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

Abstract

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.