The ongoing COVID-19 pandemic has highlighted the alarming rate at which a novel and virulent disease can spread throughout the world, exemplifying the urgent and increasing need for high performing-diagnostics. Indeed, the World Health Organization has stated that testing for COVID-19 is critical not only to track transmission of the virus, inform case management, and suppress transmission, but also to help understand its epidemiology. In response, many governments have been working to scale up diagnostic development programs so that testing is available to anyone who needs it.
To achieve this goal across as many populations as possible while maintaining test accuracy, population screening must be paired with conclusive diagnostic tests. To do so, a triple-pronged approach of point-of-care testing (POCT), consumer diagnostics, and increased lab capacity is required. This approach is one of the most effective ways to control the spread of infection – but it can’t function without rapid diagnostics. This is especially true in the case of COVID-19, where many symptoms are not easily distinguishable from the common cold or flu. That’s why diagnostics developers – whether individual laboratories or large manufacturers – must devise, manufacture, and adapt tests as quickly as the virus evolves.
Diagnostic testing methods for infectious disease harness a variety of technologies, including molecular and immunoassay platforms. Once an infectious disease outbreak is evident, polymerase chain reaction (PCR) molecular testing is the frontline response, because the required primers can be developed and implemented quickly once the viral sequence is known. Despite its high levels of sensitivity and accuracy using only a small sample of viral RNA, PCR testing requires high-quality swab specimens, expensive facilities, and highly trained technicians. That often limits its use to centralized diagnostic laboratories, which quickly reach maximum capacity.
Immunoassays can test for the presence of a specific viral antigen or for specific antibodies formed in the body’s response to the infection. Within the lab, ELISA assays offer a solution, but present the same issues as PCR in terms of capacity and accessibility. Outside the lab, the lateral flow assay (LFA) is one of the most widely used formats for POCT and consumer testing, due to its ability to produce rapid results simply and cost-effectively. The unique advantages of LFAs have encouraged their adoption across a variety of industries, from environmental remediation to medical diagnostics, as well as for analysis of a variety of target analytes, such as pathogens or biomarkers. These assays are also seen as a key method for monitoring the current pandemic. Consumer or self-test devices harnessing this technology are of particular importance to vulnerable and low-resource communities that may not have ready access to laboratory testing facilities.
However, the traditional approach to developing immunodiagnostic assays also presents the well-documented drawbacks associated with using antibodies. This includes issues of bottlenecks in assay development and production, cost to manufacture, signal sensitivity and specificity, difficult assay targets, and shelf life. That’s not to say that these assays are without hope; novel approaches such as engineered protein structures can help test developers work toward a solution for rapid, reliable, and cost-effective test development.
Intensified viral molecular testing has led to global shortages of testing reagents for COVID-19 and other targets. This only serves to further highlight the need for alternative reagents with quicker development times – or for alternative methodologies altogether. For instance, many hospitals already own the laboratory equipment needed for bead-assisted mass spectrometry, but don’t currently use it for COVID-19 testing. Applying existing technologies to COVID-19 could offer significant expansion of testing capacity.
It’s my hope that the need for mass lab-based testing will be vastly reduced by using POCT and consumer tests for population screening in parallel with highly accurate lab-based diagnostics, thereby easing the pressure on healthcare systems. Advances in the rapid development of diagnostics, and especially POCT diagnostics, are proving vital in enabling timely identification and containment of cases, preventing the spread of COVID-19 and protecting vulnerable communities that may be less equipped to tackle and recover from the outbreak.
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