Medical and Economic Burden of Heparin-Induced Thrombocytopenia: Data from the National Inpatient Sample 2009-2011

Background

Although generally safe, heparin use 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). Although older studies report incidences as high as 5% in high-risk subgroups of surgical patients, recent studies report a much lower incidence (0.02% of hospital admissions and <0.1-0.4% among patients exposed to heparin). As hospitals transition to the less immunogenic low molecular weight heparins, reassessment of the overall national burden of HIT would help inform needs for monitoring strategies for this potentially fatal complication of anticoagulation.

Methods

We used the 2009-2011 National Inpatient Sample database to identify patients aged ≥18 years with primary and secondary diagnoses of HIT (International Classification of Diseases, 9th Revision, Clinical-Modification [ICD-9-CM] code 289.84). We derived the prevalence rate of HIT overall as well as among subgroup of patients undergoing 3 types of surgeries (cardiac, vascular and orthopedic surgeries). We compared characteristics of patients diagnosed with versus without HIT, and HIT with thrombosis (HITT) versus those without thrombosis. Statistical analysis was performed using Stata 13.1, which accounted for the complex survey design and clustering. We used a 2-sided p- value of <0.05 to determine statistical significance.

Results

We identified 72,515 cases of HIT among a total of 98,636,364 hospitalizations (0.07%). Arterial and venous thromboses were identified in 24,880 (34.3%) of cases with HIT. Males were slightly more likely to be diagnosed with HIT (50.12% vs. 49.88%, odds ratio, OR 1.48, 95% CI: 1.46-1.51), but females had higher rates of post-cardiac and vascular surgery-associated HIT (OR: 1.41, 95% confidence interval, CI: 1.26-1.58, p<0.001 and OR 1.42, 95% CI: 1.29-1.57, p<0.001 respectively). Prevalence rates of HIT among cardiac, vascular and orthopedic surgeries were 0.53% (95% CI: 0.51-0.54%), 0.28% (95% CI: 0.28-0.29%) and 0.05% (95% CI: 0.05-0.06%) respectively. Patients with HIT and HITT were significantly more likely to be fatal than cases without diagnosed HIT (9.63% and 12.28% versus 2.19% respectively, p<0.001), and have significantly higher costs ($137401 and $179735 versus $35905) and length of stay (14.07 and 16.51 days versus 4.76 days).

Conclusion

Although rates of HIT appear lower in the modern era of widespread low molecular weight heparin use, patients undergoing cardiac and vascular surgeries remain at significant risk. Even in recent years, one-third of patients with HIT develop thrombosis, which significantly increases mortality, cost and length of stay. Strategies to monitor and mitigate that risk in high-risk patients appear to be warranted.