US de-authorises a second Covid-19 antibody test

US regulators’ efforts to double-check the accuracy claims manufacturers have made for their Covid-19 antibody tests have claimed another scalp. The emergency use authorisation awarded to Autobio Diagnostics’ Anti-Sars-CoV-2 Rapid Test in late April has been revoked after independent testing determined that “it is not reasonable to believe the product may be effective in detecting IgM antibodies” to the coronavirus. Autobio is thus no longer authorised to distribute the test. In its submission to the FDA Autobio claimed 99% sensitivity and specificity for IgG and IgM combined; tests conducted by the National Cancer Institute agreed with the specificity figure but found sensitivity to be 93%. The sensitivity for IgM alone was just 50%. Autobio’s is the second antibody test to have its authorisation rescinded owing to non-replicable accuracy claims; the first was Chembio’s, in June. With several authorised tests yet to undergo this independent investigation, there may well be more to come.

Note: "other" includes two antigen tests, two home sampling kits and one IL-6 test.

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