• I am going to be traveling to a different geographic location next week. Which location should I use as my input in the When To Test Calculator for Individuals?

     

    The When to Test Calculator for Individuals uses two different parameters to tell you whether and when you need to get tested: 1) Your risk of getting infected with COVID-19, and 2) Your risk of spreading it to other people. It uses the prevalence of COVID-19 in your current location to help it determine how likely it is that you will get infected. It uses the number of people you plan to see next week to help it determine how likely it is that you'll spread the disease.

    Given that, there are a couple of different ways you can handle this situation. One option would be to start by using the location you're in right now. Then recheck your results with the Calculator next week, using the location you're in at that time. When you check the Calculator this week, you'll find out if you need to get tested now, before you travel to your next location. By checking the Calculator again next week, you can find out if you need to get tested once you're in your new location.

    Another option would be to run the Calculator two times right now, to see how your results might differ in one place versus the other. Just remember that the prevalence of COVID-19 in either location might change over the course of the week. When in doubt, come back to the Calculator to find out if your recommendation has changed.

  • I checked my recommended testing strategy with both When To Test Calculators, and I got different results. Why did that happen?

     

    The two Calculators have slightly different goals and base their recommendations on different inputs.

    The goal of the When To Test Calculator for Individuals is to reduce the spread of disease in a given geographic area at a specific time. It does that by recommending that an individual get tested when it's more likely that they might be about to pass COVID-19 on to others.

    The goal of the When To Test Calculator for Organizations is to decrease the overall risk of an outbreak within a workplace or school. It does that by evaluating the COVID-mitigation strategies in place at the organization and recommending the appropriate level of testing needed to complement those strategies.

    For all of those reasons, when you use the two tools you might get different results. If your personal and organizational recommendations differ, consider taking both into account when deciding how often you should get tested for COVID-19.

  • How do my past and future contacts help the When To Test Calculator for Individuals figure out whether I need to be tested?

     

     

    The Calculator tells you whether you need to be tested in order to prevent the spread of COVID-19 in your community.

    The number of people with whom you were in close contact last week - along with the prevalence of COVID-19 in your area - tells the Calculator how likely it is that you have been infected with COVID-19.

    The number of people with whom you plan to be in close contact next week tells the Calculator how likely it is that you will infect other people.

    The Calculator uses those factors and other inputs to develop a recommendation about whether you need to be tested in order to help stop the spread of COVID-19 in your area.

  • What is the definition of a "close contact?"

     

    Both When to Test Calculators are based on CDC guidelines. Current guidelines define a “close contact” as someone who was within six feet of an infected person for a total of at least 15 minutes over the course of 24 hours. One exception to that rule is applicable only to schools: Students who were between three and six feet of an infected person are not considered close contacts as long as they were in school and “correctly and consistently” wearing masks.

    CDC — Close contact definition 

  • How should my organization go about implementing a testing program?

     

     

    The COVID-19 Testing Implementation Guide This guide provides practical guidance on the implementation of a COVID-19 testing program, including consideration of various supply, personnel, facilities, and documentation best practices.

    Open and Safe Schools This website, created by the Shah Family Foundation in partnership with the CDC, provides schools and early education centers with the tools to create a comprehensive COVID-19 testing program. It also includes a list of vendors as well as a database of contacts at schools willing to share their experiences with COVID-19 testing.

    School Testing for COVID-19 The CDC's communication toolkit for testing programs in K-12 schools.

    Chiefs for Change Project Planning Workbook This downloadable Excel spreadsheet, created by the educational leadership group Chiefs for Change, guides administrators step-by-step through the process of designing, implementing, and managing testing in a school district.

  • How does my organization's ability to identify and notify close contacts affect our testing needs?

     

    The faster your organization can identify and notify close contacts of an infected person, the lower your need for testing will be. The reason for this has to do with how contact tracing works and how it affects the likelihood of an outbreak.

    The goal of contact tracing is to identify the people who were in close contact with an infected person while they were contagious, so that those people can be prevented from spreading the disease to others. The faster close contacts are identified and notified of their status, the sooner they can quarantine, and the less likely it is that they will infect other people.

    For COVID-19, the definition of a close contact is someone who was within six feet of an infected person while they were contagious, for a total of at least 15 minutes over the course of 24 hours. When someone with no symptoms tests positive for COVID-19, it’s assumed that they were contagious for the 48 hours (two days) before they provided the sample that was tested.

    In practice, identifying exactly who has been in “close contact” with someone over the course of two days can be quite difficult unless your organization keeps good records. Schools often keep seating charts for classrooms, school buses, and lunch tables for this purpose. In addition, teachers may keep track of which students tend to walk next to one another in the hallways. In an office setting, keeping records of in-person meeting attendance and assembly-line stations may be helpful.

    NOTE: The When To Test Calculator for Organizations assumes that only 50% of an infected person’s close contacts are identified and notified of their status within 24 hours (a contact-tracing efficiency of 0.5). This assumption may be changed in the Calculator’s defaults under Advanced Settings: Main Calculator Settings.

    CDC — Close contact definition

    CDC — Contact Tracing for COVID-19

    CDC — What you can expect to happen during contact tracing

  • What are the main differences between the various test types listed on the results page for the When To Test Calculator for Organizations?

     

    The amount of testing your organization needs to do depends in part on the type of test you use. This Calculator returns results for the test categories listed in the table below, as well as additional results for other pooled testing strategies.

    NOTE: The test categories shown in the Calculator are examples only; they do not represent any one individual test.

    For more information, see the following FAQ topics:

  • Can my organization ask members of our population (i.e., employees and/or students) whether they have been vaccinated?

     

    Yes, but people may choose on an individual basis to decline to answer the question. Once an employer has information about an individual’s vaccine status, they must keep it confidential and separate from the rest of the employee’s personnel files, per the Americans with Disabilities Act (ADA).

    US Department of Health and Human Services – The HIPAA Privacy Rule

    EEOC — Coronavirus and COVID-19

  • How does mask wearing impact my organization's need for testing?

     

    The more people in your organization who wear masks consistently and properly, the less testing you will need to do to prevent an outbreak. Remember: a well-fitted mask, worn properly, covers both the nose and the mouth and does not leave gaps.

    The When To Test Calculator for Orgnanizations asks you to estimate what percentage of people in your organization wear their masks properly at all times when indoors. Most people tend to overestimate the percentage of people in their own organizations who do this, so you may want to input a number a bit lower than you were first considering.

    The Calculator assumes that most people in your organization wear cloth masks, which have a fitted filtration efficiency of approximately 30% (0.3). If your organization requires that everyone wear N95 masks (approximately 95% efficiency) or KN95 masks (approximately 85% efficiency) when indoors, that will significantly change your testing requirements, and you should adjust the Calculator’s settings accordingly. To do that, click on the Show Advanced Settings button on the results page, open the Main Calculator Settings tab, and scroll down to the Mask Efficiency setting (green arrow below).

    Find high-quality masks at Project N95.

    CDC — Use Masks to Slow the Spread of COVID-19
     

  • What is follow-up testing, and how does it work?

     

    Follow-up testing is a critical part of pooled testing. In pooled testing, samples are gathered from multiple people and mixed together into a pool. Instead of testing each individual sample on its own, the lab tests the pool. If a pool tests positive, then at least one individual in the pool may be positive for COVID-19. When this happens, follow-up testing, sometimes referred to as “reflex testing” or “deconvolution,” is required. If follow-up testing isn’t possible, then the entire pool should isolate.

    In follow-up testing, each person or each sample in the positive pool is individually retested to determine which individual(s) in the positive pool are infected. The way follow-up testing happens depends in part on how and where the samples are pooled.

    The When to Test Calculator for Organizations identifies four testing strategies for follow-up testing a positive pool. Details on each strategy appear beneath the table below.

    Automatic

    Pooling Process: Individual samples are collected on-site and taken to an off-site lab. The lab creates the pools and tests the pooled samples using PCR.

    Follow-Up Testing Process: When a positive pool is identified, the lab automatically retests the individual samples that went into the pool using PCR.

    Pros and Cons

    • Eliminates need to re-collect individual samples.
    • Results are provided faster than other pooled testing strategies.
    • May be 2-3x more costly per test than rapid antigen and on-site PCR follow-up.

    On-Site Rapid Antigen

    Pooling Process: Individual samples are collected and pooled on-site. The pooled samples are taken to an off-site lab, which tests them using PCR.

    Follow-Up Testing Process: When a positive pool is identified, all individuals in the positive pool must be resampled. Individual follow-up tests are completed on-site, using rapid antigen tests.

    Pros and Cons

    • Faster than off-site PCR follow-up.
    • Likely to be least expensive option.
    • Requires trained staff on site.
    • Slightly less accurate than PCR follow-up.

    On-Site PCR

    Pooling Process: Individual samples are collected and pooled on-site. The pooled samples are taken to an off-site lab, which tests them using PCR.

    Follow-Up Testing Process: When a positive pool is identified, all individuals in the positive pool must be resampled. Individual follow-up tests are completed on-site, using rapid antigen tests.

    Pros and Cons

    • Faster than off-site PCR follow-up.
    • Less expensive than automatic or off-site PCR follow-up.
    • Requires PCR instruments and trained staff on site.
    • Highly accurate.

    Off-Site PCR

    Pooling Process: Individual samples are collected and pooled on-site. The pooled samples are taken to an off-site lab, which tests them using PCR.

    Follow-Up Testing Process: When a positive pool is identified, all individuals in the positive pool must be resampled. Samples are shipped to an off-site lab, where individual follow-up tests are completed with PCR.

    Pros and Cons

    • Slowest pooling option.
    • More expensive than on-site follow-up.
    • Highly accurate.

    For more information on pooled testing in schools, please download the When To Test K-12 Playbook.

  • What does Emergency Use Authorization (EUA) mean?

     

    In the US, the use of medical tests is regulated by the Food and Drug Administration (FDA). These tests can only be used in this country once they’ve undergone a long approval process. In early 2020, the US was in desperate need of tests for COVID-19; we needed them as soon as possible. For this reason, the US Secretary of Health and Human Services declared that the FDA could use Emergency Use Authorization to make COVID-19 tests available more quickly.

    As its name suggests, EUA is a seldom-used type of authorization which is only allowed during public-health emergencies. It enables the FDA to authorize the use of medical products (including tests) that haven’t undergone the long approval process, provided that “certain criteria are met.” At a minimum, the product must have known and potential benefits that outweigh its known potential risks. In addition, there must be “no adequate, approved, and available alternatives” to the product receiving the EUA.

     

    There are currently no COVID-19 tests that have complete approval from the FDA. Those that have EUA have undergone a shortened version of the approval process, which ensures that they meet the criteria mentioned above, among other requirements. The When to Test Calculator for Organizations assumes that your workplace or school is using a test that has received EUA.

    FDA — Emergency Use Authorization
     

  • How does limiting the number of unmasked people who are allowed to be in close proximity indoors or to participate in high-COVID-risk activities together indoors affect my organization's testing needs?

     

    Limiting the size of groups who participate in these kinds of activities together indoors and unmasked is an extremely effective way to reduce COVID-19 transmission risk, and thus reduce your organization’s need for testing.

    With increasing levels of vaccination in the US, many organizations have decided to do away with mask-wearing altogether. However, some activities remain higher risk than others in terms of their potential for COVID transmission. Any activity that brings a group of people together in close proximity for an extended period of time – most commonly, eating and/or drinking together at the same table – carries a high risk. Other high-COVID-risk activities are those that involve breathing heavily and/or with force, such as sports activities, singing, and playing wind instruments, whether or not the participants are in close proximity to one another.

    If your organization permits either of these types of activities indoors, then the number you would input in this section of the When to Test Calculator for Organizations is the largest group that participates in such activities together. For example, if you have a choir of 10 people and a basketball team of 25, you would input “25.” Doing so allows the Calculator to factor in the additional layer of risk added by permitting these kinds of activities to happen indoors.

    NOTE: The Calculator assumes that cohorts of people eating or drinking together are physically distanced from other people in the room. Thus, if your cafeteria has 20 tables that each seat a cohort of eight people and the tables are more than six feet apart, the size of the cohort is eight.

    However, physical distancing has its limits. If people in your organization are participating in unmasked indoor group activities that involve significant exertion or air expulsion (for example, sports, gym classes, or singing), then the cohort size should be the total number of people in the room, regardless of their distance from one another.

    CDC — Resource on Cohorts in a K-12 school

    Oregon Department of Education – Cohorting  One example of a school-based cohorting system.

  • How can my organization improve our ability to identify and notify close contacts?

     

     

    For COVID-19, the definition of a close contact is someone who was within six feet of an infected person while they were contagious, for a total of at least 15 minutes over the course of 24 hours. When someone with no symptoms tests positive for COVID-19, it’s assumed that they were contagious for the 48 hours (two days) before they provided the sample that was tested.

     

    In practice, identifying exactly who has been in "close contact" with someone over the course of two days can be quite difficult unless your organization keeps good records. Schools often keep seating charts for classrooms, school buses, and lunch tables for this purpose. In addition, teachers may keep track of which students tend to walk next to one another in the hallways. In an office setting, keeping records of in-person meeting attendance and assembly-line stations may be helpful.

     

    NOTE: The When To Test Calculator for Organizations assumes that only 50% of an infected person’s close contacts are identified and notified of their status within 24 hours (a contact-tracing efficiency of 0.5).

    CDC — Contact Tracing for COVID-19

    CDC — What you can expect to happen during contact tracing

  • What kinds of tests can be used for COVID-19 screening or diagnostic testing?

     

    Both kinds of testing can be done using either a PCR (also known as molecular) or antigen test.

    PCR tests look for pieces of the virus’s genetic material. They are the most accurate kind of test for COVID-19 currently available.

    Antigen tests look for viral proteins. They are slightly less accurate than PCR tests.

    Antibody tests (also known as serology tests) look for antibodies to SARS-CoV-2 (the virus that causes COVID-19). Those antibodies can come from a past COVID-19 infection or from a COVID-19 vaccine. This kind of test cannot be used to diagnose an active COVID-19 infection.

    CDC — Interim Guidance for Rapid Antigen Testing

  • What is confirmatory testing, and why would my organization need it?

     

    Confirmatory testing is done to make sure the results of a test are correct. In most cases, confirmatory testing is used to verify whether a negative result on a COVID-19 antigen test is accurate.

    If a test with a specificity of less than 99% comes back positive, especially in low-prevalence environments, confirmatory testing is also recommended. Asymptomatic screening programs are frequently supplemented by confirmatory testing because false positives are more common when screening asymptomatic individuals.

    CDC — Interim Guidance for Rapid Antigen Testing

  • What is the difference between point of care (POC) testing and lab-based testing?

     

    In point-of-care (POC) testing, all testing steps, including sampling and analysis, take place close to or near the patient. For the When to Test Calculators, this means that testing is completed either on-site at your organization’s location or in a health-care provider's office, at a testing site, or in your home. Point-of-care tests give you results quickly. Most of them are antigen tests, but some point-of-care PCR tests are available, as well.

    In lab-based or off-site testing, samples are gathered on-site at your organization or other testing location and are sent to a central lab for processing and analysis. Lab-based tests are generally PCR tests, which are highly accurate. However, they take longer to return results than point-of-care tests do. In some cases, the turnaround time of lab-based tests is not fast enough to prevent an outbreak in an organization.

    CDC — Guidance for COVID-19 Point-of-Care Testing

  • What is R0 (R-naught)?

     

    R0 (R-naught) is a measure of the average number of people who will contract a contagious disease from one infected person. It’s a measure of viral transmissibility, or how fast the disease is spreading.

    When R0 is exactly 1.0, it means that, on average, one infected person will infect one other person. When R0 is less than 1.0, it means that the spread of the disease is decreasing within the community. When R0is above 1.0, the spread of disease is increasing. The more transmissible a disease or disease variant is, the higher its R0.

    The When to Test Calculator for Organizations bases its default R0 on CDC estimates regarding the transmissibility of the most prevalent variant of COVID-19 in the US, which is currently the Delta variant. The Calculator's default R0 for Typical conditions reflects the CDC's low-end estimate of Delta's R0, while the default setting for Hotspot conditions reflects a higher-end estimate of Delta's R0. If you know which variant is most common in your area and wish to change the R0 in your scenarios to reflect that variant, click on "Show Advanced Settings," then "Main Calculator Settings,” and scroll down to "Estimated R0."

    CDC — US COVID-19 Cases Caused by Variants

    CDC — What You Need to Know about Variants

    World Health Organization — Tracking SARS-CoV-2 Variants

    Johns Hopkins Medicine — New Variants of Coronavirus

     

  • How do COVID-19 variants affect testing?

     

    The CDC and FDA, in partnership with the major testing laboratories, continue to carefully monitor the emergence of variants and how their genetic characteristics might affect testing.

    NOTE: As part of its calculations, the When to Test Calculator for Organizations includes a default measurement of how transmissible the virus is. That measurement is called R0 (“R-naught”) or the basic reproduction number for the virus. WhentoTest.org follows CDC guidance to set the Calculator’s default for R0. If you would like to set a specific R0 in your scenarios, you can do so under Advanced Settings: Main Calculator Settings.

    CDC — What You Need to Know About Variants

    CDC COVID — 19 Pandemic Planning Scenarios

    FDA Issues Alert Regarding SARS-CoV-2 Viral Mutation

  • I understand we need a CLIA waiver to implement most tests on-site. What is a CLIA waiver, and what is involved in obtaining one?

     

    As their website states, “The Centers for Medicare & Medicaid Services (CMS) regulates all laboratory testing (except research) performed on humans in the US through the Clinical Laboratory Improvement Amendments (CLIA). . . . The objective of the CLIA program is to ensure quality laboratory testing.”

    Normally, labs need CLIA certification from CMS in order to perform testing. However, the FDA allows some tests to be performed at labs or other locations that do not have CLIA certification, as long as those sites have a CLIA waiver from CMS.

    CLIA-waived tests tend to have the following characteristics:

    • Simplicity
    • Low risk of user error
    • Conducted using unprocessed samples, such as saliva or nasal secretions
    • Unlikely to harm the patient if the test is not performed correctly

    Your organization can apply for a CLIA waiver via the CMS CLIA website or your local State Agency.

    FDA — CLIA Waiver by Application

    CMS — How to obtain a CLIA Certificate of Waiver

  • My organization is being provided with tests or has already implemented a testing program. How can I apply what I learn from the When To Test Calculator for Organizations to this situation?

     

     

    First, figure out what kind of test you are or will be using. (If you’re using pooled testing, you’ll also need to check what kind of follow-up testing you are or will be doing.)

    You can find the list of test types for which the Calculator provides results under the FAQ topic “What are the main differences between the various test types listed in the calculator results?” If you’re not sure which type of test you are or will be using, check with your test vendor for confirmation.

     

    Once you know your organization’s type of test, look at your results in calculator and find the row that matches your test type. (If you’re using pooled testing, you may need to click on “View More Pooling Options” to find the type of follow-up testing your program is or will be using.) The results on that row are the Calculator’s recommended test frequency for your organization.

     

    If the Calculator’s recommendations for your test type aren’t feasible for your organization, or if they indicate that you cannot prevent an outbreak using that type of test, consider how your organization might improve mitigation measures other than testing. By emphasizing consistent mask-wearing, incentivizing vaccination among employees, keeping better track of close contacts, or decreasing the size of cohorts that participate in unmasked activity together, you can decrease your organization’s reliance on testing as a mitigation measure. Use the Calculator to model various scenarios and predict how improvements in these areas can change your test recommendations.