Use of Low-Molecular Weight Heparin (LMWH) has increased in the US hospitals after the release of generic enoxaparin in 2010. Quality improvement projects and various professional bodies have advocated the use of LMWH over unfractionated heparin because of its superiority over unfractionated heparin for VTE prevention and because of its decreased incidence of Heparin-induced thrombocytopenia (HIT). We used a large administrative database to assess the recent trends of HIT to assess the impact of these interventions in adult hospitalized patients.


We used the 2009-2014 National Inpatient Sample database, which is the largest publicly available all-payer inpatient database in the US, to identify patients ≥18 years with primary and secondary diagnoses of HIT (International Classification of Diseases, 9th Revision, Clinical-Modifications [ICD-9-CM] code 289.84). Annual incidence of HIT was calculated for each year 2009-2014, fitted into a log-linear model and compared using Monte Carlo permutation test to study the changes in trend. Statistical analyses were done using STATA version 13.0 and Joinpoint Regression Program version


A total of 129,761 adult patients with a diagnosis (both primary and secondary) of HIT were identified during the study period. The proportion of patients who developed HIT was unchanged at 0.06 cases per 100 admissions with an annual percent change (APC) of -2.1 which was statistically not significant (95% CI: -5.7 to 1.6, p=0.02) (Figure 1). Despite the increasing awareness and ease of testing for HIT, the annual incidence of HIT with thromboses (HITT) also remained unchanged (Figure 2). There was however, an increasing total cost of hospitalization from $132,535 in 2009 to $174,253 in 2014 (APC: 6.17, 95% CI: 4.1 to 8.3, p<0.05) even when adjusted for yearly inflation (Consumer Price Index, Bureau of Labor Statistics). However, overall inpatient mortality and length of stay remained unchanged at 9.5% and 13.7 days (Table 1).


Despite ongoing push towards use of LMWH and country-wide quality improvement projects to encourage the use of LMWH over UFH in hospitalized patients, our data shows that the incidence of HIT remains unchanged from 2009 to 2014. Similarly, the rates of HITT and outcomes (mortality and length of stay) remain unchanged. Given the rising healthcare costs of HIT admissions and flat incidence curves, the need for more effective preventative and early diagnostic strategies, along with cost effective management options are urgently warranted.


No relevant conflicts of interest to declare.

Author notes


Asterisk with author names denotes non-ASH members.