Coagulation Time-Dependant Inhibitor Screen

Department of Haematology

Notes

• This test is only performed following discussion with the Consultant Haematologist.
  
• Inhibitors affecting the APTT may act immediately or be time dependent. Normal plasma mixed with plasma containing a time dependent inhibitor will initially have a corrected APTT clotting time. However, after 1-2 hours the correction will be overcome and the clotting time will again become prolonged.
  
• In elderly patients the detection of an unexplained low Factor VIII result in conjunction with a corrected APTT with normal plasma is unlikely to be a result of undiagnosed Haemophilia A or von Willebrands Disease. It is more likely to be due to the presence of a spontaneously produced Factor VIII inhibitor.
  
• Severe Haemophiliacs can produce inhibitors to the Factor VIII treatment they are receiving so should be screened for inhibitors periodically.
  
• Test performed at CGH and GRH.
  

Sample Requirements

3 or 3.5ml Trisodium Citrate tube

Reference ranges

N/A. The presence or absence of a time-dependant inhibitor will be indicated.