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Full-dose antithrombotic aids selected COVID-19 ICU patients


95% increased win ratio with full dose

The study’s primary efficacy endpoint used a win-ratio analysis that included seven different adverse outcomes that ranged from death from venous or arterial thrombosis to clinically silent deep vein thrombosis. Treatment with full-dose anticoagulation led to a significant 95% increase in win ratio.

Researchers also applied a more conventional time-to-first-event secondary efficacy analysis, which showed that full-dose anticoagulation cut the incidence of an adverse outcome by a significant 44% relative to prophylactic dosing.

The two study groups showed no difference in all-cause death rates. The efficacy advantage of the full-dose regimen was driven by reduced rates of venous thrombotic events, especially a reduction in clinically evident deep vein thrombotic events.

The primary safety endpoint was the rate of fatal or life-threatening bleeding episodes, and while life-threatening bleeds were numerically more common among the full-dose recipients (four events, compared with one event on prophylaxis dosing) the difference was not significant, and no patients died from a bleeding event.

More secondary safety bleeds

The safety difference showed up in a secondary measure of bleeding severity, the rate of GUSTO moderate or severe bleeds. These occurred in 15 of the full-dose recipients, compared with 1 patient on the prophylactic dose.

Dr. Berg highlighted that several prior studies have assessed various anticoagulation regimens in critically ill (ICU-admitted and on respiratory or cardiovascular support) patients with COVID-19. For example, two influential reports published in 2021 by the same team of investigators in the New England Journal of Medicine had sharply divergent results.

One multicenter study, which tested full-dose heparin against prophylactic treatment in more than 1,000 critically ill patients, was stopped prematurely because it had not shown a significant difference between the treatment arms. The second study, in more than 2,000 multicenter patients with COVID-19 who did not require critical-level organ support, showed clear superiority of the full-dose heparin regimen.

Notably, both previous studies used a different primary efficacy endpoint than the COVID-PACT study. The earlier reports both measured efficacy in terms of patients being alive and off organ support by 21 days from randomization.

Patients to exclude

Although Dr. Berg stressed the clear positive result, he also cautioned that they should not apply to patients excluded from the study: those with severe coagulopathies, those with severe thrombocytopenia, and patients already maintained on dual antiplatelet therapy. He also cautioned against using the full-dose strategy in elderly patients, because in COVID-PACT, those who developed bleeding complications tended to be older.

Dr. Berg also noted that heparin prophylaxis is a well-established intervention for ICU-admitted patients without COVID-19 for the purpose of preventing venous thromboembolisms without evidence that this approach reduces deaths or organ failure.

But he conceded that “the priority of treatment depends on whether it saves lives, so anticoagulation is probably not as high a priority as other effective treatments” that reduce mortality. “Preventing venous thromboembolism has rarely been shown to have a mortality benefit,” Dr. Berg noted.

COVID-PACT received no direct commercial funding. Dr. Berg has been a consultant to AstraZeneca, Mobility Bio, and Youngene Therapeutics, and he participated in a trial sponsored by Kowa. Dr. Ramacciotti has been a consultant to or speaker on behalf of Aspen, Bayer, Daiichi Sankyo, Mylan, Pfizer, and Sanofi, and he has received research support from Bayer, Esperon, Novartis, and Pfizer. Dr. Eikelboom has received honoraria and research support from Bayer.

A version of this article first appeared on


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