…serological tests can play a critical role in the fight against COVID-19 by helping healthcare professionals to identify individuals who have overcome an infection in the past and have developed an immune response.

Stephan M. Hahn, MD
FDA Commissioner

Serologic Test

Serologic tests analyze specimens, such as blood or saliva, for the presence of antibodies, and can indicate whether or not an individual has mounted a response to an infection rather than detect the virus itself. The review authors caution that their utility in diagnosing acute infections is limited, as antibody response to infection can take days to weeks to be reliably detectable. Serologic assays may be more relevant in scenarios in which patients present with late complications of COVID-19 and RT-PCR may be falsely negative due to a decrease in viral shedding.21  

In March 2020, the FDA issued a policy allowing the developers of certain serologic tests to begin administering them once accuracy and reliability has been established.22 FDA Commissioner Stephan M. Hahn, MD noted in a statement that “serological tests can play a critical role in the fight against COVID-19 by helping healthcare professionals to identify individuals who have overcome an infection in the past and have developed an immune response.” He added that, “in the future, this may potentially be used to help determine, together with other clinical data, that such individuals are no longer susceptible to infection and can return to work.”22  

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Serologic testing may also aid in epidemiologic studies, ongoing surveillance, vaccine studies, and risk assessment of health care workers. 

Home Test

At present, there are no home testing kits approved by the FDA. However on April 21, 2020 the FDA reissued the EUA for a RT-PCR assay developed by LabCorp for COVID-19, which allows for a home collection option of samples. “We worked with LabCorp to ensure the data demonstrated from at-home patient sample collection is as safe and accurate as sample collection at a doctor’s office, hospital or other testing site,” Dr Hahn remarked in a statement from the FDA.23

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Scaling Up Tests

EUAs have allowed for local public health laboratories and academic diagnostic laboratories in the United States to rapidly perform assays for SARS-CoV-2. However, the authors of the Annals review noted that it will be important to continue advancing solutions that can be implemented in less well-equipped laboratories to mitigate the spread of the pandemic on a global scale. Antigen-based tests, for example, may prove useful in both low-resource and home settings to guide quarantine and social distancing measures, especially among patients who are mildly symptomatic. Further, novel diagnostic tools such as Clustered Regularly Interspersed Short Palindromic Repeats (CRISPR) may prove useful to nontraditional and resource-limited settings, such as airports and border crossings. Finally, the review authors emphasized that efforts should be made to leverage existing surveillance networks. The CDC has already begun modifying existing systems used to track annual influenza infections and other respiratory viruses to monitor the spread of COIVD-19.24

Current Testing Guidance

For clinicians who may be considering a test for a person under investigation, the CDC recommends working with local and state health departments to coordinate testing through public health laboratories; alternatively, they may use laboratory tests for COVID-19 that have been granted an EUA by the FDA.25 

Clinicians are advised to use their best judgment to determine whether or not a patient has signs and symptoms compatible with a diagnosis of COVID-19 and whether the patient should be tested. Tests for other causes of respiratory illness should be considered as needed. At present, the CDC recommends COVID-19 priority testing for: 

  • Hospitalized patients with presentations compatible with COVID-19, including but not limited to fever, cough, shortness of breath, chills, muscle pain, new loss of taste or smell, vomiting or diarrhea or sore throat. [High]
  • Healthcare workers, workers in congregate living settings, and first responders with symptoms. [High]
  • Residents in long-term care facilities or other congregate living settings, including prisons and shelters, with symptoms. [High]
  • Persons identified through public health clusters and selected contact investigations. [High]
  • Individuals with symptoms of compatible with COVID-19.
  • Individuals without symptoms who are prioritized by health departments or clinicians, for any reason, including but not limited to:  public health monitoring, sentinel surveillance, or screening of other asymptomatic individuals according to state and local plans.

Recommended infection prevention and control practices should be implemented if a patient is suspected of having COVID-19. The CDC advises clinicians to notify infection control personnel at their healthcare facility and their state or local health department if a patient is classified as a person under investigation for COVID-19. (Note: guidance is subject to change and the latest information can be found on the CDC’s page for evaluating and testing persons with COVID-19)

Moving Forward

“Urgent clinical and public health needs now drive an unprecedented global effort to increase SARS-CoV-2 testing capacity,” noted the review authors in a concluding remark. They emphasized that “the blinding speed with which COVID-19 has spread illustrates the need for preparedness and long-term investments in diagnostic testing.”

…the ability to implement aggressive contact tracing, surveillance and testing will be fundamental to protecting vulnerable populations as the nation takes steps to reopen and Americans begin returning to their daily lives.

Robert R. Redfield, MD
CDC Director

Accordingly, the CDC announced on April 23, 2020 that they will be awarding $631 million to state and local jurisdictions using funds from the Coronavirus Aid, Relief and Economic Security (CARES) Act of 2020,26 with the goal of:

  • Establishing or enhancing the ability to aggressively identify cases, conduct contact tracing and follow up, and implement appropriate containment measures.
  • Improving morbidity and mortality surveillance.
  • Enhancing testing capacity.
  • Controlling COVID-19 in high-risk settings and protecting vulnerable or high-risk populations.
  • Working with healthcare systems to manage and monitor system capacity

Robert R. Redfield, MD, director of the CDC, believes “this infusion of additional funding into the nation’s public health infrastructure will strengthen our capacity to implement tried and true containment measures.” He also noted that “the ability to implement aggressive contact tracing, surveillance and testing will be fundamental to protecting vulnerable populations as the nation takes steps to reopen and Americans begin returning to their daily lives.”26

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This article originally appeared on Infectious Disease Advisor