Health care providers are strongly encouraged to test for SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), when patients present with any signs or symptoms consistent with COVID-19 or have had a known exposure to a person with COVID-19 infection. For those fully vaccinated, testing is no longer recommended after exposure if the person remains asymptomatic unless the patient works in healthcare, congregate setting (e.g., homeless shelter or jail) or high density workplace. Due to the nonspecific clinical presentation of COVID-19 and the potential for co-infection with other pathogens, every symptomatic person should be evaluated on a case-by-case basis and testing decisions should be based on the patient’s personal health history. Because many COVID-19 cases have been observed in persons who originally discounted their symptoms due to other existing health conditions, e.g., allergies, prompt and early diagnosis of COVID-19 infection is strongly recommended to prevent further transmission.
Two kinds of tests are available for COVID-19: viral tests and antibody tests. Viral tests, including the Nucleic Acid Amplification Tests (NAATs), rapid point-of-care (POC) NAATs, and antigen tests, are approved or authorized by the U.S. Food and Drug Administration (FDA) and are recommended to diagnose current COVID-19 infection. Laboratory-based NAATs, such as the RT-PCR, are considered the most sensitive tests for detecting SARS-CoV-2 and can be used to confirm the results of lower sensitivity tests such as POC NAATs or antigen tests. Therefore, it may be necessary to confirm an antigen or rapid POC NAAT result with a NAAT, such as a RT-PCR test, especially if the result of the rapid test is inconsistent with the clinical perspective, i.e., a negative antigen test on a symptomatic individual or an asymptomatic case when community transmission levels are high. Both situations create a high pre-test probability (probability of a person having a disease before a test is even performed). When confirming a POC NAAT or antigen test result with a NAAT, it is important that the time interval between collection of samples for the two tests is less than 48 hours, and there have not been any opportunities for new exposures between them. If more than two days separate the two collections, or if there have been opportunities for new exposures, the RT-PCR test should be considered a separate test – not a confirmatory test. Additionally, only those from specimens considered optimal for detection – nasopharyngeal, nasal mid-turbinate, and anterior nasal swabs – should be used (oral specimens are not recommended). Providers should consult the CDC’s Interim Guidance for Antigen Testing for SARS-CoV-2, for the most recent testing algorithm to assist in interpreting results and identifying if confirmatory testing is needed.
CDC recommendations for SARS-CoV-2 testing are based on what is currently known about the virus. Information on testing for SARS-CoV-2 is updated as more information becomes available. Rapid antigen tests perform best when the person is tested in the early stages of infection with SARS-CoV-2 when viral load is generally highest. They also may be informative in diagnostic testing situations in which the person has a known exposure to a confirmed or probable case of COVID-19. At this time, rapid antigen tests for screening is most appropriately used in high-risk congregate settings in which repeat testing can quickly identify persons with a SARS-CoV-2 infection to inform infection prevention and control measures, thus preventing transmission.
Antibody tests approved or authorized by the FDA are used to detect a past infection with SARS-CoV-2. Antibody testing is not currently recommended to assess for immunity to COVID-19 following COVID-19 vaccination or to assess the need for vaccination in an unvaccinated person. Since vaccines induce antibodies to specific viral protein targets, post-vaccination serologic test results will be negative in persons without history of previous natural infection if the test used does not detect antibodies induced by the vaccine. Unvaccinated persons who have tested antibody positive within three months before or immediately following an exposure to someone with suspected or confirmed COVID-19 and who have remained asymptomatic since the current COVID-19 exposure do not need to quarantine, provided there is limited or no contact with persons at high risk for severe COVID-19 illness, including older adults and persons with certain medical conditions.
Any patient for whom COVID-19 infection is suspected or who has a known exposure to COVID-19 should be instructed to isolate at home until test results are known. (Close contacts should already be in 14-day quarantine.) If the test result is positive, patients should be instructed to remain in isolation for a minimum of 10 calendar days from symptom onset (for those with symptoms) or from specimen collection date (for asymptomatic patients). If symptomatic, they should also remain in isolation until afebrile for 24 hours without use of fever-reducing medications and other symptoms have improved. Persons with severe illness, as determined by the provider in consultation with infection control experts, may produce replication-competent virus beyond 10 days that may warrant extending the duration of isolation for up to 20 calendar days after symptom onset.
Patients who test positive for COVID-19 should be encouraged to reflect on possible exposures during the 48 hours prior to symptom onset or date of specimen collection (if asymptomatic) and to answer calls from their local health department to provide important details about how they may have been infected and others they may have exposed.
Testing in Persons with Prior COVID-19 Infection
The CDC provides guidance on testing in person with prior COVID-19 Infections (See: Clinical Questions about COVID-19: Questions and Answers: Testing, Isolation, and Quarantine for Persons Who Have Recovered from Previous SARS-CoV-2 Infection). Until we have more information, the determination of whether a patient with a positive test with past COVID-19 infection is contagious to others should be made on a case-by-case basis. Consider consultation with infectious diseases specialists and public health authorities to review all available information (e.g., medical history, time from initial positive test, RT-PCR Ct values, and presence of COVID-19 signs or symptoms). Persons who are determined to be potentially infectious should undergo evaluation and remain isolated until they again meet criteria for discontinuation of isolation or discontinuation of transmission-based precautions, depending on their circumstances.
Testing in those Fully Vaccinated
Fully vaccinated persons who develop symptoms should be tested. However, current recommendations generally do not recommend testing if named as a close contact to a confirmed case, outside of a healthcare setting. For current guidance on testing fully vaccinated persons refer to CDC’s Interim Public Health Guidance for Testing Fully Vaccinated Persons and Updated Healthcare Infection Prevention and Control in Response to COVID Vaccination.
Regulatory Requirements for Performing POC Testing in Schools: Clinical Laboratory Improvement Amendment (CLIA) Waiver
Laboratory and testing professionals who conduct diagnostic or screening testing for SARS-CoV-2 with rapid antigen or rapid molecular tests must comply with Clinical Laboratory Improvement Amendments (CLIA) regulations. Any laboratory or testing site that intends to report patient-specific test results must first obtain a CLIA waiver and meet all requirements to perform that testing. For more information, see the Centers for Medicare & Medicaid Service’s (CMS) summary of the CLIA regulations. Schools can find information on how to obtain a CLIA waiver at: https://www.cms.gov/Regulations-and-Guidance/Legislation/CLIA/Downloads/HowObtainCertificateofWaiver.pdf.
Reporting of Point of Care (POC) Testing
Facilities that perform POC testing must report each individual positive and negative test result, per federal and state requirements. Facilities not currently sending Electronic Laboratory Reporting files to IDPH must report to IDPH according to the instructions below.
- Register in IDPH’s reporting system with the facility’s CLIA certificate number at: https://redcap.link/dph.illinois.gov.poccovid19registration.
- You will need your CLIA number, ordering provider, facility name, address, phone number, the type of testing platform, and the point of contact email and phone number.
- Once the facility’s registration has been processed, the individual who submitted the registration will receive an email with a link to begin reporting. This link is unique to the facility and can be shared with facility staff who will be reporting results.
- Each positive and negative test result must be reported to IDPH system within 24 hours.
- If you have questions, please email: firstname.lastname@example.org
Last Updated: 5/06/2021