Heparin-induced thrombocytopenia in a cardiac surgery patient with early and persistent thrombocytopenia and initial negative immunological and functional assays

Using novel PF4-dependent P-selectin expression assay to diagnose heparin-induced thrombocytopaenia postliver transplantation

Heparin-induced thrombocytopaenia (HIT) is a well-known adverse event associated with the use of heparin products. HIT may be difficult to diagnose in patients following liver transplantation as patients routinely require massive transfusion support and immunosuppression. As an alternative or adjunctive to the serotonin release assay, the PF4-dependent P-selectin expression assay (PEA) may be a useful diagnostic test in the determination of HIT in this patient population. In this case, we describe a 63-year-old man who had an orthotopic liver transplant that was complicated by HIT that was diagnosed using the PEA.

P-selectin expression assay in a repeatedly serotonin-release assay-negative patient with heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is an immune complication of heparin therapy caused by antibodies to complexes of platelet factor 4 (PF4) and heparin. Pathogenic antibodies to PF4/heparin bind and activate platelets to propagate a hypercoagulable state culminating in life-threatening thrombosis. The serotonin-release assay (SRA) is considered the gold-standard test to diagnose HIT. However, the sensitivity of the SRA was questioned with reported cases of clinical diagnosis of HIT and negative SRA. Herein, we present the utility of platelet factor 4-dependent P-selectin expression assay (PEA) in diagnosing HIT in a patient with thrombocytopenia and recurrent thrombosis who repeatedly tested negative with SRA.

Lung transplantation using argatroban in severe heparin-induced thrombocytopenia during extracorporeal membrane oxygenation: a case series

Lung transplantation during heparin-induced thrombocytopenia (HIT) is controversial and often considered a contraindication because of the risk of increased bleeding and thrombosis in the recipient. Although lung transplantation offers the best chance for cure in end-stage lung disease, the outcome after transplantation is still controversial in patients with HIT. In our center, two patients developed HIT type II during venovenous extracorporeal membrane oxygenation (ECMO) support for acute respiratory failure. They underwent successful lung transplantation using argatroban. The subsequent clinical course was uneventful except evacuation of post-operative hematoma in 1 patient, and they were discharged. Argatroban was successfully used during lung transplant surgery in patients who developed HIT type II during ECMO support. Further studies on the feasibility and safety of lung transplantation using a direct thrombin inhibitor in patients with HIT during ECMO are required.

False-Negative Platelet Factor 4 Antibodies and Serotonin Release Assay and the Utility of Repeat Testing in the Diagnosis of Heparin-Induced Thrombocytopenia and Thrombosis

Objective

To report a case of false-negative serological tests in the diagnosis of heparin-induced thrombocytopenia (HIT) followed by a brief review of the literature on this topic.

Case Presentation

A 75-year-old Caucasian female patient was admitted with a traumatic right ankle fracture that required open reduction and internal fixation. Despite postoperative subcutaneous heparin chemoprophylaxis, she developed deep vein thrombosis (DVT) and pulmonary embolism (PE) on day 4 and subsequently started on continuous heparin infusion. On day 5, she suffered a stroke from a complete occlusion of the right common carotid artery with tandem occlusion of the right middle cerebral artery. She underwent successful thrombectomy of both arteries. The proposed stroke mechanism was paradoxical embolism through a patent foramen ovale. Over the next few days, thrombocytopenia was noted, the heparin drip was stopped, and HIT antibodies (antibodies targeting the complex of platelet factor 4 and heparin; PF4-H AB) and serotonin release assay (SRA) tests were sent. Because of the suspicion for HIT, she was started on bivalirudin with subsequent improvement in platelet count. Initial PF4-H AB and SRA tests were negative, bivalirudin was stopped, and heparin was restarted. Subsequently, her platelets trended down, again raising clinical suspicion of HIT. Repeat PF4-H AB and SRA testing resulted positive.

Conclusions

A positive SRA in the appropriate context is considered for the diagnosis of heparin-induced thrombocytopenia. This case report highlights that false-negative serological evaluation is possible early in the course of the disease. Repeat testing is recommended in patients with high clinical suspicion.