A Guide to Rapid Testing
Testing has played a critical role in combating the spread of SARS-CoV-2, which causes COVID-19. The overall effectiveness of testing relies on accuracy, reliability, availability, and turnaround time. Currently, the most widely-used testing method collects a sample using a nasopharyngeal swab, and analyzes the sample using a technique called RT-PCR. While this technology is reliable and accurate, it falls short in turnaround time. Turnaround time (TAT) is the time it takes for a patient to receive their result after a test is performed. Furthermore, RT-PCR testing has been plagued by supply shortages of critical testing components, such as RNA isolation kits and expensive testing machinery.
As society reopens, the demand for rapid tests with a 15-minute turnaround time is growing exponentially. Rapid tests that detect an active infection are being adopted across multiple industries, including travel, education, professional and college athletics, healthcare, and public-event planning. Rapid testing allows people to be screened immediately before interacting with others, which prevents spread by asymptomatic carriers and significantly increases event safety.
There are two types of rapid tests for SARS-CoV-2 infection: diagnostic tests and antibody tests. A diagnostic test is used to determine if someone has an active coronavirus infection. If the results are positive, the patient should take steps to quarantine and self-isolate to prevent the spread of the disease. An antibody test determines if someone has already had an infection with SARS-CoV-2, which is also important information for patients and scientists.
Rapid diagnostic testing for an active infection detects SAR-CoV-2 antigens, which are proteins specific to that virus, present in a sample. These antigen tests collect a sample using a nasal or nasopharyngeal swab and provide results in about 15 minutes. The tests are specific to the virus, and positive results are highly reliable. While negative results are also generally reliable, a physician may request a non-rapid confirmation test if a person has symptoms but has a negative antigen test result. This can be caused by a patient having a low viral count in their sample. Overall, the benefits of rapid antigen screening far outweigh any downsides, and major corporations and organizations have begun adoption.
To determine a previous history of coronavirus infection, the FDA recommends antibody tests. To help fight off infections, the immune system makes antibodies, which are small molecules that stick to specific germs. The presence of antibodies that recognize SARS-CoV-2 in a person’s blood indicates a history of infection with (or exposure to) the virus. Because antibodies take several days to weeks to develop after an infection begins, antibody tests should not be used to diagnose an active coronavirus infection. The results from antibody tests are important to patients who suspect they may have had COVID-19 and to scientists studying how widespread the virus previously was in an area.
Although not yet approved by the FDA, a new type of rapid diagnostic test is generating a lot of interest. This technology utilizes a spit-cup assay that changes color in the presence of a positive sample. The technology is called rapid colorimetric assay using reverse transcription loop-mediated isothermal amplification (RT-LAMP). If approved, it aims to combine the sensitivity of a PCR-based assay with the simplicity and speed of a rapid antigen assay.
Rapid diagnostic testing and antibody testing are paving the way for safely reopening society and understanding the prevalence of infection in the population. Performing rapid testing significantly reduces the risk of human interactions, because it identifies asymptomatic carriers before they can interact with a group of people. Finally, despite advances in testing technology, good-behavior practices are still critical to stopping the spread. This includes practicing social distancing, as outlined in the CDC’s guidelines, and following the advice and regulations on the state and local level.
Writer: Joshua Stabach