Act plus clotting test

Inactivates factor Xa

2 hours via subQ/

ACT = activated clotting time; aPTT = activated partial thromboplastin time; IV = intravenous; LMWH = low molecular weight heparin; POC = point of care; subQ = subcutaneous; UFH = unfractionated heparin.

Adapted from: Yost GW, Steinhubl SR. Monitoring and Reversal of Anticoagulation and Antiplatelets. Interv Cardiol Clin. 2013 Oct 2;(4): 643–663.

Overview of the Anticoagulation Monitoring Tests

Activated Clotting Time (ACT) 1-6

• ACT is a whole blood- clotting time test that initiates clotting and measures the time until clot formation.
• Clotting is initiated in the blood sample by an activator of the intrinsic pathways (such as celite, kaolin, and glass).
• It is generally, a point of care (POC) method, with a normal range of 80-130 seconds.
• It is typically used to monitor moderate- to high-dose heparin or direct thrombin inhibitor (DTI) doses during invasive procedures, due to the fact that at lower concentrations there is more variability in results.
• It is predominantly determined by anti-IIa activity and, thus, not reliable to monitor the effect of LMWH, which predominantly inhibits factor Xa.
• Results can be affected by several factors including platelet count, platelet function, lupus anticoagulants, factor deficiency, testing method, blood volume, warfarin use, technique employed, ambient temperature, and hemodilution.
• The ACT result is device-specific, even if the activator used is the same (Table 2).
• Target ranges may depend on the device, specific test, and if a high- or low-range calibrating range card is used (e.g. typically a low-range card is used for PCI). For example, Hemochron devices yield higher results than the Hepcon or the i-STAT.
  • In a recent study, i-STAT device values were generally 43 seconds lower than Hemochron and 23 seconds lower than the Hepcon devices. All devices correlated strongly with anti-factor Xa levels.

  Table 2: Overview of Main ACT POC Devices

  Manufacturer

  Device

  ACT Test

  Reagent

  Detection Method

  Remarks

  Hemochron Jr. Signature, Signature +, and Signature Elite

  • Automatically converts results to a reference Celite-ACT value
  • Established in AHA/ACC/SCAI guidelines
  • Poor inter-instrument reliability
  • Limited unidirectional interface capability

  3 different ACT tests: FTCA510, KACT, and P214

  Celite in glass tube (high heparin levels), kaolin in glass tube (if aprotinin is present), and glass beads in plastic tube (low heparin levels)

  • Other capabilities: RxDX heparin/protamine dosing system
  • Established in AHA/ACC/SCAI guidelines
  • Poor inter-instrument reliability
  • Limited unidirectional interface capability

  Proprietary lipidated recombinant-rabbit-brain tissue factor

  Hepcon/ Hemotech HMS Plus

  • Other capabilities: heparin dose response and heparin protamine titration
  • Established in AHA/ACC/SCAI guidelines
  • Highest platform cost
  • Occupies most space
  • Largest specimen size
  • Requires more external quality control