Last updated December 18, 2021

Heparin-Induced Thrombocytopenia

Recommendations

Screening asymptomatic patients for HIT

For patients receiving heparin in whom the risk of HIT is considered low (<0.1%), the American Society of Hematology (ASH) guideline panel suggests against platelet count monitoring to screen for HIT. (2⊕ooo)
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For patients receiving heparin in whom the risk of HIT is considered intermediate (0.1%-1.0%) or high (>1.0%), the ASH guideline panel suggests platelet count monitoring to screen for HIT. If the patient has received heparin in the 30 days before the current course of heparin, the ASH guideline panel suggests platelet count monitoring beginning on day 0 (the day heparin is initiated). If the patient has not received heparin in the 30 days before the current course of heparin, the ASH guideline panel suggests monitoring the platelet count from day 4 until day 14 or until heparin is stopped, whichever occurs first, if practicable. In high-risk patients, the ASH guideline panel suggests monitoring the platelet count at least every other day. In intermediate-risk patients, the ASH guideline panel suggests monitoring the platelet count every 2 to 3 days. (2⊕ooo)
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Diagnosis and initial management of patients with suspected HIT

In patients with suspected HIT, the ASH guideline panel recommends using the 4Ts score to estimate the probability of HIT rather than a gestalt approach. If there is an intermediate- or high-probability 4Ts score, the ASH guideline panel recommends an immunoassay. (1⊕⊕⊕o)
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If the immunoassay is positive and a functional assay is available (either locally or as a send-out test to a reference laboratory), the ASH guideline panel suggests a functional assay. (2⊕⊕⊕o)
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In patients with suspected HIT and a low-probability 4Ts score, the ASH guideline panel recommends against HIT laboratory testing. (1⊕⊕⊕o)
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In patients with suspected HIT and a low-probability 4Ts score, the ASH guideline panel recommends against empiric treatment of HIT (ie, against discontinuation of heparin and initiation of a non-heparin anticoagulant). (1⊕⊕⊕o)
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In patients with suspected HIT and an intermediate-probability 4Ts score who have no other indication for therapeutic-intensity anticoagulation, the ASH guideline panel recommends discontinuation of heparin. (1⊕⊕⊕o)
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The ASH guideline panel suggests initiation of a non-heparin anticoagulant at prophylactic intensity if the patient is at high risk of bleeding and at therapeutic intensity if the patient is not at high risk of bleeding. (2⊕⊕⊕o)
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In patients with suspected HIT and an intermediate-probability 4Ts score who have another indication for therapeutic-intensity anticoagulation, the ASH guideline panel recommends discontinuation of heparin. (1⊕⊕⊕o)
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The ASH guideline panel suggests initiation of a non-heparin anticoagulant at therapeutic intensity. (2⊕⊕⊕o)
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In patients with suspected HIT and a high-probability 4Ts score, the ASH guideline panel recommends discontinuation of heparin and initiation of a non-heparin anticoagulant at therapeutic intensit. (1⊕⊕⊕o)
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In patients with an intermediate-probability 4Ts score and a negative immunoassay, the ASH guideline panel recommends discontinuation of the non-heparin anticoagulant and resumption of heparin, if indicated. (1⊕⊕⊕o)
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In patients with a high-probability 4Ts score and a negative immunoassay, the ASH guideline panel recommends discontinuation of the non-heparin anticoagulant and resumption of heparin, if indicated. (1⊕⊕⊕o)
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In patients with an intermediate-probability 4Ts score and a positive immunoassay, the ASH guideline panel recommends continued avoidance of heparin and continued administration of a non-heparin anticoagulant at therapeutic intensity. For patients who were receiving prophylactic-intensity anticoagulation, the ASH guideline panel recommends providing therapeutic-intensity anticoagulation (1⊕⊕⊕o)
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In patients with a high-probability 4Ts score and a positive immunoassay, the ASH guideline panel recommends continued avoidance of heparin and continued administration of a non-heparin anticoagulant at therapeutic intensity. (1⊕⊕⊕o)
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Management of the acute phase of HIT

In patients with acute HIT complicated by thrombosis (HITT) or acute HIT without thrombosis (isolated HIT), the ASH guideline panel recommends discontinuation of heparin and initiation of a non-heparin anticoagulant. (1⊕⊕⊕o)
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When a non-heparin anticoagulant is being selected, the ASH guideline panel suggests argatroban, bivalirudin, danaparoid, fondaparinux, or a direct oral anticoagulant (DOAC). (2⊕ooo)
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In patients with acute HITT or acute isolated HIT, the ASH guideline panel recommends treatment with a non-heparin anticoagulant at therapeutic-intensity dosing rather than prophylactic-intensity dosing. (1⊕ooo)
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In patients with acute HITT or acute isolated HIT and no other indication for antiplatelet therapy, the ASH guideline panel suggests treatment with a non-heparin anticoagulant alone rather than in combination with an antiplatelet agent. (2⊕⊕oo)
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In patients with acute HITT or acute isolated HIT, the ASH guideline panel recommends against routine insertion of an inferior vena cava (IVC) filter. (1⊕⊕⊕o)
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In patients with acute HITT or acute isolated HIT, the ASH guideline panel recommends against initiation of a vitamin K antagonist (VKA) before platelet count recovery (usually a platelet count of ≥150 × 109/L). (1⊕⊕⊕o)
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In patients with acute HITT or acute isolated HIT who are at average bleeding risk, the ASH guideline panel suggests against routine platelet transfusion. (2⊕⊕oo)
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In patients with acute isolated HIT, the ASH guideline panel suggests bilateral lower-extremity compression ultrasonography to screen for asymptomatic proximal deep vein thrombosis (DVT). (2⊕ooo)
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In patients with acute isolated HIT and an upper-extremity central venous catheter (CVC), the ASH guideline panel suggests upper-extremity ultrasonography in the limb with the catheter to screen for asymptomatic DVT. The ASH guideline panel suggests against upper-extremity ultrasonography in limbs without CVCs to screen for asymptomatic DVT. (2⊕ooo)
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In patients with acute isolated HIT and no asymptomatic DVT identified by screening compression ultrasonography, the ASH guideline panel suggests that anticoagulation be continued, at a minimum, until platelet count recovery (usually a platelet count of ≥150 × 109/L). The ASH guideline panel suggests against continuing treatment for ≥3 months unless the patient has persisting HIT without platelet count recovery. (2⊕ooo)
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In patients with subacute HIT A, the ASH guideline panel suggests treatment with a DOAC (eg, dabigatran, rivaroxaban, or apixaban) rather than a VKA. (2⊕⊕⊕o)
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Cardiovascular surgery

In patients with acute HIT or subacute HIT A who require cardiovascular surgery, the ASH guideline panel agrees that surgery should be delayed until the patient has subacute HIT B or remote HIT, if feasible. (UGPS, )
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If delaying surgery is not feasible, the ASH guideline panel suggests one of the following: intraoperative anticoagulation with bivalirudin, intraoperative heparin after treatment with preoperative and/or intraoperative plasma exchange, or intraoperative heparin in combination with a potent antiplatelet agent  (eg, prostacyclin analog or tirofiban). (2⊕⊕oo)
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In patients with subacute HIT B or remote HIT who require cardiovascular surgery, the ASH guideline panel suggests intraoperative anticoagulation with heparin rather than treatment with a non-heparin anticoagulant or plasma exchange and heparin or heparin combined with an antiplatelet agent. (2⊕ooo)
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Percutaneous cardiovascular intervention

In patients with acute HIT or subacute HIT A who require PCI, the ASH guideline panel suggests treatment with bivalirudin rather than a different non-heparin anticoagulant. (2⊕⊕oo)
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In patients with subacute HIT B or remote HIT who require PCI, the ASH guideline panel suggests treatment with bivalirudin rather than UFH. (2⊕ooo)
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Renal replacement therapy

In patients with acute HIT who are receiving renal replacement therapy and require anticoagulation to prevent thrombosis of the dialysis circuitry, the ASH guideline panel suggests treatment with argatroban, danaparoid, or bivalirudin rather than other non-heparin anticoagulants. (2⊕ooo)
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In patients with subacute HIT A, subacute HIT B, or remote HIT who are receiving renal replacement therapy, are not otherwise receiving anticoagulation, and require anticoagulation to prevent thrombosis of the dialysis circuit, the ASH guideline panel suggests regional citrate rather than heparin or other non-heparin anticoagulants. (2, ⊕ooo)
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VTE treatment and prophylaxis in patients with remote HIT

In patients with remote HIT who require VTE treatment or prophylaxis, the ASH guideline panel recommends administration of a non-heparin anticoagulant (eg, apixaban, dabigatran, danaparoid, edoxaban, fondaparinux, rivaroxaban, or VKA) rather than UFH or LMWH. (1⊕ooo)
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Emergency identification

In patients with a history of HIT in the past 3 months, the ASH guideline panel suggests carrying or wearing an emergency identifier (eg, an emergency pendant or bracelet). (2⊕ooo)
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In patients with a history of HIT more than 3 months ago, the ASH panel suggests against carrying or wearing an emergency identifier. (2⊕ooo)
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Recommendation Grading

Overview

Title

Heparin-Induced Thrombocytopenia

Authoring Organization

Publication Month/Year

November 27, 2018

Document Type

Guideline

External Publication Status

Published

Country of Publication

US

Document Objectives

These evidence-based guidelines of the American Society of Hematology (ASH) are intended to support patients, clinicians, and other health care professionals in their decisions about diagnosis and management of HIT.

Target Patient Population

Asymptomatic patients for HIT, diagnosis and initial management of patients with suspected HIT, treatment of acute HIT, and special situations in patients with acute HIT or a history of HIT

Inclusion Criteria

Female, Male, Adolescent, Adult, Older adult

Health Care Settings

Ambulatory, Hospital, Long term care, Outpatient

Scope

Diagnosis, Management

Diseases/Conditions (MeSH)

D054556 - Venous Thromboembolism, D020246 - Venous Thrombosis, D006493 - Heparin, D006495 - Heparin, Low-Molecular-Weight

Keywords

anticoagulation, Venous Thromboembolism, hit, heparin, Anticoagulation

Source Citation

Blood Adv (2018) 2 (22): 3360–3392.