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Abnormal Clot Retraction indicates on abnormal platelet numbers, abnormal glycoprotein amount or structure, abnormal platelet signaling, abnormal fibrinogen levels, or abnormal fibrinogen structure


  1. Use either the whole blood or platelet-rich plasma (PRP)
  2. To obtain PRP, collect 500 l of blood on 50 l of ACD
  3. Add 600 l of PBS, centrifuge once at 10C, 1200 rpm ( Joan, GR 412)
  4. In Glass Centrifuge Tube add 100 l of PRP and 160l of clot retraction buffer, and 50l of  working solution of thrombin (8 U/mL) and 5-10 L of erythrocytes (for visualization). Vortex briefly.
  5. Place the Dead End Glass Rod (use Pasteur Pipette)  to the bottom of the tube. Place the tube at 37C. Check the CLOT FORMATION (appearance) and RETRACTION. Measure the volume of remained solution after clot retraction, notice the color of solution, take digital picture.


  1. Clot Retraction Buffer: 400 mL of PBS x1 + 10 mL of PBS-MgCl2 (MgCm2=4g/L) + 10 mL PBS-CaCl2 (CaCl2= 5.3 g/L)
  2. Working Solution of Thrombin = 7 l of Thrombin (1250U/mL) + 1 mL of Clot Retraction Buffer


The Clot Retraction Test may be used for screening of new anti-platelet drugs, anti-platelet-antibodies, or unexplained bleeding-problems. This test does not indicate exactly what is the problem but shows the direction to look for it.


  1. Platelet Protocols. Research and Clinical Laboratory Procedures. McCabe White M. and Jennings L.K. Academic Press, 1999
  2. Azam M. et al, Molecular Cellular Biology, March 2001, p. 2213-2230, Vol. 21, No. 6
  3. Hodivala-Dilke KM et al, Beta3-integrin-deficient mice are a model for Glanzmann thrombasthenia showing placental defects and reduced survival. J. Clin. Investig. 103:229-238

created by Andrei Musaji          ::          updated : 2004