Activated Partial Thromboplastin Time Monitoring of Unfractionated Heparin Therapy: Issues and Recommendations

Semin Thromb Hemost. 2017 Apr;43(3):253-260. doi: 10.1055/s-0036-1581128. Epub 2016 Jun 6.


When administering unfractionated heparin (UFH), therapeutic levels of anticoagulation must be achieved rapidly and maintained consistently in the therapeutic range. The basic assays for monitoring UFH therapy are the activated partial thromboplastin time (APTT) and/or the chromogenic antifactor Xa or antithrombin assays. For many laboratories, the APTT is the preferred standard of practice; however, the APTT is a surrogate marker that only estimates the heparin concentration. Many factors, including patient variation, reagents of the APTT, UFH composition, and concentration can influence the APTT result. This article reviews various methods to determine the heparin therapeutic range and presents recommendations for the laboratory to establish an APTT heparin therapeutic range for all sizes of hospitals.

Publication types

  • Review

MeSH terms

  • Anticoagulants / blood
  • Anticoagulants / therapeutic use
  • Blood Coagulation
  • Drug Monitoring / methods*
  • Guidelines as Topic
  • Heparin / blood
  • Heparin / therapeutic use*
  • Humans
  • Partial Thromboplastin Time / methods*
  • Partial Thromboplastin Time / standards
  • Reference Values
  • Reproducibility of Results
  • Venous Thromboembolism / blood
  • Venous Thromboembolism / prevention & control*


  • Anticoagulants
  • Heparin