COVID-19: Understanding Testing

Abstract

Occupational health nurses need to understand tests for COVID-19 infection and antibodies, how to interpret results, and where to find credible information and resources.

Different tests detect the SARS-CoV-2 virus that causes COVID-19 infection and its antibodies. Molecular or antigen testing shows active infection; antibody testing finds people who had the virus and recovered (Centers for Disease Control and Prevention [CDC], 2020c). Occupational health nurses (OHNs) must understand the purpose of these tests, how to interpret results, and where to find credible information and resources.

The “gold standard” for clinical diagnostic detection of SARS-CoV-2 remains the molecular nucleic acid-based tests or Real-Time Reverse-Transcription Polymerase Chain Reaction (RT-PCR) assays (CDC, 2020d). RT-PCR assays detect viral RNA from upper (nasopharyngeal or oropharyngeal sources) or lower respiratory samples (sputum, tracheal aspiration, or bronchoalveolar lavage). Positive viral RNA test results (RT-PCR) indicate active infection; a negative result shows no current active infection, or the sample was collected too early in the infection for detection. (CDC, 2020a). Rapid antigen tests are immunoassays that also detect current infection. Specificity is high for both tests, but RT-PCR tests have higher sensitivity. CDC (2020d) recommends confirming negative antigen tests using the RT-PCR in symptomatic individuals or when there is known exposure to a person positive for COVID-19.

Serologic testing for immunoglobulins (Ig) IgM or IgG does not detect the SARS-Cov-2 virus, it identifies antibodies from an earlier infection (CDC, 2020b). Testing finds antibodies 1 to 3 weeks after symptoms start, but not everyone develops detectable IgM or IgG antibodies. Evidence suggests presence of antibodies decrease infectiousness and offer some immunity from reinfection for a period of time. Antibody testing may find those infected previously, even asymptomatic, and identify populations potentially protected from SARS-CoV-2 (CDC, 2020b). Testing Strategy for Coronavirus (COVID-19) in High-Density Critical Infrastructure Workplaces after a COVID-19 Case Is Identified (https://www.cdc.gov/coronavirus/2019-ncov/community/worker-safety-support/hd-testing.html) gives additional guidance on testing; a key to interpreting test results is available at https://www.whitehouse.gov/wp-content/uploads/2020/05/Testing-Guidance.pdf.

OHNs can educate workers and their families about molecular, antigen, and antibody testing and implement prevention strategies to help control this deadly pandemic. Primary prevention includes advocating for workplace policies and procedures on hand washing, mask wearing, and social distancing plus instructions on proper implementation. Secondary prevention is diagnostic testing of symptomatic workers. Anyone not masked and closer than 6 feet for longer than 15 minutes near an infected worker needs testing; there are often asymptomatic or pre-symptomatic workers with SARS-CoV-2 present at the workplace who may not know they are infected. Screening asymptomatic workers and contact tracing after positive results are crucial to prevent infection spread. The OHN must assure privacy and the workers confidentiality during testing or screening and when sharing results. For infected workers, tertiary prevention strategies involve managing health consequences and helping interpret medical information. Workers need explanations about quarantining, self-isolation, and antibody immunity along with how to protect loved ones.

The COVID-19 pandemic is a rapidly evolving global health crisis, and this information about screening and prevention strategies is based on what is currently known. Thus, OHNs must continually review credible sources and evaluate information discussed in the workplace and community to disrupt false information sharing. The CDC website offers Guidance for Healthcare Workers About COVID-19 (SARS-CoV-2) Testing (https://www.cdc.gov/coronavirus/2019-ncov/hcp/testing.html and a COVID-19) with links to information on testing workers in health care and non–health care settings plus COVID-19 One-Stop Shop Toolkits (https://www.cdc.gov/coronavirus/2019-ncov/communication/toolkits/?deliveryName=USCDC_2067-DM32915) with videos, social media, Public Service Announcements (PSAs), printed materials, checklists, FAQs, and web resources to use in your workplace. The American College of Occupational and Environmental Medicine website includes a COVID-19 Resource Center (http://acoem.org/COVID-19-Resource-Center) with links to relevant websites at all federal agencies responding to the pandemic as well as nongovernmental agencies and The World Health Organization; many sites are updated daily. Sharing credible information is vital to stopping this pandemic.