Recommendations for the clinical and laboratory diagnosis of VITT against COVID‐19: Communication from the ISTH SSC Subcommittee on Platelet Immunology

Abstract

Vaccine administration is under way worldwide to combat the current COVID-19 pandemic. The newly developed vaccines are highly effective with minimal adverse effects. Recently, the AstraZeneca ChadOx1 nCov-19 vaccine has raised public alarm with concerns regarding the rare, but serious, development of thrombotic events, now known as vaccine-induced immune thrombotic thrombocytopenia (VITT). These thrombotic events appear similar to heparin-induced thrombocytopenia, both clinically and pathologically. In this manuscript, the ISTH SSC Subcommittee on Platelet Immunology outlines guidelines on how to recognize, diagnose and manage patients with VITT.

Limb ischemia and pulmonary artery thrombosis after the ChAdOx1 nCoV-19 (Oxford–AstraZeneca) vaccine: a case of vaccine-induced immune thrombotic thrombocytopenia

“…9 In VITT, the serotonin-release assay detects anti-PF4 IgG without the addition of heparin. 11 Intravenous immunoglobulin is a suggested treatment for patients with VITT who have a worrisome clinical presentation such as bleeding and continued thrombus formation, as with HIT. We believe this treatment contributed to our patient's eventual improvement.…”

Recognizing, managing and reporting vaccine-induced immune thrombotic thrombocytopenia

“…A complete blood cell count should be ordered for any patient for whom there is a suspicion of VITT. [6][7][8][9] Thrombocytopenia and thrombosis in a patient who received a viral vector vaccine within the previous 30 days markedly increases COMMENTARY the probability of VITT. D-dimer and fibrinogen levels can help clinicians to assess for evidence of coagulation consumption.…”

“…D-dimer and fibrinogen levels can help clinicians to assess for evidence of coagulation consumption. 9 Indeed, early VITT has been reported in patients with low platelets, high D-dimer or low fibrinogen levels alone, even without thrombosis. 10 The screening test for VITT is an enzyme-linked immunosorbent assay (ELISA) for heparin-induced thrombocytopenia (HIT), which is positive in most patients with VITT.…”

“…10 The screening test for VITT is an enzyme-linked immunosorbent assay (ELISA) for heparin-induced thrombocytopenia (HIT), which is positive in most patients with VITT. 5,9 The authors of the related case appropriately mention that other antibody assays (e.g., latex-enhanced immunoassays) used to identify HIT are usually negative in patients with VITT. Clinicians should make themselves aware of which assay is used in their hospital because many Canadian hospitals do not use the ELISA assay.…”

“…Clinicians should make themselves aware of which assay is used in their hospital because many Canadian hospitals do not use the ELISA assay. 6,9 The diagnosis of VITT can be confirmed with a modification of the functional platelet serotonin-release assay with added platelet factor 4 (PF4), which is performed at the McMaster University Platelet Immunology Laboratory (Hamilton, Ont.). However, if a presumptive diagnosis of VITT has been made, 6 clinicians should promptly initiate appropriate treatment, preferably with guidance from a hematologist, without waiting for the results of confirmatory tests.…”