Incidence of Heparin-Induced Thrombocytopenia in Non-Surgical Patients

Introduction: Heparin-induced thrombocytopenia (HIT) is a life-threatening complication of heparin exposure. HIT occurs when Platelet Factor 4 (PF4) forms a complex with heparin, resulting in the formation of autoantibodies. HIT occurs more frequently in surgical patients compared with non-surgical patients due to the inflammatory release of PF4 and perioperative heparin exposure. Previously, unfractionated heparin (UFH) has been compared to low molecular weight heparin (LMWH) solely among surgical patients which has been correlated with a higher incidence of HIT relative to LMWH. However, there is little data regarding UFH versus LMWH in non-surgical patients. The purpose of this study was to determine whether there was a significant difference in the incidence of HIT between these two forms of anticoagulation in non-surgical patients. We also sought to delineate differences in incidence of HIT with respect to BMI, gender, and age.

Methods: This is a retrospective study that included all patients admitted to 14 hospitals within Hospital Corporation of America's (HCA) North Florida Division between January 2016 and September 2022. Data was retrieved and analyzed by HCA statisticians. Patient selection was based not only on whether they had been diagnosed with HIT, but various other factors including age, weight, gender and type of anticoagulation (LMWH vs UFH). Patients who had undergone surgery or even been hospitalized within the six months had been excluded. Other excluded conditions include disseminated intravascular coagulation (DIC), hemolytic-uremic syndrome (HUS), immune thrombocytopenic purpura (ITP), drug induced systemic lupus erythematosus (DILE), and systemic lupus erythematosus (SLE).

Results: A total of 2,061 patients were included. Unfractionated heparin group was significantly associated with the likelihood of the patient being diagnosed with HIT (χ ² = 184.06, p < 0.0001). The odds ratio is 0.237, indicating that patients who received unfractionated heparin were 4.219 (1/0.237) times as likely to develop HIT as patients who received LMWH. When controlling for age, sex, and BMI, age was significantly associated with the likelihood of the patient being diagnosed with HIT (χ ² = 8.423, p < 0.01). The odds ratio was 1.010, indicating that with each additional year of age, patients were 1.010 times as likely to develop HIT. BMI was also significantly associated with likelihood of HIT (χ2 = 4.892, P < 0.03), indicating that obesity was identified as a potential factor associated with the development of HIT. Female were less likely to develop HIT when compared to men overall (χ2 = 7.238, P < 0.05).

Conclusions: HIT is a rare but important cause of morbidity and mortality in patients exposed to heparin containing products. This study explored the profile of HIT incidence in non-surgical patients receiving UFH versus LMWH and in young versus older age groups. Here we provide evidence that a long-standing understanding regarding the incidence of HIT in surgical patients holds true in strictly non-surgical patients. Additionally, we have acquired evidence that age may very well play a role in HIT.