Factor Inhibitor Screen

Clinical Relevance:

Factor Inhibitors are antibodies that are targeted against specific clotting factors e.g. Factor VIII.

Circulating inhibitors that target clotting factors may be either time-dependent e.g. Factor VIII inhibitors or immediate acting e.g. Factor XI inhibitors. Inhibitory antibodies may develop in an individual with an inherited deficiency of a clotting factor e.g. Haemolphilia A or B – these are alloantibodies but but may also arise in individuals with no history of an inherited bleeding disorder – termed autoantibodies.

Reference Range: 0.0 – 0.6BU/mL
Min. Volume: The volume of blood in coagulation samples must lie within the volume range as indicated by the size of the black fill arrow present on tubes. Volumes above or below the arrow will result in sample rejection to ensure validity of results.
Turnaround Time: 24 hours
Age of Sample: Samples will be rejected if received more than 1 hour post venepuncture.
Specimen Requirements:
  • 2 blue top (sodium citrate) samples
  • All coagulation tubes must be adequately filled (see above)
  • All coagulation tubes must be mixed several times by gentle inversion immediately after venepuncture. Mixing the sample with the anticoagulant stops the sample clotting within the tube.
Limitations:
  • It is not possible to provide results on clotted, insufficient, lipaeamic or haemolysed samples. These samples will be rejected with the appropriate comment.
  • Samples tubes that have expired cannot be accepted.
Analysing Laboratory: Coagulation Laboratory, Royal Victoria Infirmary, Newcastle upon Tyne