Medical and economic burden of heparin-induced thrombocytopenia: A retrospective nationwide inpatient sample (NIS) study
In recent years, US hospitals have switched from use of unfractionated heparin to use of low-molecular-weight heparin, which is associated with lower risk of heparin-induced thrombocytopenia (HIT). In the study reported here, we retrospectively searched the Nationwide Inpatient Sample (NIS) for patients who were at least 18 years old and received a diagnosis of HIT between 2009 and 2011. Our goal was to get an updated perspective on the incidence and economic impact of HIT. We calculated the incidence of HIT overall and in subgroups of patients who underwent cardiac, vascular, or orthopedic surgery. We compared characteristics of patients with and without HIT and compared characteristics of patients with HIT with thrombosis (HITT) and HIT patients without thrombosis. Of 98,636,364 hospitalizations, 72,515 (0.07%) involved HIT. Arterial and venous thromboses were identified in 24,880 (34.3%) of HIT cases. Men were slightly more likely to have a HIT diagnosis (50.1%), but women had higher rates of HIT after cardiac surgery (odds ratio [OR], 1.41; 95% confidence interval [CI], 1.26-1.58) and vascular surgery (OR, 1.42; 95% CI, 1.29-1.57). Rates of HIT were 0.53% (95% CI, 0.51%-0.54%) after cardiac surgery, 0.28% (95% CI, 0.28%-0.29%) after vascular surgery, and 0.05% (95% CI, 0.05%-0.06%) after orthopedic surgery. HIT and HITT cases were significantly (P < 0.001) more likely than non-HIT cases to be fatal (9.63% and 12.28% vs 2.19%), and they had significantly higher costs and longer inpatient stays. HIT and especially HITT are associated with increased mortality, costs, and length of stay. Journal of Hospital Medicine 2017;12:94-97. © 2017 Society of Hospital Medicine
© 2017 Society of Hospital Medicine
Each year, approximately one-third of all hospitalized medical and surgical patients in the United States (about 12 million patients) are exposed to heparin products for the prevention or treatment of thromboembolism.1 Although generally safe, heparin can trigger an immune response in which platelet factor 4–heparin complexes set off an antibody-mediated cascade that can result in heparin-induced thrombocytopenia (HIT) and paradoxical arterial and venous thromboses, or heparin-induced thrombocytopenia with thrombosis (HITT). The incidence of HIT appears to be significantly higher with the more immunogenic unfractionated heparin (UFH) (2%-3% if treated for ≥5 days) than with low-molecular-weight heparin (LMWH) (0.2%-0.6%)2 and is significantly higher in postoperative patients (1%-5%) than in medical patients.3 Older patients and female patients, especially those who undergo surgery, are thought to be at higher risk.4 Progression from HIT to HITT can occur in up to 50% of surgical patients,5 and HITT can significantly increase mortality.4
In the United States, LMWH use has increased 5-fold since 2000—an increase attributed to the 2010 release of generic enoxaparin.6 As US hospitals switch from UFH to LMWH with its significantly lower risk of HIT, up-to-date HIT incidence data may help physicians and payers better understand the impact of the disorder on mortality and hospital length of stay (LOS) for medical patients and subsets of surgical patients and subsequently direct screening efforts to those at highest risk. Therefore, in the present study, we used national data to determine the latest incidence and economic implications of HIT overall and for high-risk surgical groups.
METHODS
In this study, we analyzed data from the Nationwide Inpatient Sample (NIS) database, part of the Healthcare Cost and Utilization Project (HCUP) of the Agency for Healthcare Research and Quality (AHRQ). The period studied was 2009-2011. We used International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code 289.84, introduced in 2009, to identify patients who were at least 18 years old and had a primary or secondary diagnosis of HIT. Validated Clinical Classifications Software (CCS) was used to identify those who underwent cardiac, vascular, or orthopedic surgery, and ICD-9-CM codes for various thromboses were used to identify those with HITT (Supplemental Figure, Supplemental Table 1). Baseline patient and hospital characteristics were compared using the Pearson’s Chi-square test for categorical variables and the Student t test for continuous variables (2-sided P < 0.05 for statistical significance) (Table 1). We calculated the incidence of HIT overall and for the 3 surgical subgroups and compared the cohorts on their mean hospital LOS, mean hospital charge, and in-hospital mortality (Table 2).
