SARS-CoV-2 testing could also be integrated right into a comprehensive approach to reducing transmission that additionally consists of screening for symptoms and contact tracing. When mixed, these methods can establish individuals contaminated with SARS-CoV-2 in order that actions may be taken to sluggish and cease the unfold of the virus.
Individuals present process testing ought to receive clear information on
- The producer and title of the take a look at, the kind of take a look at, the aim of the take a look at, the efficiency specs of the take a look at, any limitations related to the take a look at, who pays for the take a look at, how the take a look at might be carried out, how and when individuals will obtain take a look at outcomes, and;
- Easy methods to perceive what the outcomes imply, what actions must occur after somebody has destructive or constructive outcomes, the distinction between testing for office screening versus for medical prognosis, who will obtain the outcomes, how the outcomes could also be used, and any penalties for declining to be examined.
People examined are required to obtain affected person reality sheets as a part of the take a look at’s Emergency Use Authorization (EUA).
If an individual has obtained a COVID-19 vaccine, it doesn’t have an effect on the outcomes of their SARS-CoV-2 viral checks (nucleic acid amplification checks [NAAT] or antigen). As a result of the Pfizer-BioNTech, Moderna, and Johnson & Johnson COVID-19 vaccines use the SARS-CoV-2 spike protein to generate an immune response, a constructive serologic (antibody) take a look at for spike protein IgM/IgG may point out both earlier an infection or vaccination. Antibody testing isn’t at present really helpful to evaluate for immunity to SARS-CoV-2 an infection following COVID-19 vaccination or to evaluate the necessity for vaccination in an unvaccinated individual. To judge for proof of earlier an infection in a vaccinated particular person, an antibody take a look at particularly evaluating IgM/IgG to the nucleocapsid protein needs to be used (e.g., for public well being surveillance or the prognosis of Multisystem Inflammatory Syndrome in Youngsters (MIS-C) or Multisystem Inflammatory Syndrome in Adults (MIS-A)). For steering on quarantine and testing of people who are up to date with their vaccines, please go to COVID-19 Quarantine and Isolation | CDC.
Many varieties of checks are used to detect SARS-CoV-2,1 and their efficiency traits range.
- Some checks present outcomes quickly (inside minutes); others require time for processing.
- Some have to be carried out in a laboratory by skilled personnel, some may be carried out on the level of care, and others may be carried out at home or wherever.
- Some checks are very delicate (i.e., few false-negative outcomes or few missed detections of SARS-CoV-2); others are very particular (i.e., few false-positive outcomes or few checks incorrectly figuring out SARS-CoV-2 when the virus isn’t current); and a few are each delicate and particular.
- Some checks may be carried out incessantly as a result of they’re cheaper and simpler to make use of than different checks, and provides are available.
When deciding on which SARS-CoV-2 take a look at to make use of healthcare suppliers, public well being professionals, and people organizing and implementing testing ought to contemplate the context wherein they’re getting used, together with the prevalence of SARS-CoV-2 within the inhabitants being examined (See Desk 1) and the standing (indicators, signs, shut contacts) of the individual being examined.
Take a look at Varieties
Viral checks, together with NAATs and antigen checks, are used as diagnostic checks to detect present an infection with SARS-CoV-2 and to tell a person’s medical care. Viral checks will also be used as screening checks to cut back the transmission of SARS-CoV-2 by figuring out contaminated individuals who must isolate from others. See FDA’s listing of In Vitro Diagnostics Emergency Use Authorizations for extra details about the efficiency of particular licensed checks.
- NAATs are high-sensitivity, high-specificity checks for diagnosing SARS-CoV-2 an infection. NAATs detect a number of viral ribonucleic acid (RNA) genes and point out a present an infection or a latest an infection however, attributable to extended viral RNA detection, usually are not at all times direct proof for the presence of virus able to replicating or being transmitted to others. Most NAATs must be processed in a laboratory, and time to outcomes can range (~1–3 days), however some NAATs are point-of-care checks with outcomes obtainable in about 15–45 minutes. Most NAATs produce qualitative outcomes. NAATs may be carried out on higher respiratory specimens, comparable to nasopharyngeal, nasal mid-turbinate, anterior nasal, or saliva.
- Antigen checks are immunoassays that detect the presence of a particular viral antigen. Antigen checks typically have comparable specificity, however are much less delicate than most NAATs. Most are cheaper than NAATs and may be processed on the level of care with outcomes obtainable in minutes and thus can be utilized in screening applications to shortly establish those that are more likely to be contagious. Due to the efficiency traits of antigen checks, it might be mandatory to substantiate some antigen take a look at outcomes (a destructive take a look at in individuals with signs or a constructive take a look at in individuals with out signs) with a laboratory-based NAAT. Nevertheless, primarily based on the authorization from FDA, some point-of-care NAATs that present presumptive outcomes can’t be used for confirmatory testing. Use of the Antigen Testing Algorithm is really helpful to find out when confirmatory testing is required.
Appropriate interpretation of outcomes from each antigen checks and confirmatory NAATs, when indicated, is vital.
Optimistic take a look at outcomes permit for identification and isolation of contaminated individuals, in addition to a case interview to establish and notify the case’s shut contact(s) of publicity and the necessity to quarantine.
Damaging take a look at ends in individuals with recognized SARS-CoV-2 publicity recommend no present proof of an infection. These outcomes signify a snapshot of the time round specimen assortment and will change if the identical take a look at was carried out once more in a number of days. For steering on quarantine after a destructive take a look at, go to COVID-19 Quarantine and Isolation | CDC. In healthcare facilities with an outbreak of SARS-CoV-2, suggestions for viral testing of healthcare suppliers, residents, and sufferers (no matter their vaccination standing) stay unchanged.
Damaging take a look at ends in individuals who don’t have any signs and no recognized publicity recommend no an infection. All individuals being examined, no matter their outcomes, ought to discuss to their healthcare supplier about risk reduction behaviors that assist stop the transmission of SARS-CoV-2 (e.g., sporting a well-fitting mask, bodily distancing, avoiding crowds and poorly ventilated areas).
Antibody (or serology) tests are used to detect earlier an infection with SARS-CoV-2 and may help within the prognosis of multisystem inflammatory syndrome in children (MIS-C)external icon and in adults (MIS-A)2. CDC doesn’t suggest utilizing antibody testing to diagnose present an infection. Relying on the time when somebody was contaminated and the timing of the take a look at, the take a look at won’t detect antibodies in somebody with a present an infection. As well as, it’s not at present recognized whether or not a constructive antibody take a look at consequence signifies immunity in opposition to SARS-CoV-2; subsequently, presently, antibody checks shouldn’t be used to find out if a person is immune in opposition to reinfection. Antibody testing is getting used for public well being surveillance and epidemiologic functions. As a result of antibody checks can have completely different targets on the virus, particular checks is perhaps wanted to evaluate for antibodies originating from previous an infection versus these from vaccination. For extra details about COVID-19 vaccines and antibody take a look at outcomes, discuss with Interim Clinical Considerations for Use of mRNA COVID-19 Vaccines Currently Authorized in the United States.
Overview of Testing Eventualities
Diagnostic testing is meant to establish present an infection in people and is carried out when an individual has indicators or signs per COVID-19, or is asymptomatic, however has latest recognized or suspected shut contact publicity to SARS-CoV-2.
Examples of diagnostic testing embrace:
- Testing individuals with signs per COVID-19, whether or not or not they’re updated on their vaccinations.
- Testing individuals on account of contact tracing efforts.
- Testing individuals who point out that that they had shut contact publicity with somebody suspected or confirmed as having COVID-19.
Screening checks are really helpful for individuals who don’t have any signs and no recognized, suspected, or reported shut contact publicity to SARS-CoV-2. Screening helps to establish unknown instances in order that measures may be taken to forestall additional transmission.
Examples of screening embrace:
- Testing workers in a office setting
- Testing college students, school, and workers in a college or college setting
- Testing an individual earlier than or after journey
- Testing at house for somebody who doesn’t have signs related to COVID-19 and no recognized exposures to somebody with COVID-19
Public well being surveillance is meant to observe population-level burden of illness, or to characterize the incidence and prevalence of illness. Surveillance testing is primarily used to achieve info at a inhabitants stage, fairly than a person stage, and customarily includes testing of de-identified specimens. Surveillance testing outcomes usually are not reported again to the person. As such, surveillance testing can’t be used for a person’s healthcare determination making or particular person public well being actions, comparable to isolation or quarantine.
An instance of surveillance testing is wastewater surveillance.
Selecting a Take a look at
When selecting which take a look at to make use of, it is very important perceive the aim of the testing (diagnostic or screening), efficiency of the take a look at throughout the context of the extent of neighborhood transmission, want for speedy outcomes, and different concerns (See Desk 1). For instance, even a extremely particular antigen take a look at might have a poor constructive predictive worth (excessive variety of false positives) when utilized in a neighborhood the place prevalence of an infection is low. As a further instance, use of a laboratory-based NAAT in a neighborhood with excessive transmission and elevated take a look at demand might lead to diagnostic delays attributable to processing time and time to return outcomes. Optimistic and destructive predictive values of NAAT and antigen checks range relying upon the pretest likelihood. Pretest likelihood considers each the prevalence of the extent of neighborhood transmission in addition to the medical context of the person being examined. Extra info is obtainable on sensitivity, specificity, constructive and destructive predictive values for antigen tests and antibody tests, and the connection between pretest probability and the likelihood of positive and negative predictive values[458 KB, 1 Page]. Additionally see FDA’s letters to medical laboratory workers and healthcare suppliers on the potential for false-positive results with antigen tests and the potential for false-negative results with molecular tests if a genetic variant of SARS-CoV-2 is discovered within the a part of the viral genome assessed by the take a look at.
Desk 1 summarizes some traits of NAATs and antigen checks to contemplate for a testing program. Given the chance of transmission of SARS-CoV-2 from asymptomatic and presymptomatic individuals with SARS-CoV-2 an infection, use of antigen checks in asymptomatic and presymptomatic individuals may be thought-about. FDA has offered a listing of FAQs for healthcare providers who are using diagnostic tests in screening asymptomatic individuals, and the Facilities for Medicare & Medicaid Providers will temporarily exercise enforcement discretionexternal icon to allow the usage of antigen checks that aren’t at present licensed to be used in asymptomatic people at some point of the COVID-19 public well being emergency beneath the Medical Laboratory Enchancment Amendments of 1988 (CLIA). Laboratories that carry out screening or diagnostic testing for SARS-CoV-2 will need to have a CLIA certificates and meet regulatory necessities. Exams which have obtained an EUA from FDA for point-of-care (POC) use may be carried out with a CLIA certificates of waiver.
Viral Ribonucleic Acid (RNA)
Nasal, Nasopharyngeal, Oropharyngeal, Sputum, Saliva
Nasal, Nasopharyngeal, Saliva
Varies by take a look at, however typically excessive for laboratory-based checks and moderate-to-high for POC checks
Varies relying on the course of an infection, however typically moderate-to-high at instances of peak viral load*
Licensed for Use on the Level of Care
Most 1-3 days. Some could possibly be speedy in quarter-hour
Ranges from quarter-hour to half-hour
Average (~$75-$100/take a look at)
Most delicate take a look at methodology obtainable
Brief turnaround time for NAAT POC checks, however few obtainable
Often doesn’t must be repeated to substantiate outcomes
Brief turnaround time (roughly quarter-hour)+
When carried out at or close to POC, permits for speedy identification of contaminated individuals, thus stopping additional virus transmission locally, office, and so on.
Comparable efficiency to NAATs in symptomatic individuals and/or if culturable virus current, when the individual is presumed to be infectious
Longer turnaround time for lab-based checks (1–3 days)
Greater price per take a look at
A constructive NAAT diagnostic take a look at shouldn’t be repeated inside 90 days, as a result of individuals might proceed to have detectable RNA after threat of transmission has handed
May have confirmatory testing
Much less delicate (extra false destructive outcomes) in comparison with NAATs, particularly amongst asymptomatic individuals
*The decreased sensitivity of antigen checks is perhaps offset if the POC antigen checks are repeated extra incessantly (i.e., serial testing at the very least weekly).
^ Prices for: NAATsexternal icon
+Refers to point-of-care antigen checks solely.
Well being Fairness in SARS-CoV-2 Testing
CDC’s COVID-19 Response Health Equity Strategy outlines a plan to cut back the disproportionate burden of COVID-19 amongst racial and ethnic minority populations and different inhabitants teams (e.g., important and frontline employees, individuals dwelling in rural or frontier areas) who’ve skilled a disproportionate burden of COVID-19. One part to maneuver in direction of larger well being fairness and to cease transmission of SARS-CoV-2 is making certain availability of assets, together with entry to testing for populations who’ve skilled longstanding, systemic well being and social inequities. All inhabitants teams, together with racial and ethnic minority teams, ought to have equal entry to reasonably priced, high quality and well timed SARS-CoV-2 testing – with quick turnaround time for outcomes — for prognosis and screening to cut back neighborhood transmission. Efforts needs to be made to handle boundaries which may overtly or inadvertently create inequalities in testing.
As well as, completeness of race and ethnicity knowledge is a crucial think about understanding the influence the virus has on racial and ethnic minority populations. The U.S. Division of Well being and Human Providers has required laboratories and testing facilities to reportexternal icon race and ethnicity knowledge to well being departments, along with different knowledge components, for people examined for SARS-CoV-2 or recognized with COVID-19. Healthcare suppliers and public well being professionals must ask and report race and ethnicity for anybody receiving a reportable take a look at consequence and guarantee these knowledge are reported with the individual’s take a look at outcomes with a view to facilitate understanding the influence of COVID-19 on racial and ethnic minority populations.
In communities with the next proportion of racial and ethnic minority populations and other populations disproportionately affected by COVID-19, well being departments ought to guarantee there’s well timed and equitable entry to and availability of testing with quick consequence return, particularly when the extent of neighborhood transmission is substantial or excessive.
Some methods to realize this objective embrace:
- Use a social vulnerability index to help in deciding on testing websites.
- Assess the capability of those websites to increase diagnostic and screening testing to fulfill the demand for impacted areas. This consists of assessing the supply of free testing, wait instances for testing and for outcomes, and classes of accessible take a look at (NAAT vs. antigen), in addition to figuring out and eradicating boundaries to testing (e.g., options to drive-through testing for a neighborhood the place many don’t have vehicles; availability of testing on evenings and weekends).
- Enhance the supply of free testing websites in communities. Employers, community-based, and faith-based organizations may be vital companions to extend the variety of free, community-based testing websites. This enlargement ensures that wait instances each for testing and reporting of outcomes are decreased, serving to restrict the unfold of SARS-CoV-2.
- Enhance public messaging concerning the significance of testing and talk these messages in a number of languages and venues, significantly in communities at increased threat and disproportionately impacted by the virus.