Outcome of patients with positive heparin-platelet factor-4 antibodies: A retrospective multi-institutional...

Studies show increased mortality with positive heparin-platelet factor-4 (H-PF4) antibodies, especially in hemodialysis patients. We aimed to compare mortality and thrombosis in hospitalized patients with positive, equivocal and negative H-PF4 antibody results. Information was collected on these patients using a multi-institutional retrospective electronic medical record review. Patients tested for H-PF4 antibodies by commercial ELISA during the years 2006 to 2010 were identified. We compared 30-day, 90-day and 1-year mortality in patients with negative, equivocal and positive H-PF4 test and evaluated the relationship between H-PF4 status and rate of thrombosis. Four hundred and seventeen patients had ELISA testing for H-PF4 antibodies. Forty-four patients had equivocal (optical density value 0.4-0.9) and 21 had positive (value 1) H-PF4 antibody test. There were no statistically significant differences in mortality between patients with negative, equivocal and positive results at all three time points (p = 0.22, 0.27 and 0.38, respectively) even after excluding patients with thrombosis (p = 0.22, 0.24 and 0.31, respectively). Age and Charlson score were associated with increased 30-day, 90-day and 1 year mortality. Odds ratio of having thrombosis was 23.1 for positive vs. equivocal results (p < 0.001); however, there was no statistically significant difference between equivocal vs. negative results (p = 0.22). Our results revealed no association between H-PF4 status and mortality, as well as no difference in 1-year survival between the positive and negative groups.