Pharmacogenomics of Heparin-Induced Thrombocytopenia

Inclusion Criteria: 18 years of age or older; Participants with heparin/PF4 antibody and SRA testing for HIT, including:

participants with negative heparin/PF4 antibodies and negative SRA (controls), participants with positive heparin/PF4 antibodies and negative SRA(seroconversion cases), participants with positive heparin/PF4 antibodies and positive SRA (HIT cases); Treatment with unfractionated heparin or low molecular weight heparin (enoxaparin, dalteparin, tinzaparin) within 7 days of blood draw Exclusion Criteria: Less than 18 years of age; Inability to give informed consent There is no randomization involved in this study. Participants will be enrolled in equal numbers from three categories: (1) participants without HIT testing negative for heparin/PF4 antibodies (controls); (2) participants without HIT testing positive for heparin/PF4 antibodies (seroconversion cases); (3) participants with HIT testing positive for both heparin/PF4 antibodies (HIT cases).

Recruitment will be facilitated through collaborators in the Coagulation Laboratory and through key study personnel in the Banner Univerisyt Medical Center - Tucson. Patients with positive and negative heparin/PF4 antibody and serotonin release assay results will be identified in the Coagulation Laboratory and the patient's provider will be approached about potential participation in research studies. If the potential participant is interested, they will be approached by study personnel for study description and possible consent. Alternatively, clinical collaborators who are consulted and participating directly in a patients care may contact a potential participant directly for willingness to participate in the study.

Patients consenting to the study will be asked to provide a one blood sample of approximately 150 milliliters. Peripheral blood mononuclear cells (PBMCs) will be isolated from this sample and stored at -80C before use in proposed experiments. Genomic DNA will also be isolated from the sample to perform HLA sequencing.

HIT will be confirmed with a functional serotonin release assay and HIT likelihood based on clinical course. Detailed data will be collected regarding participant's hospitalization, heparin dose and duration, platelet counts, surgical history, and co-morbidities. After consent of participants, a peripheral blood sample will be acquired, CD positive T cells sorted using flow cytometry, and genomic DNA isolated as previously described.