Coronavirus Disease 2019

These guidelines are intended for use by healthcare providers, public health professionals, and those organizing and implementing testing in non-healthcare settings. Information for the general public is available at ph.lacounty.gov/covidtests (English) and ph.lacounty.gov/covidpruebas (Spanish).

Currently FDA-authorized viral tests for SARS-CoV-2 (NAATs or antigen) can be used for both diagnostic and screening* purposes. When choosing the type of test to use and when interpreting test results, it is important to consider the purpose of the testing (diagnostic or screening), the test performance characteristics (sensitivity and specificity), and the pre-test probability of infection. For a detailed discussion of COVID-19 test types, their use, and interpretation, see the COVID-19 Testing page.

*Regardless of FDA authorization, for the duration of the public health emergency, CMS has indicated all SARS-CoV-2 diagnostic tests can be used on asymptomatic people. Health plans are required to pay for COVID-19 testing for their enrollees whether they are symptomatic or asymptomatic.

Diagnostic testing

The goals of diagnostic testing are to identify persons actively infected with SARS-CoV-2 virus (based on symptoms or exposure) to help guide clinical and infection control decisions. 

Diagnostic testing is indicated when infection is suspected, such as when the person:

• Has signs or symptoms of COVID-19
  Individuals who have symptoms consistent with acute COVID-19 should be tested for SARS-CoV-2 infection as soon as possible regardless of vaccination status or recent history of previous infection.

• Is a close contact to a confirmed case, regardless of vaccination status
  Testing is required 3-5 days after the last contact with case. In addition, if the close contact is at increased risk for severe illness or if they live with someone who is, COVID-19 viral testing is recommended as soon as possible and, if negative, again on Day 5. Identifying infection early after exposure enables earlier access to treatment options (for those at risk for severe illness) and notification of exposed persons. For details, refer to instructions for close contacts: ph.lacounty.gov/covidcontacts
  Persons who tested positive for COVID-19 in the last 90 days. Testing is not required for close contacts who had a positive COVID-19 viral test in the past 90 days as long as they are asymptomatic. If their first positive test was ≤30 day prior, no testing is recommended. If their first positive test was 31-90 days ago, antigen testing is recommended.

• Is part of an outbreak investigation and response and/or case investigation
  Testing is recommended regardless of vaccination status. Investigations may include testing of asymptomatic persons with recent history of previous infection as directed by Public Health.

Nucleic acid amplification tests (NAATs) or antigen tests can be used for diagnostic testing. Negative results from less sensitive tests (e.g., antigen tests, some NAATs), should be considered presumptive and confirmation with a standard laboratory-based NAAT test (e.g., RT-PCR) is recommended if important for clinical management or infection control decisions. When testing symptomatic persons who have had a positive viral test in the past 90 days antigen tests are preferred. Per the CDC, a positive antigen test may be more be more consistent with active infection.

Screening testing

Screening testing is intended to identify people with COVID-19 who have no signs or symptoms of COVID-19 and no known or suspected exposure to SARS-CoV-2.

The rationale for screening testing is to identify persons with pre-symptomatic or asymptomatic SARS-CoV-2 infection in order to prevent additional spread of the virus.

Both types of viral test (NAAT or antigen) can be used for screening testing. Any patient with a positive viral screening test should be treated as a case and isolated. Decisions regarding confirmatory testing should be based on the pre-test probability of infection and the specificity of the test used. Confirmatory testing, ideally with a laboratory based NAAT, is recommended for persons who screen positive with a rapid antigen test. See interpretation of NAAT and antigen test sections for more information.

Post Omicron surge, LAC DPH is using the CDC COVID-19 Community Levels to assess the impact of COVID-19 illness on health and healthcare systems across the county and adopt corresponding prevention strategies, including screening testing. Priority sector screening requirements and recommendations vary by the COVID-19 Community Level. The priority sectors with screening testing recommendations by Community Level are SNFs, K-12 and early childhood education, shelters for persons experiencing homelessness, worksites, healthcare settings. 

To see the current LA County Community Level and the corresponding priority sector screening testing response visit LA County Post-Surge Dashboard. Screening recommendations are also discussed in sector-specific guidelines.

Additional screening recommendations include:

Screening testing is not recommended for:

• Persons who have had a positive viral COVID-19 test within the past 90 days and are asymptomatic
  Immunocompetent patients who have recovered from acute COVID-19 infection can continue to have detectable SARS-CoV-2 RNA in upper respiratory specimens for 3 months after illness onset and persistent positive antigen tests are possible for at least 24 days. Replication-competent virus has not been reliably recovered from such patients, and they are not likely infectious.
  
  In addition, unless they are close contacts, the probability of re-infection within 90 days remains low. To avoid false positives, they should not be part of screening programs until at least 90 days after the onset of initial illness (or after the date of first positive viral test if they never had symptoms).

All healthcare providers and systems should be able to provide their patients with timely access to SARS-CoV-2 diagnostic testing when indicated. See Health Officer Order: Access to Diagnostic Testing Through Healthcare Facilities for more information. Organizations that need assistance to identify a suitable laboratory provider are encouraged to view the resources in the laboratories section below.

Federal law requires all plans to provide coverage of COVID-19 testing

• Federal guidance: FAQs About Families First Coronavirus Response Act and Coronavirus Aid, Relief, and Economic Security Act Implementation (February 26, 2021).

Zero Cost Sharing

• All commercial and Medi-Cal health plans in California must provide COVID-19 testing and visits with zero cost sharing. Health plans must cover the testing whether the person is symptomatic or asymptomatic and regardless of whether the person has had recent known or suspected exposure to COVID-19. See Department of Managed HealthCare All Plan Letter (7-26-21).