Suspected HIT
Platelet count drop or thrombosis in patient on heparin
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Hematology & OncologyDiagnostic
Heparin-Induced Thrombocytopenia Management (ASH 2018)
Heparin-Induced Thrombocytopenia Management (ASH 2018): Suspected HIT → Appropriate Timing? → Calculate 4Ts Score → 4Ts Score Result → Score 0-3: Low Pr...
Pathway Overview
13 steps
Algorithm Steps
13 total
01Start 02Decision Appropriate Timing?
Typical onset 5-10 days after heparin start (or sooner if prior exposure)
- Typical onset: Day 5-10 of heparin exposure
- Rapid onset: <24h if heparin in past 100 days
- Delayed onset: Days after stopping heparin (rare)
03Action Calculate 4Ts Score
Clinical probability assessment
- Thrombocytopenia: >50% fall or nadir 20-100k (2), 30-50% fall or nadir 10-19k (1), <30% fall or nadir <10k (0)
- Timing: Day 5-10 or ≤1d if recent heparin (2), after day 10 or unclear (1), ≤4d without recent (0)
- Thrombosis: New thrombosis, skin necrosis, anaphylactoid (2), progressive/recurrent (1), none (0)
- Other causes: None apparent (2), possible (1), definite (0)
04Decision 4Ts Score Result
Risk stratification
05Action Score 0-3: Low Probability
HIT unlikely (<5%)
- Continue heparin if indicated
- Seek other causes of thrombocytopenia
- No HIT testing typically needed
- Reassess if clinical picture changes
06Outcome HIT Managed
Appropriate anticoagulation, platelet recovery monitoring
07Action Score 4-5: Intermediate
HIT possible (~14%)
- STOP all heparin (including flushes, coated catheters)
- Start alternative anticoagulant
- Send PF4/heparin immunoassay
- Await results before confirming/excluding
08Warning STOP ALL HEPARIN
Including flushes, coated catheters, LMWH
09Action Start Alternative Anticoagulant
Therapeutic dosing if thrombosis or high probability
- Argatroban: 2 mcg/kg/min IV (reduce in hepatic dysfunction)
- Bivalirudin: 0.15-0.2 mg/kg/hr IV (adjust for renal)
- Fondaparinux: 7.5mg SQ daily (off-label, weight-based)
- DOACs: After platelet recovery, can transition
- Avoid warfarin until platelets >150k
10Decision Laboratory Results
Immunoassay and/or functional assay
11Action HIT Confirmed
Positive immunoassay + functional assay or high-titer immunoassay
- Continue alternative anticoagulation
- Duration: Minimum 4 weeks (no thrombosis) or 3 months (with thrombosis)
- Transition to warfarin after plt >150k (overlap 5+ days)
- DOACs increasingly used post-acute phase
- Document HIT allergy in medical record
- Path rejoins step 06Shared downstream outcome
12Action HIT Excluded
Negative immunoassay or negative functional assay
- Can resume heparin if needed
- Seek other causes of thrombocytopenia
- Consider functional assay if immunoassay indeterminate
- Path rejoins step 06Shared downstream outcome
13Warning Score 6-8: High Probability
HIT likely (~64%)
- STOP all heparin immediately
- Start alternative anticoagulant at therapeutic dose
- Send PF4/heparin immunoassay + functional assay (SRA)
- Path rejoins step 08Shared downstream outcome
Guideline Source
American Society of Hematology 2018 Guidelines for Management of VTE: Heparin-Induced Thrombocytopenia
Clinical Safety Information
Clinical Decision Support — Not a Substitute for Clinical Judgment
Individual patient factors may require deviation from these recommendations.
Known Limitations
- 4Ts score has limited sensitivity - clinical judgment essential
- Functional assays (SRA) may not be available at all centers
- Does not address autoimmune HIT or delayed-onset HIT in detail
- Alternative anticoagulant selection depends on clinical context
Applicable Regions
USEUGlobal
EU: Danaparoid available; argatroban also used
US: Argatroban most commonly used; fondaparinux off-label
Version 1Next review: 2027-01-01
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Frequently Asked Questions
What is the Heparin-Induced Thrombocytopenia Management (ASH 2018)?
The Heparin-Induced Thrombocytopenia Management (ASH 2018) is a diagnostic clinical algorithm for Hematology & Oncology. It provides a structured decision tree to guide clinical decision-making, based on American Society of Hematology 2018 Guidelines for Management of VTE: Heparin-Induced Thrombocytopenia.
What guideline is the Heparin-Induced Thrombocytopenia Management (ASH 2018) based on?
This algorithm is based on American Society of Hematology 2018 Guidelines for Management of VTE: Heparin-Induced Thrombocytopenia (DOI: 10.1182/bloodadvances.2018024489).
What are the limitations of the Heparin-Induced Thrombocytopenia Management (ASH 2018)?
Known limitations include: 4Ts score has limited sensitivity - clinical judgment essential; Functional assays (SRA) may not be available at all centers; Does not address autoimmune HIT or delayed-onset HIT in detail; Alternative anticoagulant selection depends on clinical context. Individual patient factors may require deviation from these recommendations.
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