title: Heparin-associated thrombocytopenia in 24,401 patients with venous thromboembolism: findings from the RIETE Registry.
abstract: BACKGROUND
  Whether the treatment of venous thromboembolism (VTE) with unfractionated heparin (UFH) confers a higher risk of thrombocytopenia than does treatment with low molecular weight heparin (LMWH) remains controversial, and very few data are available from routine clinical practice.
  
  
  OBJECTIVE
  We assessed the incidence, risk factors and prognosis of heparin-associated thrombocytopenia (HAT) according to the type of heparin therapy, UFH or LMWH.
  
  
  METHODS
  Data were obtained from the international prospective Registro Informatizado de la Enfermedad TromboEmbolica venosa (RIETE), which included 25,369 patients with confirmed VTE until February 2009. Among them, 24,401 patients were treated either with UFH or with LMWH, and had available information about the 6-month occurrence of confirmed thrombocytopenia, defined as a platelet count ≤ 150,000 mm(-3) .
  
  
  RESULTS
  One hundred and forty-one patients receiving UFH and/or LMWH developed thrombocytopenia within a 6-month period. The incidence of HAT was significantly higher in the UFH group (1.36%, 95% confidence interval [CI] 0.79-2.17) than in the LMWH group (0.54%, 95% CI 0.44-0.64). As compared with LMWH, UFH significantly increased the risk of HAT in female patients (adjusted hazard ratio [HR] 4.90%, 95% CI 2.58-9.31, P = 0.001) but not in male patients (adjusted HR 1.60%, 95% CI 0.64-3.97, P = 0.31); P = 0.027 for comparison. In each gender, the UFH-associated excess risk was confined to patients with VTE unrelated to cancer. The poor prognosis of patients with thrombocytopenia was not influenced by the type of heparin therapy.
  
  
  CONCLUSIONS
  In routine clinical practice, treatment of VTE with UFH seems to confer a higher risk of thrombocytopenia than does treatment with LMWH, especially in women and non-cancerous patients.
authors.affiliation: Centre Hospitalier Universitaire de Dijon, Service de Médecine Interne-Unité Maladie Thromboembolique, Dijon, France. nicolas.falvo@chu-dijon.fr
authors.forename: N
authors.initials: N
authors.lastname: Falvo
authors.forename: C
authors.initials: C
authors.lastname: Bonithon-Kopp
authors.forename: K
authors.initials: K
authors.lastname: Rivron Guillot
authors.forename: J A
authors.initials: JA
authors.lastname: Todoli
authors.forename: M
authors.initials: M
authors.lastname: Jiménez-Gil
authors.forename: P
authors.initials: P
authors.lastname: Di Micco
authors.forename: M
authors.initials: M
authors.lastname: Monreal
mesh_terms: D000368:Aged; D015331:Cohort Studies; D005260:Female; D006493:Heparin / Q000009:adverse effects*; D006495:Heparin, Low-Molecular-Weight / Q000009:adverse effects; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D012042:Registries; D012307:Risk Factors; D012737:Sex Factors; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000453:epidemiology / Q000209:etiology; D054556:Venous Thromboembolism / Q000188:drug therapy*
chemical_list: D006495:Heparin, Low-Molecular-Weight; D006493:Heparin