Background: Heparin induced thrombocytopenia (HIT) prevalence ranges from 0.1-5.0%. HIT is associated with increased healthcare cost, length of stay (LOS) and complications, including thrombosis and bleeding. The 4T Score, published in 2006, is a risk-stratifying tool that guides HIT testing and diagnosis. Use of direct oral anticoagulants (DOACs) has also become routine during this time. We seek to analyze HIT incidence trends in hospitalized patients during the DOAC and 4T era.

Aims: Assess HIT incidence in admissions reported in the National Inpatient Sample (NIS). Secondary aims include assessment of HIT associated complications, LOS, and total hospital charges amongst these groups.

Methods: A population-based assessment of the incidence of HIT and associated complications was performed for years 2009-2017 using the NIS.  Poisson regression was used to examine associations between HIT incidence rates and relevant diagnosis categories for thrombotic complications.

Results: HIT Incidence 2009-2017

Thrombotic Complications in HIT

We identified 265,400,000 patients from 2009-2017, with 157,941 diagnosed with HIT. Median age was 67 years, LOS 10 days, and $92,234 total hospital charge compared to 59 years, 3 days, and $24,104 in non-HIT patients, respectively. No association with gender was found. Between 2009-2017, incidence of HIT significantly decreased (figure 1), a trend seen in all risk groups: surgical, trauma, and non-surgical. Prevalence of thrombotic complications have increased in HIT patients during the same time, while remaining stable in non-HIT patients
(figure 2).

Conclusions: Decreasing incidence of HIT over time and in all categories (including surgical) argues against DOACs causing the drop, as bypass patients still require exclusive use of heparin. One possible explanation is improved clinical identification of HIT following 4T Score implementation. This is further supported by the increased prevalence of thrombotic complication amongst HIT patients over time compared to stable findings in non-HIT patients. We may be more accurate in our diagnosis, which is important given the downstream costs and complications of HIT.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/incidence-of-heparin-induced-thrombocytopenia-2009-2017-analysis-of-the-national-inpatient-sample-database/