Abstract
BackgroundHeparin-induced antibodies (HIA) are responsible for causing heparin-induced thrombocytopenia and thrombosis. Research has shown that the temporality of heparin-induced antibodies does not follow the classic immunologic response. The immunobiology of HIA generation remains unclear with varying in vitro and in vivo data. Outpatients undergoing hemodialysis (HD) are exposed to heparin chronically. The HIA immune response can therefore be investigated in vivo in this population.MethodsWe examined the time between the start of HD using unfractionated heparin and HIA levels in 212 outpatients during a 6-year period. Antibodies were detected on enzyme-linked immunosorbent assay. HIA levels were analyzed to determine significance of the trend over time. HIA subgroups were also analyzed for correlation with subsequent thrombotic events and platelet count during follow up.ResultsOverall, the HIA response in HD was found to peak early with waning antibody response despite continued exposure to heparin. The peak prevalence of a strong immune response (optical density > 1.000) was early and short lived, while weaker immune response (optical density 0.400–1.000) persisted for the first 6 months then declined. The mean follow-up time per patient was 2.3 ± 1.4 years. Despite circulating HIA, including high titers, no patients developed HIT in this sample. There was no association between HIA and thrombocytopenia. There was increased incidence of thrombosis in patients with strong HIA compared to other groups, but this did not achieve statistical significance.ConclusionsThe data suggest a significant temporal pattern of HIA in outpatients undergoing HD using unfractionated heparin. Positive HIA was not found to be significantly associated with thrombocytopenia or thrombosis risk in these patients. However, while not achieving statistical significance, subsequent thrombotic events occurred most frequently in the strong positive HIA group (optical density > 1.000). Further research into HIA and risk of thrombosis in this population is needed.
Highlights
Heparin-induced antibodies (HIA) are responsible for causing heparin-induced thrombocytopenia and thrombosis
Overall HIA prevalence and distribution Heparin-induced antibodies were detected in 32.5% (69/212) of the sample using the enzymelinked immunosorbent assays (EIA) threshold of optical density (OD) ≥ 0.400
When a positive EIA was combined with positive heparin neutralization procedure (HNP) testing (OD ≥ 0.400 and HNP > 50%) prevalence was 15.6%
Summary
Heparin-induced antibodies (HIA) are responsible for causing heparin-induced thrombocytopenia and thrombosis. Research has shown that the temporality of heparin-induced antibodies does not follow the classic immunologic response. The HIA immune response can be investigated in vivo in this population. With the advent of novel therapies, heparin is one of few medications to have endured the test of time, and recently crossed 100 years of use. This year marks 60 years from the first report of heparin-induced thrombocytopenia (HIT) [1]. Over the past two decades there has been an explosion of research into the antibody response causing HIT. Our current understanding of HIT is an atypical misdirected antibacterial host defense mechanism involving platelets, monocytes, endothelial cells, innate and adaptive immunity [2,3,4]
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