21 April 2020 Blog Post: On Why I Don't Offer Antibody Testing... Yet

Several days ago I posted the rationale behind my reluctance to begin COVID-19 antibody testing in the office – this after a number of questions asking about its availability. My primary concern at that time was for the lack of validation data. This was lacking because the FDA had not required companies to submit such as part of the approval pathway (this position has since been reversed).
Over the weekend I read a story about a reporter who drove to Orange County, remained in his car in line for 2 hours and received an antibody test purported to be of 90% accuracy. The reported noted that “90% seemed like a good deal to me.” However, 90% is not a good deal as there are two errors that can be made in testing – a falsely positive test and a falsely negative test. An HIV test for example is 99.9% and 99.5% accurate in these measures.
The FDA has now issued a letter warning healthcare providers about the limits of serological tests to detect SARS-CoV-2 antibodies. The agency is urging clinicians to “not use serological (antibody) tests as the sole basis to diagnose COVID-19 but instead as information about whether a person may have been exposed.”
In mid-March, the FDA “provided regulatory flexibility” (I think this is a generous description but I applaud the author for their linguistic creativity) for test developers. This has resulted in scores of antibody tests quickly hitting the market without the agency’s usual review. As of April 18, just four antibody assays had received emergency use authorization from the FDA.
The agency said it “is not aware of an antibody test that has been validated for diagnosis of SARS-CoV-2 infection.” (Stunning.)
A New York Times story details the low accuracy seen with many of the tests on the market — sometimes as low as 20–30%. One infectious disease expert told the Times: “People don’t understand how dangerous this test is. We sacrificed quality for speed.”
I am hopeful that within these tests is one that is effective and accurate. Now we just need to take the time to identify which one that is.


𝗦𝗶𝗴𝗻 𝗨𝗽 𝗳𝗼𝗿 𝗢𝘂𝗿 𝗡𝗲𝘄𝘀𝗹𝗲𝘁𝘁𝗲𝗿

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