Following international probes into rare blood clots among recipients of Johnson & Johnson and AstraZeneca’s COVID-19 vaccines, blood testing company Versiti has put forward a suite of antibody tests to help identify patients that may be at risk.
While these cases only number in the dozens among the millions of shots administered worldwide, one of the more dangerous aspects of these potentially severe clots—known as cerebral venous sinus thrombosis—is that the typical anticoagulation treatment can make matters worse.
The blood thinner heparin is often used to treat blood clots, but in patients carrying certain platelet-activating antibodies, heparin can trigger harmful drops in platelet counts that could lead to spontaneous bleeding, worsening of their original clots and other complications, according to the Centers for Disease Control and Prevention (CDC).
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Versiti’s blood tests screen for these antibodies, to help healthcare providers choose alternative anticoagulation therapies.
They include an ELISA diagnostic for the PF4, heparin-dependent antibody, followed by additional heparin-induced thrombocytopenia testing or serotonin release assays, depending on the initial result.
The company also offers antibody identification panels if the patient shows low platelet counts in a standard blood draw. The American Society of Hematology recommends testing for PF4 antibodies ahead of treatment for vaccine-induced thrombotic thrombocytopenia, which it describes as an evolving disorder based on limited data.
After a 10-day pause on the use of the J&J vaccine in the U.S.—while the FDA and other agencies reviewed safety data, including the deaths of three recipients—a CDC advisory panel last week recommended restarting nationwide distribution.
The shot, like AstraZeneca’s, will carry warnings about rare and severe blood clots and guidance for proper treatment. Both use adenovirus-based vectors to deliver the vaccine’s instructions into human cells.