Point-of-care (POC) SARS-CoV-2 tests, which can deliver results in a matter of minutes, could mark a shift away from traditional clinical diagnostic lab tests that take days to POC tests that can be performed in the field.
These POC tests are based on a variety of technologies and formats both old and new: conventional antigen-based tests for detecting viral proteins; isothermal nucleic acid amplification and loop-mediated isothermal amplification (LAMP) for the detection of viral genetic material; and newer CRISPR-based diagnostic tests, which detect viral genetic material but in fewer steps and dispense with polymerase chain reaction (PCR) machines. POC tests are easy to use as they can be deployed in high-risk environments, such as homes or educational institutions, and require little or no specialist training. Furthermore, some POC tests will be suitable for home use once given the go-ahead by regulators. In this way, POC tests promise to be, at the very least, a useful adjunct to lab-based PCR diagnostic testing.
SARS-CoV-2 antigen tests are cost-effective as they are based on the same lateral flow immunoassay (LFIA) format used in home pregnancy tests, and could help track and contain the spread of the pandemic due to ease of use in clinics and eventually homes. Although the sensitivity of antigen-based POC tests is about two orders of magnitude lower than that of a PCR test, the repeated rapid testing of the general public, also known as surveillance testing, could do a better job at identifying contagious individuals than reliable but cumbersome PCR tests. Large-scale rollouts of POC antigen tests have yet to be deployed, but if successfully done, will set a precedent for rapid development and deployment of antigen tests should another Covid-19 outbreak or pandemic occur. Low-income countries cannot afford population-wide testing, but are interested in POC antigen testing as a core diagnostic strategy due to its cost-effectiveness.
Covid-19 antibody tests serve as a cautionary tale, as at the beginning of the pandemic back in March and April, there was great excitement for Covid-19 antibody tests to provide “immunity” testing for those who had already had Covid-19 and now perhaps were immune to the disease. However, time has shown this furor to be misplaced as the initial uptake of Covid-19 antibody tests has still yet to find a strong foothold and function in the Covid-19 testing market. Covid-19 antigen test developers could face a similar dilemma. Because antigen tests have lower specificity than PCR tests, antigen tests can generate higher levels of false positives in low-prevalence settings, that is when a person’s probability of infection and a test’s false positive rate are similar. Because of this, a confirmatory PCR test is still required if an asymptomatic patient tests positive, or if a symptomatic patient tests negative with an LFIA antigen test.
An emerging POC Covid-19 test is CRISPR-based assays, which are reported to be as accurate as PCR tests. CRISPR Covid-19 tests can detect a positive result in five minutes, whereas PCR tests can take up to one or more days. A huge advantage of CRISPR tests is that they can also quantify the amount of virus in a sample, which could allow doctors to tailor treatment decisions to each patient’s condition. CRISPR Covid-19 tests are both highly sensitive and specific, which could eliminate many of the uncertainties associated with traditional POC tests, such as LFIA antigen tests. This begs the question, will CRISPR replace PCR and other traditional POC tests? Now that CRISPR has proven to be as accurate as PCR, the next challenge is to increase CRISPR’s throughput, such that it can be used on many samples per day. Currently, it is tough for a completely new diagnostic technology like CRISPR to compete with the familiarity and infrastructure that accompanies a 20-year old diagnostic technology like PCR.
GlobalData expects POC tests to gain market share in 2021 in the Covid-19 testing market as testing will continue to be one of the most important tools in containing the pandemic. Furthermore, GlobalData expects the successful rapid development and deployment of POC Covid-19 tests to pave the way for new and old POC technologies alike to be developed for other indications, as well.