title: Activated clotting time versus activated partial thromboplastin time for therapeutic monitoring of heparin.
abstract: OBJECTIVE
  To compare and contrast the activated partial thromboplastin time (aPTT) and the activated clotting time (ACT) for the therapeutic monitoring of heparin therapy.
  
  
  METHODS
  Relevant articles were identified through an English-language MEDLINE search from 1966 to 1995. Additional sources were identified from the reference lists of these articles.
  
  
  METHODS
  Studies that investigated the use and limitations of the individual assays and those offering direct comparisons were chosen for review.
  
  
  METHODS
  Features demonstrating clinical applications and limitations of the aPTT and the ACT were extracted. Where possible, data suggesting preferential application of either assay also were extracted.
  
  
  RESULTS
  Both the aPTT and ACT are clinically useful for the monitoring of heparin therapy. The aPTT is used more frequently for routine monitoring; the ACT is used in specialized situations requiring large heparin doses. The ACT is typically performed at bedside and is capable of yielding results rapidly and perhaps at a lower cost than an aPTT performed by a central laboratory. Most practitioners are familiar with the central laboratory aPTT. A bedside aPTT device is available, but is not yet in widespread clinical use. Both assay techniques are subject to various limitations.
  
  
  CONCLUSIONS
  The ACT is theoretically equally as useful as the aPTT for the routine monitoring of heparin therapy, but has not been well-studied. The ACT appears more useful in situations in which high serum concentrations of heparin are required. Further cost-effectiveness and clinical outcome studies directly comparing the ACT and the aPTT is specific clinical situations are needed.
authors.affiliation: Department of Pharmacy Practice and Pharmacy Administration, Philadelphia College of Pharmacy and Science, PA 19104, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Simko
authors.forename: F F
authors.initials: FF
authors.lastname: Tsung
authors.forename: E J
authors.initials: EJ
authors.lastname: Stanek
mesh_terms: D000925:Anticoagulants / Q000627:therapeutic use*; D016903:Drug Monitoring; D006493:Heparin / Q000627:therapeutic use*; D006801:Humans; D010314:Partial Thromboplastin Time; D014914:Whole Blood Coagulation Time
chemical_list: D000925:Anticoagulants; D006493:Heparin