Corresponding author: Ian D. Plumb, iplumb@cdc.gov. Some information may be out of date. CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination. The chart summarizes the first follow-up antigen test result for each person during the 59 days after illness onset, or after the initial positive test result if asymptomatic. The Centers for Disease Control and Prevention (CDC) cannot attest to the accuracy of a non-federal website. All rights reserved. Abbreviations: NAAT = nucleic acid amplification test; Ref=referent group. Despite this, the sudden drop in viral load means testing too late might produce a false negative. Persons were recommended to isolate for 10 days but could end isolation after 59 days if the follow-up antigen test was negative; all persons were advised to wear a well-fitting mask around others and to avoid close contact with persons at elevated risk for severe COVID-19, until the end of the 10-day period. By Valerie DeBenedette In this case, and where rapid test turnaround time is critical, there is value in providing immediate results with antigen tests. Correlation might vary between some tests or after introduction of the Omicron variant, although initial viral titers appear to be similar between Omicron and B.1.617.2 (Delta) variants. Fourth, approximately 22% of persons who were 59 days after illness onset or an initial positive test result opted to have a follow-up antigen test, introducing potential selection bias. PCR tests are more sensitive, and are able to detect the presence of the virus earlier. Updated guidance based on new published studies on antigen test performance. The authorized instructions for use for each test, including when and how to read each test, can also be found at FDAs In Vitro Diagnostics EUA. Sometimes an at-home COVID-19 antigen test can have a false-negative result. Self-isolate as soon as you have tested positive for COVID-19 or start having symptoms. Although antigen tests generally have lower sensitivity compared to NAATs, they can also be used to test for infection with specific attention to the context in which they are used, described below. In a multivariable model, a positive antigen test result was more likely after 5 days compared with 9 days (adjusted odds ratio [aOR]=6.39) or after symptomatic infection (aOR=9.63), and less likely after previous infection (aOR=0.30), receipt of a primary COVID-19 vaccination series (aOR=0.60), or after both previous infection and receipt of a primary COVID-19 vaccination series (aOR=0.17). Clinical performance of NAATs and antigen tests may differ from clinical utility when considering issues of test availability, quality of specimen collection and transport, and turnaround times of results. Compared with asymptomatic infection. A positive test result for coronavirus (COVID-19) means it's very likely you had COVID-19 when the test was done. For more information, see CMS How to Obtain a CLIA Certificate. They help us to know which pages are the most and least popular and see how visitors move around the site. For example, a low likelihood of SARS-CoV-2 infection would be a person who has had no close contact to a person with COVID-19 and resides in a community where the COVID-19 Community Level is low. Our website is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Medical News Today has strict sourcing guidelines and draws only from peer-reviewed studies, academic research institutions, and medical journals and associations. A person has droplets on their hand and then touches their nose or mouth. Gronvall works with the centers COVID-19 Testing Toolkit. See CDCs guidance for Nucleic Acid Amplification Tests (NAATs). Typically, the incubation and latency periods overlap, but the latency period is slightly shorter. For more information on proper specimen processing and handling for COVID-19 testing, including point-of-care tests, see CDCs guidance on Point-of-Care Testing, and Interim Laboratory Biosafety Guidelines for Handling and Processing Specimens Associated with Coronavirus Disease 2019 (COVID-19). Nick Blackmer is a librarian, fact-checker, and researcher with more than 20 years experience in consumer-oriented health and wellness content. During this time, a person may test positive and have the potential to transmit the virus to others. CDC does not recommend NAATs that use oral specimens (e.g., saliva) for confirmatory testing and instead suggests the use of specimens that are considered optimal for detection, such as nasopharyngeal, nasal mid-turbinate, and anterior nasal swabs. Among persons in this study with symptomatic infection, 64% received a positive antigen test result during the 59 days after symptom onset. A more cautious approach involves testing daily and continuing to wear a mask. See FDAs list of In Vitro Diagnostics EUAs. According to the CDC, mild to moderate cases of COVID-19 remain infectious no longer than 10 days after symptom onset. Some research has aligned more closely with the CDC isolation guidance, which assumes most people will no longer be infectious after five days. For whatever reason, there is still viral genetic material hanging out in their nose.. Positive rapid antigen test results after SARS-CoV-2 infection have been associated with the presence of viable virus, but the role of antigen tests in isolation guidance for persons with SARS-CoV-2 infection is unclear. mmwrq@cdc.gov. Among 541 persons who received a primary vaccination series, 285 (52.7%) had a positive antigen test result, including 127 of 215 (59.1%) persons who had received a booster dose and 158 of 326 (48.5%) who had not received a booster dose. The proportion of positive results declined over time. You can find out more about our use, change your default settings, and withdraw your consent at any time with effect for the future by visiting Cookies Settings, which can also be found in the footer of the site. 241(d); 5 U.S.C. Whether a person is experiencing symptoms of COVID-19 or not, they may wish to take an at-home test. The antigen level in specimens collected either before symptom onset, or late in the course of infection, may be below the tests limit of detection, resulting in a false negative antigen test result, while a more sensitive test, such as most NAATs, may return a positive result. Andrejko KL, Pry J, Myers JF, et al. These cookies allow us to count visits and traffic sources so we can measure and improve the performance of our site. Nasal, Nasopharyngeal, Oropharyngeal, Sputum, Saliva, Varies by test, but generally high for laboratory-based tests and moderate-to-high for POC tests, Varies depending on the course of infections, but generally moderate-to-high at times of peak viral load*, Most 13 days; some could be rapid 15 minutes, Short turnaround time for NAAT POC tests, but few available, Usually does not need to be repeated to confirm results, Short turnaround time (approximately 15 minutes)+. For confirmatory testing, CDC recommends using a laboratory-based NAAT that has been evaluated against the FDA reference panel for analytical sensitivity. Positive results on an antigen test are fairly reliable, meaning that the test is generally positive only when the COVID-19 virus is present in your specimen. *The decreased sensitivity of antigen tests might be offset if the point-of-care antigen tests are repeated more frequently (i.e., serial testing at least weekly). Immunocompromised people have immune systems that don't function well. Information collected included age, sex, whether the person was of the American Indian or Alaska Native race, and whether any symptoms were reported during follow-up. There are two main types of tests COVID-19 that can be used to detect an active infection. If more than 48 hours separate the two specimen collections, or if there have been opportunities for new exposures, a laboratory-based NAAT should be considered a separate test not a confirmation of the earlier test. COVID-19 testing: Choose a home test or an in-person PCR Test. SARS-CoV-2 infection diagnosed by NAAT or antigen test. Reporting of negative results for non-NAAT tests (rapid or antigen test results) is no longer required. It depends on several factors, experts say, and the most important part is which test you use. The Centers for Disease Control and Prevention (CDC) recommend testing at least 5 days after exposure. All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. Using a long nasal swab to get a fluid sample, some antigen tests can produce results in minutes. The Conditions of Authorization in the antigen EUAs specify that CLIA-certified laboratories and testing sites are to follow the manufacturers instructions for use, typically found in the package insert, when performing the test and reading test results. She is the former managing editor of Drug Topics magazine. The proportion of positive test results declined with time since infection and was lower after asymptomatic than symptomatic infections. It is important for healthcare providers and testing professionals to understand the performance characteristics, including sensitivity, specificity, and positive and negative predictive values, of the antigen test being used, and to follow the manufacturers instructions for use, which summarize performance characteristics. Rapid antigen test results have previously been shown to correlate with real-time reverse transcriptionpolymerase chain reaction cycle threshold values (5), and with detection of viable virus, for several days after infection (1,3,6). These cookies may also be used for advertising purposes by these third parties. Going to a Super Bowl Party? J Infect Dis 2022;225:1908. After 59 days, 396 of 729 persons evaluated (54.3%) had a positive antigen test result, with a declining percentage positive over time. * SARS-CoV-2 infection diagnosed by NAAT or antigen test. In general, for all diagnostic tests, the lower the prevalence of infection in the community, the higher the proportion of false positive test results. She is the former managing editor of Drug Topics magazine. Sensitivityindicates how likely a test is to detect a condition when it is actually present in a patient. Any positive test is a positive result, so you will just be wasting scarce test kits.. Facilities should refer to CDCs LOINC In Vitro Diagnostic (LIVD) Test Code Mapping for SARS-CoV-2 Tests. Buder F, Bauswein M, Magnus CL, et al. NAATs that generate presumptive results are not appropriate for use in confirmatory testing. The clinical performance of diagnostic tests largely depends on the circumstances in which they are used. By the day of the initial positive test, 541 (74.2%) had completed a primary COVID-19 vaccination series 14 days earlier, including 215 (39.7%) who had also received a booster dose; 21 (2.9%) persons were partially vaccinated, and 167 (22.9%) were unvaccinated. See CDCs Interpreting Results of Diagnostic Testsfor additional information on the relationship between pretest probability and the likelihood of positive and negative predictive values. Based on their instructions for use, some point-of-care NAATs may not be used for confirmatory testing. Thats why the CDC recommends that people be exempted from any sort of PCR surveillance testing for 90 days after a positive test, Gigi Gronvall, PhD, senior scholar at the Center for Health Security at the Johns Hopkins Bloomberg School of Public Health, told Verywell. Excluded 21 persons with partial vaccination, and 36 unvaccinated persons with previous infection (overall 57 excluded, 41 symptomatic infections and 16 asymptomatic infections). Revised section on evaluating the results of antigen tests, introducing a new testing algorithm, and reflecting what has been learned about the performance of antigen tests and the need to implement confirmatory testing. You should continue wearing a mask and wait at least 48 hours before taking another test. However, the multivariable model accounted for changes in reported characteristics over time. Adjusted analyses excluded 21 persons (14 symptomatic and seven asymptomatic). Persons are classified as symptomatic if symptoms were reported during routine interview or isolation follow-up call. In multivariable models, a positive antigen test result was more likely after 5 days than after 9 days (aOR=6.39; 95% CI = 3.3912.03), symptomatic infection (aOR=9.63; 95% CI = 6.0315.37), and less likely after previous infection (aOR=0.30; 95% CI = 0.190.46), receipt of a primary COVID-19 vaccination series (aOR=0.60; 95% CI = 0.390.93) or after both previous infection and receipt of a primary COVID-19 vaccination series (aOR=0.17; 95% CI = 0.090.33) (Table 2). Experts recommend that you continue isolating or limiting contact if you still test positive. ** 45 C.F.R. Users are referred to the electronic PDF version (https://www.cdc.gov/mmwr) https://www.medrxiv.org/content/10.1101/2022.02.01.22269931v1.full.pdfpdf iconexternal icon. Comparable performance to NAATs in symptomatic persons and/or if culturable virus present, when the person is presumed to be infectious, Longer turnaround time for lab-based tests (13 days), A positive NAAT diagnostic test should not be repeated within 90 days, since people may continue to have detectable RNA after risk of transmission has passed, Less sensitive (more false negative results) compared to NAATs, especially among asymptomatic people. However, this study only looked at early SARS-CoV-2 transmission prior to widespread infections with new variants, so these numbers likely vary. The original SARS-CoV-2 virus and early variants had latency periods of 34 days. What we know about quarantine and isolation. If You Have COVID-19, Is It Really Safe to Only Isolate for 5 Days? Quality assurance procedures should be followed to prevent cross-contamination and inaccurate test results. CDC has developed an algorithm for community testing for people who do not live in congregate settings. How long does it take to get COVID-19 test results? Is there a link between overactive bladder and COVID-19? The incubation period is the time between a persons exposure to an infection and the onset of their symptoms. Sect 3501 et seq. A person can reduce the risk of passing on the virus by avoiding others, especially people who may be medically vulnerable. Antigen tests might be a useful tool to guide recommendations for isolation after SARS-CoV-2 infection. The persistence of a positive result depends on which test was used, since the polymerase chain reaction (PCR) test is more sensitive than the rapid antigen tests that can be administered at home. A positive antigen test result for a symptomatic person generally does not require confirmatory testing; however, it could be considered if the person has a lower likelihood of SARS-CoV-2 infection. QUESTION: Do I need to have another COVID-19 test before I return to work or regular activity following the five days of isolation? Vaccinated was defined as being 14 days after 2 doses of an mRNA COVID-19 vaccine (Pfizer-BioNTech or Moderna) or 1 dose of the Janssen (Johnson & Johnson) COVID-19 vaccine. 4. For this reason, repeat testing after the initial diagnostic test is not recommended during the period of isolation or as a test of cure. Interpreting the results of an antigen test for SARS-CoV-2 depends primarily on the clinical and epidemiological context of the person who has been tested (e.g., symptoms, close contact to others with COVID-19, setting in which they live, likelihood of alternative diagnoses, or disease prevalence in their geographic location). Laboratory and testing professionals who conduct diagnostic or screening testing for SARS-CoV-2 with antigen tests must also comply with Clinical Laboratory Improvement Amendments (CLIA) regulations. 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