Diagnostic tests (molecular or antigen) for SARS CoV-2 virus are becoming more available. Healthcare providers and systems are encouraged to test more symptomatic persons as resources allow.
The testing landscape is expanding and changing rapidly as many commercial clinical labs, most hospital systems, and many academic centers are now performing molecular tests for SARS-CoV-2. There are now several molecular tests and one antigen test approved for the point of care (POC) setting. In addition, self-collection of specimens is now available which reduces the need for PPE and the potential for staff exposures. The FDA has also authorized the first at-home sample collection.
The LAC DPH Public Health Laboratory (PHL) continues to test specimens from high priority patients and settings, view the PHL COVID-19 Testing page for PHL testing criteria and specimen instructions.
The County of Los Angeles is now offering free drive-up mobile testing to L.A. County residents on a priority basis.
LA County Public Health Laboratory (PHL): Diagnostic testing for SARS-CoV-2 infection is available from PHL for high priority patients and settings. View the PHL COVID-19 Testing page for PHL testing criteria and specimen instructions.
Commercial Clinical Laboratories: Testing is available from a variety of commercial clinical laboratories. Please visit their websites for more information. There is no need to contact DPH unless the test result is positive - see Reporting.
All laboratories (regardless of their location) that test Los Angeles County residents must register with the California Department of Public health (CDPH).
Both molecular tests and antigen tests with an FDA emergency use authorization (EUA) can be used to diagnose COVID-19, however antigen tests are less sensitive for SARS-CoV-2. Serology tests have more limited uses.
Read More for Discussion of Diagnostic and Serologic Tests
The term "diagnostic test" is generally used to refer to molecular or antigen tests, both of which can be used to diagnose infection with the SARS-CoV-2 virus.
Molecular Tests (also known as reverse-transcriptase polymerase chain reaction [PCR] tests or nucleic acid amplification tests [NAATs]) detect the presence of viral RNA. The test is typically performed on nasopharyngeal swabs, but can also be performed on other respiratory tract specimens (e.g., oropharyngeal swabs, lower respiratory tract samples). A positive molecular test for SARS-CoV-2 generally confirms the diagnosis of COVID-19. However, false-negative tests from upper respiratory specimens have been well documented. Molecular test diagnostic accuracy is dependent on adequate specimen collection, clinical probability of disease, and the specific test characteristics. See Diagnostic Testing for SARS-CoV-2 for more information.
Antigen Tests detect the presence of viral proteins that are part of the SARS-CoV-2 virus. These tests are often faster and simpler tests to run. Antigen tests are very specific for the virus but are not as sensitive as molecular tests. This means that a positive result is highly accurate, but there is a higher chance of false negatives, so a negative result does not rule out infection. Negative results from an antigen test may need to be confirmed with a molecular test prior to making treatment decisions or to prevent the possible spread of the virus due to a false negative. The FDA has recently issued an EUA for an antigen test and anticipates more will be authorized soon.
Serology Tests detect antibodies to SARS-COV-2 in the blood. There is great interest in using serology tests to determine past or present SARS CoV-2 infection and immunity in patients. At this point in time, however, there are no antibody tests that have been validated for the diagnosis of SARS-CoV-2 infection and the utility of the currently available serologic assays has not been established. Providers should use caution when interpreting the results of serologic tests for SARS CoV-2 until there is additional data on their best use because of concerns of both false negative and false positive results.Use of Serologic Tests
The following are settings where serology tests for SARS CoV-2 should not be used:
See new CDPH Serology Indications guidance for a discussion of possible uses such as the identification of false negative PCR.
If providers choose to use serology tests, it is important to select a serology test that has been fully validated using plasma or serum from confirmed COVID-19 infected individuals or well-characterized reference samples and should read the FDA-approved fact sheet for healthcare providers that accompanies the EUA. A list of EUA authorized serology tests plus performance information can be found here.
On May 4, 2020, The FDA revised the policy allowing companies to market serology tests without FDA review. The FDA now requires companies with antibody tests for SARS-CoV-2 to submit their data validating the tests' accuracy within 10 days. See Insight into FDA’s Revised Policy on Antibody Tests: Prioritizing Access and Accuracy.
Guidance for patients on home isolation and quarantine based on diagnostic test results and FAQs on serology are in multiple languages on the DPH COVID-19 webpage.
Healthcare providers and systems are encouraged to expand SARS CoV-2 molecular testing to more patients with symptoms of COVID-19. Serology tests are not recommended at this time. As facility resources allow, consider using the following testing prioritization scheme.
Rationale includes, ensuring optimal care options for all hospitalized patients, lessening the risk of nosocomial infections, and detecting and preventing outbreaks in in acute- and subacute-care health facilities and non-healthcare congregate living settings.Testing is Encouraged
Rationale includes, ensuring that those who are at highest risk of complications are rapidly identified and appropriately triaged.Consider Testing
As resources allow, test mildly ill individuals to decrease community spread.
Zero Cost Sharing: All commercial and Medi-Cal health plans in California must provide all medically necessary COVID-19 testing and visits with zero cost sharing. All Plan Letter.