Prevalence of Heparin Induced Thrombocytopenia Antibodies During the Period 2004–2011. Relevance to Heparin Contaminants

Abstract 4326

In conjunction with an ongoing program to investigate the prevalence of HIT antibody (HIT Ab) in ESRD, blood samples were collected from patients (n=53–89) on maintenance hemodialysis and retrospectively analyzed for the presence of these antibodies during the period February-April 2004–2011. Specified cut off levels were used to determine the positive and negative results. Two ELISA methods (GTI. Brookfield, WI) and (Aniara, Mason, Ohio) were used to quantitate the HIT antibodies. The prevalence of the HIT Ab during the period 2004–2011 was < 15% with the exception of 2007 where it was 35% and in 2008 it was 30%. While the assay based differences were noted, overall there was a decreased prevalence during the period 2009–2011 (13–15%). The antibody titers as quantified by optical density measurement were relatively higher during the year 2007 and 2008. Moreover, the subtyping of these antibodies in 2007 and 2008 showed a higher proportion of IgG subtype. Interestingly the platelet counts did not differ in the different groups. Similar trends were noted in the prevalence of HIT antibodies when other methods to detect HIT antibodies were used. None of the patients recruited in this study exhibited any clinical signs of HIT syndrome. Moreover, the serotonin release assays were also negative on all these patients. Some of the batches of heparin and low molecular weight heparins used during the period 2007–2008 were found to contain varying amounts of dermatan sulfate (up to 30%) and OSCS (up to 30%). Thus the presence of these carry over products and intentionally added OSCS are most likely to contribute to this increased prevalence and seroconversion of HIT antibodies. In conclusion, these observations suggest that heparin contaminants may have contributed to the higher prevalence of HIT antibodies during the period 2007–2008.