title: Activated partial thromboplastin time versus antifactor Xa heparin assay in monitoring unfractionated heparin by continuous intravenous infusion.
abstract: BACKGROUND
  Unfractionated heparin (UFH) has been used clinically for 5 decades. Despite being a cornerstone of anticoagulation, UFH is limited by its unpredictable pharmacokinetic profile, which makes close laboratory monitoring necessary. The most common methods for monitoring UFH are the activated partial thromboplastin time (aPTT) and antifactor Xa heparin assay (anti-Xa HA), but both present challenges, and the optimal method to monitor UFH remains unclear.
  
  
  OBJECTIVE
  To compare the performance of the aPTT with the anti-Xa HA for efficiency and safety of monitoring intravenous UFH infusions.
  
  
  METHODS
  This was a single-center, retrospective, observational cohort study conducted in an 852-bed academic medical center.
  
  
  RESULTS
  One hundred patients receiving intravenous UFH for a variety of indications were enrolled in the study; 50 were assigned to each group. The mean (SD) time to achieve therapeutic anticoagulation was significantly less in the anti-Xa HA group compared with the aPTT group (28 [16] vs 48 [26] hours, p < 0.001). In addition, a greater percentage of anti-Xa HA patients compared to aPTT patients achieved therapeutic anticoagulation at 24 hours (OR 3.5; 95% CI 1.5 to 8.7) and 48 hours (OR 10.9; 95% CI 3.3 to 44.2). Patients in the anti-Xa HA group also had more test values within the therapeutic range (66% vs 42%, p < 0.0001). A significant difference was seen between the 2 groups in the number of aPTT or anti-Xa HA tests performed per 24 hours (p < 0.0001) and number of infusion rate changes per 24 hours (p < 0.01), both favoring the anti-Xa HA group.
  
  
  CONCLUSIONS
  Monitoring intravenous UFH infusions with the anti-Xa HA, compared to the aPTT, achieves therapeutic anticoagulation more rapidly, maintains the values within the goal range for a longer time, and requires fewer adjustments in dosage and repeated tests.
authors.affiliation: Department of Pharmacy, Shands Hospital, University of Florida, Gainesville, FL, USA. guervd@shands.ufl.edu
authors.forename: David J
authors.initials: DJ
authors.lastname: Guervil
authors.forename: Amy F
authors.initials: AF
authors.lastname: Rosenberg
authors.forename: Almut G
authors.initials: AG
authors.lastname: Winterstein
authors.forename: Neil S
authors.initials: NS
authors.lastname: Harris
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Johns
authors.forename: Marc S
authors.initials: MS
authors.lastname: Zumberg
mesh_terms: D000046:Academic Medical Centers; D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D000990:Antithrombin III / Q000032:analysis; D001780:Blood Coagulation Tests; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D016903:Drug Monitoring / Q000379:methods*; D065427:Factor Xa Inhibitors; D005260:Female; D006493:Heparin / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D010314:Partial Thromboplastin Time; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: D000925:Anticoagulants; D065427:Factor Xa Inhibitors; D000990:Antithrombin III; D006493:Heparin