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ASH Clinical Practice Guidelines on Venous Thromboembolism

ASH Guidelines on Use of Anticoagulation in Patients with COVID-19

ASH has issued recommendations for the use of anticoagulation in critically and acutely ill patients for which the evidence will be re-evaluated in a continual fashion. This webpage will be updated as the evidence for recommendations are evaluated.

Access an updated guideline published in Blood Advances on November 2, 2021:
American Society of Hematology living guidelines on the use of anticoagulation for thromboprophylaxis in patients with COVID-19: July 2021 update on post-discharge thromboprophylaxis

Access the guidelines published in Blood Advances on February 8, 2021:

American Society of Hematology 2021 guidelines on the use of anticoagulation for thromboprophylaxis in patients with COVID-19 


Critically Ill Patients – Recommendation 1A and 1B


In patients with COVID-19 related critical illness who do not have confirmed or suspected venous thromboembolism, should we use prophylactic-intensity vs. intermediate-intensity anticoagulation?

Recommendation 1a (Updated April 7, 2021)

The American Society of Hematology (ASH) guideline panel suggests using prophylactic-intensity over intermediate-intensity anticoagulation for patients with coronavirus disease 2019 (COVID-19)–related critical illness who do not have suspected or confirmed venous thromboembolism (VTE) (low certainty of evidence).

Remarks: The ASH guideline panel plans to continue to update this recommendation when the full results of other trials become available. Clinicians should weigh the potential benefits and harms based on the most up-to-date available evidence in caring for their patients.

A now expired recommendation published on October 27, 2020 compared therapeutic-intensity or intermediate-intensity with prophylactic-intensity anticoagulation in patients with COVID-19-related critical illness. With the emergence of new evidence, this recommendation has now been split into two recommendations: a recommendation comparing intermediate-intensity vs. prophylactic-intensity anticoagulation (Recommendation 1A) and a separate recommendation comparing therapeutic-intensity vs. prophylactic-intensity anticoagulation (Recommendation 1B).

Patients with COVID-19–related critical illness are defined as those suffering from an immediately life-threatening condition who would typically be admitted to an intensive care unit (ICU). Examples include patients requiring hemodynamic support, ventilatory support, and renal-replacement therapy.

An individualized assessment of the patient’s risk of thrombosis and bleeding is important when deciding on anticoagulation intensity. Risk-assessment models to estimate thrombotic and bleeding risk in hospitalized patients are available, but they have not been validated for patients with COVID-19. The panel acknowledges that higher-intensity anticoagulation may be preferred for patients judged to be at high thrombotic risk and low bleeding risk.

At present, there is no direct high-certainty evidence comparing different types of anticoagulants. The selection of a specific agent (eg, low-molecular-weight heparin, unfractionated heparin, etc) may be based on availability, resources required, familiarity, and the aim of minimizing personal protective equipment (PPE) use or staff exposure to COVID-19–infected patients as well as patient-specific factors (eg, renal function, history of heparin-induced thrombocytopenia, concerns about gastrointestinal tract absorption).

This recommendation does not apply to patients who require anticoagulation to prevent thrombosis of extracorporeal circuits such as those on extracorporeal membrane oxygenation (ECMO) or continuous renal-replacement therapy (CRRT).

View the evidence profiles and evidence-to-decision framework here.


Draft Recommendation 1b – Forthcoming

In patients with COVID-19 related critical illness who do not have confirmed or suspected venous thromboembolism, should we use therapeutic-intensity vs. prophylactic-intensity anticoagulation?


Acutely Ill Patients – Recommendation 2A and 2B

In patients with COVID-19 related acute illness who do not have confirmed or suspected venous thromboembolism, should we use prophylactic-intensity vs. intermediate-intensity vs. therapeutic-intensity anticoagulation?

Recommendation 2A - Forthcoming 

Draft Recommendation 2b (Updated as of September 15, 2021)

The ASH guideline panel suggests using prophylactic-intensity over therapeutic-intensity anticoagulation in patients with COVID-19 related acute illness who do not have suspected or confirmed VTE (conditional recommendation based on very low certainty in the evidence about effects).

Remarks: Between the time this recommendation was published online (October 27, 2020) and when it was published in Blood Advances, a press release was issued describing the results of a planned interim analysis of three randomized controlled trials, REMAP-CAP, ACTIV-4, and ATTACC (NCT 02735707, 04505774, and 04372589, respectively). In these trials, therapeutic-intensity anticoagulation was compared with prophylactic-intensity anticoagulation in moderately ill hospitalized patients with COVID-19. The ASH guideline panel plans to update this recommendation when the full results of REMAP-CAP, ACTIV-4, and ATTACC become available. Clinicians should weigh the potential benefits and harms based on the most up to date available evidence in caring for their patients.

Patients with COVID-19–related acute illness are defined as those with clinical features that would typically result in admission to a medicine inpatient ward without requirement for advanced clinical support. Examples include patients with dyspnea or mild to moderate hypoxia.

An individualized assessment of the patient’s risk of thrombosis and bleeding is important when deciding on anticoagulation intensity. Risk-assessment models to estimate thrombotic risk in hospitalized patients have been validated in COVID-19 patients, with modest prognostic performance. No risk assessment models for bleeding have been validated in COVID-19 patients. The panel acknowledges that higher-intensity anticoagulation may be preferred for patients judged to be at high thrombotic risk and low bleeding risk.

At present, there is no direct high-certainty evidence comparing different types of anticoagulants in patients with COVID-19. The selection of a specific agent (eg, low-molecular-weight heparin, unfractionated heparin, etc) may be based on availability, resources required, familiarity, and the aim of minimizing PPE use or staff exposure to COVID-19–infected patients as well as patient-specific factors (eg, renal function, history of heparin-induced thrombocytopenia, concerns about gastrointestinal tract absorption, etc.).


Anticoagulation for Patients with COVID-19 Being Discharged From Hospital – Recommendation 3

In patients with COVID-19 who are being discharged from the hospital and who do not have confirmed or suspected venous thromboembolism, should we prescribe post-discharge prophylactic-intensity anticoagulation or not?

RECOMMENDATION (UPDATED November 2, 2021)

The ASH guideline panel suggests not using anticoagulant outpatient thromboprophylaxis in patients with COVID-19 who are being discharged from the hospital and who do not have suspected or confirmed VTE or another indication for anticoagulation (conditional recommendation based on very low certainty in the evidence about effects).

Remarks: An individualized assessment of the patient’s risk of thrombosis and bleeding and shared decision-making is important when deciding whether to use post-discharge thromboprophylaxis. Validated risk assessment models to estimate thrombotic and bleeding risk in COVID-19 patients following hospital discharge are not available. The panel acknowledged that post-discharge thromboprophylaxis may be reasonable in patients judged to be at high thrombotic risk and low bleeding risk.

Guideline Implementation Tools and Resources

Webinar

This webinar highlights the guideline recommendations along with the underlying evidence and rationale for the recommendations. A slide set is available from the webinar.

Watch Webinar

  • ASH Guidelines on Use of Anticoagulation in Patients with COVID-19 Webinar

Apps

The ASH Clinical Practice Guidelines App provides easy access to every recommendation from all guidelines published by ASH, including rationale for each recommendation, benefits and harms associated with each recommended course of action, and links to the complete evidence-to-decision tables used to develop the recommendations. This app is also available via web interface.

Download for iOS |  Download for Android

Slide Set

Help your colleagues treat VTE in Patients with COVID-19 with the following teaching slide designed for easy dissemination:

  • Teaching slides for the Use of Anticoagulation in Patients with COVID-19
    Powerpoint | PDF

Additional Tools

ASH guidelines are primarily intended to help clinicians make decisions about diagnostic and treatment alternatives. Other purposes are to inform policy, education and advocacy, and to state future research needs. They may also be used by patients. These guidelines are not intended to serve or be construed as a standard of care. Clinicians must make decisions on the basis of the clinical presentation of each individual patient, ideally through a shared process that considers the patient’s values and preferences with respect to the anticipated outcomes of the chosen option. Decisions may be constrained by the realities of a specific clinical setting and local resources, including but not limited to institutional policies, time limitations, or availability of treatments. These guidelines may not include all appropriate methods of care for the clinical scenarios described. As science advances and new evidence becomes available, recommendations may become outdated. Following these guidelines cannot guarantee successful outcomes. ASH does not warrant or guarantee any products described in these guidelines.

Statements about the underlying values and preferences as well as qualifying remarks accompanying each recommendation are its integral parts and serve to facilitate more accurate interpretation. They should never be omitted when quoting or translating recommendations from these guidelines. Implementation of the guidelines will be facilitated by the evidence-to-decision frameworks and summary of findings tables linked above and by other implementation tools linked below.

For more information, see Izcovich et al. A user guide to the American Society of Hematology clinical practice guidelines. Blood Adv (2020) 4 (9): 2095-2110.
https://doi.org/10.1182/bloodadvances.2020001755.

Publication Information

In June 2020, ASH formed a multidisciplinary, international panel to develop guidelines on the use of anticoagulation in patients with COVID-19.

The McMaster University GRADE Centre supported the guideline development process. In collaboration with experts on the guideline panel, the team conducted urgent systematic reviews of available evidence on the baseline risk of thrombosis in patients with COVID-19 and on the use of prophylactic versus higher intensity anticoagulation in patients who are acutely or critically ill.

These guidelines are informed by living systematic reviews of available evidence, i.e., monthly literature searches and, as needed, updates to estimates for the baseline risk of thrombosis or the effects of anticoagulation. If and when estimates change, the guideline panel will reconvene to consider changes.

Cuker A, Tseng EK, Nieuwlaat R, et al. American Society of Hematology 2021 guidelines on the use of anticoagulation for thromboprophylaxis in patients with COVID-19. Blood Advances. 2021;5(3):872-888.  For additional information regarding update history, contact quality@hematology.org.

Available Guidelines

Coming Soon

  • Thrombophilia
  • Adaptation of ASH Prophylaxis of VTE Guidelines for Latin

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Public Comment

All are welcome to comment on draft recommendations, including physicians, patients, caregivers, and members of the public.

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ASH Webinar

This webinar highlights recommendations along with underlying evidence and rationale for the recommendations for the ASH Guidelines on Use of Anticoagulation in Patients with COVID-19.

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user guide to Guidelines 

Learn how patients, clinicians, policymakers, researchers, and others may interpret and apply guideline information.

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