Original Research

Clinical Outcomes After Conversion from Low-Molecular-Weight Heparin to Unfractionated Heparin for Venous Thromboembolism Prophylaxis

Journal of Clinical Outcomes Management. 2017 August;24(8)

Author(s):

References

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From the Anne Arundel Health System Research Institute, Annapolis, MD.

Abstract

Objective: To measure clinical outcomes associated with heparin-induced thrombocytopenia (HIT) and acquisition costs of heparin after implementing a new order set promoting unfractionated heparin (UFH) use instead of low-molecular-weight heparin (LMWH) for venous thromboembolism (VTE) prophylaxis.
Methods: This was single-center, retrospective, pre-post intervention analysis utilizing pharmacy, laboratory, and clinical data sources. Subjects were patients receiving VTE thromboprophyalxis with heparin at an acute care hospital. Usage rates for UFH and LMWH, acquisition costs for heparins, number of HIT assays, best practice advisories for HIT, and confirmed cases of HIT and HIT with thrombosis were assessed.
Results: After order set intervention, UFH use increased from 43% of all prophylaxis orders to 86%. Net annual savings in acquisition costs for VTE prophylaxis was $131,000. After the intervention, HIT best practice advisories and number of monthly HIT assays fell 35% and 15%, respectively. In the 9-month pre-intervention period, HIT and HITT occurred in zero of 6717 patients receiving VTE prophylaxis. In the 25 months of post-intervention follow-up, HIT occurred in 3 of 44,240 patients ( P = 0.86) receiving VTE prophylaxis, 2 of whom had HITT, all after receiving UFH. The median duration of UFH and LMWH use was 3.0 and 3.5 days, respectively.
Conclusion: UFH use in hospitals can be safely maintained or increased among patient subpopulations that are not at high risk for HIT. A more nuanced approach to prophylaxis, taking into account individual patient risk and expected duration of therapy, may provide desired cost savings without provoking HIT.

Key words: heparin; heparin-induced thrombocytopenia; venous thromboembolism prophylaxis; cost-effectiveness.

Heparin-induced thrombocytopenia (HIT) and its more severe clinical complication, HIT with thrombosis (HITT), complicate the use of heparin products for venous thromboembolic (VTE) prophylaxis. The clinical characteristics and time course of thrombocytopenia in relation to heparin are well characterized (typically 30%–50% drop in platelet count 5–10 days after exposure), if not absolute. Risk calculation tools help to judge the clinical probability and guide ordering of appropriate confirmatory tests [1]. The incidence of HIT is higher with unfractionated heparin (UFH) than with low-molecular-weight heparin (LMWH). A meta-analysis of 5 randomized or prospective nonrandomized trials indicated a risk of 2.6% (95% CI, 1.5%–3.8%) for UFH and 0.2% (95% CI, 0.1%–0.4%) for LMWH [2], though the analyzed studies were heavily weighted by studies of orthopedic surgery patients, a high-risk group. However, not all patients are at equal risk for HIT, suggesting that LMWH may not be necessary for all patients [3]. Unfortunately, LMWH is considerably more expensive for hospitals to purchase than UFH, raising costs for a prophylactic treatment that is widely utilized. However, the higher incidence of HIT and HITT associated with UFH can erode any cost savings because of the additional cost of diagnosing HIT and need for temporary or long-term treatment with even more expensive alternative anticoagulants. Indeed, a recent retrospective study suggested that the excess costs of evaluating and treating HIT were approximately $267,000 per year in Canadian dollars [4].But contrary data has also been reported. A retrospective study of the consequences of increased prophylactic UFH use found no increase in ordered HIT assays or in the results of HIT testing or of inferred positive cases despite a growth of 71% in the number of patients receiving UFH prophylaxis [5].