Department of Haematology


  • 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

3ml Trisodium citrate

Reference ranges

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