FDA warns of false positives from SARS-CoV-2 antigen tests

By Erik L. Ridley, LabPulse.com contributing writer

November 3, 2020 -- The U.S. Food and Drug Administration (FDA) has alerted clinical laboratory staff and healthcare providers of the potential for false positive results from antigen tests for rapid detection of SARS-CoV-2.

These false positive findings can occur many reasons, for example when users do not follow instructions for the tests, according to the FDA. The FDA offered several recommendations for clinical laboratory staff and healthcare providers:

  • Be aware that the conditions of authorization in the antigen emergency use authorizations (EUAs) specify that authorized laboratories are to follow the manufacturer's instructions for use, typically found in the package insert, when performing the test and reading test results. If you no longer have the package insert for the test you are using, you can contact the manufacturer. The authorized instructions for use for each test can also be found on the FDA's COVID-19 IVD EUA webpage.
  • Be aware that processing multiple specimens in batch mode may make it more challenging to ensure the correct incubation time for each specimen. Refer to the package insert and ensure proper timing for each specimen when processing the specimen in the test device and reading the results.
  • Be careful to minimize the risks of cross-contamination when testing patient specimens, which can cause false positive results. Insufficient cleaning of the workspace, insufficient disinfection of the instrument, or inappropriate use of protective equipment (for example, failing to change gloves between patients) can increase the risk of cross-contamination between specimens with subsequent false positive results. Consider the U.S. Centers for Disease Control and Prevention (CDC) guidance for changing gloves and cleaning work areas between specimen handling and processing.
  • Consider the CDC's recommendations when using antigen testing in nursing homes and other settings. For positive results, especially in low-incidence counties, consider performing confirmatory a reverse transcription polymerase chain reaction (RT-PCR) test within 48 hours.
  • Remember that positive predictive value (PPV) varies with disease prevalence when interpreting results from diagnostic tests. PPV is the percent of positive test results that are true positives. As disease prevalence decreases, the percent of test results that are false positive increases. Healthcare providers should also take the local prevalence into consideration when interpreting diagnostic test results.
  • Consider positive results in combination with clinical observations, patient history, and epidemiological information.
  • Be aware that the conditions of authorization in the antigen EUAs specify that authorized laboratories are to collect information on the performance of antigen tests and report any suspected occurrence of false positive or false negative results and significant deviations from the established performance characteristics of which they become aware to both the FDA and the test manufacturer.
FDA clears Foundation's FoundationOne Liquid CDx
The U.S. Food and Drug Administration (FDA) has cleared Foundation Medicine's FoundationOne Liquid CDx for companion diagnostic use in patients who might...
Beckman Coulter nabs EUA for COVID-19 IgM assay
The U.S. Food and Drug Administration has granted emergency use authorization (EUA) to Beckman Coulter's Access SARS-CoV-2 immunoglobulin M (IgM) assay,...
Test reveals COVID-19 patients at risk for severe illness
A new test for SARS-CoV-2 viral proteins may help identify COVID-19 patients most at risk for becoming critically ill, according to a study published...
Qiagen to launch rapid portable SARS-CoV-2 antigen test
Qiagen plans to launch the Access Anti-SARS-CoV-2 antigen test, a rapid portable test that can detect novel coronavirus antigens in people with active...
FDA authorizes Abbott's COVID-19 real-time antigen test
The U.S. Food and Drug Administration (FDA) has issued an emergency use authorization for a COVID-19 antigen test developed by Abbott Diagnostics Scarborough...

Copyright © 2020 LabPulse.com

Last Updated ls 11/3/2020 5:38:31 PM



Register below for our weekly Letter from the Editor to receive the latest Clinical Lab news and insights.
Email
Subscribe Today
Do you want to be a Microbiology Insider?

When LabPulse gets hot new information, our Insiders are the first to find out. Stay current in today's competitive market by receiving our exclusive free email updates.

Yes, Keep Me Current