Abstract Number: PB1426
Meeting: ISTH 2020 Congress
Background: Heparin-induced thrombocytopenia (HIT) is caused by heparin administration, which results in the production of anti-platelet factor 4 (PF4)/heparin IgG with platelet-activating properties (HIT antibodies). Previous publications demonstrated that disease severity influences the risk of HIT immune response.
Aims: To investigate how the underlying causes that necessitated heparin administration influenced HIT immune responses and clinical outcomes in HIT patients.
Methods: Using a nationwide HIT registry, we obtained data of 835 patients who were clinically suspected of having HIT. Among them, 222 patients were ultimately diagnosed with HIT according to clinical probability scores (4Ts) and the presence of HIT antibodies, which were detected in a washed-platelet activation assay. We excluded patients who developed rapid-onset HIT and those whose HIT antibodies were not assessed within two weeks of HIT onset. Then, we categorized HIT patients into four groups based on their underlying cause: trauma, cardiovascular surgery, hemodialysis, and others.
Results: As shown in Table 1, HIT antibodies with heparin-independent (i.e., strong) platelet-activating properties developed significantly more frequently in trauma patients than in hemodialysis patients, possibly resulting in trauma patients’ significantly higher incidence of HIT-associated thromboembolic events. The optical density values in ELISA for anti-PF4/heparin IgG were lower in the hemodialysis group than in other groups. However, platelet count reduction did not differ among the four groups. The onset of HIT-associated thromboembolic event tended to be earlier in the trauma group and the onset of HIT appeared to be later in the hemodialysis group. Interestingly, 18.8% of hemodialysis patients developed HIT more than 14 days after the initiation of heparin.
Conclusions: These results suggest that patients’ underlying causes differentially impact HIT immune responses, especially the development of HIT antibodies with strong platelet-activating properties, and thus influence clinical outcomes. This information may make it possible to diagnose and treat HIT patients more appropriately by carefully considering their underlying causes.
|Underlying cause||Trauma such as traffic accident or fall||Cardiovascular surgery with unfractionated heparin anticoagulation||Initiation of hemodialysis with heparin anticoagulation||Others (mainly prevention or treatment of thromboembolic event using heparin)|
|Number of HIT patients (Total: 184)||10||37||32||105|
|Patients who developed HIT antibodies with heparin-independent platelet-activating properties||3/10 (30%)||4/37 (10.8%)||1/32 (3.1%)||14/105 (13.3%)|
|*Optical density value in ELISA for anti-PF4/heparin IgG/A/M||2.478 (1.301-2.967)||2.282 (1.585-2.804)||2.162 (1.267-2.642)||2.517 (1.806-2.857)|
|*Optical density value in ELISA for anti-PF4/heparin IgG||1.949 (1.689-2.084)||1.990 (1.490-2.236)||1.620 (1.123-2.642)||2.062 (1.458-2.291)|
|*HIT-associated thromboembolic events [arterial, venous, both]||8/10 (80%) [0%, 80%, 20%]||17/37 (45.9%) [41%, 35%, 23%]||12/32 (37.5%) [8%, 83%, 8%]||69/105 (66%) [20%, 62%, 17%]|
|*Onset of HIT-associated thromboembolic events (day)||9 (7.5-9.75)||12.5 (9.75-15.25)||13 (11.5-23.5)||11 (8-13)|
|*Reduction in platelet count (%)||66.8 (56.0-73.6)||72.4 (59.2-83.3)||76.8 (61.8-83.9)||81.8 (71.8-87.7)|
|*Onset of HIT (first day with more than a 30% reduction in platelet count) [Patients with late HIT onset (> day 14)]||9 (7.25-9.75) [0/12 (0%)]||9 (8-10) [3/37 (8.1%)]||11.5 (8.75-14) [6/32 (18.8%)]||9 (7-11) [4/105 (3.8%)]|
|*: median (1st-3rd quartile)|
[Table 1. HIT antibody development and clinical outcomes in HIT patients with different underlying causes]
To cite this abstract in AMA style:Miyata S, Kokame K. Underlying Causes Greatly Influence the Development of HIT Antibodies and Clinical Outcomes in Patients with Heparin-induced Thrombocytopenia [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/underlying-causes-greatly-influence-the-development-of-hit-antibodies-and-clinical-outcomes-in-patients-with-heparin-induced-thrombocytopenia/. Accessed December 5, 2021.
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