Heparin-induced thrombocytopenia (HIT) is an immune-mediated adverse drug reaction to heparin products which results in a prothrombotic state. Heparin-induced thrombocytopenia generally occurs several days after the start of unfractionated heparin or low molecular weight heparin and is diagnosed based on clinical presentation, and presence of thrombocytopenia. HIT has an incidence of 0.1% to 5% and if recognized early can help prevent major complications. As of November 2014, the responsibility for documenting heparin allergies in the electronic medical record (EMR) has shifted from the physician/medical resident to the pharmacy resident. The purpose of this study is to compare the number, rate, and appropriateness of heparin allergy documentation in order to help decrease adverse medical events related to heparin.

Heparin-induced thrombocytopenia is a unique form of drug induced thrombocytopenia associated with increased clotting risk. The incidence of HIT ranges from 0.1% to 5%. Heparin-induced thrombocytopenia occurs when an antibody forms a complex with platelet factor 4 and heparin. This complex activates platelets which increases the risk of thrombus formation. Normally, HIT presents 5 to 14 days after exposure, but can occur with heparin exposure within the past 100 days. The presentation of HIT is often first suspected secondary to a decrease in platelet counts of 50% or more from baseline.

At Rush University Medical Center (RUMC), HIT is diagnosed through a combination of clinical factors and laboratory tests. When HIT is first suspected, a 4T HIT score, which is used to estimate the probability of true HIT, is calculated. The following score ranges correspond to the probability of true HIT; score of 0-3 indicates a low probability, score of 4-5 indicates an intermediate probability, and a score of 6-8 indicates a high probability of true HIT.

If the score indicates a likelihood of HIT, a HIT-Ab is sent off. This test has a sensitivity of more than 95% and a specificity of 74% to 86%. Accordingly, if this HIT-Ab test result is negative, HIT is ruled out. If the result is equivocal or positive, a confirmatory Serotonin Release Assay (SRA) test should be performed (sensitivity of 89% to 100% and a specificity of 88 % to 100%).

Prior to 2014, there was no formal process for evaluation of patients with HIT. In November of 2014, an EMR tool was created in an effort to improve heparin allergy documentation and HIT management. This EMR tool prompts the medical team to perform the 4T score, displays the appropriate HIT labs, alternative anticoagulation strategies, instructs the nurse to apply an allergy bracelet, and notifies the pharmacy resident through the order verification queue. The pharmacy resident then performs an independent 4T score, discontinues all heparin products, documents the heparin allergy in the medical record, and assesses the need for alternative anticoagulation.

Many studies have shown the value of the 4T HIT scoring system and the use of pharmacists in reducing the inappropriate use of alternative anticoagulation and unnecessary testing. Pharmacists have helped to improve patient outcomes and decrease costs associated with HIT. The purpose of this study is to evaluate the impact of an EMR tool and pharmacy residents on allergy documentation and the management of HIT.

Inclusion Criteria:

• HIT-Ab ordered
• Aged ≥ 18 years of age

Exclusion Criteria:

• Previously documented and confirmed HIT allergy prior to placement for new HIT-Ab
• Pregnancy

The study will be retrospective, and collected data will be a result of routine care. Adult patients 18 years of age or older with an order for a HIT-Ab while admitted to RUMC will be assessed for inclusion

Patients will be reviewed from 01/01/2014 to 09/30/2015. A list of patients will be generated by a laboratory order for HIT-Ab (Heparin Induced Thrombocytopenia AB [LAB0002639]).