Three kinds of tests are currently available in the US to determine COVID‑19 infection: polymerase chain reaction (PCR), antigen, and antibody. A PCR test reveals if one has a current infection and detects disease by looking for traces of the virus’ genetic material on a sample most often collected via a nasal/nasopharyngeal swab. A PCR test is considered the “gold standard” to detect active infection. Antigen tests (sometimes referred to as rapid diagnostic tests) detect specific proteins on the surface of the coronavirus. Positive antigen test results are highly specific, meaning that if you test positive you are highly likely to be infected. However, these tests have lower specificity, meaning that there is a higher chance of false negatives with antigen tests compared to PCR tests. An antibody (serology/blood) test detects the presence of COVID‑19 antibodies and might indicate past and/or ongoing infection. The FDA has so far granted emergency-use authorization to more than 200 different tests meant to detect a current or past infection from SARS‑CoV‑2, the virus that causes COVID‑19.56
It is important to note that antibody testing measures the proteins your body produces to protect against a specific disease-causing microorganism rather than live virus and has been used for epidemiologic surveillance throughout the pandemic to detect infections that may have been asymptomatic or mildly symptomatic. This is especially useful in detecting asymptomatic carriers, or “silent spreaders,” who do not get tested because they have no symptoms and do not feel ill but may spread up to 80% of infections.57
Another testing modality may also be on the horizon, using a smartphone for more rapid results. It involves swabbing the nose, placing the sample into a devise, and getting a readout in 15-30 minutes. It uses CRISPR diagnostics and can enhance gold-standard PCR-based testing if researchers can make it rapid, portable, and accurate. Current testing for COVID‑19 using PCR requires DNA.58 The coronavirus is an RNA virus. Using PCR, the viral RNA must be converted to DNA, and there must be enough DNA present to be able to perform a reliable test. This 2-step process requires a reaction called amplification, which makes the required amount of DNA to test. It is a time-consuming, cumbersome procedure and requires specific laboratory reagents that can be expensive and difficult to procure.58 CRISPR-Cas13a can quantitatively detect SARS‑CoV‑2 RNA without pre-amplification. A mobile phone-based device can allow for portable, private, and sensitive readout of the assay.58
Finally, on December 15, 2020, a NIH-funded home test receieved FDA authorization.59 The test does not require a presciption. The test is completed using a nasal swab, and the sample is inserted into a single-use cartridge that returns results in 15 minutes. The at-home test analyzer connects to the user’s smartphone through Bluetooth and pairs with a downloadable app that provides step-by-step instructions and displays results. The cost ranges from approximately $100-150.