High Prevalence of Antibodies to the Heparin-Platelet Factor 4 Complex in Hemodialysis Patients.

Heparin-induced thrombocytopenia is a serious complication of systemic heparin therapy. Patients with this disorder develop antibodies to the heparin-platelet factor 4 (H-PF4) complex. Patients with H-PF4 antibodies are at higher risk of venous and arterial thrombosis independently of the platelet count. Hemodialysis (HD) patients are repeatedly exposed to heparin to prevent thrombosis of the extra-corporeal circuit. However, thrombosis remains a frequent complication of vascular access, which accounts for up to 20% of all hospitalization in HD patients. Studies to date on H-PF4 antibody and vascular access thrombosis in HD patients have produced conflicting data but have been limited by small sample sizes. We sough to determine the prevalence of H-PF4 antibodies in a large cohort of HD patients and the correlation with vascular access thrombosis.

Pre-dialysis blood samples were drawn on 419 HD patients; 107 cases with access thrombosis and 312 controls that never had access thrombosis. H-PF4 antibodies were measured twice using an ELISA (GTI PF4 Enhanced, GTI Diagnostics). The average of the two measurements was used in this analysis. All patients received unfractionated heparin while on dialysis. The mean age was 64 16 yrs with 62% male patients. Antibodies to H-PF4 were positive in 54 (12.9%) patients. H-PF4 antibodies were present in 10 (10.5%) of patients with confirmed access thrombosis and in 44 (15.1%) of controls. Hemodialysis with repeated exposure to systemic unfractionated heparin is associated with a high prevalence of H-PF4 antibodies. Although H-PF4 antibodies contribute to hypercoagulability leading to thrombotic complications, our results are not supporting a correlation between H-PF4 antibodies and vascular access thrombosis. Given the potential for venous and arterial thrombosis and the implications of our findings further investigations are needed in this population.