title: Heparin-induced thrombocytopenia in patients treated with unfractionated heparin: prevalence of thrombosis in a 1 year follow-up.
abstract: BACKGROUND
  Patients with unstable angina are usually treated with unfractionated heparin and aspirin, but very little is known about the prevalence of heparin-induced antibodies and their relation to thrombotic complications some time after the acute phase of unstable angina. The aim of the present study was to establish the prevalence of heparin-induced thrombocytopenia and the prevalence of heparin-dependent platelet-reactive antibodies in patients treated with unfractionated heparin and the occurrence of thrombosis in a 1 year follow-up.
  
  
  METHODS
  Patient population included 124 consecutive patients with unstable angina treated with unfractionated heparin for almost 5 days. The prevalence of heparin-dependent platelet-reactive antibodies using an ELISA assay was measured before the beginning of heparin therapy and after 7 and 40 days. The platelet count was measured at the same time and the presence of thrombotic occurrences was checked. Clinical follow-up lasted 1 year.
  
  
  RESULTS
  At baseline no one patient was positive for heparin-induced antibodies. On day 6, 38 patients (30%) produced a positive heparin-induced antibody result and 30 patients (24%) had an intermediate result. The majority of patients (74%) who developed antibodies became positive after 6 days of heparin therapy. The combined incidence of death, myocardial infarction, recurrent angina, urgent revascularization and stroke was 66% in patients with antibodies and 44% in patients without antibodies during a 1 year follow-up. The incidence of combined primary end points was statistically higher in patients positive for antibodies. The log-rank test was statistically significant (chi2 = 4.39, p < 0.01).
  
  
  CONCLUSIONS
  No one patient developed a clinical evidence of thrombocytopenia. Nevertheless thrombotic events during follow-up were more common in patients who developed heparin-induced antibodies. These patients need a more accurate evaluation and surveillance after hospital discharge.
authors.affiliation: Division of Cardiology, University of Modena and Reggio Emilia, Italy. mattioli.annavittoria@unimo.it
authors.forename: A V
authors.initials: AV
authors.lastname: Mattioli
authors.forename: L
authors.initials: L
authors.lastname: Bonetti
authors.forename: S
authors.initials: S
authors.lastname: Sternieri
authors.forename: G
authors.initials: G
authors.lastname: Mattioli
mesh_terms: D000368:Aged; D000789:Angina, Unstable / Q000188:drug therapy*; D000888:Antibodies, Anti-Idiotypic / Q000032:analysis; D000925:Anticoagulants / Q000009:adverse effects* / Q000627:therapeutic use; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005500:Follow-Up Studies; D006493:Heparin / Q000009:adverse effects* / Q000276:immunology / Q000627:therapeutic use; D006801:Humans; D007074:Immunoglobulin G; D008297:Male; D008875:Middle Aged; D010978:Platelet Factor 4 / Q000276:immunology; D013921:Thrombocytopenia / Q000139:chemically induced*; D013927:Thrombosis / Q000209:etiology* / Q000276:immunology
chemical_list: D000888:Antibodies, Anti-Idiotypic; D000925:Anticoagulants; D007074:Immunoglobulin G; D010978:Platelet Factor 4; D006493:Heparin