The prevalence of antibodies to the platelet factor 4 -heparin complex and association with access thrombosis in patients on chronic hemodialysis
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INTRODUCTION: Heparin-induced thrombocytopenia is a serious complication that can lead to thrombocytopenia, venous and arterial thrombosis. Patients with this disorder develop antibodies to the platelet factor 4-heparin (PF4-H) complex. Hemodialysis patients are repeatedly exposed to heparin and are at risk for developing PF4-H antibodies. We sought to determine the prevalence of PF4-H antibodies in a large cohort of patients on chronic hemodialysis and to evaluate the relationship between PF4-H antibodies and hemodialysis vascular access thrombosis in a case-control study. MATERIAL AND METHODS: Pre-dialysis blood samples were drawn on 419 patients; 107 cases with access thrombosis and 312 controls that never had access thrombosis. All samples were screened for PF4-H antibodies using an ELISA assay (GTI PF4 Enhanced, GTI Diagnostics). All positive and indeterminate samples were then tested using an IgG-specific PF4-H ELISA assay and a platelet serotonin-release assay. RESULTS: Antibodies to PF4-H were positive in 54 (12.9%) patients using the screening ELISA assay. Nine (2.1%) patients had IgG-specific PF4-H antibodies. None of the patient's had a positive platelet serotonin-release assay. No relationship between hemodialysis access thrombosis and PF4-H antibodies was noted using the screening ELISA assay (unadjusted odds ratio 0.63; 95% CI 0.30-1.30; P = 0.21), the IgG-specific ELISA assay (unadjusted odds ratio 0.83; 95% CI 0.17-4.06; P = 0.82) or indeterminate platelet serotonin-release assay results (unadjusted odds ratio 0.97;95% CI 0.10-9.44;P = 0.98). CONCLUSIONS: Hemodialysis with repeated exposure to unfractionated heparin was associated with a moderately elevated prevalence of PF4-H antibodies. However, our results do not support a relationship between PF4-H antibodies and hemodialysis vascular access thrombosis.
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