side, this test is saliva-based so you won’t have to impale your nasal cavity with a Q-Tip to collect your sample. Results will be available within 24 - 72 hours through the company’s web portal.

Similarly, the CRL Rapid Response COVID-19 Saliva Test can be purchased from the Walgreens website for $119 and returns results in a scant 24 - 48 hours. If you test positive, the company will have a telemedicine rep reach out to discuss the diagnosis and potential next steps.

Though all of the fully at-home tests showed 90 percent-plus accuracy during their clinical trials, those figures can fluctuate when regular folks perform the tests themselves, so don’t treat a negative result as some license to get out and mingle. "When manufacturers are preparing data to submit to FDA, they are conducting studies under very specific, highly controlled conditions that optimize the performance of the test,” Kelly Wroblewski, director of infectious disease programs at the Association of Public Health Laboratories, told the AARP.

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