COVID-19 Molecular Testing

A Dynamic Situation

The emergence of SARS-CoV-2 in late 2019 led to tremendous upheaval as COVID-19 transitioned from a localized epidemic to a global pandemic. Since that time, the global biomedical and public health communities have accomplished groundbreaking work, with the rapid development of molecular diagnostic tests and, approximately a year later, a number of highly effective vaccines.¹

Despite vaccine availability in much of the developed world, localized COVID-19 surges continue to appear due to the development of new SARS-CoV-2 variants, such as the more transmissible Delta variant², and more recently the Omicron variant. With ongoing challenges to global vaccine distribution³, it’s become increasingly clear that new variants will be a constant threat⁴, and that even regions with high vaccination rates will need to be prepared for new disease surges.

A Continued Need for COVID-19 Molecular Testing

Given the continued threat of new variants, testing remains a critical and much needed component of ongoing pandemic response measures, although demand may vary over time as caseloads change.^6–8 While there are many different types of tests that have emergency use approval (EUA) in the United States, including molecular diagnostics/nucleic acid amplification tests (NAAT), antigen tests, and serological tests, molecular testing remains the gold standard for identifying SARS-CoV-2 infection.⁹

“Current diagnostic tests for the SARS-CoV-2 pandemic use nucleic acid, antibody and protein-based detections, but viral nucleic acid detection by RT–PCR remains the gold standard.”

–Kevadiya, et al.¹⁰

Table 1. Molecular diagnostic testing vs. antigen testing at a glance (excerpted and adapted from CDC’s Overview of Testing for SARS-CoV-2 (COVID-19) page¹¹)

*The decreased sensitivity of antigen tests might be offset if the POC antigen tests are repeated more frequently (i.e., serial testing at least weekly).
**The Talis One COVID-19 Test System delivers central lab quality test results in less than 30 minutes in a variety of health care settings.
***Refers to POC antigen tests only

Different Scenarios for COVID-19 Testing

As we move into cycles of COVID-19 containment and spread, there are a number of different ways COVID-19 testing can be implemented¹¹:

• Diagnosis—Testing people with COVID-19 symptoms for presence of the virus
• Containment—Testing asymptomatic people who have been in close contact with individuals who have tested positive for SARS-CoV-2
• Screening—Testing asymptomatic individuals to limit disease spread in specific settings, such as places of work, schools, universities, and other large gatherings

Different types of tests are better suited for each of these scenarios. Antigen testing is most accurate with symptomatic people and early in infection when viral load is high^10,11, making it best suited for diagnostic applications or potentially for screening when the frequency of testing is high.¹¹ NAAT is suitable for all three applications, although assays that are performed in a central lab are not scalable or fast enough for screening applications.

Note that the current CDC guidelines recommend using a symptom-based approach to ending isolation and precautions for individuals diagnosed with COVID-19 instead of using a test-based approach.¹¹