Now that diagnostic companies can sell COVID-19 antibody tests without FDA authorization, healthcare teams should work closely with clinical laboratory experts to ensure that these tests are thoroughly validated and used appropriately. A new opinion piece in AACC’s Clinical Chemistry journal emphasizes that this is critical to minimizing the risk of inaccurate results from these tests, which could have potentially life-threatening consequences.
According to a release issued by AACC, after it became clear that FDA’s regulations were hampering COVID-19 testing, the agency relaxed its rules to the point that commercial diagnostic manufacturers can now sell COVID-19 antibody tests without FDA authorization. This change has allowed a flood of coronavirus antibody tests to hit the market, with more than 100 diagnostic companies offering or planning to offer these tests. The surge in availability of these tests has also led to rising hopes that these antibody tests could help to reopen the country. This is because antibody tests are essential to population screening efforts that aim to determine the full extent of the COVID-19 outbreak, which government officials need to know in order to decide when and how to safely ease social distancing measures.
However, worrying reports have emerged that many of these antibody tests give inaccurate results, and that some healthcare institutions are inappropriately using these tests to try to diagnose COVID-19 or to determine who is immune to the virus. These issues could lead to consequences such as people getting exposed to COVID-19 because they mistakenly believe they are immune — and in a worst-case scenario, these problems could even potentially mislead government officials to lift stay-at-home orders prematurely.
To mitigate these risks, Drs. Christopher W. Farnsworth and Neil W. Anderson — lab experts from the Washington University School of Medicine in St. Louis — emphasize that it is up to the clinical laboratory community to fill the vacuum left by FDA and thoroughly examine the performance of antibody tests before they are used. The authors then go on to lay out recommendations for labs to follow when validating these tests. For example, labs should account for how widespread COVID-19 is in their area when designing test validation studies, since disease prevalence actually affects antibody test performance. Farnsworth and Anderson also recommend that labs use specimens from different sources to determine the likelihood that a test will give an inaccurate result. These sources should include symptomatic patients who have tested negative for COVID-19 using standard PCR tests for the virus, as well as patients who have tested positive for the milder coronaviruses that were already common in the U.S. prior to the COVID-19 outbreak.
In addition to validating COVID-19 antibody tests, Farnsworth and Anderson urge labs to communicate with healthcare providers about the scenarios in which these tests should and should not be used. For example, antibody tests should not be used for COVID-19 diagnosis. As the authors observed, the median time from onset of symptoms to patient presentation at their hospital is 3 days, but the most accurate COVID-19 antibody tests can’t detect antibodies until 7–14 days after symptom onset. The authors also point out that antibody tests have limited utility as a backup for molecular COVID-19 tests. At their hospital, only about 1 percent of symptomatic, PCR-negative patients went on to test positive for antibodies.
“In conclusion, while serological assays have generated much hype, there is a need for data to support their clinical utility,” say Farnsworth and Anderson. “When not properly evaluated they have the potential to misdiagnose and misinform. It is also crucial for laboratories to rigorously validate assays to assure they are suitable for their ultimate use. Furthermore, as the general public becomes enamored with the promise of COVID-19 serological testing, it is the responsibility of laboratory professionals to remind everyone of the potential peril.”