Factor assays are commonly undertaken when there is prolongation of the APTT or PT and a suggestion of a deficiency of one or more clotting proteins. Individual factors can also be requested to monitor a patient with a known factor deficiency

Clinical Relevance:

Acquired factor deficiencies can be caused by conditions including liver disease, acute conditions such as disseminated intravascular coagulation (DIC), or a deficiency in Vitamin K.

Inherited deficiencies where the factor is reduced or absent are rare. Haemophilia A and B are the most common examples of inherited disorders. They are X-linked deficiencies of factors VIII and IX respectively, and occur predominantly in men (women are usually carriers who are asymptomatic or have mild bleeding). Other inherited factor deficiencies, not associated with the X chromosome, are found equally in both men and women.

Reference Range:
  • Factor II: 73 – 121%
  • Factor V: 66 – 141%
  • Factor VII: 51 – 151%
  • Factor VIII: 56 – 174%
  • Factor IX: 62 – 138%
  • Factor X: 67 – 139%
  • Factor XI: 58 – 157%
  • Factor XII: 59 – 143%
  • Factor XIII: 59 – 181%
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: Urgent: 2 hours
Routine: 1 Week
Age of Sample: Samples will be rejected if received in the laboratory more than 1 hour post venepuncture.
Specimen Requirements:
  • 3 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, or haemolysed samples. These will be rejected with the appropriate comment.
  • Sample tubes that have expired cannot be accepted
  • Heparins and thrombin inhibitors (e.g. hirudin and dabigatran) present in the sample to be tested may lead to an under-estimation of the Factor levels.
  • The presence of Lupus anticoagulant may lead to under-estimation of Factor VIII level or poor correlation between each dilution.
Analysing Laboratory: Coagulation (JCUH)
Referral Laboratory: Samples from patients on certain treatment such as Refacto. Idelvion, and Emicizamab will be referred to the Royal Victoria Infirmary (RVI) in Newcastle for analysis.