These assays are available from the UAB Coagulation Service to monitor heparin therapy. The PTT is used routinely to monitor standard unfractionated heparin. The anti-Xa heparin assay is necessary for monitoring low molecular weight or synthetic heparin. Click on each for further information.

• Partial thromboplastin time (PTT)
• Heparin anti-Xa chromogenic assay
  The name "anti-Xa assay" is regrettably similar to the "factor X assay."
  Please select "confusing test names" for more information.

The antithrombin assay, also called ATIII, may occasionally be used to detect the cause of heparin resistance. For assistance in test selection, please refer to the Anticoagulant Therapy Monitoring Guidelines. For consultation, please contact the UAB Coagulation Service.