Antibody tests should be thoroughly validated before production use in labs

May 1, 2020

A new opinion piece in the journal Clinical Chemistry, published by the American Association of Clinical Chemistry (AACC), emphasizes that healthcare teams should work closely with clinical laboratory experts to thoroughly validate COVID-19 antibody tests and ensure that they are used properly to minimize the risk of inaccurate results from these tests, which could have potentially life-threatening consequences, according to a news release. 

The authors also said these steps are necessary because the Food and Drug Administration (FDA) allows diagnostic companies to sell this these tests without first going through a formal approval process.

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 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 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 three days, but the most accurate COVID-19 antibody tests cannot 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,” said 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.”

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