title: [Correlation between aPTT and antifactor Xa to determine therapeutic ranges for unfractionated heparin].
abstract: BACKGROUND
  The therapeutic range (TR) of activated partial thromboplastin time (aPTT) for unfractionated heparin (UFH) dosing was established in the 1970 decade. Since then aPTT determination has changed. Current TR may be sub or supra-therapeutic depending on the reagents of the test, and therefore, responsible for complications of therapy.
  
  
  OBJECTIVE
  To establish the TR for UFH dosing in our institution using antifactor Xa analysis as reference standard.
  
  
  METHODS
  After obtaining an informed consent, 43 blood samples were obtained for aPTT determination and antifactor Xa assay in 23 patients treated with intravenous UFH. Samples were processed at Emergency and Hemostasis Labs. We excluded patients receiving other anticoagulants, with thrombophilia, pregnancy or liver disease.
  
  
  RESULTS
  Mean aPTT values in the Hemostasis and Emergency labs ​​were 57.1 ± 18.9 and 56.6 ± 18.3 seconds, respectively (p = 0.77). The squared correlation coefficients between aPTT and antifactor Xa at hemostasis and emergency labs were R2 0.5 and 0.45 respectively, p < 0.001. Using a linear regression analysis, therapeutic aPTT range values ​​in our laboratory were established between 50 and 80 seconds, corresponding to antifactor Xa values of 0.3 to 0.7 IU/mL.
  
  
  CONCLUSIONS
  According to current recommendations, validation of aPTT determination with reference techniques should be done in every institution.
authors.forename: Leopoldo
authors.initials: L
authors.lastname: Mariné
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Sánchez
authors.forename: José Francisco
authors.initials: JF
authors.lastname: Vargas
authors.forename: Pamela
authors.initials: P
authors.lastname: Zúñiga
authors.forename: Andrés
authors.initials: A
authors.lastname: Aizman
authors.forename: Renato
authors.initials: R
authors.lastname: Mertens
authors.forename: Michel
authors.initials: M
authors.lastname: Bergoeing
authors.forename: Blanca
authors.initials: B
authors.lastname: Muñoz
mesh_terms: D000925:Anticoagulants / Q000008:administration & dosage*; D065427:Factor Xa Inhibitors / Q000097:blood*; D006493:Heparin / Q000008:administration & dosage*; D006801:Humans; D007202:Indicators and Reagents; D049451:Nomograms; D010314:Partial Thromboplastin Time / Q000379:methods*; D012015:Reference Standards; D012016:Reference Values; D012044:Regression Analysis; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D000925:Anticoagulants; D065427:Factor Xa Inhibitors; D007202:Indicators and Reagents; D006493:Heparin