Retrospective Cost Analysis of Testing for HIT Antibodies in a Community Hospital

Background: Heparin-Induced Thrombocytopenia is a serious, immune-mediated complication of heparin therapy. At Lenox Hill Hospital when HIT is suspected, a test for heparin associated antibodies is ordered. Like many community hospitals, Lenox Hill Hospital does not perform this test “in house”, so it is sent to a reference lab. We use the Mayo Clinic Laboratory as our reference lab. It takes about 7 days for results to come back to Lenox Hill Hospital from the Mayo Clinic Lab. Meanwhile, patients are started on Argatroban or Lepirudin infusions in order to avoid thrombosis. We performed a retrospective review of all patients suspected of having HIT in a one year period, in order to assess the cost effectiveness of sending out these tests and treating these patients with alternative anticoagulants while waiting for the test results.

Methods: We performed a retrospective review of all patients who were tested for HIT Antibodies. We obtained a list of patient specimens sent to Mayo Clinic for heparin associated antibodies from January 2007 to January 2008. A list of patients placed on either Argatroban or Lepirudin infusions was also obtained for the same time frame from our Pharmacy Department. We then recorded the results for the ELISA test for the HIT antibodies from our computer system.

Results: There were 150 patient samples sent for heparin associated antibody tests to the Mayo Clinic Laboratory during these 12 months. Only 12 out of 150 patient samples tested positive for HIT by ELISA. Four out of 150 tested equivocal for HIT. All the remaining reports were negative. The hospital was charged $300 for each ELISA test, so our community hospital spent $ 45,000 in one year on heparin associated antibody testing. 15 of these patients were placed on Argatroban infusion while awaiting lab results. All fifteen patients who were placed on Argatroban ultimately tested negative for HIT. Four patients were started on Lepuridin infusions. Only one of the patients on Lepuridin tested positive for HIT. In total, there were 19 patients treated with either Argatroban or Lepuridin during this 12 months period. Only one patient, out of the 19 treated patients tested positive for HIT.

The 12 months cost analysis showed that 100 vials of Lepirudin were used at a cost of $158.80/vial, for a total of $15,880. The 12 months cost analysis for Argatroban showed that 15 vials were ordered each month at a cost of $985/vial for a total of $177,300.

The total amount spent including testing and expectant came to $238,180.00. Only one patient truly needed to be treated with an alternative anticoagulant.

Discussion: Lepirudin and argatroban are two accepted drugs for treatment of HIT. These are direct thrombin inhibitors that are given intravenously. Argatroban binds to the catalytic site of thrombin. It gets metabolized by the liver and should be dose adjusted with careful monitoring in patients with hepatic impairment. No dose adjustment is necessary in patients with renal dysfunction. Lepirudin binds to both catalytic and a fibrinogen-binding site of thrombin. It gets excreted in the urine and should be carefully monitored in patients with renal insufficiency. Both drugs can lead to bleeding complications. These drugs should be used with great caution when there is an increased risk of a hemorrhagic event. The cost of Argatroban and Lepirudin infusions was obtained from the pharmacy purchase orders. The cost of HIT antibody testing was obtained from our main labarotory. The cost of the machine at the Mayo Labarotory that is used in the Special Coagulation laboratory (DSX ELISA processing system) was $52,000. The machine was purchased prior to 2004. We concluded that our community hospital spends a total of $238,000 per year in the evaluation and expected management of heparin-induced thrombocytopenia.

Conclusion: In this retrospective review of 150 patients who have had HIT antibodies testing and 19 who were started on anticoagulation therapy and have had their HIT antibodies tests sent out for HIT confirmation, only 1 had a positive result. We concluded that our community hospital spends a total of $238,000 per year in the evaluation and expectant management of heparin-induced thrombocytopenia. The hospital would save money and improve patient care if it purchased the laboratory equipment and ran the tests in-house, providing faster turn around and more accurate assessment of risk.