Testing for SARS-CoV-2 in your Setting
COVID-19 Testing should begin with the determination of Who Should Get Tested. As a Health Care Professional (HCP), your goal is to have all the information you need, including information about diagnostic, serological, and lab testing options for SARS-CoV-2. In considering who should get tested, the CDC is recommending the following considerations at the minimum. First, people who have symptoms of COVID-19 should be tested. People who have close contact with a confirmed case of COVID-19 can be tested, even if they present asymptomatic. Lastly, as their HCP provider, your patients who have been asked or requested individuals to be referred to get testing performed should be tested. This clinical judgment can be based on symptomatic or asymptomatic individuals. Also, consider those persons under investigation, required inpatient stay, or even upcoming outpatient procedure. Lastly, as an HCP provider, you may want to look at the seroprevalence of a population. Special populations of healthcare workers, pregnant women, and medical practice populations may consider routine testing to determine the presence of infection or evidence of past infection immunity.
The hallmark symptoms of this virus – coughing, shortness of breath, fever, and loss of taste or smell –the first thing your patients need to do is get a test.
Before looking at testing your chosen population, protect yourself and others by wearing a mask, wash hands often, stay 6 ft from others as often as you can. Testing is currently achieved in two different ways. The first is viral testing, including nucleic confirmation diagnostic tests such as PCR and antigen testing, determining if you have the SARS-CoV-2 virus active in your body and typically indicates you have an active infection. Antigen tests are immunoassays that detect a specific viral antigen, which implies current viral infection. Antigen tests are currently authorized to be performed on nasopharyngeal or nasal swab specimens placed directly into the assay’s extraction buffer or reagent. The second is an antibody test, which could indicate if you had a past infection, and it has been shown to take between 1-3 weeks after infection for proper detection. The presence of antibodies that help fight off infections can provide immunity protection against reinfection.
According to the CDC, Antibody tests should not be used to diagnose a current infection, and all nucleic testing protocols can indicate that you are infected only at the time of testing. Therefore, it is possible and maybe even ideal for testing windows to exist, to help determine infection and help reduce coronavirus spread. Below is an estimate of general biomarker levels during the typical progression of COVID-19/SARS-CoV-2 infection. Please note that this is purely illustrative and should not be used as a primary reference. Refer to the CDC website for tools to help “Stop the Spread,” a self-checker and reporting guidelines. (https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/testing.html). CDC also provides clinical guidelines.
What is the Difference Between Antibody Tests and Diagnostic Tests?
Antibody tests cannot be used to confirm if you currently have the virus, while diagnostic tests cannot confirm if you have immunity to the virus. Both are equally important. A forward-thinking concept of Dual Testing has been looked at in research. At first, antibody testing was thought to aid diagnostic testing in diagnosing infection with those who present late. However, it was discovered that false-negative testing and the need for repeated testing in patients with suspicion of SARS-CoV-2 infection given that up to 54% of COVID-19 patients may have an initial false-negative RT-PCR (doi: https://doi.org/10.1101/2020.04.16.20066787).
In consideration of specific populations, remember it has been shown that the sensitivity of PCR testing is impacted by the timing of sample collection and sampling technique. For example, those undergoing surgery experienced higher mortality rates if the procedure occurs during the incubation period (doi: https://doi.org/10.1016/j.eclinm.2020.100331).
Protecting healthcare workers, outpatient procedures, and patient populations of medical practices can have a unique Dual Test opportunity. The Methodist Health system discovered delaying surgeries in some serology patients with a negative PCR test, even without symptoms who are unlikely to be currently infected. However, with Antigen Testing, a reliable test is available to distinguish who is currently infected. Although uncertainty remains, with this approach, almost by definition will need to pivot as the prevalence of population exposure increases. Our knowledge increases about antibody persistence and titer relevance, and as vaccination impacts these results and their interpretation. As a healthcare provider, familiarize yourself with CDC plans, which can be found on this website. https://www.cdc.gov/vaccines/covid-19/vaccination-resources.html.