Haematologist involvement essential in diagnosis and treating VITT: new guidelines

New UK guidelines on management of vaccine-induced immune thrombocytopenia and thrombosis (VITT) post COVID-19 vaccination highlight the importance of getting the right diagnosis and consulting with a haematologist before starting treatment, even before the syndrome is confirmed.

The National Institute for Health and Care Excellence (NICE) has published recommendations defining how to identify and treat VITT based on advice issued by the UK Expert Haematology Panel as reported by the limbic in May [read story here].

Commenting on the recommendations, Dr Sue Pavord, Consultant Haematologist at Oxford University Hospitals, told the limbic  that “the key issue for haematologists is correct diagnosis of the case, because there is a wide spectrum of disorders that can occur after COVID-19 vaccination and VITT has a specific diagnostic criteria.” 

The diagnosis pathway starts with a full blood count to look for evidence of thrombocytopenia, followed by a coagulation screen (including Clauss fibrinogen assay and D-dimer measurement), and a blood film, with final confirmation via the ELISA (enzyme-linked immunosorbent assay) test, which detects the antibody platelet factor 4 (PF4).

NICE’s recommendations state that a clinical haematologist should be involved in any decision relating to starting, modifying or stopping VITT treatment, and include advice on preventing and treating thrombosis in patients as well as addressing the VITT immune response. 

For management of thrombosis linked to VITT, anticoagulation therapy should be administered as soon as the benefit outweighs the risk of bleeding, including in patients who have only had arterial thrombosis.

NICE also recommends use of non-heparin drugs for anticoagulation, such as direct oral anticoagulants, fondaparinux, danaparoid sodium and argatroban, and that when using argatroban patients should be switched to fondaparinux or a direct oral anticoagulant as soon as the bleeding risk has reduced.

Use of heparins, including heparin flushing solution, should be avoided in patients with VITT, and warfarin should not be used until platelet count has returned to normal.

For people with VITT without confirmed thrombosis, but who have thrombocytopenia with very high D-dimer and a positive ELISA test, venous thromboembolism (VTE) thromboprophylaxis should be considered, after taking into account the benefits and risks of treatment. Again, in this setting treatment should be with non-heparin drugs such as direct oral anticoagulants, fondaparinux, or danaparoid sodium, with regular assessment of the benefit-risk profile. 

The expert panel also agreed that fibrinogen replacement therapy – with fibrinogen concentrate or cryoprecipitate – may be needed alongside anticoagulation to balance the overall risks of thrombosis and bleeding in patients.

On managing the VITT immune response, patients should also initially receive intravenous (IV) immunoglobulin. However, should there be a subsequent progression of thrombosis, or the platelet count fails to reach an acceptable level, then the addition of corticosteroids can also be considered. Plasma exchange is recommended for patients with more severe disease.

As a newly-recognised syndrome that is not yet well understood, timescales for monitoring and stopping VITT treatment are not yet definitive and guidelines will be continually updated as new evidence becomes available, the Institute said.

Dr Pavord confirmed to the limbic that “platelet factor 4 antibodies appear to stay in the system for several weeks, so after discharge from hospital close monitoring of patients is essential”, and also highlighted the importance of psychological support during this time. 

VITT is currently considered a rare condition. In Australia, the rate is estimated to be about 1-2 per 100,000 vaccinated with COVID-19 Vaccine AstraZeneca. For those under 60 years of age, the rate is estimated to be higher, about 2-3 per 100,000 people.

Click here for the guideline in full.

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