The International Society of Thrombosis and Haemostasis (ISTH) has significantly revised its guidelines for antithrombotic treatment in patients with COVID-19, with new potentially life-saving recommendations driven by an “abundance” of fresh data.

Lead author Professor Sam Schulman, a Professor of Medicine at McMaster University, Hamilton, Canada, told the limbic that the new guidelines, which are applicable globally, could significantly improve outcomes for patients if fully adopted.

The revised advice, published in The Journal of Thrombosis and Haemostasis [link here] now contains a total of 19 recommendations instead of 12, with five that are totally new and the majority of those in the prior version having undergone some change in light of new clinical evidence, he said.

A major addition to the 2024 guidelines is the recommendation that thromboprophylaxis with low-molecular-weight heparin (LMWH) should not be used in non-hospitalised patients with symptomatic COVID-19, as evidence suggests it does not confer a clinical benefit.

Also, the guideline group added prevention of death as a potential outcome for non-critically ill patients hospitalised with COVID-19 when treated with therapeutic-dose LMWH or unfractionated heparin (UFH), alongside reducing the risk of thromboembolism and end-organ failure, on the back of new evidence from RCTs.

This is “hugely important as there are many hospitals that still hesitate to give heparin or LMWH to patients hospitalised for COVID-19, and we think it’s important to point out that it can save lives,” Prof Schulman said.

Also for hospitalised but non-critically ill patients therapeutic-dose apixaban can be considered to reduce end-organ failure and death if treatment with LMWH is not possible, the guideline group concluded.

Whilst the evidence for this is still weak, one large-scale RCT (FREEDOM COVID) found that both therapeutic dose apixaban and LMWH similarly reduced mortality compared to prophylactic doses.

“However, the results contradicted those of a a smaller [ACTION] RCT (AntiCoagulaTlon cOroNavirus) with a different DOAC (rivaroxaban). For this reason, the recommendation informs that it is “not well established”, the authors stressed.

Also new, in hospitalised patients not deemed at high risk for complications, routine post-discharge prophylactic dose direct oral anticoagulant is not recommended to reduce the risk of death or thromboembolism.

Vaccine and VITT

Another major addition to the 2024 guideline is a new section on vaccination against COVID-19 and vaccine-induced immune thrombotic thrombocytopenia (VITT).

This recommends use of antiplatelet factor 4 enzyme immunoassays to diagnose VITT when there is clinical suspicion of the condition, and treatment with a non-heparin anticoagulant when VITT is confirmed, or if not available then with UFH or LMWH.

Treatment with IV immune globulin may also be considered for reducing the risk of death in patients with VITT, according to the recommendations.

However, prophylaxis with anticoagulants or an antiplatelet agent in patients non-hospitalised patients with thrombophilia who receive a COVID-19 vaccine is not recommended for reducing risk of adverse outcomes, as evidence to date shows not benefit from such an approach, the guideline authors stressed.

Click here to read the new recommendations in full.