This page provides answers to frequently asked questions relating to uses for COVID-19 tests (surveillance, screening, and diagnosis).
This section includes questions and answers regarding the policies outlined in the Immediately in Effect Guidance for Clinical Laboratories, Commercial Manufacturers, and Food and Drug Administration Staff: Policy for Coronavirus Disease-2019 Tests during the Public Health Emergency (Revised). In this section, this guidance is referred to as the Policy for Coronavirus Disease-2019 Tests.
For a directory of FAQs related to SARS-CoV-2 testing, see FAQs on Testing for SARS-CoV-2.
A: Yes. Laboratories performing molecular diagnostic COVID-19 tests for the qualitative detection of SARS-CoV-2 report test results as being positive or negative. Under the molecular diagnostic emergency use authorizations (EUAs), laboratories can also report cycle threshold (Ct) values for authorized molecular diagnostic COVID-19 tests they perform. Ct values indicate the number of amplification cycles needed to reach the threshold at which a molecular diagnostic test can detect a positive signal. Ct values are not comparable between tests and may not be comparable between different lots of the same test, as they are dependent on various factors such as the specimen collection, storage, transport, time from collection, nucleic acid target, primers and probes, extraction method, amplification method, instruments used, etc. Therefore, if the same sample from an individual is tested with two different tests, or even the same test from different lots, they are likely to return different Ct values, even if both tests return a "positive" test result.
While a low Ct value is generally considered to indicate a higher viral load in a patient specimen (i.e., less amplification is needed to detect a positive), and a high Ct value is generally considered to indicate a lower viral load in a patient specimen (i.e., more amplification is needed to detect a positive), currently there is no consensus as to whether or not particular Ct values correlate with a person being or not being infectious or risk level for disease severity. So, appropriate care should be taken with interpretation of Ct values.
A: Surveillance for COVID-19 includes ongoing systematic activities, including collection, analysis, and interpretation of health-related data, essential to planning, implementing, and evaluating public health practice. It is generally used to monitor for an occurrence, such as an infectious disease outbreak, in a population or community, or to characterize the occurrence once detected, such as looking at the incidence and prevalence of the occurrence. Surveillance testing is primarily used to gain information at a population level, rather than an individual level. Surveillance testing may be random sampling of a certain percentage of a specific population to monitor for increasing or decreasing prevalence and determining the population effect from community interventions such as social distancing. FDA generally does not regulate surveillance testing. An example of surveillance testing is a testing plan developed by a State Public Health Department to randomly select and sample 1% of all individuals in a city on a rolling basis to determine local infection rates and trends.
Generally, if at any time a patient-specific result is to be reported by a facility, it must first obtain a CLIA certificate appropriate to the test system the laboratory intends to use and meet all requirements to perform testing. For more information on CMS and CLIA policies, including new policies during the COVID-19 public health emergency, see:
- Research Testing and Clinical Laboratory Improvement Amendments of 1988 (CLIA) Regulations (PDF)
- Frequently Asked Questions: SARS-CoV-2 Surveillance Testing (PDF)
- CLIA University Lab Testing (PDF)
Screening for COVID-19 is looking for occurrence at the individual level even if there is no individual reason to suspect infection such as a known exposure. This includes broad screening of asymptomatic individuals without known exposure with the intent of making individual decisions based on the test results. Screening tests are intended to identify infected individuals prior to development of symptoms or those infected individuals without signs or symptoms who may be contagious, so that measures can be taken to prevent those individuals from infecting others. FDA regulates screening tests as in vitro diagnostic devices and has provided recommendations and information regarding EUA requests for COVID-19 screening tests in the EUA templates referenced in the Policy for Coronavirus Disease-2019 Tests. Examples of screening include testing plans developed by a workplace to test all employees returning to the workplace regardless of exposure or signs and symptoms and testing plans developed by a school to test all students and faculty returning to the school regardless of exposure or signs and symptoms, with the intent of using those results to determine who may return or what protective measures to take on an individual basis.
Diagnostic testing for COVID-19 is also looking for occurrence at the individual level but is performed when there is a particular reason to suspect that an individual may be infected. Diagnostic tests are intended to diagnose an infection in patients suspected of COVID-19 by their healthcare provider such as in symptomatic individuals, individuals who have had a recent exposure, individuals who are in a high-risk group such as healthcare providers with known exposure, or testing to determine resolution of infection. Diagnostic tests may also be appropriate in areas of high community spread, at the discretion of the ordering healthcare provider. FDA regulates diagnostic tests as in vitro diagnostic devices and has provided recommendations and information regarding EUA requests for COVID-19 diagnostic tests in the EUA templates referenced in the Policy for Coronavirus Disease-2019 Tests. Examples of diagnostic testing include testing symptomatic individuals presenting to their healthcare provider, testing individuals who indicate that they were exposed to an individual with a confirmed or suspected case of COVID-19, and testing all individuals present at an event where an attendee was later confirmed to have COVID-19.
A: No. Most EUA-authorized SARS-CoV-2 molecular diagnostic tests have been authorized for use in individuals suspected of COVID-19 by their healthcare providers. Individuals suspected of COVID-19 infection or exposure can be symptomatic, pre-symptomatic, or asymptomatic. Testing of any of these individuals is at the discretion of the healthcare provider ordering the test. Additionally, certain SARS-CoV-2 molecular diagnostic tests have been authorized with a screening claim, for use in individuals without symptoms or other reasons to suspect COVID-19.
A: If you would like to develop and offer a diagnostic test for testing any individual regardless of whether they are suspected of COVID-19 by a healthcare provider -- including the screening of asymptomatic individuals without known exposure with the intent of making decisions based on the test results -- please see the EUA templates for recommendations on how to validate the test for this intended use and submit your EUA request to the FDA.
Diagnostic tests that are authorized for use on individuals suspected of COVID-19 by their healthcare provider are authorized for use on symptomatic individuals and asymptomatic individuals suspected of having COVID-19, such as because they have been exposed to an infected individual. Diagnostic tests offered by the test developer for the screening of any asymptomatic individual, however, are to be validated by their developers and authorized by the FDA specifically for screening purposes.
The FDA recognizes that the CDC has issued guidance relating to screening and that organizations may want to conduct screening of asymptomatic individuals as part of a strategy to assure the safety of their employees, patients, students, and others. Screening using a highly sensitive test, especially given the asymptomatic testing population, leads to the most accurate results when rapid turnaround times are available. The FDA has provided validation recommendations designed to establish high sensitivity for tests intended for screening in the templates referenced above. We encourage developers who want to offer a less sensitive test for screening to discuss validation approaches or alternative testing strategies, such as serial testing, with us.
The FDA's In Vitro Diagnostics EUA page provides information on the performance of each EUA-authorized test. However, available performance data may vary depending on how the test was validated. At the beginning of the pandemic, there were few patient specimens available and developers validated their molecular diagnostic tests using contrived specimens spiked with SARS-CoV-2 viral RNA in different amounts. Doing so allowed tests to be validated quickly while providing a measure of confidence in test performance appropriate at that point in the public health emergency. However, validation with contrived specimens instead of patient samples does not provide a true determination of clinical performance (sensitivity and specificity) and, therefore, comparing the performance of tests using these different specimens, and identifying which ones are more sensitive, is difficult. As the pandemic progressed and more patient specimens became available, the FDA began recommending that developers validate their tests with actual patient specimens. In May, the FDA developed a reference panel to use with EUA-authorized molecular diagnostic tests which will identify which tests are more sensitive than others. Information on tests that have evaluated the reference panel can be found on the FDA's SARS-CoV-2 Reference Panel Comparative Data webpage.
A: An asymptomatic individual may be suspected of COVID-19 by their health care provider for various reasons, such as known exposure or working in a high-risk environment. Such use is within the authorized indications for use of tests intended for individuals suspected of COVID-19 by their health care provider. For licensed health care practitioners who are prescribing or administering an authorized SARS-CoV-2 diagnostic test to be used off-label (outside the authorization) to screen asymptomatic individuals not suspected of having COVID-19, we recommend they consider the information below, as well as the HHS guidance on PREP Act coverage.
Although the current available literature suggests that symptomatic individuals with COVID-19 and asymptomatic individuals without known exposure may have similar levels of viral genetic material, there is limited data on the distribution of viral loads in individuals with and without symptoms across demographics, different settings, and specimen types. Therefore, when screening asymptomatic individuals, health care providers should consider using a highly sensitive test, especially if rapid turnaround times are available. If highly sensitive tests are not feasible, or if turnaround times are prolonged, health care providers may consider use of less sensitive point-of-care tests, even if they are not specifically authorized for this indication (commonly referred to as "off-label"). For congregate care settings, like nursing homes or similar settings, repeated use of rapid point-of-care testing may be superior for overall infection control compared to less frequent, highly sensitive tests with prolonged turnaround times.
If less sensitive tests, such as some rapid point-of-care tests, are used, health care providers should be aware of the performance of the tests and may want to consider different testing approaches, such as serial testing. "Negative" results should be considered as "presumptive negative," and health care providers should consider them in the context of clinical observations, patient history, and epidemiological information. Thus, if there is a significant new outbreak in a congregate care facility or high clinical suspicion of an infection in an individual resident, a negative point-of-care test should be confirmed with a highly sensitive molecular test (refer to CDC guidelines). It is not necessary to perform confirmatory high-sensitivity molecular tests on individuals with negative antigen test or other point-of-care test results if they are obtained during routine screening or surveillance.
Test developers submitting an EUA request to the FDA for tests to screen asymptomatic individuals should consider the validation recommendations outlined in the EUA templates for such use.
A: The FDA does not generally regulate the use of a test for surveillance purposes, such as determining the prevalence of acute infections in a population. The FDA understands that results have been returned to individuals tested for COVID-19 surveillance purposes. If surveillance testing is performed by a non-CLIA certified laboratory, an individual who tests positive for SARS-CoV-2 should have a confirmatory test performed by a CLIA-certified laboratory. Surveillance with return of results and surveillance with pooled or batched testing should be validated on a test platform and test of high sensitivity and positive tests should have a confirmatory test.